ademid

When driving my scoob (my95) in fourth gear boost comes in, peaks at 15psi drops to about 12.5psi and then slowly creeps up to about 14.5 psi the longer you keep the loud pedal down?? Anybody got any idea's?? All the other gears are fine, really stable boost (peak 15psi holds at 12.5psi).

My reason for asking is that I am looking into raising the boost slightly but until I get it consistant in all gears I worry about possible damage.

Cheers

Ade

brickboy

Is yours modded in any way? You may be getting slow boost creep in 4th 'cos it's the only gear you can really keep your foot down in .... in 1st 2nd and 3rd you'll just hit the limiter before the boost starts creeping up from 12.5psi, and in 5th by the time you're at decent rpm then you're waaayy past the legal limit.

But in 4th it will pull hard and long, and give the ECU time to spike at 15psi, modulate to 12.5, then adjust slowly upward as the ECU works out it isn't pinking etc. Doesn't sound like too much of a problem, at least the boost isn't bouncing around all over.

ademid

Cheers for info brick boy

Have modded it a touch : Blitz NUR spec mid and B/B, scoobysport D/P, Blitz cone filter, Bailey dump valve and racelogic ecu.

The main reason this is bothering me is that I have had the D/P fitted recently and have also fitted a bleed valve to up the boost a touch (was getting a constant 12psi). But since fitting either the D/P or Bleed valve I can't get a fixed boost figure in fourth therefore cannot feel safe about tweeking it up a bit.

Was going to aim for 14psi stable in all gears but as you can see this is not as simple as I though.

Ade

brickboy

Like you say, just a few mods ;-)

The bleed valve is almost certainly causing the boost creep ... like I said earlier, in 4th, the boost has time to spike, stabilise then creep.

I think this is happening because after the wastegate has opened initially, the bleed-off through the bleed valve will slightly reduce the pressure the wastegate sees, and the wastegate actuator spring will start to close the wastgate a little and let the boost rise. It sounds like you're pretty close to ideal if boost is stable most of the time, if you crack the bleed valve much further it might get out of control.

ademid

Cheers Brickboy

I plan to change all the vacuum piping for new stuff just to try and stabilise the boost. But I guess I shall have to find another way of getting more power

Ta for help

Ade