another boost/performance loss question

[BigV]

Sorry for yet another boost question guys..... but I am having an issue with my c70 at the moment..... seems a bit down on power and on fitting a boost gauge I notice that the car is hitting approx 17psi but gradually fading off to about 12psi, then hitting 17 again on the final upshift into 4th? (auto box)


IT almost feels as though the car is being held back at times, I mean it is still faster than stock but the MPG and performance is certainly down on what it was when I first had the remap done. Kick down also doesn't seem as aggressive and I can't shred the tyres like I used to!

So far I have had one minor air leak fixed, new dizzy cap etc, spark plugs checked, Oil and filter changed and inspected all the boost/vacuum pipes visually too.

Have I still got a leak or is it worth changing the BCS? Injector cleaning?


I can't really afford to throw money at the car right now as I have just paid out for 2 tyres, new discs & pads all around, the wheel bearing needs doing and my insurance & MOT is due soon....Ouch , so any wise suggestions would be greatly appreciated!

[Wobbly Dave]

I wouldnt trust AM boost gauges as far as I could throw 'em. I've been thrown many a curve ball by them before.

Has the car been remapped because 17psi seems high for a standard map.

Boost spikes may be a result of a badly adjusted actuator - poorly MAF - airleak - all kinds of things which are not possible to diagnose on a thread.

[Alan M]

I would check for possible boost leaks around the inlet system first before spending any cash. I had funny boosting issues which turned out to be a faulty Boost control valve which I replaced with a later style Boost control solenoid and I now get a steady boost value with no fluctuation reaching 17psi in the higher gears.