intake manifold modification

[tassie wombat]

gday looking at modifying the intake manifold on my 4.2 tdi any ideas?hopefully this is where oldmav will step in!! :bowdown:

[OldMav]

Hi Tassie basically the biggest single improvement to the std runner system is to raze the top 50mm. This has the effect to allow the centre entry air to enter the plenum more effectively or more so to allow the plenum to have a chance to have equal pressure across all runners. This is not a KW gain as such but does allow a few point of extra AFR hence more fuel can be added to gain the benefit. More to the point it allows The air to enter the plenum so it can slow down a bit so basically a accumulator more so than a distribution plenum. This has the effect of allowing the air to enter the runners at a much more straighter angle hence will allow more air to enter the runners and promote better cylinder filling through the valves. This usually shows up on the dyno as a quicker torque rise and a few more Nm of torque the stuff we should be concerned about. This sort of thing you can feel in the seat of your pants and the stuff that makes a 4x4 diesel fun to drive.

Now I must add you can over come all this by just adding a lot more boost but by the nature of turbo's we just don't have a turbo big enough with a small enough turbine to allow the pressures required to do this effectively as a simple top lift. Sure it is possible to get 200rwkw from this std manifold I did this nearly 24 years ago, with my first turbo. But you couldn't drive the beast it was just madness. So with a lot of trial and error and a bit of logic I spent more hours driving my flow bench than I did driving my Mav. But I did learn how to make our TD a more effective high output engine. Now much of what I have done is to improve the effectiveness of a above 150rwkw TD system but much of this stuff does work for the lower tune values like the 50mm lid lift.

To note the std runner system after a lid lift now becomes the main restriction factor to cylinder filling ability. To explain a bit here and to try and put this in a way that can be understood. I have modified my flow bench to reverse flow so it blows into the manifold just like a real turbo engine unlike a std bench which works on pulling air from the combustion chamber through the valves and runner. Sure I have to sacrifice some of the measuring equipment like the calibration plate ( the main thing you set your measurement criteria and gauges from) in the measuring plenum boxes but it still gave me a good indication of what was improved. I did all testing on a std head single cylinder as I had stuffed the other runners and valves through failed experiments. Anyway with hand held measurement probes I discovered when I cycled the valves with an electric motor set up to depress the valve just like a real engine at a simulated 200orpm or 1000rpm cam revs I found when the valves open in those short millisecond points there was vacuum holes in the std runners. This is what locks out any ability to approach cylinder filling ability of the head without the manifold and the limiting factor to outright power and torque rise. Hence my suggested statement that porting the head runners is a very small marginal gain in torque and outright KW. And in my experience and very expensive fails is usually a reduction in torque and kw. But a slightly bigger intake valve does seem to reduce the vacuum hole as the valve cycles, hence a bit more cylinder filling ability which reflect better torque rise the stuff we want.

So as you can see there is a limit to what we can achieve with the std runners and just about all other modifications to the manifold past lifting the lid top 50mm is only very marginal increases hence my common reference to 1%ers. Sure as cool effective boost is increased or more effective turbo's are used we can do things to achieve better results. I can point these out if needed if above 150rwkw is your goal.

Now to explain the whys here and how it effects spool or torque rise, If we improve cylinder filling we can effectively get better combustion for a better fuel ratio hence a better volumetric ratio this in turn produces a higher velocity of exhaust gas which in turn spins our turbine wheel faster with more force inturn our compressor accelerates quicker and faster to produce more volume/pressure earlier in the rev range hence more torque on a flatter curve. Our intake manifold is only one item in this chain that can be improved to get better usable torque/power where it is needed most. Unlike my first 200rwkw effort.

Ok until next time or more question to spark more info locked away in my silly head.

[Robo]

Nice info there buddy.
It's great that someone who obviously loves his job is willing to spend the time to share.
Thankyou.

This upgrade improves both non and intercooled equally.
A 50mm alloy spacer, or some exotic material (for other gains if any) .
Is a spacer available or needs to be custom made.
Will fuel settings need to be tweaked or left as is?.

[OldMav]

Makes no difference intercooler or not. You don't have to change fuel settings but from experience a lot more fuel can be added in the spool area so compensator adjustments are required to get the best results. What happens is you basically gain 2 afr in the spool area for example on a 2860 setup before manifold gave 16 afr lowest after manifold was 18 afr lowest but this did reflect about a 2 to 3 AFR gain through out the rev range. So there is a lot of room for extra fuel.

The modification is quite simple and doesn't have to be anything flash something like this pic is fine..

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Another test I did was on a std manifold to see what was going on inside using the bench in reverse with all the intake valves cycling, with this much volume required I could only obtain a bit under 4 psi pressure in the manifold. I used a very fine dust material magnetite. This stuff deposits where turbulence or flow is distorted or limited flow areas are.

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You can see the very large deposits around 1 and 6 cylinders hence the huge problems with distribution. I did the same thing with a 50mm raised lid like the previous pic but for some reason I cannot find those images. Any way the difference is very different as their is no deposits on any of the dividers just like 3 and 4 dividers in the image.

Now I didn't know this at the time but much later testing suggested a very different reason why there is so much black deposited magnetite in the bottom of the runners the deposits are all the same on all runners right in the angle bit of the runner bottom. I had always thought this was due to the sharp angle there causing a change of direction. later testing as suggested in the above post has nothing to do with the bend but this is caused by that vacuum lock caused by the valve opening. As pressure is raised this deposits moves further into the runner but not quite into the head runner. What is happening here is as the valve opens the valve sucks in some air but not enough air can accelerate fast enough to fill the void hence we get a flow lock at this point so very little air can enter the combustion chamber as you would expect. but once the valve reaches about max stroke the boost pressure does over come the disturbance hole. But we have significantly reduces the time boosted air can flow into the cylinder through the valves. Now all the is not perfect as my bench is sort of set in reverse as suggested so I do have a closed system other wise the bench doesn't work so we do have some vacuum under the head just like the real operating engine but obviously I cannot simulate the exact vacuum the cylinder can produce so you can see this is a serious limitation to our manifold. Also I have opened many std manifolds, and have seen this sort of carbon deposits in the same places, this just gives more weight to my theory.

