Power Down Problems

[sav man]

My problem is that when I put my foot down on left hand corners i just get wheel spin, the car dosn't go sidways, i can just hear wheel spin, and the car dosn't power out of the corner very well at all, i've follewed similar powered GT-R's round the track, and I get slaughtered out of left handers, and the car tends to understeer as i can get the back to come round under power.

But out of right handers I get awsome power down, and the car will go sideways if I want.

I suspect my diff might need some attention, but i'm also wondering how much some proper suspention will fix it.

The shocks on my car are some Tenebe stuff (came with it), and some slightly firmer springs (sk calc'd F: ~3.2kg, R: ~2.5), I'm looking at the SK kit with the coil over conversion +bigger spings (from djr's thread), just don't have the $$ at the mom . tyres are Dunlop D02's.

I just want to know how to fix it, weather it's the diff, suspetion, or somthing else.

Here's some pics of me vs R33 with identicle power and screw type HA Bilsteins (i think they are firmer than the SK ones) coming out the hairpin at Symmonds Plains.

and me on the sweeper leading to the start/finish at Symmonds.

thanks

[Ryanrb25]

yea its your diff.

[Abo Bob]

Defintely diff and not suspension.

Whose that guy that does good work with these diffs? I think Stuart Wilkinson motorsport or something like that. Someone please correct me. I know that's the place to go to get it fixed up properly.

[Roy]

Sounds like the diff could need attention?!?!?!?! Perhaps a fluid change can buy you some time. I know my std diff came good for a few thousand kms with soem fresh castrol oil in it.

But, when the dollars permit i woudl be doing the suspension before the diff. Just like my recent problems with braking stability. In goes new suspension and brakign stability problem all fixed. With more competent track suspension you may find that the diff problem is helped to the point that its nto as noticable. Better suspension will help you every corner. Better diff will help you on the slower stuff. LOL though both probably need attention

Who knows it could be right hand side shock is blown and the cars attitude is different from left to right unloading the car more one side to the other ??? LOL i dont know. I have just had recent experience with trying to use street suspension on the track with semis and actually going reasonably quick....suspension can be the root of all evil

[giant]

hey roy

nothing wrong with street suspension , been using that for two years in r32!! hehe

sound like diff, mate

cheers russ

[sav man]

Thanks for that, thought it was the diff. The suspention forum seems to get more responses than the drivetrain one

haha just noticed that there is a nice single from the left rear on the top pic.

looks like more money to spend

[260DET]

Thanks for that, thought it was the diff. The suspention forum seems to get more responses than the drivetrain one

haha just noticed that there is a nice single from the left rear on the top pic.

looks like more money to spend

Yeh and the rear wheel looks more blurred in the pics than the front. Wheelspin .

[readyGO]

yea its your diff.

x2

When did you last change your diff oil? Try this otherwise just find a nice aftermarket item

[Beer Baron]

the other thing I would look at is transfer case. I have a similar problem in my 32 GTR. car is a nugget at corner exit. revs flare up, sounds like wheel spin, but the attitude of the car changes very little (if at all) which lead me to thing clutch slip, but I cannot replicate it in a straight line, and loadded up, launching, shifting hard whatever the clutch does not slip. which has brought me to conclude slipping transfer case. an easy way to find out is if it's trasfer or diff is do a few laps in RWD and see if you still get the same feeling. if you do, then obviously it's diff, if not then I would be looking at transfer. good suspension wont hurt it either though.

[djr81]

the other thing I would look at is transfer case. I have a similar problem in my 32 GTR. car is a nugget at corner exit. revs flare up, sounds like wheel spin, but the attitude of the car changes very little (if at all) which lead me to thing clutch slip, but I cannot replicate it in a straight line, and loadded up, launching, shifting hard whatever the clutch does not slip. which has brought me to conclude slipping transfer case. an easy way to find out is if it's trasfer or diff is do a few laps in RWD and see if you still get the same feeling. if you do, then obviously it's diff, if not then I would be looking at transfer. good suspension wont hurt it either though.

Well an unloaded, ie inside wheel that spins will have much less an of an affect on the balance of the car than you may otherwise get. Remember that the GT-R drivetrain as standard only has a rear LSD, the front is open. Even then it isn't the tightest thing in the world & it you listen to most GT-R's on tight circuits you will hear the wheelspin. Mostly it doesn't upset the balance of the car.

