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MBC (ebay version) Boost Spikes?

 
Old 10-20-2007, 09:23 PM
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Default MBC (ebay version) Boost Spikes?

Anybody have experience with these MBCs?

Just installed it and with it fully turned down it spikes to 8 then settles down to 4...If I turn it up it is about the same delta...aprox. 4 psi

INSTALLATION
The T restrictor is inbetween the compressor and the wastegae with arrow pointed torwards wastegate..adjustment valve is conected to the bottom of T with arrow pointing torwards the T....lines are snug and do not move but not zip-tied
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Old 10-20-2007, 09:29 PM
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why not just turn the boost up by shortening the Wg rod.
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Old 10-20-2007, 09:40 PM
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Lar.
And if your still not happy with just messing with the WG a little, then Get a helper spring. That would fix that up.
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Old 10-20-2007, 11:00 PM
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Dude, there are a dozen different eBay MBC's... post a link.

With the MBC removed, how does your boost curve look.

Slidin is right, could be a problem with your wastegate rod... make sure when your flapped door is closed the rod actually has some tension on it. You do not want the rod holding the flapper closed loosely.

Also, since a properly functioning wastegate should not let you lower the boost below the spring pressure and I know of no common wastegate actuator that has a spring setting of 4psi that's one more reason to suspect your wastegate actuator or rod itself is not set properly.

On most manual boost controllers you can tighten the spring hard enough that the ball will never move and you essentiall get unlimited boost. The fact that you've done this and are only getting an 8psi spike indicates that you've done something wrong. We need pics of your MBC installed.

Also, boost creep/spike is very common in T25's... but you don't mention anything about your setup. Fill out your signature with a short list of your setup, it helps us help you way better... and maybe change your Location listing to a city so somebody local could offer to come over and help you out.

I suspect a combination of rod adjustment and improper MBC install. Until you get some answers, bypass the thing entirely.
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Old 10-20-2007, 11:11 PM
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sounds like the retarded one i have. i didnt run a t i ran the boost controller in line.and mine is verry shitty as far as adjustability. it goes from 7psi to 12 psi in one click.
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Old 10-20-2007, 11:14 PM
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Originally Posted by drftem View Post
sounds like the retarded one i have. i didnt run a t i ran the boost controller in line.and mine is verry shitty as far as adjustability. it goes from 7psi to 12 psi in one click.

What I did was drill an extra hole closer to the wastegate if i needed more boost
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Old 10-21-2007, 01:11 AM
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Sam, here is a link to the MBC

http://cgi.ebay.com/ebaymotors/TURBO...spagenameZWDVW

It is installed as Brain shows in the thread below

https://www.miataturbo.net/showthrea...roller+install

I checked the wastegate rod and there is tension on the rod (no slop or play).....and without the MBC I get 4-4.5 PSI ....

I will add to my signature.. Thank you for the help
I am in Northern California

Last edited by Silverhare; 10-21-2007 at 01:29 AM. Reason: spelling
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Old 10-21-2007, 02:18 AM
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slidin lives in sac, maybe he can help you out
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Old 10-21-2007, 02:28 AM
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Martinez is kinda far aint it?
And I dont know much about mbc.
I try not to run em.
I like messing with the waste gate alot better.
And with a helper spring, you can get it to boost very nicely with very little spike.
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Old 10-21-2007, 02:12 PM
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No Thanx Slidin, good luck kid....I will do some research and leave this one for the experts
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Old 10-21-2007, 07:41 PM
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search "helper spring"
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Old 10-21-2007, 07:59 PM
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Old 10-21-2007, 08:02 PM
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Originally Posted by Silverhare View Post
No Thanx Slidin, good luck kid....I will do some research and leave this one for the experts
Hehe. :gay:
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