Is Over-boosting At Mid-range Ok?

[Andi]

Hey all, I tried my idea of having two boost settings by just turning on and off the factory solenoid. It works thankfuly. With stock set up you can have settings of 7psi and 10psi.

I installed my spring-n-ball (Turbotech from Mark) MBC it doesn't hold boost the way I like it. What happens is say if I've got the MBC set to have the car run 12psi it will boost linearly up to 15-16psi at around 4100rpm and then drops down to 12psi and holds that until redline.

When I flick the switch to the high boost level it does the same thing i.e. boost up to 18-19psi then drops to 15psi. I'm not 100% sure what rpm where 15-16psi and 18-19psi hits but I'm assuming/guessing it's around 4100rpm and 4400rpm respectively. That said, the level from the over-boost drops very quickly back to the set/prefered level.

So are these boost levels ok at 4000-4500rpm? I've got the Bosch 984 and Sard FPR set to about 38psi base pressure (workshop manaul states it should be 36psi factory setting). I'm thinking topend (5000-75000rpm) is where too much boost isn't good and where AFR's are extremely important, but I'm not sure about midrange 4000-5000rpm so I'm keen for your opinions.

Thanks guys!

Andy

[predator]

got exact same problem on mine.. seems those turbotech valves are quite overrated..

[Andi]

Perhaps our ones are just duds, many other people seem to be using them fine. At first it was working perfectly, but I then took it off the car because I didn't have proper fuel management - when I did have enough fuel I then lost the spring and ball.

Mark's a top bloke so he sent me out a replacement spring and ball free of charge but now it doesn't hold the boost level properly. So not sure whats wrong.

[Andi]

Any thoughts on the overboost part people?

[predator]

well personally i don't think its too good as the ecu may not have time to react to the spike, and its not consistent for it to fuel correctly.

I actually turned down mine, as to get it to hold at level I wanted, i had to set it well above.. which I didn't think was too safe it sitting on 15, then back to 12 or whatever.

when i have some money.. think will just have to go an EBC.. They have more intelligent solenoids which can infinitely adjust levels via its "brain" to hold the exact boost you set. ProfecB did the trick for me in the last car. Its more money, but at least it works well.