I have built plastic models of a 3 cylinder manifold using the centre runner on the head for testing to try and reduce this issue. Basically we need to have vertical dividers and not horizontal dividers. I haven't built and tested a real life example but I have passed this idea on to a another fellow other forum member who has built a real example. First impressions look very good but dyno testing etc needs to be done to prove the idea..

[tassie wombat]

Thanks oldmav,so basically as long as the inlet pipe is at least 50mm higher than a standard manifold that's all that is needed,all the new chamber does is increase the volume of air that the manifold holds.doesn't need any special baffles or diverter plates.?

[OldMav]

Yes mate that's about it. But I really have no idea except good guesses at what point this plenum volume needs to get bigger to accommodate higher boosts levels and at what point do we need to consider direction turbulence issues. But I do know at about 150ish rwkw volume does make improvements.

You don't need baffles or dividers or any such things just a open chamber.

[tassie wombat]

thanks again mate,just have to find a spare manifold now so the cars not off the road,and do some homework on how to adjust the fuel pump!

[mudski]

Thanks also as i just picked up my td42t to start the rebuild and was wondering about this mod.

[tassie wombat]

do you know if an intake of a tb42(petrol) would be the same as the diesel one oldmav??

[BigRAWesty]

do you know if an intake of a tb42(petrol) would be the same as the diesel one oldmav??

I'm pretty sure both diesel and tb42 carby are the same, the efi is different.

I'm watching this with interest guys as I'm a fan for NA power. Imo more reliable.

Im looking at modding the front airbox for more flow.
I also like the idea of the manifold increase. Did you trial any different designs or just that square increase??

[OldMav]

The petrol manifolds do not fit.
And yes I did test a round lid makes no difference as this is not a true plenum as such. And I have built and tested many designs but most near all were for 200rwkw in mind.
I have not done any testing to improve vacuum for the N/A engine. But if you emulated the square to tube runners and about 130mm tube runner length and about half the engines capacity for the volume of the plenum you would probable produce a stronger torque curve. But you may not realise for a 2000rpm cam sweet spot it is very difficult to get a N/A diesel to react to this sort of thing like a petrol does. Your gains are usually about half of what you would expect compared to a petrol. hence turbo best bang for your buck.
As for reliable well this engine is a freak and was designed with little compromise for strength. There are many of these engines with double and triple the std power doing way past I million KLMs treated correctly.

This is the design I am runner at the present.

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[Ben-e-boy]

Pete.

what gains have you actually made with this current manifold design as opposed to the basic lid lift like my ARE one.
is it more to do with velocity and responce than power?
cheers
Benny

[nissannewby]

Pete.

what gains have you actually made with this current manifold design as opposed to the basic lid lift like my ARE one.
is it more to do with velocity and responce than power?
cheers
Benny

Air speeds are lower at the valve, so better cylinder filling is achieved, which the equates to a faster torque rise. I believe the curved design also helps with reducing turbulence.

[BigRAWesty]

So going back to the well known fact that 1 & 6 starve a little a better designed intake paired with eextractors will aid a bit.. Sure a turbo is best bang for buck.. But I can make all the NA myself, I can't make a turbo..
I'm not thinking anything huge like above, but a neat intake setup will a bettering flow and storage..

[Ben-e-boy]

Air speeds are lower at the valve, so better cylinder filling is achieved, which the equates to a faster torque rise. I believe the curved design also helps with reducing turbulence.
Hmmm.
I would like to put my manifold on the bench and see what happens.

[OldMav]

Pete.

what gains have you actually made with this current manifold design as opposed to the basic lid lift like my ARE one.
is it more to do with velocity and responce than power?
cheers
Benny

Benny This current manifold with cooler attached is for big power but more so with big capacity turbo's like GTX3071 where by there is ample capacity left over including near instant pressure response like the GTX can do. Hence the large volume from cooler and plenum can be negated unlike a front mount which no matter what people say they do lag compared to this set up. The actually manifold design has as best as I can tell has zero Turbulence issues unlike the other simular looking high top systems. Hence if does flow very well and past what I would expect from the std runners.

But for this 200rwkw area as said you can get this from the std manifold but you will not even come close to the torque response of torque rise of this manifold. Like Mat has said air speeds are very low right into the runners hence no turbulence locks and as long as you have pressure in the plenum it is very evident it fills the cylinders very close to what can be achieved with head only values. It still develops that vacuum hole at max torque revs but nothing like a std manifold or a 50mm lid lift or the simular looking high top systems. From testing to the best of my ability I can nearly suggest there is no vacuum locks in the runner in the real world because the GTX 3071 turbo once it hits its sweet spot it develops 15 psi to 50+psi in a vertical line on the dyno less than 150rpm with this system so it is probably not possible to develop a vacuum lock in the runners. But on the bench I cannot simulate this type of turbo response, so I can only suggest my logic here.

We are still very much in real world testing mode here with this system and a tricky turbine housing to obtain this stupid response result. But when this testing was done the liner let go on the dyno so ended out testing (not my engine but a very good friends engine) Before dyno work ceased it saw values past 200rwkw and torque rise values and response in the unheard of area, and we hadn't even got to fuel tune the thing yet. As said all still in the development mode. My rig has the same system but the turbo is a dumb down version so we have something to compare too.

So to answer your question Ben its a big YES to all of those things.

[OldMav]

So going back to the well known fact that 1 & 6 starve a little a better designed intake paired with eextractors will aid a bit.. Sure a turbo is best bang for buck.. But I can make all the NA myself, I can't make a turbo..
I'm not thinking anything huge like above, but a neat intake setup will a bettering flow and storage..

Westy to be very honest I really couldn't tell you. Only some very early learning how the bench worked using a draw through I had very conflicting results doing this testing on different style lid lifts Sure there were improvements but really they were confusing. But I can tell you without doubt that a 50mm lid lift on your N/A engine will give you a torque rise and a flatter curve so not a lot of taper off after peak torque and will allow 1&6 to actually get some air. But I have never tested this on a N/A on the dyno. This is only what the bench tests have suggested to me. But I did get confusing and non consistent results but this could of been operator induced. Also being N/A the final results will be small gains. But I could suggest to you and I always suggest this and I feel many are getting sick of me saying it but the real key to response and big improvements to out TD engine is in the air induction system N/A or Turbo. I cannot stress enough the ZD30 air box is a huge air velocity restrictor, the piping to the turbo or N/A manifold is sooooooo important more important than the manifold even the turbo itself. There is a lot of feel in your pants power here more than you could dream off. And this includes the ZD30 engine as well. I will stick my neck out here and say this with passion from testing and experience this air box is fail in a big way and that includes with a funny lid. Sure you can improve it but it is still fail even for the N/A engine Westy.. but if you can some how stick a proper cleaner on top of the manifold this will be your very best option for best results. Try it with a pod to see if the improvement is worth doing..

