OldMav technical information thread!

G'day folks,

I thought i would set-up a dedicated technical information thread to OldMav (Peter)

So that OldMav is not pulled from pillar to post regarding technical advised, i thought it would be easier if i set-up a dedicated technical information Q & A thread. This way you Lounge Lizards can ask Peter a question and when Peter is ready and available he can get back to you on this thread.

Having someone of the caliber of OldMav on this forum from time to time, is a fantastic result for the forum members. As previously stated, i have spoken to Peter on several occasions regarding advice with my GU TD42 turbo diesel build and I have also perused many of OldMav's extremely informative articles and advise on his Patrol 4x4 forum over the years.

Once again Peter thanks for sharing your time and well researched knowledge with us!
Kind regards,

RLI
:cheers:

I think we could use a sub forum, with different threads in it.
In one thread it'll all get lost..

Paul I brought a Nissan patrol coil cab/chassis March 1990 I had ordered it 3 months earlier, back then it was impossible to buy one off the floor But when I was picking it up a youngish pretty married property owner had come into the office very upset as her husband had given her a hard time about the new Maverick cab chassis she had ordered and pickup the afternoon before. He had told her to buy a Maverick him thinking Mavs came with coil springs lol. She was crying somewhat when my uncle who owned a nissan/Ford dealership told her you cannot buy a Nissan coil CAB/ chassis without at least a 3 month wait. Mmm she had that country pretty look and I gave in and told my Uncle to swap our rigs. So I ended up with quite a few thousand dollars extra in my pocket as she brought her Maverick primary producers discounted Tax etc in those days + a bonus of 3 years Rego free lol. So I was very happy even though I had leaf springs which didn't bother me as I had some serious mods I could trial to see if it worked on leafs. I never drove my rig N/A it was pushed into the workshop and I removed the engine for a full blue print and balance. silly eh. + a turbo and, and, etc, etc.

I am still in rebuild mods and haven't done any tuning with the new turbo GTX3071. But the KKK it replaced was always fuelled for 180rwkw about 141cc/1000 shots. I have had it at 200rwkw or a bit more but having done torsional vibration analysis back in the 90's it suggested 180 should be a safe tune before crank issues become apparent. I have always had torque in the low 700nm 690Nm area and boost at the 28 psi mark all in buy 2100 rpm. I tuned this thing to do odd accelerations but I can tell you a HSV dunnydoor looks pretty silly compared to this rig in 4 gear 80 to 120 klms or for that matter most sports cars. We will see how it goes with the new turbo. All this is about torque response not outright KW's. so the new turbo will be set up with the same sort of tune I hope.

Fuel economy well I never really think about that as it is what it is. But remember this thing has a 12mm element so lots of fuel can be pumped if required. If my Dad drives he will consistently get 26MPG or 10.8 litres per 100 but I have never got those figures ever. I usually see 20MPG or 14's litres/100 but I have actually got 12.5 once at night and empty on the very odd time I actually drove on bitumen highway. Water injection set at 11psi and cruising at 110+klms with 10 psi and that + is a big plus.

I have left this forum!

Great bit of read that look forward to reading more in the future!


Cheers,
Eric.

Thanks Paul. I'm sure I will be asking for advise during my td42t build.
Just read Oldmavs story. I can see my build getting expensive already.

Pete.

I'm going to branch away from turbo tech and move into your link suspension. Did you design it or did you just put the links where they fit.

I have a few designs drawn up which should fit, but I have no real world experience with 4 links and how changes in the on paper figures translate into the real world.

Cheers
Ben

Ben

First I have designed the system. But this suspension game is all about huge compromises. The Nissan system even though it does quite well, considering it was never designed for the massive travel we seem to see many of the suspension people dial into this system. For the 200mm travel it has as standard it does ok but for anything that one would consider handling it is very sub standard if we were to compare it to say a jeep or the older live axle range rover. So with this in mind I set out what I wanted to achieve and what I considered I could compromise. I decided I want the rig to handle at highway speeds dirt/road and didn't have the the STD Nissan tell tail rear end wanders in one direction only I wanted a balanced feeling rig. to do this I need no more than -1 roll axis angle on the rear. Also I didn't want to see articulation stupid rear steer a patrol has so roll axis angle at -1 has very little rear steer. To compare a STD Nissan has about -12 degrees and a lifted 3 inch patrol has near -18 degrees on full articulation. My system is still -1 deg at full articulation so no silly rear steer.

