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Old 15th April 2005, 12:28 PM   #1 (permalink)
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Transfer case mods

Does anybody on here
"Know" about the removal of the non driven plates in the r32 transfer-case modification which speeds up the torque transfer rate ???
Any Info appreciated.
cokey
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Quote "Itís GT-R lore now that the 1989 - 94 BNR32 GT-R sold at a loss for about 5,000,000 yen, when in actual fact it cost 12,000,000 yen to produce"
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Old 15th April 2005, 12:52 PM   #2 (permalink)
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I posted a thread about it a while back but when I tried to find out more information it came to a dead end. I would be careful of removing plates as Nissan put them in there in the first place for a very good reason I'm sure .
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Old 15th April 2005, 01:01 PM   #3 (permalink)
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I was asking after reading this quote from Mick Trainer,


OK let me start by saying that no one in their right mind would be looking to turn Attessa off if they are looking for good times around a race track. The Attessa AWD system will allow any decent driver to pull huge chunks of time out of their lap times.

I think this is a very good question and discussion point however due to the number variables in it is a hard question too answer. The attessa system as we all know is an electronicly controlled "variable" all wheel drive system that allows more drive to be placed too the front wheels as the system desifers that it is required. This system then will tranfer through a "tranfer case" power to the front wheels. It is in the variable system and tranfer case that things get tricky.

As we all know what signals to the attessa system that power is required is the 2 Longnatudinal and 1 latitudingal scensors situated under the centre consol. These scensors measure the amount of G-forces in all directions and will alter the drive to the front wheels under various conditions generally through measuring the angels that the car is at. So for this system to work correctly suspension componants must be in very good working condition so as not to exagerate the level of force being exude on the car and thus altering what levels of power tranfer must be given to the front wheels.

The other aspect that can further complicate things is the transfer case. In the early 32 many people found that the car had excessive oversteer due to the tranfer case not transfering power fast enough. Nissan tried to adress this in the v-spec and 33 series by altering this. This can lead to very different handling characteristics from car to car. Further to this I have found that alteration to the tranfer case is a very positive modification as taking out non-drive plates makes the system hook up much faster making the cars ability to accelerate out of corners simply incredible. This is for me the way Nissan probably wanted the system to be so that the Race teams could easily modify the car to drastically improve it's handling.

So when adressing how to drive with the Attessa system it depends a lot on the car, it's suspension, and what the car is doing now. When I first got my GTR it had very poor suspension which made the charateristics seem as though they were one way. Then I replaced the shockes to Koni Adjustibles and that made the car alter again and gave me the ability to alter it through the shock adjustment. The further aquisition of King Springs has further changed the car again to what I consider and extremely impressive handling car that is very neutral in handling with fantastic braking potential and extremely impressive hook up when coming out of a corner which is extrmely easy to control and set up for correct lines etc.

To help this discussion along I will talk about all different characteristics that the car went through.

Like I said when I got the car it had very worn suspension both springs and shockes. It had little if any rebound and bump ability and would rock and roll a lot. This made the car quite understeery as the back would drop as soon as the car was under any real acceleration causing the rear to grip but of course the attessa system would push heaps of power to the front wheels which where of course almost in the air and had no real weight upon them. This would cause the car to simply push through the corner creating more understeer. To further exagerate this would be the fact that if you truned into a corner with still under brakes the suspension was having so much trouble just with the braking force that it simply could not handle the lateral force that came with the side ways thrust from the front wheels so it would understeer in and understeer out. This is much more like the characteristics of a wrx than I thought the GTR would be.

So clearly the shocks had to go (as the car sat at the correct heights I though that the springs where OK). So I put Konis on the car. This enabled me to dial out the understeer under braking to an extent and allowed me to adjust the suspension to alter the characteristics of the car. As I prefer a tail car to and understeery one I set the car up like this. To get this I would run 1/4 to 1/2 a turn more pressure on the front shocks. This would leave the rear softer but not massivly and thus would allow the car to step out under strong acceleration which the attessa would correct to a large extent but I would have to correct through throttle control (backing off) and correctiove steering (opposite lock). However here there is a big difference with the attessa as due to it putting power to the front wheels the level of throttle and steering correction were vastly less than would have been in a 2wd car. In most cases it would simply be a very small adjustment than would bring the car back into alignment and straighten the chassis. The car would still be rocking around a fair bit but overall the car was more neutral and driveable.