[OldMav]

Hmmm.
I would like to put my manifold on the bench and see what happens.

Draw through flow bench will only tell you half the story Ben. My situation has changed a bit in my life and my flow bench and dyno I had no room to store, A very old friend asked for a long term lend so he has it to do a project.. Otherwise I would gladly offer to test your manifold..

[Ben-e-boy]

Benny This current manifold with cooler attached is for big power but more so with big capacity turbo's like GTX3071 where by there is ample capacity left over including near instant pressure response like the GTX can do. Hence the large volume from cooler and plenum can be negated unlike a front mount which no matter what people say they do lag compared to this set up. The actually manifold design has as best as I can tell has zero Turbulence issues unlike the other simular looking high top systems. Hence if does flow very well and past what I would expect from the std runners.

But for this 200rwkw area as said you can get this from the std manifold but you will not even come close to the torque response of torque rise of this manifold. Like Mat has said air speeds are very low right into the runners hence no turbulence locks and as long as you have pressure in the plenum it is very evident it fills the cylinders very close to what can be achieved with head only values. It still develops that vacuum hole at max torque revs but nothing like a std manifold or a 50mm lid lift or the simular looking high top systems. From testing to the best of my ability I can nearly suggest there is no vacuum locks in the runner in the real world because the GTX 3071 turbo once it hits its sweet spot it develops 15 psi to 50+psi in a vertical line on the dyno less than 150rpm with this system so it is probably not possible to develop a vacuum lock in the runners. But on the bench I cannot simulate this type of turbo response, so I can only suggest my logic here.

We are still very much in real world testing mode here with this system and a tricky turbine housing to obtain this stupid response result. But when this testing was done the liner let go on the dyno so ended out testing (not my engine but a very good friends engine) Before dyno work ceased it saw values past 200rwkw and torque rise values and response in the unheard of area, and we hadn't even got to fuel tune the thing yet. As said all still in the development mode. My rig has the same system but the turbo is a dumb down version so we have something to compare too.

So to answer your question Ben its a big YES to all of those things.

Thanks.

So my next question is can you go too big?
I have just had a look at my setup and if everything was still in its current position versus your setup I would have a bit more volume.
Would there be a relation between cooler size and plenum size?

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[OldMav]

Ben to comment without being critical here the system is good but the only issue I have found with testing a system like that which I have had in the past with a KKK turbo is you stuff up flow capacity hence turbulence with the small connection cooler to manifold. Bench testing will tell you nothing here you have to bench the cooler and manifold together. And Yes Ben I tested this system against my now system. And yes it does flow better in the pre torque max rev area mmmm a lot better. Now you are using a bigger cooler than I am which is fine but more volume and funny things happen to flow in the manifold when you speed up volume with that connection type. Also remember I am using water/methanol pre turbo injection as I have always done so I just do not need such a big cooler any more. Hence why I have gone for the cooler connected directly to the plenum.

Ben remember this stuff is all 1% ers now.

PS I forgot YES you can go to big, Hence the half size cooler hehe. But I don't know what to big is as yet..

[Ben-e-boy]

Draw through flow bench will only tell you half the story Ben. My situation has changed a bit in my life and my flow bench and dyno I had no room to store, A very old friend asked for a long term lend so he has it to do a project.. Otherwise I would gladly offer to test your manifold..

Thanks..good luck with the new path.


Ben to comment without being critical here the system is good but the only issue I have found with testing a system like that which I have had in the past with a KKK turbo is you stuff up flow capacity hence turbulence with the small connection cooler to manifold. Bench testing will tell you nothing here you have to bench the cooler and manifold together. And Yes Ben I tested this system against my now system. And yes it does flow better in the pre torque max rev area mmmm a lot better. Now you are using a bigger cooler than I am which is fine but more volume and funny things happen to flow in the manifold when you speed up volume with that connection type. Also remember I am using water/methanol pre turbo injection as I have always done so I just do not need such a big cooler any more. Hence why I have gone for the cooler connected directly to the plenum.

Ben remember this stuff is all 1% ers now.

PS I forgot YES you can go to big, Hence the half size cooler hehe. But I don't know what to big is as yet..

Very interesting, I suppose if were to increase the 3 inch joiner gradually, and a bit of dyno time and see what comes off it.

I do like the 1%ers:D 5x 1%ers is 5% and 5% of power/torque at current figures is 9kw and 38Nm, just shy of the 200kw/800Nm combo and a noticable increase :D

[MudRunnerTD]

Great Thread. Should combine this into the 200kw club thread maybe?

Thanks Oldmav, your articulate and clear. Clearly knowledgable far beyond where I'm at so thanks for sharing.


I'd be interested to hear your view on Air/water IC setup too. I'd also be interested in some pics of your Methanol/water injection setup too.

Cheers MR

[nissannewby]

Yes Oldmav is highly knowledgable and his knowledge retention is insane. He certainly is a top bloke for sharing it all.

I'm sure he will be along shortly to tell you the benefits of w2a cooling and his methanol ( which I will be utilizing on my GU ) and I'll warn you now a second mortgage might be necessary with the motivation he will give you lol.

[OldMav]

Thanks..good luck with the new path.



Very interesting, I suppose if were to increase the 3 inch joiner gradually, and a bit of dyno time and see what comes off it.

I do like the 1%ers:D 5x 1%ers is 5% and 5% of power/torque at current figures is 9kw and 38Nm, just shy of the 200kw/800Nm combo and a noticable increase :D

The 4 inch does do a bit. I actually fitted a 5 inch on the manifold lol it did give a increase on the dyno Kw and Nm. Which gave me the motivation to do the current cooler manifold system.

[OldMav]

Great Thread. Should combine this into the 200kw club thread maybe?

Thanks Oldmav, your articulate and clear. Clearly knowledgable far beyond where I'm at so thanks for sharing.