Next I was not after a drag car type traction and I didn't want the rear bouncing or hopping every time I tried to climb any sort of ledge or climb a hill. I wanted a bit more torsional load and weight transferred into the springs and not the links like the std patrol. so I decided on a anti squat of 65% so the rig will squat a bit on power and has less chance to hop on ledges or hill climbs. I wanted roll centres a bit high so the cornering loads would resist tilt angle so I would not need stabilizer bars for normal street use, and give a acceptable stiffness on big off camber bush driving.

To get this much control in geometry adjustment I had to go for double triangulated link arms. The top links don't do a lot except control instant centres and hold the diff central so I had to compromise some roll axis adjustability and roll centre height because the arms have to be at about 40 degrees and need to be at about 70% of the length of the lower arms so I could keep diff pinion angle change to acceptable amount I settled for 5 degrees of change from the std 3 deg we need to match the transfer case output angle. Ok that's the basis of the rear.

For the front we have to compromise soooo much but I wanted my roll axis angle to be the same as the rear so I had a balanced rig at highway speeds and slippy dirt road high speed stability I also wanted to dial in enough resistance so I didn't need stabilizer bars, so I have the same -1 degree roll axis. But I had to compromise instant centre height and distance but not as much as the radius arm on the STD patrol actually I am about 425% better off but not ideal and not as good as a damn !@#@#$ JEEP.
But I have more high speed stability than a JEEP even though I am some 200mm higher ride height than a jeep. And I don't need stabilizer bars. This was my compromise not bad I think. Now for anti squat after a lot of pissing about I decided it is what it is and 53% is it. So it will be great on ledges as it will tend to make the body squat and climb unlike a patrol that just lifts the body and loose traction and usually just hops as weight is transferred into the radius arms. But I gain a lost of braking force and weight transfer onto the front axle so it could be a good think time will tell. Obviously I cannot use a triangulated 4 link on the front beside it cannot fit but also you would have bump steer to break your arms and full hydro steer is not legal. So I settled for 3 link and panhard bar. My panhard bar is a bit longer and better set angle with a small change angle than the standard patrol so I will not get the Nissan body roll steer that is so prominent when lifter to 500mm chassis to ground clearance. Also with the 3 link I have a very small diff pinion change angle so minimal uni issues for my 17.5 inch of front and rear travel. I had to compromise link separation on the front diff but I am using a forged Johnny joint with 30 degrees of twist. I have not compromised rear link length so I have very little geometry change for the 17.5 inch of travel the front link lengths are compromised a bit due to space and positions to attached the triangulated lower links around the transmission.

Also to get this to work like I wanted I had to move my centre of gravity back some 175mm and make it a bit closer to the centre of the car so now its pretty close to the top of the gear knob in second gear. I had to move the front axle 65mm further forward than the STD coil cab but only 15mm further forward than the leaf cab. Also I had to loose 400KG's of vehicle weight hence the extensive use of aluminium including my exhaust pipe. Also the spare tyre has to be behind the tray and a storage box at the end of the tray and needs to have 20 kgs in it. lol. I needed batteries behind the cab and all the fuel and water just behind the cab so it all worked very nicely in the end with a few little painful head scratching. So you see with my rig I have compromised many things to get my suspension to my ideal set compromises. Also I have set much of this geometry with a good balance in my opinion so I have little change in rig manners with 33" or 35" tyres fitted. But the rig will have very nice manners with 33"obviously. To note my top link arms are level and the lower arms are less than 6degrees so on full droop I will not be able to have body jacking due to torque this was something I wouldn't compromise.

Also this is my 3rd link system/air bag design on a vehicle, a SWB F100 a Range Rover and now the Maverick. The Mav system on paper is very much the best design, as so many things are just ideal with the patrol leaf chassis. also I have learnt so many things with the RR to be able to set my ideal geometry compromises. Also I didn't do any of this for suspension travel I would have been happy with 12 inch of travel like the RR but the system on the patrol was so nice it just was a free bonus, so I made it happen. If I had made travel a setting compromise I could of had 22 inches of travel with this design but my setting criteria was 12inch so the extra few inchers was a bonus without compromising my set criteria's of feeling solid, safe and stable at speed dirt or hard top..

