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Discussion Starter #1
So I finally got my cx racing dual core FMIC all hooked up, as well as cxracing pre-turbo pipes, and put the car back down on four wheels. It idles steady at -9.1 or 9.2 PSI(18-19 in/Mg), but the second I go into boost the turbos start SCREAMING to the point where they sound like a supercharger and the car falls right on its face like it hit a wall. I've gotten it to make around 4 psi of boost before I got too scared and got off it. Also during the process of the FMIC install I eliminated the clutch vacuum reservoir and the charcoal canister and capped off their respective lines.

The CXracing kit I got is the one with the BOV included(currently vented to the atmosphere) so it doesn't come with a bung before the throttle body, as a result I had my EBC hooked up after the TB initially to test it until I could get one welded on. I figured that might be the problem and disconnected it and nothing changed. My turbos didn't make any sounds out of the ordinary before this kit was installed, and when doing the pre-turbo pipes I checked the compressors and they had zero shaft play and looked almost new(I've attached pictures) so I don't think my turbos are bad. I'm obviously going to do a boost leak test, but I don't think a boost leak will cause this problem. Any ideas?
 

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Boost leak test is certainly where I would start.

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100% leaks

-sent from my Galaxy Note 9
 

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Discussion Starter #4
Would a leak really explain the noise though? I mean it is a very loud noise that only occurs when under load. Revving in neutral doesn't produce the sound whatsoever. I'm almost tempted to say it sounds like a turbo trying to compress air into a blockage or something. I'll try to get a video and log of it.
 

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Simply said, leaks cause the turbos to work harder to produce the same boost regardless of setting.
 

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Would a leak really explain the noise though? I mean it is a very loud noise that only occurs when under load. Revving in neutral doesn't produce the sound whatsoever. I'm almost tempted to say it sounds like a turbo trying to compress air into a blockage or something. I'll try to get a video and log of it.
I bet it sounds like pressure forcibly escaping a loose coupler... As has been said, Pressure test.
 

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Discussion Starter #7
Alright so I did a boost leak test and found a few small leaks that I fixed. I got a little more brave and the car will make boost(up to 9psi at 3300rpm is as high as I went), but the turbos are still super loud. A log doesn't really show anything eventful, just small knock counts(1-3) right before crossing into boost which was an ongoing problem before the FMIC. I did notice there are a few areas where my TPS is reading an even 20% instead of having a 8 decimal places like the rest of the readings. I'm also posting two videos that were taken from inside the car with windows down, to give you an idea of what they sound like. Any ideas?


 

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lol that must make for an amusing albeit annoying drive. You mentioned eliminating the "clutch vacuum reservoir" but to what extent? Did you just cap off the hardline adjacent to the battery and TB, or did you delete the hardline alongside the firewall too? The reason I ask is you should have either retained both booster hoses with check valves or at least consolidated them into sharing one. Leaking coupler and/or vacuum line aside, the sound in the video reminds me boost reaching the clutch/brake boosters.

How much pressure did you test with, and how did you find the leaks? i.e. listening/feeling for air escaping or soapy water solution

//edit// How did the included BOV test? That could be another suspect.
 

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Discussion Starter #11 (Edited)
lol that must make for an amusing albeit annoying drive. You mentioned eliminating the "clutch vacuum reservoir" but to what extent? Did you just cap off the hardline adjacent to the battery and TB, or did you delete the hardline alongside the firewall too? The reason I ask is you should have either retained both booster hoses with check valves or at least consolidated them into sharing one. Leaking coupler and/or vacuum line aside, the sound in the video reminds me boost reaching the clutch/brake boosters.
You called it that I just capped the hard line near the battery/throttle body, so I followed a guide on here to delete the hard line and merge the brake booster and clutch booster into one. Using the stock check valve hose for the clutch booster(sucking direction plugged into side of plenum) I put a T connector in, and ran a line down to the brake booster, and another line down to the clutch booster, then capped off the brake booster line directly on the back of the plenum. I fired up the car and my LCDBC was showing it idling at -2.1psi. So I somehow managed to lose 7psi of vacuum compared to yesterday.