I'd be interested to hear your view on Air/water IC setup too. I'd also be interested in some pics of your Methanol/water injection setup too.

Cheers MR

Mmm this is probably two whole new threads lol.. A bit of background first. I have had to change my front radiator inner panel 3 times now due to not enough metal left to hold the radiator so from that you can guess how many front mounts I have played with. I am also on my second bonnet but I have only tried 3 top mounts but they got modified many times. Water to Air I have only had one core the one I still have it is a Garrett core and bloody expensive. But I have had many different distribution chambers fitted for different systems.

My opinion only here but I did fit probes in and out to all of them and used a fluke meter which will data record. First top mounts compared to a W/A cooler you just cannot compare. Reason the temps are just way to erratic even with a fan fitted under them. Even with the last one I built which was 725mm long and 400mm wide 75mm tube and fin, fitted with 2 spal 14 inch fans fitted under it, This one was a front mount original I was testing. The temps were still way to erratic and I still saw above 90C without pre turbo injection, at odd low speed situations, you just cannot get enough air off the bonnet to get them to be stable on a GQ. And yes I know a GU bonnet does work a lot better due to its greater angle. But still they do work well just not as well as a W/A.

Front mounts I spent a lot of time with this system I liked them a lot but truly trying to compare to a W/A cooler its just not fair. Even the cooler mentioned above as a front mount which worked better by far as a front mount just doesn't cut it compared to a W/A but still it was damn good and kept temps at a nice 50 to 55 C but do any sort of sand work and mmm 90 to 140+ C is seen easy, no water injection.

Remember here this is all done on a total stupidly Blueprinted and balanced engine which more often than not produced 180rwkw.

Water to Air well no question, no doubt what so ever, total stable temps, general driving about, traffic or just wheeling about it is rare to see 5C above ambient. My old radiator/condensor which was about 100mm smaller than my new condenser I saw 50C a couple of times but 2 x14 inch spal fans set at 50C would turn on in anger for a few minutes, temp would plummet to ambient. But usually the fans would do erratic switching for a bit because they were to good.

Now I really have to mention here I use Water Methanol pre turbo injection so my compressor outlet temps never ever get above 100C. On the KKK turbo which is about the size of a 3071 with out pre injection it can reach 180C quite easily in anger. Oddly enough I drove about a lot without any cooler due to mods or leaks or just sh#t playing. I had a 3 inch tube set up so I could easily fit for those times I didn't have a cooler but this tube had two large W/M jets fitted along its length plus the usual pre turbo injector. Well sadly this system worked better than any air to air I ever fitted. Buuuut it used water at near the rate of fuel haha. I remember one time playing in the sand I used up my 100 litre under tray water tank in 20 minutes. I mention this because it really is a good option for the lower tune engine if you have the room to fit a good size water tank, due to tune it wouldn't use the quantity my engine needed to cool the heated compressor air.

Any way I have been using W/M since my first diesel Landrover then a H then 2H then my Mav and a number of V8 petrol engines in between and a few fool mate who thought I knew what I was doing lol. Now days it is a lot easier to set one up with safety. I use a coolingmist system about $1000 for one of these units but that with 2 jets solenoids filters flow meter etc etc. This is the only system you would dare use for pre turbo injection the other units just are not progressive enough or have the failsafe system built in. I do not advise people to do as I do pre turbo injection, it does take a bit of knowledge and some balls to do it. There is risk but todays coolingmist is near bullet proof but there is still a high risk of wearing away your comp wheel fast if you are not careful. But for me the benefits out way the risk, comp billet wheels are cheap now days. For this top end engine, W/M and pre turbo injection can easily take a 180rwkw engine to 210rwkw concretive no extra fuel. But the main reason for W/M even in small volumes will lower EGT 100C on our TD engine so you can add more fuel/boost to get more power/torque.

There are many reasons to use water methanol or just water but I am only outlining here why I use it. That being pre turbo injection lowers out put temps dramatically not only that it tricks the comp wheel into thinking it is a bigger turbo hence faster spools and faster higher torque rise more boost with more volume due to lower temps. It lowers EGT's where you need too, for towing or hard playing. And it cleans your engine of carbon including rings so you do get a better seal hence you can extend your oil changes. Because you get less carbon deposits transfer to your oil. But the best part you can just use water its free and in a diesel it adds torque and power via the steam engine effect so it adds to the combustion force to drive the piston down and again its free fuel in other words for free power. Truly outside of a turbo this is the biggest bang for your dollar, no other mods can equal the benefits and free power gain of water injection or add a 50/50 mix methanol and you get a nice extra power boost.

As said I could right a book about these subject and to be fair it really does need another thread to do it justice.

[tassie wombat]

Thanks again for sharing your wealth of knowledge mate,I'm sure the forum will benefit from the advice that you give as the other site has for many years,and just remember, I'm more than happy to kick one of the kids out of their bedroom just so you've got a nice comfy bed to sleep in after a big day of tuning my wagon! 😁

[sooty_10]

Maybe you should write a book Pete. A how to modify and tune the powerful TD42 for dummies :) Would probably sell quite a few in auto stores. A question about water only, what water do you use? Can you use tap water? Area dependant on how heavy it is? I'd be keen to give it a look in if I could get an easy source of water and potentially a dual purpose water tank, drinking/injection. If touring how hard would it be to source a viable water source, with decent drinking quality filter? Looks like a few questions but it is really one long one ;)

[Alitis007]

Very interesting OldMav and thanks for sharing. I have tinkered a little bit with petrol intake systems and have found larger throttle bodies show on a dyno a 5kw increase and larger plenum about 7kw on std internals at higher rpm but with a cam you can potentially gain up to an extra 50kw on top of what the cam would normally produce. Another thing as you would know petrol systems are alot more sensitive than diesels, so why don't they make a tuned length runner plenum system ? Wouldn't that help direct the air to the valve?

[nissannewby]

No real difference in the sensitivity mate. Due to our diesel being a slow revving motor and only making its peak torque and hp so low in the rev range we cannot achieve the velocities that a petrol can to make a tuned length runner work. Also in a turbo application a diesel is on boost pretty much the entire time your driving, Oldmav's ute Makes boost at idle. To allow us to get better values we require the shortest possible distance to the valve to allow better cylinder filling, filling the cylinder more efficiently increases our volumetric efficiency and in turn our turbo works better for our low speed engine.

