Struggling to maintain boost

[360beast]

Originally Posted by 960kg

A good quality basic bleed valve is all that is needed to up the boost but only to 14psi otherwise the boost limiter kicks in and it will reduce it to standard even if you go to 15psi the limiter will kick in. std.boost 3psi??......i thought it was 8psi as it was on my `91 Wentworth 940 turbo.

If you suspect the actuator diaphragm is weak then put a 10p piece behind it to strengthen the spring .....the actual diaphragm is about the most reliable part on a turbo Volvo and give no problems whatsoever even at very high mileages.

If your boost still leaks look at the lever on the actuator where it goes through the turbo casting and this hole wears elongated at high mileage and unless the engine or turbo is very hot to help expand the fit it will leak and not hold max. boost.

He has an LPT which is 3 psi the HPT is 7 or 8 psi

[TonyS9]

There is no boost limiter, it doesn't measure pressure or have any other sensors. There are some strange devices on my 95 car (possibly EGR related), but these don't exist on my 87 B230FT engine in my 360. The boost doesn't work above about 15psi and the engine dies, I believe this is because of a weak mixture. Also no gains above about 13psi so I think this is the mixture becoming weak.