From here I really was still not 100% happy and always thought that the car could of handled better. To this end I fitted the car with King Springs (they make up a modded pack for the GTR"s) which drops the front a long way and changes the ratio between front a rear spring rates to make the car softer in the rear (as well as increasing overal spring rates by about 32% from memory). This casued a massive change in the handling characteristcs of the car. As the front is held down better due to it's lower set up and higher spring weight the car brakes extremely well and extremely flat thus allowing better turn in. More weight on the front as the wheels turn in makes this even more pronounced. The turn in speed that the car has has risen massively. The softer rear (proportionately anyway) allows it to bite harder andthus reduce oversteer. However the biggest difference I think is in the attessa as it now works pretty much as it should. It really does deliver the correct power to the fron wheels as it is needed causing the car almost zero understeer ability on exiting the corner. The car is incredible neutral upon entry and exit of corner and has massive grip levels. In many tight corners where I drive the car is a full gear up on where it was when I first got it.

So how do I drive it? Basically now that it is handling correctly I think that getting it through the corner and out of it fast is all in the set up (corner set up not car). Clearly with a Turbo car you want the car to be on boost early so that power is delivered fast without lag, so getting on the power early is important and the turbos spooling before you really are exiting the corner so left foot braking can be a bonus. Ok coming to a tight corner from high speed I will leave the braking very late and come in hard (well jeez theres a big shock) and I am happy if I am carrying ina little bit of brake when I am entering the corner just to make sure the weight balance is hard over the front wheels. Clearly I dont was to much brake but if I am backing off the peddle for the first 1/2 a second after the first reall step of turn in that is about right. From here I try to point the car juts outside where I have judge the apex to be which will usually be a late apex. I now start to get onto the power to go through the middle part of the corner. However I usually will increase throttle more sharply than would be normal. I do this for 2 reasons. Firstly to get the car up on boost (revs are so not really a problem) but also to start the rear moving around just slightly towards the outside of the corner which will bring the nose tighter into the corner. Dont get me wrong the ass is not hanging right out, just slight sideways movement. This should now put the car onto the true line I have chosen. I will hold this charateristic through the total mis corner sqeezing on more as we go right up until just before true coner exit where I just try to settle it a little. Once I am looking at the exit I really start to squeeze it on. At this point the car will start to step out and our instinct and years of driving rwd cars tells us to get off the loud peddle and start to bring on the opposite lock but we must resist that urge as the attessa has started to drive power to the front wheels and backing off or correcting to far will make the attessa reverse this or the car get very ugly and want the turn hard to the outside of the corner. Instead hold throttle (unless of course you have way to much on) and only staightne the wheel slightly (maybe 1/4 of a turn) the car should very quickly start to correct itself and drive very strong and straight out of the corner.

In the end the GTR is and extrmely good hanlding car but you do need to learn how to drive it. On off throttle techniques do not work, nor does just turn in, wait to see exit and hit it (if you like that get a WRX). The GTR is a drivers car for someone who wants to play around to get 10/10ths out of it and it will reward such a driver.

So in short check the car's suspension out it may not be the best. Dont run huge spring rates it really males a mess of things. Be smooth with it and dont jump off it to quickly, and really set your line right from the start.

Sorry if this is too long but I used to teach this stuff I belive driving to be a science. Hope that this helps.

Mick.

Long but Interesting. Any more cimments ?
cokey
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Quote "Itís GT-R lore now that the 1989 - 94 BNR32 GT-R sold at a loss for about 5,000,000 yen, when in actual fact it cost 12,000,000 yen to produce"
Cool, but they are clawing it back now.

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Old 15th April 2005, 01:21 PM   #4 (permalink)
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I asked this on SDU and nobody had a clue

Id like to know though...
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Old 15th April 2005, 03:41 PM   #5 (permalink)
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What are you trying to achieve exactly? The ATTESSA can be fooled in several ways. Are you after more cornering torque, faster straight line transfer response or both?
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Old 15th April 2005, 04:10 PM   #6 (permalink)
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Ah Mr Combat,
Bit of both really I would like to sharpen the response time of the attesa system.
It seems to me that nissan intended for the transfer box to have a certain adjustability albeit for track use. And that these undriven plates are the key to it. I suppose the people to ask are the teams who actually campaigned the 32 on the track!! As this is old info , it no longer confers any racing advantage ! Hopefully some of the aforementioned may see fit to impart the wisdom they gained in the "glory days'.
feel free to Pm me details of your latest generation controller though mate.
Cheers Cokey
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Quote "Itís GT-R lore now that the 1989 - 94 BNR32 GT-R sold at a loss for about 5,000,000 yen, when in actual fact it cost 12,000,000 yen to produce"
Cool, but they are clawing it back now.

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Old 15th April 2005, 05:12 PM   #7 (permalink)
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I wouldn't take much notice of someone who claims a drastic front lowering of the GTR's front ride height helps handling. The kinematics of the front suspension go TOTALLY to pot when lowered more than about 15mm, and driveshaft angles become very iffy.