Most of this stuff is all for to help the turbo work the way it was designed, ideally what we are wanting the achieve is a drive ratio for the turbo at 1:1 or better (imp:emp ratio). When we achieve this we can push ve above 100%.

[OldMav]

Back on topic, Good Question Alitis007 As you say, petrol's are a lot more sensitive than a diesel in the N/A area. This is due to a diesel has twice the compression ratio and a higher operating vacuum. You can use all the petrol tuned length formula's to calculate a ideal torque point if you factor in compression ratio and the extra air required for diesel fuel energy. But the tube lengths gets very long, then response time in the tube becomes a even more greater issue, and cylinder filling ability starts to counteracts volume transfer so it negates any gains. I have spent a lot of time investigation this idea. And I did build a long tube runner to plenum using a front mount cooler results were dismal and I mean very dismal I lost 50+rwkw and the EGT gauge reacted like a tacho. I never got this system of the dyno but it was really only to prove my own theories. I did try different length tubes just on trial and error to see what the torque curve did. The results were as the tube lengths got shorter and shorter I gained more kw and the torque curve became flatter and higher the shorter the tube runner got. I even tried bell mouths in the plenum no difference none at all. Using this real world stuff and using this info on the bench I found 110mm to 115mm from the centre of the valve was the ideal and no vacuum locks in the runner. So that leaves you about 20mm max for a runner past the head. Which doesn't leave much room to fit injector tubes between the runners. Now for the reason why here which is we are using pressure and no vacuum hence why the tube length gets shorter and shorter as the boost pressure rises. So the tube length I have given here is for the ideal of 30 psi at 2100 rpm to gain the best torque rise etc etc.. More pressure or less pressure will change this but not by a great deal for example 115mm is 20 psi..

Cam shafts mmmm I have limited experience here but a lot of knowledge from research I can tell you the over lap cannot be made shorter otherwise your EGT will shy rocket as you add more boost/fuel/power. So a regrind is not a option for our TD. Because you cannot put metal on the cam lobe you can only remove it to change the profile. Doing this you have to reduce the overlap. So its a very BIG NO to a regrind. The only option is to have a new billet made so you can increase the overlap and increase the duration and or total cam lift. But there are some tricks we can do like increase the rocker ratio which increases all these values but same of these values may not be ideal. You also could change your lifters to mushroom lifters then uses the extra duration to regrind the cam for a increased overlap and lobe centres. The STD T cam we already have is quite good anyway so unless you are after over 900Nm and 230+rwkw it a waste of money for returns to your dollar. Besides that our crank will not survive this sort of neck snapping torque value. But there is good gains to be had with overlap times as we can offset EGT's hence use a much tighter turbine AR but its not really the ideal way to gain Spool times, Besides that we really want to increase out Volumetric efficiency so the below 1:1's EMP (exhaust manifold pressure) to IMP (intake manifold pressure) is the best way to go .

[PMC]

Hi Tassie basically the biggest single improvement to the std runner system is to raze the top 50mm. This has the effect to allow the centre entry air to enter the plenum more effectively or more so to allow the plenum to have a chance to have equal pressure across all runners. This is not a KW gain as such but does allow a few point of extra AFR hence more fuel can be added to gain the benefit. More to the point it allows The air to enter the plenum so it can slow down a bit so basically a accumulator more so than a distribution plenum. This has the effect of allowing the air to enter the runners at a much more straighter angle hence will allow more air to enter the runners and promote better cylinder filling through the valves. This usually shows up on the dyno as a quicker torque rise and a few more Nm of torque the stuff we should be concerned about. This sort of thing you can feel in the seat of your pants and the stuff that makes a 4x4 diesel fun to drive.

Now I must add you can over come all this by just adding a lot more boost but by the nature of turbo's we just don't have a turbo big enough with a small enough turbine to allow the pressures required to do this effectively as a simple top lift. Sure it is possible to get 200rwkw from this std manifold I did this nearly 24 years ago, with my first turbo. But you couldn't drive the beast it was just madness. So with a lot of trial and error and a bit of logic I spent more hours driving my flow bench than I did driving my Mav. But I did learn how to make our TD a more effective high output engine. Now much of what I have done is to improve the effectiveness of a above 150rwkw TD system but much of this stuff does work for the lower tune values like the 50mm lid lift.

To note the std runner system after a lid lift now becomes the main restriction factor to cylinder filling ability. To explain a bit here and to try and put this in a way that can be understood. I have modified my flow bench to reverse flow so it blows into the manifold just like a real turbo engine unlike a std bench which works on pulling air from the combustion chamber through the valves and runner. Sure I have to sacrifice some of the measuring equipment like the calibration plate ( the main thing you set your measurement criteria and gauges from) in the measuring plenum boxes but it still gave me a good indication of what was improved. I did all testing on a std head single cylinder as I had stuffed the other runners and valves through failed experiments. Anyway with hand held measurement probes I discovered when I cycled the valves with an electric motor set up to depress the valve just like a real engine at a simulated 200orpm or 1000rpm cam revs I found when the valves open in those short millisecond points there was vacuum holes in the std runners. This is what locks out any ability to approach cylinder filling ability of the head without the manifold and the limiting factor to outright power and torque rise. Hence my suggested statement that porting the head runners is a very small marginal gain in torque and outright KW. And in my experience and very expensive fails is usually a reduction in torque and kw. But a slightly bigger intake valve does seem to reduce the vacuum hole as the valve cycles, hence a bit more cylinder filling ability which reflect better torque rise the stuff we want.

So as you can see there is a limit to what we can achieve with the std runners and just about all other modifications to the manifold past lifting the lid top 50mm is only very marginal increases hence my common reference to 1%ers. Sure as cool effective boost is increased or more effective turbo's are used we can do things to achieve better results. I can point these out if needed if above 150rwkw is your goal.

Now to explain the whys here and how it effects spool or torque rise, If we improve cylinder filling we can effectively get better combustion for a better fuel ratio hence a better volumetric ratio this in turn produces a higher velocity of exhaust gas which in turn spins our turbine wheel faster with more force inturn our compressor accelerates quicker and faster to produce more volume/pressure earlier in the rev range hence more torque on a flatter curve. Our intake manifold is only one item in this chain that can be improved to get better usable torque/power where it is needed most. Unlike my first 200rwkw effort.