How good it will be only time will tell but I know for certain it will be nicer to drive than a damn JEEP.

Thanks

At the moment I am only thinking of the rear,mI am very happy with the hybrid arm front end. I am also happy with the long arm rear I have now but the only thing is the roll steer that bugs me, if I calculate right it has dropped to about 8 degrees even with 14 inchs of travel, but it still as an effect particulaly on off camber decents it likes to crab walk

The goal is better high speed handling as I want to be able to pass a swerve test with 100mm of suspension lift and stability offroad.

My 4 link is designed around 35 inch tyres and 16 inch of travel, ( 6 inch bump and10 inch droop) but I plan to build in adjustments on the upper links both at axle and chassis to suit 33's for the road and possibly 37's in the future

One thing I have been thinking about is trying reposition the front panhard and a redesigned pitman arm to suit to try and match RC's the best I can. But I will only move to the front once I know how the rear will perform. It will be a slow process but lack of real world experience and being hard to please will certainly draw that out lol.

This is the design I think is the best I can come up with, it should fit with minimal difference to the plan I hope. I dont know the exact COG, myself and a mate are searcing for some cheap corner scales or some decent weighbridge time to find out and the unsprung weights are also a guess.

Attachment 40912

Cheers
Ben

Ben you have the right idea, But experience tells me from the F100 experiment that you get to much torque jacking loads when you have the suspension at full droop one side with the top arms at that sort of angle a degree or 2 is fine but that is too much, it dramatically twists the car well it did on the F100 but it had a 460 in it. Also at highway speeds on turns its very sloppy has no inbuild resistance. Another thing the top arms have to be more angled that isn't enough to control diff shift on cornering loads the ass end will feel sloppy because the diff will move from side to side even 5 mm is too much you feel it on evey weight shift. Truly Ben it is a lot nicer in all departments when the arms are near flat. But as said it depends on what you want to compromise from my F100 experience I had very simular to that and it felt terrible to me, you may feel different as this is about what you feel is good. I removed the complete system on the F100 and make the rig lower and made the arms flatter it was ohhhh so much nicer in every situation. Just my experience here Ben. I even compromised clearance under the chassis by having the lower link chassis end half the bush lower than the chassis. I have done the same compromise on the Mav.

Ok. I have changed the upper arm measurment which should give more lateral support Later in the day I will hop under the ute and go over with the tape measure and do some double checking and see what I can come up with.

I dont reall want to have the lower links chassis mount lower then the chassis as the location is where I belly out on some of the big steps I usually drive on, so there is compromise #1 and a decent one really.

Back to the beginning of all this, I went so see an engineer in Geebung about getting my long arms, a torsion bar style swaybar and extended shock mounts engineered. Which he said I could do, but me being me got home and though if I can get this done why not a 4 link, and if I can get the shock towers done why not get rid of the spring perches and coil over the rear etc and it all started compounding from there as it does :D

Now incase I cannot get a 4 link legal my now second option is to go with the original option ( if that makes sense), and keep the long arms a swaybar and coil overs

So this leads me to another set of questions.

Panhard bar. I undestand that it determines the roll centre. But am I correct in saying that the higher the roll centre in relation to the COG means the shifting forces from cornering or offcamber need to be greater in order for it roll but inturn in say an offcamber situation high speed cornering less warning that you are about to roll over, and more body roll with a lower RC in relation to COG, and with a lower RC can the subsequent body roll be tuned out with good damping and sway bars?