I cannot fathom out how a clutch pack can work AT ALL with the none driven plates removed, the packs operation needs both. Application time would be better addressed via port size in the hydraulics, like upping an air rifles muzzle velocity with a bigger air port. End torque handling could be addressed by raising line pressure. A Moog valve operated system could control everything electronically. I know an ex Lotus F1 active suspension engineer, such control stuff was relatively expensive back then, but not so much so nowadays. Racecar Engineering ran a few articles on Moog valve operation. The electronics would be totally out of my field, but probably fairly straightforward to the requisite experts.
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Old 15th April 2005, 06:00 PM   #8 (permalink)
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One of the 1st things to look at is the contition of the plates. They wear out pretty quickly. My old transferbox only transmitted 20% where at the gauge said 50%. I don't know what my new box does, but its only covered 20,000ms not 200,000kms.
As for something to exaggerate the forward acceleration and make the transfer faster, its totally do-able. It's the opposite of what I've made but 2 channel, one for each g-meter.
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Old 15th April 2005, 06:11 PM   #9 (permalink)
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Quote:
Originally Posted by Chris Wilson
The kinematics of the front suspension go TOTALLY to pot when lowered more than about 15mm, and driveshaft angles become very iffy
The Group A cars were a lot more than 15mm lower than stock and used stock suspension pick-up points etc.

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Old 15th April 2005, 08:36 PM   #10 (permalink)
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Transfer boxes

I have rebuilt a good number of transfers and yes the driven plates are doubled up back to back, I believe to aid there durability. I beleive nissan did this for a reason. The only way to sharpen up the action is to replace the worn plates and by selection lower the end float to a minimum. This feels a bit sharper on the roadbut shows up really well on the dynapack as it shows front and rear torque split.Having said that it is far easier to invoke power on understeer with a car fitted with a "sharp" transfer than one with a soft one.It does not suit everyone.

Tony
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Old 5th June 2005, 06:29 PM   #11 (permalink)
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Quote:
Originally Posted by Philip
The Group A cars were a lot more than 15mm lower than stock and used stock suspension pick-up points etc.

Phil
The Group A cars also ran some super nasty camber. I do think that the front suspension used some different components. It might have just been for the single lug hub though.

I am working on a Super Taikyu R34 - its lower than 15mm in the front.

I know that it was recommended we rebuild the transfercase fairly often. I haven't taken apart any of the spare transfercases we have to look at them.

The problem I see is if you remove too much, or shim it up too much - you will create drag under normal circumstances. Drag is also heat.

Alter the pressures and speed of the lockup by altering the output of the ATTESA pump.
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Old 6th June 2005, 01:58 AM   #12 (permalink)
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I think HPI magazine did an article on this issue - I'll see if I can find it.
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Old 6th June 2005, 02:22 AM   #13 (permalink)
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Thanks for the input shaun.
I have a spare one here and am going to take it apart just to help me understand mechanically what is happening. Most likely I will go with some sort of control , either the one off here or the aus version which has an led to tell you which setting its on.
Ultimately you would have to strip and examine your clutch-pack to determine the condition. And once returned to near factory spec - experiment with the activation systems ie pump , G-force sensors etc.
I just wondered after reading the posted report, if it was a common adjustable parameter. and if so was the info available.
Mostly fueled by the later model systems improvements in response.
Albeit with a different actuating system, re hydraulic versus electric.
Cheers Cokey

Mate would love to see that , if you can find it.
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Quote "Itís GT-R lore now that the 1989 - 94 BNR32 GT-R sold at a loss for about 5,000,000 yen, when in actual fact it cost 12,000,000 yen to produce"
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Old 6th June 2005, 04:55 PM   #14 (permalink)
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The Group A cars, and other Nissan race cars with ATTESA had driver adjustable torque bias. You could set it to give you more front torque.

On the Group A and Bathhurst cars they have a round knob on the dash above the gearshift.

Some of the other cars have them other places.
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Old 6th June 2005, 05:15 PM   #15 (permalink)
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Quote:
Originally Posted by tyndago
The Group A cars, and other Nissan race cars with ATTESA had driver adjustable torque bias. You could set it to give you more front torque.

On the Group A and Bathhurst cars they have a round knob on the dash above the gearshift.

Some of the other cars have them other places.
Andy's (R32_combat) device does basically what the racing Skylines had (as spoke about by Dirk S etc) in that you could alter how it dealt with torque transfer in corners to make it transfer more of the torque to the front at the apex of the corner (also see http://blog.gtroc.com/dino/2005/04/nismo_skyline_g.html as Z-Tune also transfers more of the torque to the front on corners than std). The R32's slower transfer pick up was done probably to give the driver a smoother transition from oversteer to understeer (rear bias to front drive change) and a bit more fun.
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Old 6th June 2005, 06:04 PM   #16 (permalink)
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