My car has developed an odd boost problem and I think it may be my Forge BOV.

About 1 out of every 10 times I go WOT, when the turbo starts to spool it won't build boost even to wastegate pressure because it sounds like the BOV is venting all the pressure. If I stay in it, then when it gets up higher in the RPMs, whatever is leaking will then seal up and the boost spikes back to normal. I initially suspected my boost controller, but then it occurred to me that it can't be that since boost isn't even reaching wastegate pressure (about 20 psi with my actuator in these winter temps). I suppose it could be another boost leak somewhere, but what other sort of boost leak would fix itself with more pressure from the turbo?

The only thing I can think of is the Forge 1G BOV. I think the problem may have started when I started trying different springs in the BOV, though now I've returned to my original spring and the problem persists. I noticed some grease in the BOV, so maybe it needs to be lubricated and is sticking? What kind of grease would I use in there?

 

Take a look at this thread.

https://www.evolutionm.net/forums/sh...4&page=1&pp=15

I use mobil 1 fully synthetic bearing grease.

 

Thanks. That's a really long thread, but I read through it all and will look for some of that grease. I think if I had the problems people are talking about in that thread I'd sell my MBC in a heartbeat and get something else. I guess I should be grateful to have random underboosts rather than random overboosts

 

I still use the Forge UNOS, but it's not the only MBC i've heard of that's done this. Try some of this grease and see what happens. Can't hurt, it's super cheap, and takes about 10 minutes to do.

 

I took apart my Forge diverter valve and found that the grease inside was all black in certain sections (it's red grease). Maybe that was polishing residue mixed in with the grease? I also found that the internal part of the valve that opens and closes on the valve seat was starting to gall from friction. I cleaned all this black crud out, regreased with Mobil 1 grease and so far it seems to have fixed the problem. I had only a few thousand miles on this valve, so I'd say that it wasn't properly cleaned and lubed from the factory. This might be similar to the issues with the Forge MBC -- i.e., polishing residue causing internal issues. In any case, anyone with this valve might want to take the time to clean and regrease. It's very easy to do.

 

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