Ok until next time or more question to spark more info locked away in my silly head.

G'day Peter,

Thanks again for your in-depth and quality information, i always look forward to reading your posts, has i always continue to learn something new!

Regards,

Paul

[OldMav]

Maybe you should write a book Pete. A how to modify and tune the powerful TD42 for dummies :) Would probably sell quite a few in auto stores. A question about water only, what water do you use? Can you use tap water? Area dependant on how heavy it is? I'd be keen to give it a look in if I could get an easy source of water and potentially a dual purpose water tank, drinking/injection. If touring how hard would it be to source a viable water source, with decent drinking quality filter? Looks like a few questions but it is really one long one ;)

Sooty there is no real reason to use distilled water or any other special dollar value water, Due to our usage its fine to use tap water. The only thing is to use good filtering for example a good fine stainless gauze or quality plastic gauze filter as a primary filter at the tank then always use the supplied inline fine filter supplied by the W/M injector supplier. As the jets are very fine and do require clean water. And yes the jets need to be serviced regularly to remove calcium deposits forming on the tip that can distort the spray pattern but good quality town water this is never a issue.

[Robo]

Humm after looking around for an WTA system I noticed on ebay a modified inlet that looks neat.
Plazmaman Ebay item 161119490377.
Note, it's not for the inlet only a pic of someone else's work

WTA Kit was near 3K but didn't include the plenum.
If you look closely at it, it has plazmaman logo on it.
scroll down the page and there is a very good pic of it polished
so maybe a modified linlet as described can be purchased on line

[OldMav]

Sadly these guys and I will not write there name but its only a STD manifold made pretty. these guys missed the boat and the opportunity to do something special. I haven't flow benched this manifold but I already know from experience it is marginal and as pressure rises it will get less results than the Bog STD manifold due to the absolutely silly radiuses on all edges. Even the Nissan engineers knew this and made there radius 15mm radius minimum.. Also $1500 for a pretty looking no better than a STD manifold is a joke.

[sooty_10]

Thanks for the confirmation on running tap water Pete. I have had others saying that you shouldn't use tap water. Due to deposits etc. but yeah have been seriously contemplating it and that was my major limiting factor. I would have a reasonable quality drinking water filter and then split the line to a water outlet and W/M line with as you say a finer filter inline. Time to start some planning and a shopping list.

[PMC]

Air speeds are lower at the valve, so better cylinder filling is achieved, which the equates to a faster torque rise. I believe the curved design also helps with reducing turbulence.

Stop talking porn. lol

Regards,

RLI

[PMC]

G'evening Lounge Lizards,

Due to me selling my 4.2 turbo diesel GU wagon, as previously advised, i am currently putting my Patrol back to stock. Therefore, i will be taking off the UFI inlet manifold built by Matt Craig in WA, which is designed to fit to the Cross Country intercooler set-up.

PS, i will keep you posted when i offer it up for sale.

Regards,

RLI

[sooty_10]

G'evening Lounge Lizards,

Due to me selling my 4.2 turbo diesel GU wagon, as previously advised, i am currently putting my Patrol back to stock. Therefore, i will be taking off the UFI inlet manifold built by Matt Craig in WA, which is designed to fit to the Cross Country intercooler set-up.

PS, i will keep you posted when i offer it up for sale.

Regards,

RLI

Good to know Paul, I'd be interested in some pics if you have any to throw up here?

Ps. I hope your getting another patrol ??? Edit: just seen your patrols post.... Definitely an upgrade :)

[PMC]

Good to know Paul, I'd be interested in some pics if you have any to throw up here?

Ps. I hope your getting another patrol ???

G'evening sooty,

Check out page 26 on my build thread RLI's Patrol in the members ride section. I also match ported the manifold with the gasket.

Regards,

RLI

[Alitis007]

Back on topic, Good Question Alitis007 As you say, petrol's are a lot more sensitive than a diesel in the N/A area. This is due to a diesel has twice the compression ratio and a higher operating vacuum. You can use all the petrol tuned length formula's to calculate a ideal torque point if you factor in compression ratio and the extra air required for diesel fuel energy. But the tube lengths gets very long, then response time in the tube becomes a even more greater issue, and cylinder filling ability starts to counteracts volume transfer so it negates any gains. I have spent a lot of time investigation this idea. And I did build a long tube runner to plenum using a front mount cooler results were dismal and I mean very dismal I lost 50+rwkw and the EGT gauge reacted like a tacho. I never got this system of the dyno but it was really only to prove my own theories. I did try different length tubes just on trial and error to see what the torque curve did. The results were as the tube lengths got shorter and shorter I gained more kw and the torque curve became flatter and higher the shorter the tube runner got. I even tried bell mouths in the plenum no difference none at all. Using this real world stuff and using this info on the bench I found 110mm to 115mm from the centre of the valve was the ideal and no vacuum locks in the runner. So that leaves you about 20mm max for a runner past the head. Which doesn't leave much room to fit injector tubes between the runners. Now for the reason why here which is we are using pressure and no vacuum hence why the tube length gets shorter and shorter as the boost pressure rises. So the tube length I have given here is for the ideal of 30 psi at 2100 rpm to gain the best torque rise etc etc.. More pressure or less pressure will change this but not by a great deal for example 115mm is 20 psi..

Cam shafts mmmm I have limited experience here but a lot of knowledge from research I can tell you the over lap cannot be made shorter otherwise your EGT will shy rocket as you add more boost/fuel/power. So a regrind is not a option for our TD. Because you cannot put metal on the cam lobe you can only remove it to change the profile. Doing this you have to reduce the overlap. So its a very BIG NO to a regrind. The only option is to have a new billet made so you can increase the overlap and increase the duration and or total cam lift. But there are some tricks we can do like increase the rocker ratio which increases all these values but same of these values may not be ideal. You also could change your lifters to mushroom lifters then uses the extra duration to regrind the cam for a increased overlap and lobe centres. The STD T cam we already have is quite good anyway so unless you are after over 900Nm and 230+rwkw it a waste of money for returns to your dollar. Besides that our crank will not survive this sort of neck snapping torque value. But there is good gains to be had with overlap times as we can offset EGT's hence use a much tighter turbine AR but its not really the ideal way to gain Spool times, Besides that we really want to increase out Volumetric efficiency so the below 1:1's EMP (exhaust manifold pressure) to IMP (intake manifold pressure) is the best way to go .

