Can any of you "modders" give me any sensible advice re this...

MY99 PPP, Pace FMIC and Pipercross running 1.25bar (with HKS evc) and standard recirc dump valve.

The problem...accelerating hard (full boost), come to bend, back off slightly and bang! it just dumps all boost setting the car into "lift off oversteer", a very violent experience. :(

It also happens when I pull away from the lights fast, between gear changes it trys to put you through the windscreen.

I was thinking about a "staged" let off of the boost, I presume that the sequential dv from HKS might be the answer I seek (?)

Any takers (please)?

Moles Dad.

Bob, thanks for the reply, I can assure you that it is not an overboost problem.

It will only happen on "lift off" of the accelerator, NOT on full acceleration...in fact it boosts up and holds no problem.

We had our lesson on overboost after fitting the FMIC over Christmas, then got HKS boost controller.

Hope this makes things clearer.

Regards, Moles Dad.

It sounds like your BOV isn't operating correctly. When you close the throttle butterfly, pressure isn't being released from the intercooler, turbo basicly hitting a brick wall and stalling. Have your BOV and tubing checked out. If it's stuffed then it's a good excuse to get the HKS sqv. If nothing else it will make a sweet sound!

Pob, thanks for the reply, I would agree that it is a dv problem but I'm not too sure that it is "not working".

When shutting off it still "whooshes" and dumps the boost as you would expect.

It is only vicious when in the higher boost areas, but again, it is clearly audible.

Any road up! gonna have to try the sqv dv :D

Cheers, Moles Dad.

Moles dad,
it may still be relieving pressure. If it's sticky, it will need a bigger inlet manifold to intercooler pressure differential to operate it, which sounds like what's happening. Check your original valve unless you really want an SQV anyway. They are very good incidentally. Lovely sound and nice flames when combined with catless system!

Could it also be the case that the standard DV / BOV cannot vent enough of the pressurised air in the system? Ie it can't flow enough. It may be opening up early enough but just not venting enough pressure.

I have a similar problem with my MY00 with FMIC, although I run less boost (approx 1.05 - 1.1 bar), as I'm only running the standard TD04. And am thinking of moving to a bigger higher flowing DV that still vents internally.

Thanks lads, I think I will try the SQV and see what happens !

Does anyone know if the "sequential" part isactually sequenced, by that I mean does it dump some but not all of the boost?

Also what dia is the SQV "outlet"...is it larger than the o/e dump valve?

Cheers, Moles Dad.

Moles Dad,

Not sure if this helps but my car used to do that. MY99 full decat + ITG + Forge BOV with blue spring. Swapping back to the original BOV and backing of the throttle was no where near as violent as before. I'm not technically minded so not sure if this is the same as your problem.

DaveW

Cheers but I'm not sure if thats the same problem either, it does sound similar.

I am going with the "needs bigger" theory, have just bin reading about HKS Ssqv on another site...looks like the one for us!

:D

:)

Glad you got the problem sorted out.

Have you tried "feathering" the throttle during gearchanges yet?

You can make the car sound like it's got 2 turbos, or 4 or 6 or....! :D :D

Agreed, grins are not nearly big enough.

You are hitting the overboost fuel cut, its classic "brick wall" syndrome. The BOV won't help at all, you need to stop the overboost with an EBC or some other method.

[Edited by Bob Rawle - 2/3/2002 10:00:53 PM]

Well we gonnan dunnit !!!

Fitted HKS ssqv dv today...wow what a difference.

Has certainly cured the "lift off shudder", and what an addictive sound...on a technical note I do think that the standard dv was letting some of the boost leak, the car "feels" more alive, maybe the boost is now staying where it should !

I wont post any smilies cos they are not big enough today!!!

ps Thanks to John for turning up with the goods...cheers :)

Cheers all, Mole and his grinning Dad.

[Edited by mole - 2/9/2002 5:31:31 PM]