Delica Canada | Mitsubishi Van Club

I can tell you with 100% certainty that *my* Delica, when stock, made 8 psi at full throttle with the occasional 10psi spike.

That increased to 10psi at full throttle with 12psi spikes when I blanked off the blowoff valve, which suggested the blowoff valve was a bit weak and had been leaking boost.

Does that help?

There is another question which is, how accurate is your boost gauge? Ive had a few, and none were terribly accurate. Good for a subjective look at boost level but off by several psi from what I could judge.

I think the boost level most people run is to low and results in excessive EGT values. I have been running a typical maximum of 15 psi and occasionally if I need it up to 18 or 19 for the last 50 000 km. I know some on this site have the boost maximum of over 20 psi. If I can maintain 15 psi the EGT values never go over 950 F, as soon as the boost starts to drop due to loss of RPM the EGT will climb quickly. I can't imagine going back to 12 psi boost.

Right so, I would check the wastegate is free to move, to rule out it being stuck open. Also, I would check the injector pump, because actually you could have a fuelling issue. The turbo makes more psi as a product of the fuel being turned into gas, so the amount of gas you can make dictates the amount of spin you can get out of the turbo. The turbo supplies boost to the top of the pump where it presses on a diaphragm to increase the fuelling as boost increases, for a given throttle position. A fault there could cause some problems, and so could a blocked fuel or air filter come to think of it.

Oops, just read you'd done the filters! Blocked fuel line?

I'm sure there's an actual procedure to test it in situ, but if you remove the top cover the diaphragm is clearly visible. Look for any holes or splits.

(If you're going to remove the diaphragm, mark its position first- the cone shaped pushrod attached to it is eccentric, and replacing it in a new orientation will change your on-boost fuelling).

I once lost all boost when the small hose between the turbo and the compensator popped off, could it be that you've got a leak in that hose? Or if you've teed your boost gauge into that line, is there a leak in the boost gauge hose? Those hoses are often a push-on fit and can come loose- I now have cable ties acting as hose clamps to hold them in place.