I don't have much experience with diesels and don't have a great deal to do with them so i find all this intriguing. Your extensive R&D shows in your answer because you answered a question i thought of after i made the earlier post which was the bell mouthed/ tunnel rammed plenum, i'm guessing it was similar to a RB26dett with pre chamber ? Regardless its gives me a lot to think about. Thanks once again mate and best of luck with your plenum design

[Robo]

Sadly these guys and I will not write there name but its only a STD manifold made pretty. these guys missed the boat and the opportunity to do something special. I haven't flow benched this manifold but I already know from experience it is marginal and as pressure rises it will get less results than the Bog STD manifold due to the absolutely silly radiuses on all edges. Even the Nissan engineers knew this and made there radius 15mm radius minimum.. Also $1500 for a pretty looking no better than a STD manifold is a joke.

presume this is to do with ebays pic of manifold .
agree $1500 lol.

more radius adds turbulence if air is introduced centrally?

Now I'm a little confused,
gtr's plenum round, in all 3 dimensions.

[Ben-e-boy]

The 4 inch does do a bit. I actually fitted a 5 inch on the manifold lol it did give a increase on the dyno Kw and Nm. Which gave me the motivation to do the current cooler manifold system.

Ok, I wouldnt be able to fit a 5 inch pipe to my manifold.... is it better to be round?

Would I be right in saying that the first major goal of manifold design should be equal flow to all cyclinders? Then chase better allround figures?

Maybe off topic a bit, but with an intake system is there a boundry layer of air and what affect can that have on design?

Cheers
Benny

[OldMav]

presume this is to do with ebays pic of manifold .
agree $1500 lol.

more radius adds turbulence if air is introduced centrally?

Now I'm a little confused,
gtr's plenum round, in all 3 dimensions.

Robo Yes the comments are towards the ebay pic manifold only. For runner entry or divider edges there can be no sharp edges above 15mm radius edges give diminishing returns but under 15mm radius entry edges to the runner create vortex turbulence at those edges which extend into the runner causing choke or less area for fast accelerating air to pass in other words makes the runner entry smaller as air accelerating air. This manifold has no more than 5mm radius edges. For our diesel plenum lid it a accumulator not a plenum as such so the lid top makes no difference for top entry position, But for front entry systems then at least the radius of the entry tube does have a minimal improving effect.

[PMC]

Robo Yes the comments are towards the ebay pic manifold only. For runner entry or divider edges there can be no sharp edges above 15mm radius edges give diminishing returns but under 15mm radius entry edges to the runner create vortex turbulence at those edges which extend into the runner causing choke or less area for fast accelerating air to pass in other words makes the runner entry smaller as air accelerating air. This manifold has no more than 5mm radius edges. For our diesel plenum lid it a accumulator not a plenum as such so the lid top makes no difference for top entry position, But for front entry systems then at least the radius of the entry tube does have a minimal improving effect.

G'day Peter,

I am now going down the chev V8 diesel path. I wonder if you have had much to do with those engines, if so, do they also suffer from intake manifold problems as well?

I have just sent the following e-mail to Jim from Baylock.

"G’day Jim,

The last time I wrote to you I was seeking advice regarding your switchblade turbo set-up to suit a Nissan Patrol 4.2 turbo diesel engine.

However, things have now changed, I am currently in the market place to purchase a Nissan Patrol with a Chev 6.5 turbo intercooled diesel engine conversion.

Question: Jim do you provide a switchblade turbo set-up to fit this type of engine?

If yes, what would be the cost mate?"

I will keep both you and nissannewby informed of my progress.

Regards,

RLI

[OldMav]

Ok, I wouldnt be able to fit a 5 inch pipe to my manifold.... is it better to be round?

Would I be right in saying that the first major goal of manifold design should be equal flow to all cyclinders? Then chase better allround figures?

Maybe off topic a bit, but with an intake system is there a boundry layer of air and what affect can that have on design?

Cheers
Benny

Benny Your manifold is a very nice manifold and addresses the distribution component very well but the issue here is not the manifold its the air speed changes that happen when air has to change its acceleration speed so many times. For example high speed air entering the cooler then abruptly slows down to be cooled then has to speed up again to exit the cooler then slow down again as it enters the plenum. The cooler to plenum caused a backup effect when you are trying to go from high boost to low boost situations, due to the shortness of the system unlike a front mount this in my experience helps to causes surge. Even just a 4 inch pipe there does reduce this effect allowing the plenum and cooler volume to reduce this effect as a accumulator. Hence my cooler to plenum connection system. This is only my experience for fast spooling high volume turbo's like the 3071 type.

[OldMav]

Hi Paul
Yes mate I have looked at the 6.5 Chev..I have actually rebuilt one only and driven a number on long trips and in play. I am going to try to be positive here and that is really really difficult to do when you are looking at 1940's diesel design. But if you like lazy power with very short revs connected to a manual Nissan gearbox not suited to its short torque curve then they are a great engine as there is no replacement for displacement. But I will warn you this engine is not designed with strength as a paramount virtue. The head has odd smallish runners with odd curves and a manifold that is designed around petrol design and vacuum. But they do react to a turbo quite well but you have a limit as to how much air volume you can pump into the combustion chamber, As pressure doesn't automatically mean volume.

To answer your question that's a yes they do have intake induction system issues, but fixing them is difficult to do with centre V induction.

[tassie wombat]

G'evening Lounge Lizards,

Due to me selling my 4.2 turbo diesel GU wagon, as previously advised, i am currently putting my Patrol back to stock. Therefore, i will be taking off the UFI inlet manifold built by Matt Craig in WA, which is designed to fit to the Cross Country intercooler set-up.

PS, i will keep you posted when i offer it up for sale.

Regards,

RLI
Gday mate,sent you a pm,not sure if you got it though??

[PMC]

Gday mate,sent you a pm,not sure if you got it though??

G'day mate,

I received your PM, I will contact you soon.

PS, i am a lazy bastard at times. lol

Regards,

Paul

[tassie wombat]

No worries mate,cheers.