Cheers

Made this a Sticky

Yes the Panhard bar controls RC but because it moves in a odd arc on cycle and articulation at speed if travel is great it causes odd handling characteristics especially on the off side. This is usually not a big issue if it can be held at flatter angles. This is obviously constrained by the drag link on the front as bump steer is something you just cannot compromise at speed but it can be improved dramatically. On the rear is can be made flatter or near level but its length is compromised by shocks being fitted behind the diff. To fixed this put shocks infront of the diff so a very much longer panhard bar can be used. The 4 link addresses this issue with link control so angle change is a lot less so axis angle changes little in comparison. Roll centre to COG does help roll resistance due to weight transfer. but this isn't exponentially equal to the separation so there is diminishing returns as it gets higher. As I understand the concept RC height to COG causes resistance or slows weight transfer from COG but it doesn't really get to a point then extra weight gets transferred so it tips quickly it just slows the process so you can use springs and shocks to adjust the roll speed or swerve speed to a level your like so again how it feels to you. Sway bars are a thing you use because they fix a roll compromise you think is a issue. Race cars use these bars to keep the suspension within the ideal design geometry but also to make the car a lot more responsive to swerve loads or changing loads. For us it can help COG issues on off camber situations but really it is very minor, unless the roll centre is below the axle.

Until next post lol when I have more time.. I have written this in a hurry.

That makes more sence...

I was planning on installing the coilovers on the top of the axle housing, so if I stick with the current setup should be able to to add 80-100mm on the rear panhard.
If I start rearranging the panhards will I need to beef up the chassis mounts.

How will handling be affected if the RC's are not equal heights?

Cheers

first coil overs are very nice because you can dial in height with a certain amount of progressive rated loads, But to get the most out of them they really do need to be at the axle end or close to it. on the GU/GQ this is difficult to do without chassis mods so to be honest it will take a bit to tune your coil overs even then in my one only experience with them and some research you loose the progressive benefit not having them near the axle end. Its a compromise of course but still may be viable.

The panhard bar has no different loads long or short higher or lower than where it is now but if the axle end is raised it will need beefing up due to leaver loads. The chassis end is ok but the comp boys do brake them.

RC is a funny thing at different heights it can be noticed without sway bars the lower end is not as stiff on corners its not unnerving but is apparent. But if roll axis is the same it seems to lesson the effect because the car is a lot more balanced and feels solid on the road or dirt. And doesn't do any of those funny dances across the corrugated road on corners which the high lifted patrol is famous for.

Hmmmm ok.

So , seeing that the panhards are chassis mounted to the same side of the patrol, would it make any differnce if they are chassis mounted on opposite sides?

Its about balance Ben a car has to be predictable when you drive it, a good car does every thing slowly or progressively but still maintaining response and feel. I did mention the off side before with panhard bars they over steer corning into the bar and quite a bit less away from the bars direction, having the panhard bar on the front it needs to be the same way other wise it feels odd and unbalanced. So for our patrol the lower long arms kit it is said they fix the geometry well to be honest they don't do much for geometry except lower the very compromised values slightly but what they do is reduce the over steer of the rear off side so it feels more like the front so more balanced. For our patrol the top arms are the problem they are stupidly way to short for our suspension travel lengthening the lower arms just slows down the handling because the change values get slower as the suspension travels, but pinion angle change is greater, this is the compromise for long arms. The top arms are a compromise for Nissan as they had to fit rear seats and foot wells into the wagon hence the short top arms. But for the travel they assumed it had, this is fine at their STD set height. Your ute doesn't have the back seat compromise so Nissan should of had longer top arms for the ute but this is a production cost so would never be considered.

Thanks Pete, that about rounds off my panhard questions, they were a big grey area for me.

All good Ben happy to help.

Hey Pete,

Thanks for all your input here mate, appreciate your involvement and knowledge. I am thinking that we might need to have a rethink on this thread though as there is some great stuff being presented but it could get lost in the soup once this thread is 20 pages spread across TD42, Suspension, Ratios, Geometry. 1 Big thread is not going to help the Search function at all hey ;)

Need to have a bit of a think about some structure to get the best advantage from your input mate. Got a couple of ideas and it will probably involve cutting this thread up a little and building something. Dont be surprised if something like that happens. Your input on how best to do that would be welcomed here or via pm to mate.

Cheers Darren.

Quote:

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Originally Posted by RLI

G'day Pete,

I note that you might be putting 35'inch tyres on your Patrol in the future, if so, what diff ratios will you be using?

Is there any chance for you to give the forum members one of your informative tutorials on the importance of getting the right diff and gearbox ratios when putting larger wheels/tyres on your vehicle.

PS, also could you please advise me again on which is the best automatic gearbox to suit the chev 6.5 V8 diesel engine. unfortunately, my phone was dropping in and out the other day when you were explaining to me about the military spec automatic transmission.

