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Old 12-29-2009, 09:46 AM   #1
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Default new install; vacuum issues?

Installed a greddy turbo and other hardware this past weekend (see stuff in my sig for details of my setup). Installation went smoothly, but my knuckles would say otherwise. I had an idle issue at first startup, but reason was apparant in a vacuum leak between the BOV and IM (loose air hose). The car then idled fine. I have driven the car a couple times this week and have been careful not to boost (I lied, boosted twice to 4psi).

What are your thoughts on this? --> When letting off the gas (blipping gas in the driveway, or stopping in neutral for a light), the RPMs will fall but will stay around 1700-2200 RPM and fall a few hundred RPM then raise back, then fall again, and repeats this cycle a few times before stabilizing. It eventually falls back and idles at 900RPM. I'm thinking I still have a vacuum leak somewhere. Listening closely to all the airline tubing joints and connections, I hear a hiss from the MBC. Is that a normal characteristic of a MBC? Any other ideas?

I have an EMB ready to go, along with autotune and 02 clamp, and 310cc injectors, that I will install after I fix this problem.
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Old 12-29-2009, 11:20 AM   #2
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Sounds like a vacuum leak to me.
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Old 12-29-2009, 11:23 AM   #3
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What are your thoughts on this?
I've read that running a BOV with a mass air meter is a terrible idea because of the driveability issues it creates. But people can't resist the rice.
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Old 12-29-2009, 11:29 AM   #4
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ok hyper!!
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Old 12-29-2009, 11:34 AM   #5
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I've read that running a BOV with a mass air meter is a terrible idea because of the driveability issues it creates. But people can't resist the rice.
Um, bov needs to be vented back into the intake tract, right?
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Old 12-29-2009, 11:47 AM   #6
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ok hyper!!
I'm not sure what hyper means in the context of this thread, but ok. I'll check for vacuum leaks again later and report back.
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Old 12-29-2009, 11:54 AM   #7
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thats what happened to my last turbo car running atmospheric bov with a maf.

try unhooking your bov and blocking its vac line... just for a second.

if it is the problem, and it happens alot you will go through a set of spark plugs in a week from running so rich in those conditions.
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Old 12-29-2009, 11:56 AM   #8
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thats what happened to my last turbo car running atmospheric bov with a maf.

try unhooking your bov and blocking its vac line... just for a second.

if it is the problem, and it happens alot you will go through a set of spark plugs in a week from running so rich in those conditions.
Thanks. I'll give that a try.
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Old 12-29-2009, 12:41 PM   #9
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If you have a Bosch blow off valve, then it should actually be a recirculating valve. If it has an outlet like this then you just need to get an inlet installed on your hot side pipe, and then hook the two up with a rubber hose:
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Old 12-29-2009, 12:52 PM   #10
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Originally Posted by dustinb View Post
If you have a Bosch blow off valve, then it should actually be a recirculating valve. If it has an outlet like this then you just need to get an inlet installed on your hot side pipe, and then hook the two up with a rubber hose:
It is a recirculating valve. So on the hot side pipe? The pipe leading from the IC to the IM has a mounting hole for the BOV, which is where it is at presently..
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Old 12-29-2009, 02:24 PM   #11
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Originally Posted by G Rat View Post
It is a recirculating valve. So on the hot side pipe? The pipe leading from the IC to the IM has a mounting hole for the BOV, which is where it is at presently..
The BOV should be mounted on the cold side as close to the throttle body as possible, the recirculating side of it should be he hooked up somewhere after your air flow meter.
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Old 12-29-2009, 08:08 PM   #12
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Originally Posted by webby459 View Post
Um, bov needs to be vented back into the intake tract, right?
Yeah I meant bad idea for a vent to air setup.
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Old 12-29-2009, 08:15 PM   #13
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Yeah I meant bad idea for a vent to air setup.
unless you have a standalone
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Old 12-30-2009, 09:03 AM   #14
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I removed the BOV last night, vacuum issues completely gone. Took it out for a quick spin - hell yeah. Next is to get the EMB and 02 sensor installed. Thanks everyone.
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Old 12-30-2009, 10:56 AM   #15
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I removed the BOV last night, vacuum issues completely gone...
Eventually you are going to need a BOV. Also I know there has been ppl that have had compressor surge even at 6psi.
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Old 12-30-2009, 11:02 AM   #16
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Originally Posted by buffon01 View Post
Eventually you are going to need a BOV. Also I know there has been ppl that have had compressor surge even at 6psi.
There is a capped tube between the MAF and turbo, I'll run a tube from the output of the BOV to there when I get a chance this weekend.
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Old 12-30-2009, 11:08 AM   #17
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Oh ok, also all I saw in your sig is FPR, are you planning on getting any real engine management??
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Old 12-30-2009, 11:39 AM   #18
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Oh ok, also all I saw in your sig is FPR, are you planning on getting any real engine management??
I'm a newbie to engine management, having only used a bandaid voodoo box for my old FM turbo. I'd like to just get the EMB sorted in the car first (and learn the greddy software) before moving on to a GM 3 bar sensor and wideband 02 sensor (both of which I already have). The EMB is ready to go (including ignition/injector harness), I soldered the connections in the ECU for easy PNP to the factory wiring harness.
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