bit of technical advice please.

[tassie wombat]

gday all,im just chasing after a bit more go out of the old 4.2tdi(2004) it was tuned before I got it, running 12psi of boost(according to my autron gauge) egt's will hit 650.c occasionally,big hill driving hard,but generally sits on 300.c on the highway,doesnt blow hardly any smoke,so my question is if I adjust the boost to say 15psi do I need to adjust the fuel pump at all or is this what the compensator does?? and will the extra 3psi make much difference,its a 2004 4.2tdi (295000 k's) 3" lift ,33"s 4.3/1 diff ratio,thanks for any advice.

[nissannewby]

It's not really ideal to push the factory turbo past about 12psi as it really just starts to become a heat pump.

Do you have a 3" exhaust?

Pumping more boost in without adding more fuel won't really do anything, you need the fuel to make power. That's not to say you could try pushing the boost up a touch and see how it goes.

There are good gains to be had by running 4" all the way from snorkel to turbo even on the factory turbo. The best way really would be to upgrade the turbo and intercooler.

As for the fuel adjustment you can do some tweaking to the compensator, this is where to start before actually adjusting the fuel screw.

[pearcey]

Sorry mate can`t help, but 600c is a bit high
I would back off a bit and change down as I know what your hills are about especially when they stick a bend halve way up and you need to do a 3 point turn to get around .
I would think a slight adjust would only help but make sure it doesn`t over fuel.
By the way GU Camper is on the island and may try to catch up.

[tassie wombat]

It's not really ideal to push the factory turbo past about 12psi as it really just starts to become a heat pump.

Do you have a 3" exhaust?

Pumping more boost in without adding more fuel won't really do anything, you need the fuel to make power. That's not to say you could try pushing the boost up a touch and see how it goes.

There are good gains to be had by running 4" all the way from snorkel to turbo even on the factory turbo. The best way really would be to upgrade the turbo and intercooler.

As for the fuel adjustment you can do some tweaking to the compensator, this is where to start before actually adjusting the fuel screw.

Yes mate sorry,3" straight through.

[tassie wombat]

Sorry mate can`t help, but 600c is a bit high
I would back off a bit and change down as I know what your hills are about especially when they stick a bend halve way up and you need to do a 3 point turn to get around .
I would think a slight adjust would only help but make sure it doesn`t over fuel.
By the way GU Camper is on the island and may try to catch up.
Good to hear from you old fella,if your talking to him tell him he's more than welcome to pop in.

[tassie wombat]

It's not really ideal to push the factory turbo past about 12psi as it really just starts to become a heat pump.

Do you have a 3" exhaust?

Pumping more boost in without adding more fuel won't really do anything, you need the fuel to make power. That's not to say you could try pushing the boost up a touch and see how it goes.

There are good gains to be had by running 4" all the way from snorkel to turbo even on the factory turbo. The best way really would be to upgrade the turbo and intercooler.

As for the fuel adjustment you can do some tweaking to the compensator, this is where to start before actually adjusting the fuel screw.
So what does the compensator do ?

[nissannewby]

So what does the compensator do ?

Adjusts how the fuel is delivered in relation to boost.

[tassie wombat]

Ok,so if I gave it a tad more boost,say 1-2 psi the compensator would adjust itself to suit? Would this drop my egt's at all ?

[nissannewby]

Ok,so if I gave it a tad more boost,say 1-2 psi the compensator would adjust itself to suit? Would this drop my egt's at all ?

Not quite. You could try a touch more boost and see how you go, but this is will only really have an effect at full boost. Your cruising temps won't change.

[tassie wombat]

Right,no worries, it will cruise all day on flatish roads on 300'c but bigger hills are when the temps rise.

[tassie wombat]

Thanks for all the replies, looks like I'll be leaving it as is until I can at least buy a bigger intercooler.

[slamnsam]

your best bet would be to upgrade your intercooler, a cooler charge at the same boost will make more power.

[GreyGU]

Totally irrelevant but I don't know how to start a thread (only new), just wondering what does it mean when you have oil on the intercooler fins on a zd30? It's a 2002 gu

[ctaylor58]

GreyGU - Probably a leaking intercooler - depending on how much oil is there you may have a blow by issue or the engine isn't breathing

[ctaylor58]

+1 for intercooler etc. Cooler air will give you more power and high exhaust temps can quite commonly be caused by being to lean so more boost and no more fuel will cause higher exhaust temps. More fuel 'should' help exhaust temps.

