OK, this has started happening after the downpipe was fitted. want to know if it's me or if there is a problem.

ok, here goes. driving along in 3rd or 4th, give it some gas and as revs get to 3000 or above there is what I can only describe as a surge and the boost gague hits around .9 bar and the car then moves rather quickly. the 'feeling' side of it is like you're starting off and getting wheelspin then grip comes and off you go, but in this case your moving and then shoot off.

Now, I'm a thick old sod, and my guess is that what is happening is that the downpipe is causing the turbo to spool/spin up faster, thus at 3000 it's up to speed, whereas before the dp was put on it would not be, thus it's just that now the boost, well, just 'there' and therefore of I go a charging into the sunset.

so, would I be correct (if any of you guys are at the sussex meet on sunday I can take you out and show you what I mean if that helps any) in my assumption??

is this overboost??

 

Hiya Markus!

It sounds like overboost, I experienced something like that when I got my fully decatted exhaust on, in the higher gears, sometimes under certain conditions when boost came on, I had a brief moment of "no" power, it felt like a misfire, and nothing like the violent face-meets-the-windshield-stuff I'd read about.

(Get a link, you know you want to. )

It can be sorted with restrictors, get a pro to sort it for ya.

/J

 

Thanks Jerry.

as for link, tell me about it, I'd love to get one, think I'll get the wheels and brakes first.

what damge will overboost do?

 

The occational overboost won't do anything really...that's why it's there - to protect from silly levels of boost.



/J

 

On late models the solenoid steps in to control boost - if you fit a downpipe and the peak goes a bit high your boost will not nicely fall to closed loop controlled held value but will undershoot before settling. This is mild and some drivers don't even notice it. In severe form you can have your foot on the floor and see the solenoid oscillate boost from 12-18 PSI like riding a kangaroo or something. In my opinion a car that peaks so much that the ECU then undershoots once or more before stabilising on held is disappointing to drive. There are three ways to sort it - get your restrictor slightly enlarged (earlier models may be different), fit a boost controller and disconnect the factory solenoid (£26-600 depending on what you choose) or remap (£1000+).

But the only way to know is seeing if your boost either comes up to held quickly and stops there or peaks a bit and stops. If it peaks, drops a few and then goes up again you have mild overboost.

[Edited by john banks - 03/01/2002 15:00:24]