Johnny50

I've recently fitted a Forge VTA d/v to my 98 Wagon.

Over the past few days i've been experiencing a problem.
At certain revs, normally between 3-4000rpm, i lose all power for a split second, and the car gives a severe jolt.

Is this overboost ? And do you think it's related to the d/v ?
Only other mod on the car is a Magnex rear box and ITG panel filter. But never had this problem before the d/v was fitted.


Thanks
Johnny

jameswrx

iTrader: (4)

is that on wide open throttle?, if so it would be about when full boost would come in on WOT?.

From what you describe and if it's WOT then sounds like fuel cut..like you say from overboost.

The mods you've got though I wouldn't expect it to do that.

Don't see how it could be related to your dumpvalve.

Try cleaning the boost solenoid out as it might have just been coincidence it started hapening after d/v fitting. Or perhaps your std re-circ one was leaking slightly and the new d/v combined with a dirty boost solenoid could have brought on the fuel cut.

Personally I'd try cleaning the solenoid

Johnny50

Hi James.
Yep, always happens on WOT. If i creep up through the revs in a high gear, it's fine.

I'll try cleaning the solenoid, if that doesn't help, i'll throw the standard recirc back on and see what it runs like.

Thanks

Johnny

911

That's fuel-cut alright!
Exactly as on my STi V3 except it hit at 4500 rpm. Tried all the tricks mentioned here, ended up with a Blitz Toubo boost control set to 1.25 bar, and now have a clean running engine, WOT or anyhow, and a wopping 314 bhp.....
Graham.

jameswrx

iTrader: (4)

graham, did you have de-cat though?, and possibly induction kit?

if not your car shouldn't do it either, unless actuator rod was shortened?

don't forget johnny has a pretty much std car (backbox and panel filter) and had no previous problems.

dhorwich

If it was fuel cut its like hitting a wall, and if you keep your foot to the floor it wont accelerate. If when this happens you keep your foot down and it then hesitates and keeps going then its not fuel cut...

If it was fuel cut due to overboost you would probably get an engine warning light come on.

Could be either something like plugs or oil in the boost solonoid, is your oil level ok and not overfull...???

Dan

911

Interesting comments.
My STi first did it a cold early morning blast, but if I kept my foot flat out it would drive past the lurch and scream on to 8000 rpm. the engine was bog standard then. I cleaned the solenoid and pipes and nothing came out.
I then added a full decat (magnex) and it did exactly the same!
Power Engineering advised me and took 900£ also to do the booost controller. They said that they had seen 2 cars, both STi V£'s do this trick. The rollers showed a full 1.6 bar at 4500 and then CUT!

Ouch.
Graham.

Johnny50

Yep, it's like hitting a brick wall, infact, first time it happened it threw the car out of gear !

The second time it happened, i kept my foot on the gas to see if it would clear and rise through the revs, but it kept cutting, and then every 2-3 seconds (still on WOT), which i presume is the boost building back up...then cutting again.

Johnny

911

Yes, mine did that. If you have the nerve ease back the acellerator a touch and she will drive through it and on again to red line.
My STi also avioded the CUT buy driving the car ABOVE 3500/4000 all the time, then the car was ballistic and NO CUT(!) even on WOT. Killer speed = Killer mpg.............
Graham.

Johnny50

Unfortunately driving at those revs just to clear it isn't really an option, i just stick to not going on much boost.

Will be taking the d/v off tomorrow and see what the results are like.