[Roy]

hey roy

nothing wrong with street suspension , been using that for two years in r32!! hehe

sound like diff, mate

cheers russ

LOL...By street I mean soft springs well under 200lbs that are at home with crappy low grip tyres and bumpy roads but not all that great when driven in anger on a track with grippy tyres. Tein Super Street with double the spring rate is whilst still street suspension…not what I was meaning.

Even if the diff was playing up…I would think that new suspension will make the car quicker even with a worn diff then the same supple, possibly worn suspension with a nice new diff

[Beer Baron]

Well an unloaded, ie inside wheel that spins will have much less an of an affect on the balance of the car than you may otherwise get. Remember that the GT-R drivetrain as standard only has a rear LSD, the front is open. Even then it isn't the tightest thing in the world & it you listen to most GT-R's on tight circuits you will hear the wheelspin. Mostly it doesn't upset the balance of the car.

yeah that is why it's been hard for me to pin down, it sounds like wheel spin and feels like wheel spin (lack for rapid forward motion) but the attitude of the car doesn't change much which makes me think i'm losing power somewhere in the driveline (elimated clutch and rear diff) so that only leave the front (open) diff and the transfer case. I'm about to change all this though. nismo diff going in the rear and will get transfer case seen to and hope that fixes it.

[Abo Bob]

In this case you can see black marks dead in line with the offending rear tyre.

Troy - sometimes you have to think inside the box despite the damage it does to your psyche.

[sav man]

last track day i stopped trying to feather the throttle and just planted it. and i found that when i do that i get revs rising going no where, then i see the tourqe gauge move, revs drop, and off you go. But by the time the R32 ecu pick's up wheel-spin, and decides to transfur the tourqe i've lost a fair wack of time (well it seems like it when a similar car is screaming away from you). So i'm thinking the trasfure case might be alright, had crossed my mind though. Just seems odd that out of right handers the car is awsome.

I assume the diff oil was changed at import time (10,000k ago), but i'm gunna see if i can get some oil and change it before the track day this sunday.

BB: the 2wd idea had crossed my mind aswell, might try it this weekend.

[Roy]

Troy - sometimes you have to think inside the box despite the damage it does to your psyche.

LOL...that nail in my head hurts :laughing-smiley-014:

Looking at the black lines... yep ok.

sav man, did you get your Porka brakes all sorted? Be interested to hear how the car is under brakes with regards to pitching. Such a heavy car with such soft springs. When you say D02 Dunlops you means the DZ semi slicks ?

[sav man]

yep the dz semi's.

The semi's made a huge diference to the braking, still pitches, but as it's got grip now so it dosn't squrm round everywhere under braking. And according to the flag marshal at the Symmonds hairpin i was the latest on the brakes all day, so the pitching can't be hurting it too much. The porka brakes are awsome, no fade after a session (5L, sessions are about 45 mins and less apart) and the rotors are bright blue when i get back to the pits.

I still need a bigger master cylinder, currently tossing up between a 1" R33 one, and a 1&1/16" Partrol one.

[Duncan]

sav you need an attessa controller as well as a new diff

[MrStabby]

I'd get the alignment checked anyway - eg too much negative camber at the back will affect power down. But yeah diff - some oils will tighten it up more than others if you want an interim solution. Does anyone know the theory here? I was told that redline light shockproof will make it a bit more shuddery when turning hard at low speed - so i guess that means the LSD plates grip more. Sort of make sense, because its also recommended for worn synchos. Or i could be talking out of my a** again.

There was also a thread on shimming diffs to tighten them up. Hello Mr Searchy.

[Abo Bob]

LOL...that nail in my head hurts :laughing-smiley-014:

Looking at the black lines... yep ok.

sav man, did you get your Porka brakes all sorted? Be interested to hear how the car is under brakes with regards to pitching. Such a heavy car with such soft springs. When you say D02 Dunlops you means the DZ semi slicks ?

This is why everyone loves you Troy.

What's the theory behind a bigger master cylinder? Firmer pedal? Less travel?

[Roy]

What's the theory behind a bigger master cylinder? Firmer pedal? Less travel?

Headaches as the theory probably doesnt match reality Will know in the next few weeks when i make a dramatic change in caliper size then maybe try to balance it out with MC size?!?!?!?!