Turbo Question

[rxangus]

Hi All,

Something strange happening with my \'96 FD. I had the cat removed and ever since, in 3rd or 4th gear I sometimes get huge hesitation at 4500 rpm when the second turbo comes in. This is momentary but can be quite violent. Is this too much exhaust back pressure? Almost feels like one big backfire....

Car is 1996 RB - one of the first 16 bit ECUs. Fuelling has been checked on rolling road and is fine. Problem doesn\'t happen in 2nd gear.

Any ideas?

Ta

Angus

[bill shurvinton]

Too little back pressure. Its a known issue with tuned twins that you get a dip before the second cuts in. Can\'t remember exact mechanism, but look on the US forums.

Never looked at how to fix it though, but I\'m sure someone will relieve you of money in return for a magic box

[JayDee]

Is it still on the standard ecu? if so it is fuel cut from overboost.

[rxangus]

Yes it\'s still on the stock ECU (I believe anyway)

With much respect to both answers so far, aren\'t they contradictory??

Thanks

Angus

[JayDee]

Want does your boost spike to?
You really should have a ecu or at least a boost controller on the car.

Jason

[bill shurvinton]

We are both right sort of. The cause could be either, but if you don\'t have an FCD jay is more likely right. If you do,  I am right.

Or we are both wrong.

Bill

[Steve Burnett]

Hi Angus,
I would deffinatly get the ECU seen to or put a CAT back in. Due to you having a back box, Apexi induction kit & no cat on the I would say the car needs one. I think the nearest place that could sort that out would be Pip.
By taking out the CAT you have increased the flow (too little back preassure) and the standard ECU can\'t cope with the extra fuel required.
I think putting the cat back in might be easyer and cheeper.

This is all just my very limited in knowledge opinion. Pip would know, and im sure a couple of other guys on here. See is Carl replies on this thread, if not send him a PM.

[bnaellis]

I agree with Jason even though I don\'t understand why this only happens at transition from 1st to 2nd turbo. I have seen this before on a car with onlky induction kit and catback and was hitting .8 bar very easily and did the same thing at transition only.

rgds

[rxangus]

So if I were to fit an after market cat, would this cure the problem? I appreciate emissions testing etc is another matter altogether.

Angus