[OldMav]

Right,no worries, it will cruise all day on flatish roads on 300'c but bigger hills are when the temps rise.

Tassie You really need to reduce your peak EGT's or at least do that with your foot. As already said your STD turbo isn't really good at above 12 psi but you could increase this boost to see if your peak EGT's will stay under 550C post turbo. But really you probably should turn your full fuel screw a little probably a bit less than about 1/8 of a turn will do the trick without changing your idle speed to much other wise you will need to change this as well.. This will not change to much of your driveability as this just reduces the over all fuel the compensator will allow at peak loads. But if you are confident to dive into the compensator then this is another option to tune your engine properly for better results driveability that is. You are on the other forum and there are threads on how to do this in lots of detail. But there is a world of improvement to response and make your rig a lot better to drive by fixing up your induction system like all that crappy piping form airbox to turbo and that horrible hose pipe system turbo to cooler even the air box and more so the element can vastly make your rig feel very much better to drive and will without a doubt lower your EGT's and feel a lot stronger to drive. And probably more economy if you don't get suckered into using the extra response.

On these STD turbo engines many tuners seem to get confused with timing and end up setting it to high so when the engine reaches full load and your big foot is flat on the floor activating that Jesus box attached to the accelerator you have max timing, this condition on a STD TDI will and can induce higher than expected EGT's. Seeing as you have had your rig tuned maybe this has caused the issue, this might be your first point to check. now you will ask how do I do this mmm your manual has a good instruction on the how to do and ebay has the dial indicator and adaptor.

[nissannewby]

I know someone with a username like that :).

[OldMav]

I wonder who that would be lol .

Anyway I will add a bit more tech without prejudice about coolers. The STD cooler is fine for the STD TD42ti. Fitting a bigger cooler give very marginal results due to the HT18 turbo is flat out pumping 12 psi to start with at a reasonable output temp for the cooler to work. All it will do is lower boost pressure slightly due to cooling effect but stuff all volume is increased due to the higher output temp from the turbo. At 15 psi no cooler has a chance to do its job due to the tiny increase volume with excessive output temps. Above 12 psi is just to far outside of the HT18's efficiency map to gain any real effective results it just doesn't have the pumped volume for this near all the volume supposed pressure here is generated by heat.

MMmm now to tackle the other posts without prejudice. We are talking diesel so rich lean is not the proper terms here they are the domain of petrol or sparked ignition systems. So for auto ignition systems lean is good above 30 AFR is good and surprise surprise lower EGT's less heat. Now low AFR or rich is bad news this means fuel burning in the exhaust manifold and onward to the turbo which melts Sh#t. High EGT's usually with a turbo not working past its limit you add more boost this adds more oxygen and better still a cooler to lower this a bit more so more oxygen per set volume of air hence fuel burnt more completely in the combustion process hence more power and lower combustion temp due to a faster flame front. But this sort of thing is not possible with a HT18 working past 12psi as it pumps no more volume just pressure induced by temp. Now the other thing that happens when we have a turbo working within its map. We have a thing called valve overlap which is the same as petrol its called the scavenge process where by both valve are open so what happens with a adequate turbo is we have enough air volume to flush out and spent gas and a bit extra to slightly cool the spent exhaust gas lowering EGT's so even more fuel can be added because we don't have any spent gas still in the chamber reducing our volume of oxygen this will gain better effective power or in our case here torque.

Arr well nothing to dramatic to start my first post on eh.

[tassie wombat]

so whens your next holiday down to Tassie oldmav????????

[OldMav]

Dude I wish, I love the Tassie offroad scene but alas it wont be this year. Your issues really is a 5 minute fix and I would love to fix it for you. But if you can just gain a bit of confidence to have a go yourself with a bit of armed knowledge it really is a simple adjustment and a hell of a lot of fun knowing you did it yourself better than the paid mechanic who never bothered to learn the fundamentals.

And Tassie to answer your other question the deflector place is a non issue it doesn't work. If you want to start a thread on intake manifolds I am happy to dumb it down for you and for anybody else who is confident in having a go.

[tassie wombat]

thanks for that mate,you make it sound so easy,if it was a good old small block chev id be all over it,it just a bit daunting that this little thing called a fuel pump that id be adjusting could potentially cost me thousands of dollars if I do something wrong!! and thanks for the other answer,ill post another thread regarding the manifolds and im sure many others would appreciate your knowledge as well,cheers,wombat