I have installed a Turbo XS MBC and I can decrease the boost but not increase it more than the stock level. My prior cars were all big turbos so this wouldn't be an issue with external wastegates but I don't know what's going on with this actuator, I have capped the N75 valve and ran the MBC straight up to the actuator from the charge pipe nipple that went to the N75 valve and I have also ran the boost source straight from the manifold to the actuator and nothing, as I said I can decrease it with the controller but I can't up it. I tried disconnecting the plug from the N75 valve and the car surely spools slower but still the same amount of boost. What am I missing here? I hear that the remaps take you to around 15 psi, so being that the case the actuator spring should be alright, so why can a remap increase it but I can't manually when bypassing the N75 valve. And if you are thinking why don't I just get the remap and be done with it, the answer is that I'm going big turbo in a couple of months and I won't waste six hundred bucks on something that will be worthless in three months.. that I'm not clamping the MAP could be the reason? or do I need to bypass the N249. I'm not leaking anywhere so why the restriction ?

 

MK1 180 Quattro..

 

If you are using a standard xs mbc, it only goes 12psi over waste gate pressure. Most likely psi drop at the pos intercooler or a small boost leak causing the 1-2psi drop

 

Well, won't go past 10 psi which is what the car was boosting without it. There is something wrong with the set up. The MBC has a side nipple and a bottom one. Bottom to the wastegate and side to the source is the way I always had my controllers hooked up. I think that in this case I need to add the other side nipple and connect the wga and source through the sides and bleed from the bottom.. I'll hit that option later this evening..

 

Mbc is set up correctly. Have another mbc to try?

 

I'll buy a cheap ball spring one and see what's up with that, the bleed type's gotta have something to do with this issue, either that or the wastegate arm ain't pulling hard enough, I can't see a damn thing back there.. Is it adjustable ?

 

It is adjustable and the nuts have been known to become loose.