Instant Boost Loss
Jun 27, 2014, 10:58 AM
#1
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Instant Boost Loss
Doing a 3rd gear WOT pull I hit 5K rpm, full boost at 25psi, AFR was reading 10-10.5 on 91 octane. Lost boost instantly and went into vacuum at 22-24 InHg, RPMs held at 5K. Let off the gas and shifted into 4th, after I changed my shorts I checked to see if it would hold boost pressure again which it did through all of the gears. Now I usually never go above 5K in 3rd so I've never experienced this before and when I do my pulls it's usually in 4th. I checked the plug gap and they checked about .024" and cylinder 1 was about .026" so I closed it up to match the others, other than that the plugs looked great. Checked all my vacuum hoses and clamps on all of the piping and everything checked out but I did tighten the clamp connecting my intake to the turbo a bit. Now I do have a rev hang issue that starts at 4k but only when I'm at full boost, the revs will jump 800-1000 when I clutch in. It's been a couple years since it was last tuned so I'm due for a new tune but I think these need to get worked out before I come in so my car doesn't blow up on the dyno. Attached is a video I found while researching this problem.
So far it seems like the general consensus is a bad BOV, I'm currently in the market for a stock metal Evo IX BOV. What do you guys think? I will be running a compression test and boost leak test this weekend, I will post results when completed. Any help is appreciated! Thank you.
So far it seems like the general consensus is a bad BOV, I'm currently in the market for a stock metal Evo IX BOV. What do you guys think? I will be running a compression test and boost leak test this weekend, I will post results when completed. Any help is appreciated! Thank you.
Jun 27, 2014, 01:13 PM
#2
Doing a 3rd gear WOT pull I hit 5K rpm, full boost at 25psi, AFR was reading 10-10.5 on 91 octane. Lost boost instantly and went into vacuum at 22-24 InHg, RPMs held at 5K. Let off the gas and shifted into 4th, after I changed my shorts I checked to see if it would hold boost pressure again which it did through all of the gears. Now I usually never go above 5K in 3rd so I've never experienced this before and when I do my pulls it's usually in 4th. I checked the plug gap and they checked about .024" and cylinder 1 was about .026" so I closed it up to match the others, other than that the plugs looked great. Checked all my vacuum hoses and clamps on all of the piping and everything checked out but I did tighten the clamp connecting my intake to the turbo a bit. Now I do have a rev hang issue that starts at 4k but only when I'm at full boost, the revs will jump 800-1000 when I clutch in. It's been a couple years since it was last tuned so I'm due for a new tune but I think these need to get worked out before I come in so my car doesn't blow up on the dyno. Attached is a video I found while researching this problem.
So far it seems like the general consensus is a bad BOV, I'm currently in the market for a stock metal Evo IX BOV. What do you guys think? I will be running a compression test and boost leak test this weekend, I will post results when completed. Any help is appreciated! Thank you.
So far it seems like the general consensus is a bad BOV, I'm currently in the market for a stock metal Evo IX BOV. What do you guys think? I will be running a compression test and boost leak test this weekend, I will post results when completed. Any help is appreciated! Thank you.
Jun 27, 2014, 01:38 PM
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Sounds good, I'll double check everything. Anything in particular I'm looking for?
Jun 27, 2014, 01:51 PM
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I could be wrong, but it sounds like it doesn't bypass/blowoff until you let off the throttle. It almost seems like once your gauge peaks/beeps, it drops off on the gauge, but by the sounds of it, the car still holds boost until you let off. I could be hearing things.
Jun 27, 2014, 01:57 PM
#6
A malfunctioning wastegate shouldn't cause absolute loss of boost... He should still be able to hold SOME boost atleast with a malfunctioning wastegate...
How are you controlling boost?
Yeah I was thinking it was super rich. I should probably shoot for around 11-11.5?
11.2-11.6 is the way to go. During spool it would be good to have low 12s then tapering to 11.2 at redline.
Sounds good, I'll double check everything. Anything in particular I'm looking for?
11.2-11.6 is the way to go. During spool it would be good to have low 12s then tapering to 11.2 at redline.
Sounds good, I'll double check everything. Anything in particular I'm looking for?
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Jun 29, 2014, 02:00 PM
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Compression test results are 155-155-162-162. Waiting for the JB Weld to cure and then I'll do a boost leak test. Checking BOV and Wastegate now.. Wastegate looked alright. I think the BOV is the issue. I ordered a IX MR OEM metal one, should be here in a week or so! Also, no leaks found during the test.
Last edited by spiniker; Jun 30, 2014 at 08:46 AM.
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