Regards,

RLI

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Paul yes I am going to try 35" tyres legal side disregarded here for the moment but I will do the basis for my own experiment. Gearing is about response and feel so its very much engine torque and power related and at what point the torque peaks. For my engine which is now different with its torque response and amount of torque. I have decided to venture into loading up the rig using gearing hence the turbo will respond to this different load. So I have chosen to use 3.9 gears on 35" tyres giving me a 2050 ish rpm for 100 klms. Obviously this will make boost a bit higher at cruse speed, but if torque is high enough and volumetric efficiency is high enough there is the potential to gain economy and still have good 80 to 120 klm passing times. But also because I am using a GTX3071 I will have my boost level in its lower sweet spot hence torque rise is higher and I have the bonus of pre water injection to make the engine/turbo respond to change rather over fuel added to gain this response. This sort of thing can be improved in the lower revs/ gears if the cam and turbo is matched, there is always going to be a under boost point unless we use a switchblade type designed turbo with I am working on for future improvements.

But basically for this first bit we try and match our engine torque to our gearing, diesels have the added bonus of producing a wider more consistent torque curve so there is the ability to match our torque to the gearing to make the turbo more responsive and progressive so the rig feel a lot stronger without having to add higher revs and power KW's to do so.

Which brings us to your 6.5 which as I have told you is a lazy slow short torque engine, This is not a terrible thing but hopeless if you want a manual gearbox or a manual gearbox with only 4 gears and over drive. There is not enough gear ratio to spread across the rev torque range. This becomes even worse if you are trying to match a std type turbo too this engine, as you just don't get enough rev or engine load time to get the turbo to build torque to its potential because you are constantly running out of rev duration time.

The Allison auto box is very special it doesn't function like a normal old school auto where by it has to change gears in sequence of have oil flow to adjust its load transfer. So what we have here is a gearbox that is always in its right gear or can be adjusted to be in it right gear always. It sort of doesn't change down it just is in the lowest gear required for that rev/torque point of the engine when adjusted, then changes up as the torque drops off not so much engine rev related. The military combination of the 6.5 is very near as good as the duramax/Allison but not as good because that engine has many electronic to adjust and control how the box changes gear. If you ever get to drive a duramax with Allison or the newer Merc BMW you will understand about always in the right gear and near undetectable up changes its all so effortless. The military 6.5 has this type of gearbox and works with the same effortless moving the rig forward ability, sort off lol. But even for this the 6.5 is still to short in its torque response or range to be ideal so doesn't feel so effortless as the duramax combo. But I can tell you the military spec Allison combo will make the 6.5 slug feel so much stronger and will allow the turbo to actually find its legs to be a benefit.

But it will still need gearing to be selected to get the 6.5 and turbo enough time to build torque to revs to get the best potential relative to the weight of your rig. Which brings me to my other experimental very important criteria as to why I have chosen 3.9 gears to 35" tyres, gross weight, my rig will not weigh much more than 2200kgs fuel and water. For example my rig with the KKK which was a very quick and responsive rig to drive but it weighed 2750kgs with this weight loss with the KKK and my 180rwkw I have given back to my engine a full 65rwkws. So I can use some of this unused torque to drive my turbo into its sweet spot for longer so to speak. I know its a difficult subject but I am sure this will explain the concept.

Hi Pete.

A quick question about vertical separation. I have taken onboard what you said about flatter links and I am at the stage where I dont want to lower the links at the chassis end any further.

I have raised the axle end slightly, it is still below the axle centre line.
I understand the consequences if there isnt enough vertical sepration but I dont know how little is too little.

25% of the tyre size comes to mind but I cant remember where I read it or who told me, or whether it is right.

I have been using that figure in the latest changes, which is 8.75 inches, the upper links still sit just above the housing andthe lower links are a bit over an inch below the axle horizontal centreline

Is that a sufficient amount of separtion?

Thanks
Ben

Here is another attempt, the links are a bit flatter and hopefully enough angle on the upper arms for lateratal support.
Attachment 41304

The STD Nissan separation is 230mm, I used that dimension for my system because it is a good compromise for 33 or 35 tyres and allows the links to be set within the chassis for the ride height that can be achieved to get my ideal best compromise.