Thinking I did something wrong I basically just put it back to "normal" without the hard pipes. So stock brake booster line with the check valve back on the plenum nipple, with a line running directly to the brake booster. For the clutch booster I did the same thing, stock check valve line connected straight to the clutch booster. Fired it up and still showing -2.1psi. Went back to the "deleted" version, still showing -2.1psi but took it for a drive this time. Goes into boost like normal showing what I believe is the correct value(got to 10 PSI of boost), BOV works as normal, and the sound that started this whole mess is still there. The brakes and clutch also seemed to work just fine, with the clutch feeling no different from normal after start up. This leads me to beleive that it is hooked up correctly...so now I'm at a complete loss.

How much pressure did you test with, and how did you find the leaks? i.e. listening/feeling for air escaping or soapy water solution

//edit// How did the included BOV test? That could be another suspect.
To be completely honest I've never gotten the system to actually hold pressure even before the FMIC, but when I do it I use soapy water and spray the fuck out of everything. Everything up to the throttle body isn't leaking as best I can tell. There is a leak at the BISS that's been there since I owned the car so I know pressure is making it that far at least.

Edit: For curiosity sake I tried running it off the brake booster line and nipple to see if anything changed, and got the same -2psi of vacuum.
 

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Discussion Starter #13
Okay so update: The sound is gone, bboyalan called that it was the BOV. It was leaking at the BOV gasket. She sounds and spools like a dream now but the vacuum is still showing -2.3psi at idle.

Even though I didn't touch the fmic piping when removing the hard lines, I rechecked it again and it is still good. The brake booster nipple on the plenum is capped, and the clutch booster nipple is operating the clutch and brake boosters still. Both the brake and clutch pedals feel perfect. Car also seems to idle perfectly, here is a log of it idling. The dip from 812rpm to 750rpm is when the fans kicked on.

Any ideas?
 

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Okay so update: The sound is gone, bboyalan called that it was the BOV. It was leaking at the BOV gasket. She sounds and spools like a dream now but the vacuum is still showing -2.3psi at idle.

Even though I didn't touch the fmic piping when removing the hard lines, I rechecked it again and it is still good. The brake booster nipple on the plenum is capped, and the clutch booster nipple is operating the clutch and brake boosters still. Both the brake and clutch pedals feel perfect. Car also seems to idle perfectly, here is a log of it idling. The dip from 812rpm to 750rpm is when the fans kicked on.

Any ideas?
Where do you have your boost reference hooked up?
 

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Discussion Starter #15
Where do you have your boost reference hooked up?
Boost reference hasn't changed since I initially hooked it up, and it is the nipple directly to the right of the brake booster nipple off the plenum. When I cross into boost my LCDBC seems to be reading correctly. I also noticed that at it's current state of saying -2.3psi turning on the AC doesn't affect the reported vacuum. Prior to this I'd have -9 to -9.5 vacuum at idle with no AC and with AC on it would dip down to -8 to -8.5psi. There is a setting in the LCDBC to reset the pressure sensor, which I did and nothing changed.
 

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Boost reference hasn't changed since I initially hooked it up, and it is the nipple directly to the right of the brake booster nipple off the plenum. When I cross into boost my LCDBC seems to be reading correctly. I also noticed that at it's current state of saying -2.3psi turning on the AC doesn't affect the reported vacuum. Prior to this I'd have -9 to -9.5 vacuum at idle with no AC and with AC on it would dip down to -8 to -8.5psi. There is a setting in the LCDBC to reset the pressure sensor, which I did and nothing changed.
Did you recently switch MAP sensors..? I was under the impression the internal sensor on the LCDBC did not measure vacuum, only boost. I use a GM 3bar sensor and get vacuum readings.
 

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Discussion Starter #17
Did you recently switch MAP sensors..? I was under the impression the internal sensor on the LCDBC did not measure vacuum, only boost. I use a GM 3bar sensor and get vacuum readings.
I haven't changed anything. I know some of the earlier versions couldn't measure vacuum, but the current versions can as they use a different sensor.
 

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Discussion Starter #19
You mean check the LCDBC with a vacuum pump to compare the displayed value vs what is on the pump is showing? Or check the source nipple itself?
 
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