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Help me understand why my MBC does not function properly

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Old Apr 25, 2007, 09:14 AM
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I will once I have time.

I'm back with the same problem. Vac line popped off my EGR.. fixed that and now I'm back to hitting 28-30psi then dropping to 19/20 by 6000rpm.

I'm really getting frustrated I will check for boost leaks again.. take apart the Forge MBC and DV and see if anything is wrong there.
Old Apr 25, 2007, 10:41 AM
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Originally Posted by justchil
Ihitting 28-30psi (no air is getting to WGA) then dropping to 19/20 by 6000rpm (air is getting to WGA).

I'm really getting frustrated I will check for boost leaks again.. take apart the Forge MBC and DV and see if anything is wrong there.
I'mn sure you already know that but sometimes you should step back and look at whats going on simply.

For ex: The bleed port between MBC out and WGA in may still be holding air on diaghram.

Or preload might be enough to hold exhaust at lower exhaust volume/higher manifold pressure at lower rpms, and at higher rpms the exhaust energy increases against WG and manifold psi decreases to the WG cracks open sending efficency downstairs
Old Apr 25, 2007, 10:55 AM
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A little more preload on the WGA perhaps.
Old Apr 25, 2007, 11:06 AM
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I'm having a similar problem except mine is to the opposite degree and its scaring the hell out of me.

I'll just post the PM i sent to forgemotorsports who decided not to respond. mike@forge has his PMs blocked for some reason too so i guess ill have to make it public.

i'm having a serious problem with your boost controllers. i have a black one and a polished one. friend of mine gave it to me when he got an electronic in hopes that it would be better than my black one.

the black one would keep getting stuck at 22 psi all the time. now that's fine and all. much better than the ladder which im about to explain.

i put in his and this has happened 3 times now in the past 3 days.

sunday morning i got on it after the car warmed up and i heard hard backfires like 3 times in a row. scared the crap out of me. i thought my licp blew off, which has been happening a lot lately. i need to put some hair spray on it but anyhow. on the way back home after leaving my moms place to see where my boost was at. it spiked around 1.9 bars and i quickly let off. it was previously set to 1.6 bars. turned it down a lot even though nothing was changed from when it was at 1.6 bars and tried again, 1.9 bars. turned it down as low is it could go. 1.9 bars still. when i got home i opened it up and the ball bearing was jammed into the bottom of the boost controller. i took an allen wrench and poked it through to unlodge it. it was stuck in there pretty good. all seemed fine and dandy and it happened again yesterday. fixed it.

this morning on the way to work i was late and started speeding and punched it in 6th, BAM back fired again. 1.9 bars. babied it to work out of boost and ill fix it at lunch but i gotta tell you. im seriously starting to fear blowing my engine from using your products. 29-30 psi on pump gas just doesn't go over well with me.
Old Apr 25, 2007, 11:24 AM
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Yet some people have no problems out of them... I've had problems with two of them both less than a week old. I've also had problems with the WGA and the DV.

Any idea what's happening in your case? I'm so sick of boost issues I'm getting close to selling the car or dropping it off at Buschur Racing with a blank check.
Old Apr 25, 2007, 11:39 AM
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Originally Posted by cfdfireman1
A little more preload on the WGA perhaps.
I'm at the highest "recommended" setting of 4 full turns right now. I dunno I need to get off work to troubleshoot I guess.
Old Apr 25, 2007, 11:49 AM
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Hmm, I was wondering what was going on with mine as well. I sold the previous Forge mbc I had to go another route, didn't like that route and went back and purchased another one. I had no spiking with the other one at all. I put the new one on, after changing to the stiff, turned the thing all the way down, and 30 psi!! I run alky so I wasn't too scared but I backed off, and I backfired a couple of times as well. I also made no other real changes. I finally replaced the stiff spring with the softer spring that it came with and after lots of clicks I seem to have a happy medium of 26 lbs.

I had to put the stiff spring in the older one I had but maybe the newer ones don't require the stiffer springs?

