black smoke under load. boost leak?

[Ninja_Bear]

this just randomly started about a week ago, where whenever my car is under load, say taking off up a good hill, or just punching it in a higher gear, anything that requires boost. The car will build boost, and the car will pull hard only for a brief moment then it feels like I just hit a brick wall in the powerband, the car all of a sudden loses all toquey-ness, and black smoke starts to come out the back. I took the car apart this weekend, and ran a compression test 150+ in every cylinder and almost no play in the turbo. The engine runs smooth like normal, and idling and under normal driving, the car runs perfect, it only does it under load, and even then, the turbo seems to spool just fine (you can hear it spool like normal).

Does this sound like boost leak? The smoke is black (no blue in it)? Im not running hardpipes, and the hose clamps seem sketchy to me.

any help or advice appreciated.

thanks

Brandon

[gregc]

Bad fuel pressure regulator?

To check your intake for leaks:
Take a PVC cap the same diameter of your turbo inlet
Tap the cap and put a airchuck in it for an air compressor
Use a piece of hose and a couple hose clamps to put the cap on your turbo's inlet
Hook the aircompressor up to it and listen for leaks.

[talntid]

Boost leak would possibly cause this because the ECU is still putting in enough fuel to compensate for the air the Turbo is creating - but if the air is leaking out somewhere, there will be too much fuel for the air that is actually entering the engine. Check for boost leaks as Greg recommended. Black smoke is unburnt fuel.

Also, are you venting to the BOV to the atmosphere? What color is the back of your bumper above the exhaust? Is it black? If you lightly get into the throttle to build boost, does it happen? How much boost are you running?

[Ninja_Bear]

Eric, Im running stock boost pressures on a stock engine, stock recirculating BOV, if I lightly build boost, it doesnt smoke/choke until I hit around 3-4lbs. The bumper is black around the exhaust.

I totally agree with your strategy, but now to find the leaks... I'd like to go hardpipes, but dont have the cash at the moment.

[talntid]

Make a boost leak tester: http://vfaq.com/mods/ICtester.html

This article is for a DSM, but with a little measuring, you can make one for your turbo. It makes finding boost leaks simple :)

[sefus]

To add to Gregs boost leak checking steps,*a*soapy solution sprayed around your couplers will bubble up. Little easier then doing the hearing test for the small leaks anyway.

[talntid]

right - and don't try to start the car with the checker installed.

[gregc]

Make a boost leak tester: http://vfaq.com/mods/ICtester.html


Haha... Check the Talon Digest archives from 1997-98 (can't remember which year it was) and see who came up with that idea to check for leaks. ;)

[talntid]

link?

[ntrcptr90]

It sounds to me like you have a MAP going nuts. Try switching that with a known good one. MAP's have a tendency(sp?) to have issues with the moisture that can build up in them, freezes. Usually factory boosted cars is what this occurs in.

[talntid]

do a boost leak check first, though. :P

[96gsx]

Which car is this?

[Ninja_Bear]

88 supra turbo.

[gregc]

link?


http://www.dsm.org/archives/t/1998/02/19980220.txt

Closer to the end. Post #56

[Ninja_Bear]

I feel retarded, should have seen it earlier, theres about a half-inch long tear in one of my intercoolers cores. *punches self in face.

New intercooler goes in this weekend I guess. I already picked up the IC froma friend, but wasnt planning on putting it in til this weekend. Meh...

[talntid]

Boost Leak check would have shown that ;)

[Ninja_Bear]

it did.

[talntid]

:) good - have fun

[Ninja_Bear]

All boost leaks finally gone. Car spins through 3rd. Yay!