Attachment 41318

Also I have calculated a few assumed torque load values like 1000Nm on that separation using STD Nissan rubber bushes with 75 duro rubber hardness this loading will compress the rubber about 35% so is well within a expected longevity for our bushers.

My DWG is for a leaf spring chassis so it is a bit different and probably a bit more ideal for fitting connection positions.

There can be to little separation of course as this will put to much or more load on the bushers causing then to deform or reduce their usage life. But also the separation does help with torque hop as well but 8 inchers is ok for our diesel and 800Nm for a constant load using 33 or 35 tyres. Also the separation does allow the loading to be reduced on the links but 44mm 6mm wall Dom tube is fine for this loading with the lengths we can use on our patrol.

Remember Ben all this has to fit in the patrol chassis and the simulator is only a guide and a tool to understand how the values interact. Trying to get ideals in the excel sheet first is difficult because it all changes when you try and fit it in your rig. I started with my chassis first using CAD, fitting the links then transferred this to the excel sheet to try and fiddle my ideals and to adjust within my chassis confines for the ideals I wanted so compromise was very high but still quite good in the end.

Quote:

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Originally Posted by OldMav

The STD Nissan separation is 230mm, I used that dimension for my system because it is a good compromise for 33 or 35 tyres and allows the links to be set within the chassis for the ride height that can be achieved to get my ideal best compromise.

Attachment 41318

Also I have calculated a few assumed torque load values like 1000Nm on that separation using STD Nissan rubber bushes with 75 duro rubber hardness this loading will compress the rubber about 35% so is well within a expected longevity for our bushers.

My DWG is for a leaf spring chassis so it is a bit different and probably a bit more ideal for fitting connection positions.

There can be to little separation of course as this will put to much or more load on the bushers causing then to deform or reduce their usage life. But also the separation does help with torque hop as well but 8 inchers is ok for our diesel and 800Nm for a constant load using 33 or 35 tyres. Also the separation does allow the loading to be reduced on the links but 44mm 6mm wall Dom tube is fine for this loading with the lengths we can use on our patrol.

Remember Ben all this has to fit in the patrol chassis and the simulator is only a guide and a tool to understand how the values interact. Trying to get ideals in the excel sheet first is difficult because it all changes when you try and fit it in your rig. I started with my chassis first using CAD, fitting the links then transferred this to the excel sheet to try and fiddle my ideals and to adjust within my chassis confines for the ideals I wanted so compromise was very high but still quite good in the end.

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Thanks Pete. I really do appreciate the help.

To be honest being the first time with only an excel spread sheet and only enough knowledge to be dangerous it is a bit daunting for me.
There is just so many variables and compromises in which you can build something that ends up being pretty ordinary.

I am planning on making eveything with as mush adjustment as possible in order to try and gain a getter understanding through real world experience.

Thanks
Ben

Give me a bit of time and I will do a coil chassis mock-up with a excel sheet for you to play with. That will give you a starting point to play with values. But really Ben its really what fits then adjust your ride height to get closer to ideals your see as best. I will find some sites with good write-ups to give you an understanding of the different values and their effects. Do you have a CAD program like autocad and know how to use it.

Quote:

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Originally Posted by OldMav

Give me a bit of time and I will do a coil chassis mock-up with a excel sheet for you to play with. That will give you a starting point to play with values. But really Ben its really what fits then adjust your ride height to get closer to ideals your see as best. I will find some sites with good write-ups to give you an understanding of the different values and their effects. Do you have a CAD program like autocad and know how to use it.

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That would be great thanks. We have autocad at work but I dont really know how to use it besides doing electrical schematics

Quote:

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Originally Posted by OldMav

Give me a bit of time and I will do a coil chassis mock-up with a excel sheet for you to play with. That will give you a starting point to play with values. But really Ben its really what fits then adjust your ride height to get closer to ideals your see as best. I will find some sites with good write-ups to give you an understanding of the different values and their effects. Do you have a CAD program like autocad and know how to use it.

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G'day OldMav,

I am back, sorry about the abrupt manner in which I left the forum, unfortunately I have been suffering in a dark place in my mind. Depression is a horrible illness.

Could you please grace us with you outstanding knowledge again please Peter.

Kind regards,

Your humble servant Paul