Last edited by 8thWonder; Apr 25, 2007 at 11:51 AM.
Old Apr 25, 2007, 11:51 AM
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Ive had same problem to set my boost, after pushing more boost 28psi on 20g-9-6 blade with methanol. The boost was jumpy as hell, 28psi? it went down to like 19-20- I did boost leak, umm different MBC, check everything what i could.

Problem was Forge WGA, i did open, there was so much **** inside + MUD not only rusted water. I had stock WGA at the house so i decided to preload it and install it on the car, when i went for a test drive my second gear and boost was just amazing how quickly it responded and hit 24psi right away.

I did call forge, the guy on the phone told me , just to clean it and install it and the stiffest spring they have is red which comes with it, well i cant see the color of the spring because is rusted, he said its normal and wont hurt any performance.

as far hallman? I would trust that MBC! this is the only mbc i would actually trust!

now my boost hits 28- and drops to 24-25 by red line, I think its normal on 3rd gear pull from 3k, as far 4th gear it sits steedy at 28psi.

Btw which boost gauge are you using? did you test the boost gauge? try to do boost leak and see if it holds aat 30psi.

I got forge BOV, fully rec and AMS MBC, still I would like to run that FORGE WGA insteead of stock one.

Last edited by tweakdsm; Apr 25, 2007 at 11:57 AM.
Old Apr 25, 2007, 12:11 PM
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im about to just say fk it all and buy an ebc. my friend andy has had really good luck with his apexi one. he swears by it. im tired of this spiking crap because if it keeps happening, my motor is going to blow and i know its going to all be forges fault.
Old Apr 25, 2007, 12:14 PM
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That's basically what happened to me.... and i had everything sorted out.. then the EGR vac line popped off and things are back to where they were before. It could be related to this I'm not sure.

I'm using a Zetronix 3.5bar map sensor to monitor boost. I do have a minor leak at the shaft seals on the TB (which I've replaced twice with no luck) but other than that nothing. I haven't had a lot of time to work on things lately but I'll troubleshoot as soon as I get home today.

If I can find something to connect my vac lines here at work I'll unhook the mbc to see if the WGA is holding properly now.

I'm really amazed getting full of water/rust is normal for the forge WGA. My spring is rusted just like yours was... it seems to me that would effect the integrity of the spring but I'm no expert.
Old Apr 25, 2007, 12:16 PM
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Kee: how much boost you're running? you should be no more than 22-23psi max! , if ur car pops! that means you're running lean and you need a tune.

just my .02
Old Apr 25, 2007, 12:19 PM
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Agree, first of all there should be no rust! at all... who knows when we did pressure test on forge WGA, it did made a hissle sound in the beggning and stayed open, the stock wga dosnt sound like that, it just pops and open.

Iam not an expert nether and iam not sure how new forge wga works and sounds when you pressure test it I dont want to bash anyones product, still why it collects gunk/rust/water? who knows, I dont want to pull out WGA every few months and do cleaning maintnance... Iam thinking to get rid of it.


Can you put Hallman MBC back on and see what happens? - the best mbc out there is hallman pro RX i think.

Still i wwould like to test yellow spring on forge BOV and see what happens.

Last edited by tweakdsm; Apr 25, 2007 at 12:24 PM.
Old Apr 25, 2007, 12:28 PM
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I wish.. I lost half of the parts to the hallman. I have 2 Forge MBC's I could sell but after people read threads like this I doubt they are going to buy them.
Old Apr 25, 2007, 12:31 PM
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Originally Posted by tweakdsm
Kee: how much boost you're running? you should be no more than 22-23psi max! , if ur car pops! that means you're running lean and you need a tune.

just my .02
jestr tuned me with 24psi and no knock. he stands by his tuning. im not worried. i definitely appreciate the concern though.
Old Apr 25, 2007, 12:31 PM
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so you're saying forge mbc is not good?

Umm try to find some local evo owner and test his mbc on your car.


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