BOV and MBC wont cooperate

[visualsinz]

I have a 96' GST Spyder. ive got a couple mods, but my manual boost controller and my Greddy type RS boost controller don't seem to want to cooperate. whenever i get my bov sounding like its supposed to, i boost spike rally bad. whenever i get the boost leveled off my bov sounds like crap. i have the mbc t-d off of the BOV. tried to t off elsewhere and get bad boost spike. ANY SUGGESTIONS???

 

[visualsinz]

Correction: i have a greddy Type RS BOV not manual boost controller.

 

[crunchymilk]

get that MBC on a different line. Run it so that the lines are as short as possible

 

[visualsinz]

I tried running it on three vacuum lines. it came with a special t that has a ball and spring in it. i tried running it on a regular t and it spiked.

 

[visualsinz]

which vaccuum line on the throttle body should i try. the one closes to the firewall, middle or closest to the engine. i dont know what they run to or there function.

 

[zippyshoe]

If you are running the stock 2g turbo, then your turbo's compressor housing will have a port for a vacuum line. I would run a short length of vacuum line between this port and your MBC and use this as your "boost source". Then run a second short vacuum line between the MBC and the wastegate actuator.

EDIT: Just wanted to clarify - Your MBC should contain two separate vacuum ports (assuming you are using a typical ball-spring type MBC): one that is meant to connect to your "boost source" and another that is meant to connect to your wastegate actuator. Make sure you have correctly identified which port is which on your MBC.

 

[visualsinz]

ok hooked it up to the turbo, and still boost spiking.

 

[zippyshoe]

What have you done regarding the vacuum line running from your intake to your BOV? You will just want to run a single vacuum line from your intake to your BOV (no tee's) now that your MBC is no longer connected to this line.

 

[visualsinz]

i hooked up the mbc to the c. housing. i have the bov hooked up directly (no t's). im still getting boost spike bad. could all this be caused by a vacuum leak somewhere. i have a muse motorsport mbc if that helps. just got it because my crappy ebay mbc was spiking. i have the hose going to the wastegate closest to the knob, which is the way that all the ball and springs are set up. my boost guage only reads to 20 psi and when i hit the gas in 2nd 3rd etc it shoots right to 20, thats only at about 1/2-3/4 throttle.

 

[zippyshoe]

When your boost shoots up to 20psi, does it quickly fall back to a lower boost pressure (the level that your MBC is set to) or does it remain at 20psi? If it remains at 20psi (or higher) then what you are experiencing is all-out overboost (uncontrolled boost) rather than boost spike. If your MBC is functioning properly, connected properly using reasonably short vacuum lines, any true boost spike you might see should be no more than a few psi. If you are seeing overboost, then one of the following is probably the culprit:

1. Defective MBC.
2. Improperly connected MBC.
3. One of the vacuum lines connected to your MBC is leaky.
4. Defective wastegate (defective wastegate actuator, defective/bent wastegate arm, etc.)

As a test, you might want to try bypassing your MBC altogether by connecting a single vacuum line from the turbo compressor housing to the wastegate actuator. This should return you to stock boost pressure. If it does not, then you probably have a defective wastegate. If it does return you to stock boost, then I would suspect the MBC or the vacuum lines connecting your MBC.

 

[visualsinz]

just a question but if i have my vac. hoses backwards on the mbc, would it boost unlimited or would it boost really low. i can't tell if it drops back down because whenever it overboost i have to let off the throttle. i'll do the test on it as soon as the weather clears.

 

[visualsinz]

if the test confirms that the wastegate is not the problem then i'll try to rearrange how i have the vac. hoses arranged on the mbc. the dial is back-asswards so maybe the vac. hoses are to. to increase boost i turn clockwise which is normal, but it screws out which is backwards.

 

[zippyshoe]

just a question but if i have my vac. hoses backwards on the mbc, would it boost unlimited or would it boost really low. i can't tell if it drops back down because whenever it overboost i have to let off the throttle. i'll do the test on it as soon as the weather clears.

I believe if these lines are backwards on the MBC, this would result in uncontrolled boost. With the MBC connected backwards, the wastegate actuator will never receive a pressure signal from the MBC telling the wastegate actuator to open the wastegate. If the wastegate never opens, then your boost pressure will keep climbing, only limited by the capabilities of your turbo to generate boost.

 

[visualsinz]

thanks for being patient with me. im going to try some more of this stuff. remind me when this is all said and done to give you credit for all this so i can help get your rating up. you might have to explain how to me.

 

[MrBoxx]

Does your boost controller by any chance look like this?:

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If so, I haven't heard of a single person who has gotten this type of MBC to run correctly. There are several threads on here about how it doesn't perform as well as it should. If this is the MBC you have, I suggest not using it and buying something with a better reputation, i.e. Hallman, Joe P, TurboXS, etc.

 

[visualsinz]

i hooked a direct vacuum to the c. housing and the wga and it boosted 11 psi evenly. then knowing that it wasnt the wastegate, i switched the vac. lines around on the MBC. still overboosting to 20 and climbing.

 

[visualsinz]

i've been had. i just read the thread about the muse motorsports mbc. im going to put my ebay special mbc back on and let ya'll know how it went!!!

 

[visualsinz]

im disputing this piece of crap MBC on paypal. these people have made me 38HOT!!!

 

[zippyshoe]

i've been had. i just read the thread about the muse motorsports mbc. im going to put my ebay special mbc back on and let ya'll know how it went!!!

Should you ever decide on buying a new MBC, I've had good luck with the Hallman Pro series boost controllers. They are very easy to hook-up and make adjusting your boost a breeze. You really can't go wrong with any of the MBC's mentioned by MrBoxx. Glad to hear that your wastegate is functioning properly.

 

[visualsinz]

thanks fellas. im orgering a hallman pro fri. afternoon. keep you guys posted. by the way how do i help your reps.

 

[visualsinz]

just a question, if i was to hook the c. housing directly to the WGA, what would b the negative side affects besides low boost? this will be temporary until the new controller comes in...

 

[delta448]

just a question, if i was to hook the c. housing directly to the WGA, what would b the negative side affects besides low boost? this will be temporary until the new controller comes in...

None. This is probably the safest way to run right now without using the stock BCS. Your boost will be pretty limited however.

 

[zippyshoe]

thanks fellas. im orgering a hallman pro fri. afternoon. keep you guys posted. by the way how do i help your reps.

To add to anyone's rep points, just go to one of their posts. In the section to the left (the profile), click on the little symbol just to the right of the "Online"/"Offline" text. The Hallman Pro MBC's come with a length of vacuum line. I found that it took some effort to install this line onto the ports of the MBC. A drop of engine oil may make this process easier. Once you connect your MBC, I doubt you will ever have to worry about the lines ever popping off the MBC. Connect the port closest to the knob to the wga and connect the other port to the turbo compressor housing. Simply turn the knob clockwise to increase boost/counterclockwise to decrease boost. Good luck with your new MBC.

 

[visualsinz]

thanks

 

[visualsinz]

by the way, off subject, i've been hearing crankwalk this crankwalk that... what is the def. of crankwalk. i know it's worse in 2nd gens. so i would just like to know.