New Diff fitted - car out of tune?

[Steve]

I just fitted a 2 way diff, vs the stock viscous item. Its an excellent upgrade, and really highlights the deficiencies with the stock unit, but something strange seems to have happened.

Initially the torque down low appeared to have increased noticeabley, which surprised me, but I put down to perhaps being a 4.3:1 diff (I bought it second hand off someone who didnt know much about it) BUT, now my car is now starting to register knock ALOT higher than before. Previously I was getting knock reading between 15-30 when on the foot and under high load (up hills). All was good. Now, after just fitting the diff, my knock has gone up to 70 - thank god for the check engine light. I pulled 2 degrees timing and it still went up around 40 on the knock sensor, I pulled 3 deg total and it sorted the problem but of course the car is a bit more sluggish.

Also, for some reason, I cant boost past 1.3bar????

My thoughts are that the characterists of the new diff (the fact that it gets alot more power down than the stock one, perhaps a different ratio) are such that load on the engine has changed enough to throw the tune compeletely out?

Does anybody have any ideas on what might be the problem? I do intend on getting a retune very soon, but would like to know if it could be the diff, or if I have a problem elsewhere?

Cheers

Steve

[Jay95R33]

Hmm, initially I thought that you may have been spinning one wheel with the stock diff, but now the 2 way your not, and therefore there would be more load on the motor = pinging..

BUT, not being able to boost upto what you were before would suggest a tuning problem or something else wrong.

I hope you get it sorted.

J

[Guest RedLineGTR]

I"d also get the car on a dyno to check the speedo cos if you dont know what the diff ratio is your speed might be higher or lower than the original diff..and it could be also out..

[Bl4cK32]

This may sound stupid, but is the new diff "noisier" than the std. item? ie does it make noise / vibration through the car?

I ask cos i read something about "interference" noise or something that the knock sensors can pick up.

Maybe try swapping the old diff back

[Steve]

No way the old diff is going back. the car handles 10,000% better (ok I exagerate a little). Seriously, everything about the car is better, its quicker off the line (no more chirps every time I take off), much flatter through corners (the car is so much quicker to punt around corners on or off power) and pulls harder first, second and third. Plus the back end is so predictable and it doesnt do crazy 'back end into the next lane' action when putting the boot in, just a gentle sway:) If I realised how much improvement was available over the stock diff, I would have seriously done this along time ago.

The diff is pretty quiet actually, makes a few small clunks at low speed when taking off esp if going around a tight bend, but other than that its all good.

[Bl4cK32]

so where can i get me one then

[CGB_R32]

How much did this cost Steve... i had my line checked over by Gavin Wood i could tell myself it was a little more noiser than what it should be.... so rang up the warranty company and the diff is currently getting looked at.... according to the warranty i can claim upto 1500 soo any help we be awsome.

Peace

Michael

[Steve]

No warranty for me:) I got it second hand for $350. It was sold to me sight unseen as a 1 way diff of unknown origin out of an R33. when it got here I checked it out and its a 2way nismo. The diff definately is working well, infact it behaves better (less NVH) than cars I have been in with os giken or kaaz diffs.

Bl4cK32, if you are quick, I heard a rumour that Z Imports (south tce wingfield) have a 2 way and only want around $500 for it, which is a bargain.

[Steve]

CGB_R32 just re-read your post - I hope you are not confusing the extra noise a mechanical diff makes with the diff being rooted. Mechanical diffs do clunk and grind a bit at low speeds esp when manouvering, such as in a car park, or tight cornering at low speeds. the stock viscous one wont do this.

[PRO_32]

Just got a nismo 2 way yesterday and were putting it in tonight hope i have the same gains in drivability minus the knock offcoarse :wassup:

[Steve]

I first thought the knock could be because of extra load on the engine, but the more I think about it, the more I think the knock would be lower. I am pretty sure (will be checking on the weekend) that the diff is higher ratio, which is why I am getting the extra torque down low, that and the fact that both my wheels now put the power down.

PRO 32, dont worry, you will absolutely love it, the difference is unbelieveable:)