[Robo]

Robo Yes the comments are towards the ebay pic manifold only. For runner entry or divider edges there can be no sharp edges above 15mm radius edges give diminishing returns but under 15mm radius entry edges to the runner create vortex turbulence at those edges which extend into the runner causing choke or less area for fast accelerating air to pass in other words makes the runner entry smaller as air accelerating air. This manifold has no more than 5mm radius edges. For our diesel plenum lid it a accumulator not a plenum as such so the lid top makes no difference for top entry position, But for front entry systems then at least the radius of the entry tube does have a minimal improving effect.

Think I'm reading you, given the preferred radius and---
so adding volume/space by raising the top by 50mm gives the air flowing inwards room to become less turbulent and thus allows for a larger air volume to enter & flow though the runners.
and at the same time keeping inlet manifold size optimal to not suffer pressure drop.

[OldMav]

Think I'm reading you, given the preferred radius and---
so adding volume/space by raising the top by 50mm gives the air flowing inwards room to become less turbulent and thus allows for a larger air volume to enter & flow though the runners.
and at the same time keeping inlet manifold size optimal to not suffer pressure drop.

Plenum design has a maths to the volume size for petrol capacity, vacuum only this has to be with petrol as they work in vacuum 90% of the time, a turbo diesel works near 100% of the time in pressure. But for N/A diesel you can adjust this for diesel considering the higher compression ratio and vacuum associated with this mechanic. This mod to raise the lid 50mm is more about slowing the incoming pressurised air so it has a chance to distribute along the plenum log which isn't ideal for this. The other thing it addresses is to allow enough volume to distribute to the end runners or cylinders. What happens here over and above the STD log manifold is the air has a bit more room above the dividers where considerable turbulence happens which chokes off air passage to 1 and 6 cylinder. For example from the bench which I cannot exactly remember set pressure I think it was 4 psi or 1 psi but regardless the STD manifold flows 173 cfm 1 and 6 and 205 for number 4 which is the highest obviously due to the intake sitting over the top of number 4 runner. With the lid lift your get all the cylinders flowing very close to 235 cfm there is only one or 2 points separation different. As you can see it allows more even distribution and some more flow for this set pressure. Obviously as the pressure gets higher or more pumped volume the values get more separation hence a larger lid lift or more plenum volume is required. As I said before my bench is old very old and the new benches are very much better at this sort of accurate values I was only after change and the increase of change hence I am very reluctant to state values because they are only indicative to my bench which was running with a calibration system that is not ideal.

I do have a results sheet for a super flow 110 bench of the STD manifold in blow through format and my 20+ year old results do show the same spread of values but mine are a bit lower output values. From all this testing and stuffing about I didn't get results to suggest the plenum could be to large as the spread results just got better as the inlet got further away from the runner/ dividers. but the biggest change didn't happen until a 50mm lid lift hence my suggestion here after 50mm the spread results didn't really change. The reason for this is the turbo's we fit mostly except for the HT18 have a bigger capacity to pump volume than the runner can flow so we always have a over supply except that pressure will overcome flow into the runners to a point where diminishing returns happen this is in my best guess and happens at about the 150-160rwkw mark or about 22 psi in the real world.

You have to remember here this is for outright KW's I have never been about this I have always been about torque response and torque rise to make the engine produce torque over a wider rev range so a flatter curve which is much more fun to drive and if you are about acceleration times this is the stuff that makes a diesel really fun to drive on road or off. KW's are just a product of torque so it is what it is.

So far in my search I have not seen a pressure drop due to volume capacity from the turbo's I have used but I have seen it with the tiny STD HT18 but to be fair its not really the turbo's fault its a product of a really REALLY crap induction system and air box system. Letting this little turbo breath with out restriction it can flow enough volume to not see plenum pressure drop when this turbo is set to 12 psi and within its map sweet spot. So I really cannot suggest if there is a optimum plenum size for a given turbo size as I think the runners and head start to be the limiting factor for that given pressure capacity of that turbo.

To note a front mount has other issues that cause pressure drop and due to the length of tubing and its size its a trade off against response due to tube restriction bends and the sheer volume in the induction system. And yes this can be offset with turbo selection and its pressure ratio etc etc so you can design a front mount without detectible lag for a diesel.. Its just that for me I like the simplicity of the induction system top mount W/A system and the advantage of minimal volumes in comparison, so response to me is paramount and tube length, bends and huge volume Air to Air front mounts are just to much to compromise, My opinion only of course.

[OldMav]

Found the Super flow 110 results that were sent to me 10" H2O so 1 psi so my results must have been for 1 psi also.
#1 184
#2 185
#3 181
#4 218
#5 192
#6 183

And from another Super flow forgot what model done at 15"
#1 204
#2 207
#3 192
#4 241
#5 215
#6 203

PS obviously when you lift the lid you would by logic fit the inlet exactly centre so this fixes the issue with number 3 cylinder. And is the obvious reason why #3 cylinder fails with the STD manifold when you try to inject too much fuel sometimes, or a logical reason why we see failed pistons with 1, 3 and 6..

[Robo]

Thanks heaps.

Info like this gives us novices a chance to make better informed decisions.
Champion Oldmav.*****

[OldMav]

Well I found some numbers that will make sense to compare to the STD manifold. Its for my manifold I am using now with cooler. At 1 psi about 10 inch H2O. on my bench.

#1 274
#2 274
#3 275
#4 275
#5 274
#6 274

This is about the best you can get with the std runners you can half this again plus if you have vertical dividers to the runners.. which is more than the head runners can handle..

[Ben-e-boy]

Well I found some numbers that will make sense to compare to the STD manifold. Its for my manifold I am using now with cooler. At 1 psi about 10 inch H2O. on my bench.

#1 274
#2 274
#3 275
#4 275
#5 274
#6 274

This is about the best you can get with the std runners you can half this again plus if you have vertical dividers to the runners.. which is more than the head runners can handle..

I like seeing figures like this, what does the actual head runners flow?

[OldMav]

MMMmmm Benny this will confuse you but any way I will spill out the data at about 10" the head port without valve will flow about 295 but with valve at .4 inch lift it will flow pretty close to 100 cfm just for interest the exhaust flows about 80 at .4 lift cannot remember or find what it flows open. This is going to be difficult to explain if you ask why lol. Mmmm But just think of this stuff is about total Kw's and what we are after is filling the cylinder more completely within the valve open duration. And remember this is about continuous flow and not how the engine operates.