RedScoob

Hi guys and gals,
Just a quick one....
What is the usual difference in boost expected from a warm day to a cold morning?
Mine usually goes from just under 0.9bar (cold morning) to around 0.8 bar (hot day). Is that normal, or should I be looking for more consistent boost?
Thanks!


p.s. Mine's a MY95 WRX saloon.

Ben v7

sounds about right to me... I notice quite a bit of a difference in performance between summer and winter.

RedScoob

Thanks.
I'm really surprised that the indicated boost pressure varies by that much... But if it's the norm, I won't worry too much...

theotherphil

Surely the set boost figure is the one the ECU actually tries to hit? Mine is rock steady summer or winter, always 1.4bar. It does feel quicker though in the winter mainly bacause of the denser charge.

RedScoob

That's exactly my query... It's not a case of the car feeling quicker or slower, but the boost pressure actually dropping in warm weather (indicated on the gauge).
Could an intake leak cause this type of thing, or am I really worrying unnecessarily?

Ben v7

My car doesn't hit the same boost targets that it does when the weather is hot as opposed to cold. The air is less dense when hot so you simply can't expect it to. In cold (sub 10 degrees) it will hit 1.3 ish bar - but when hot (over 20 deg) about 1.2 bar. I reckon I lose in the region of 10-15bhp on a hot day!

RedScoob

Cheers mate... Seems to be a drawback of tubocharged motors.... Got to say though, my quattro seemed to be pretty consistant. Maybe it was the gauge that just read approximately, like the fuel gauge............

silent running

I think it's more to do with the fact that there seems to be no air temp correction on a lot of Scoobs. If you're used to other turbocharged motors, it seems incredibly backward, but there you go. I've seen differences of 1 or 2 psi going from a cold morning to a hot afternoon for example.

I might be wrong on the air temp correction thing, but in my experience of other cars, differences in temperature give the same boost readings - the only difference being how quick the car feels i.e. on a cold morning the same boost level feels faster and when it gets hot the same boost level feels sluggish.

RedScoob

Thanks for your input everyone.
Update.....
Took the intercooler off today to straighten the fins with a toothpick (what a boring job!!!) and found one bolt missing on the hard intake hose to the intercooler. One of the other bolts was also loose and there was a 1mm gap between the mating surfaces!!! So, I've replaced the bolt and tightened everything up. Boost is now up to factory specs and the turbo is ALOT quieter (used to whistle under boost). It's a different car!!!
Thanks again for all your help, hopefully this will help anyone else experiencing the same symptoms!!!