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MBC=Slower SPOOL?!

 
Old 02-26-2007, 02:59 PM
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Default MBC=Slower SPOOL?!

So i put on my mbc, its adjusted to 7.5ish psi..

The wastegate is set at about 5.5 psi, the max.

I have the MBC plugged in right, using the nipple off of the turbo like the instructions said.(I also tried it off of the intake manifold, no good.)

Im getting full spool of 7.5 psi at about 6k rpms, i used to get a full spool of 5.5psi at 4k, and was told these MBC's are supposed to INCREASE spool?!

Only other thing i can think of is setting the wastegate at the lowest psi setting, but id like to get some input before i go ahead with it.

(the MBC is a generic ebay one, with bleeder hole drilled in the side)
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Old 02-26-2007, 03:01 PM
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Have you tried putting it backthe way it was it sounds like you have an exhaust leak to me.
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Old 02-26-2007, 03:02 PM
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Come on buddy, it takes longer to build more boost :gay:
greddy downpipe right?
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Old 02-26-2007, 03:25 PM
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but do you still make 5.5psi at 4k? the stock greddy DP stinks for spool
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Old 02-26-2007, 03:29 PM
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Ahh i should have specified..

No, im not making 5.5psi at 4k anymore, its coming on about 5.4k, really late.
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Old 02-26-2007, 03:48 PM
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and nothing else was changed? if you go back to pure vacuum line it will still be faster?
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Old 02-26-2007, 03:48 PM
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what kind of bc is it? bleed valve? as in lets boost build at the WG while it builds at the gauge?

might want to supplement with the ball 'n spring type. they are the best for improving spool.
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Old 02-26-2007, 04:01 PM
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i'm still on the greddy downpipe i hit 10psi before 4k if i remember right
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Old 02-26-2007, 04:16 PM
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Originally Posted by Mach929 View Post
i'm still on the greddy downpipe i hit 10psi before 4k if i remember right
In what gear? Using what device to measure boost?

With the mbc set for 10 psi, my datalogs show that I don't get to 10psi until 5k rpm, I then overshoot to 12, and settle back to 10 towards redline

If you don't mind, see if you have any datalogs to verify. Would be interesting if you spool that much quicker than my car (and I'd want to know why).
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Old 02-26-2007, 04:22 PM
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Im pretty certain if i went back to straight vac line i would have no problem hitting 5 psi before 4k rpm.

I drove to the PO box to pick up my MBC, hitting 6ish psi at about 4k, i then installed it in the parking lot and played with it until i got it to max out around 7psi, after all of this i watched my boost gauge and tach closely only to discover i spool a few thousand rpms LATER.

ahhh, man i feel like my car is so shitty right now it sucks...

The ******* engine dies every other stoplight...

AHHHHH!'

lol.
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Old 02-26-2007, 04:35 PM
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whats your idle? does you dashpot work? does it only do it if the BOVs dumps, or if you come to a soft stop it doesnt die?
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Old 02-26-2007, 04:49 PM
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if i very slowly come to a stop using the gear to let the rpms come down to where idle is it will not mess up much.

If i just drop the throttle from 3 or 4k rpms the engine will pretty much die.

At idle the BOV is for sure not leaking, are you thinking it may be venting and causing the idle droop?

I bevelive the dashpot is working just fine, my dad(ex mazda mechanic) said it seems to be working correctly, and we sprayed it with wd just in case.
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Old 02-26-2007, 05:00 PM
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maybe increase the base idle with the screw?

clutch in or out make a difference?
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Old 02-26-2007, 05:03 PM
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Sounds like what was happening to me.. Mine ended up being a dashpot and idle adjustment problem. Yours sounds alot like a vacuum issue (venting).
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Old 02-26-2007, 05:41 PM
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have the MBC backwards? That would produce the results you are seeing. Just installing an MBC shouldnt change anything. Maybe you blew off a coupler with the increased boost, that would account for the stalling too. check that ****.
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Old 02-26-2007, 05:45 PM
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If you BOV isn't leaking then you may have a vacuum/boost leak due to the install (hence the stalling). Try replacing the lines from the manifold to the MBC and the MBC to the canister. If the problem is still there try blowing into your MBC and see if it is the cause of the leak.
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Old 02-26-2007, 06:00 PM
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Originally Posted by Ben View Post
In what gear? Using what device to measure boost?

With the mbc set for 10 psi, my datalogs show that I don't get to 10psi until 5k rpm, I then overshoot to 12, and settle back to 10 towards redline

If you don't mind, see if you have any datalogs to verify. Would be interesting if you spool that much quicker than my car (and I'd want to know why).

3rd gear i think it does but maybe i'm off i haven't driven the car in months so i could be wrong, i don't have any datalogs either
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Old 02-26-2007, 07:46 PM
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Originally Posted by AndyFloyd View Post
have the MBC backwards? That would produce the results you are seeing.
Actually, installing the MBC backwards would result in the wastegate not seeing any boost (or very little), resulting in MASSIVE boost overshoot. It would be akin to a pinched vacuum/boost line for the wastegate actuator can.
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Old 02-27-2007, 03:22 AM
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Take it apart and see if the spring is stuck open like this... Sorry paint is all i have lol I know that the poor mans boost controller will do it now and then
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Old 02-27-2007, 06:20 PM
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Hmm will do, thanks for the tip!
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