Boost spike issues...

[Cool Mr Steve]

I have a Big16g with (I believe) a standard size wastegate flapper. I ported the wastegate opening and the o2 housing before installing it. I have a Hallman MBC (the one with the little bleeder hole on it, I'm not quite sure if they all do...) and I really don't know what the boost is set to. My boost will spike all the way up to about 23.5 or so, settle around 18-19, and by redline seems to drop to around 17 or lower. What do you think may be causing this? I know a lot of people have problems with bleeder type MBC's, but even though it has the little bleeder hole, it's a ball and spring, isn't it?

 

[paec311]

I don't know about the Hallman MBC, but I do know Big16gs that are internally gated are known to boost creep. I had an Evolll 16g with ported 02 and wastegate with the larger flapper, and mine boost creeped as well. I would say look into a 38mm external. Also, colder climates, like in Washington, will be more prone than warmer areas.

 

[trd-2-dsm]

yeah try get an external or you could put the boost contrioller down so that when it creeps it won't be that high

 

[fourreGsixty3]

Tone the MBC down to like 16psi or so, that should help, and YES switch it out to an external, because the internal WGs will boost creep under heavy loads.

 

[Cool Mr Steve]

My problem is not with it "creeping," but rather with it simply spiking for a split second. I hit about 23-24 for under a second, then it settles. I don't want to get an external wastegate. I understand what causes the creep issues that so many people have, but it seems much different than what I'm experiencing. Does anyone else have any other input?

 

[paec311]

By any chance, your clutch isn't slipping is it? At WOT, pref 3rd gear, see if your rpms jump and come back down the same time as your boost.

 

[JayRolla]

I have an evo3 with no creep at all and its internally wastegated. But my turbo did spike with a MBC that my mechanic made me. Ive heard a lot of top brand MBC cause spike. My brother has the nice greddy profec controller and is very nice. It always hits the boost it should.

 

[Cool Mr Steve]

I'm thinking about getting either a different MBC or a 34mm wastegate flapper. Does anyone else have an idea? It seems like my boost is reverse creeping. It creeps downward. Grrrr...

 

[fourreGsixty3]

I would go with the 38mm flapper.

 

[donmagicjuan]

You're right that this problem seems less like a creep issue and more like one of poor responsiveness from your MBC. Are the lines from the boost source to your MBC and to the WGA reasonably short and unobstructed? I would also check the integrity of these lines, as a leak would kill your controller response as well. I'm not sure which Hallman you're describing, but I have the Pro model, and it performs rather remarkably.

EDIT: Just saw that this thread is almost 5 months old! What'd you dig this one up for, fourreGsixty3?