Guess the condition

drmatera · 04-08-2011, 04:09 PM

A video for your viewing pleasure. We broke in my mechanic's new Dynapack dyno with my old clunker.

Note the puff (2:17) of smoke during the pull. Any idea's on what it may be?

IMR-Merlin · 04-08-2011, 05:34 PM

waste gate opening?

WERK I · WERK I's Garage

Looks like oil smoke. One possibility is a lack of scavenging effect from the turbo sump while the car was idling for those extended periods. My guess would be the oil backed up from the turbo sump tank and leaked out the seals when the engine went on boost......just a guess.

drmatera · 04-08-2011, 10:57 PM

Werk1 - interesting comment, my mechanic said the same basic thing

drmatera · 04-08-2011, 11:03 PM

Merlin - also an interesting point, we thought maybe on the boost ramp up it hit some pretty rich cells on the map, but oil kind of seems more like the culprit

jsveb · jsveb's Garage

A friend of mine followed behind me yesterday. After cruising (low RPM). I floored it and he said, just after I took off the car gave a puff of smoke. I didn't see it, but he described it much like this.
My 930 is CIS. The car drove fine, and I didn't feel a thing.

pkracer21j · 04-09-2011, 07:17 AM

looks like fuel...mine will do that if i sit on the boost threshold in the midrange.

JFairman · 04-09-2011, 08:43 AM

Never heard a missfire with it. The motor sounded consistant and linear as the revs climbed through the quick puff of smoke. That and the light color of the smoke puff makes it look like oil smoke after combustion which would be from the turbo.

If you've only seen it once I wouldn't worry about it.

Remove the turbo charge pipe and see if the insides of it and the intercooler are misted with oil.

If it becomes more often or consistant also take a look at your sparkplugs for burnt oil deposits and the sparkplug threads for wet oil.

If it was from a worn exhaust valve guide which often wear out fast in these motors you will see the burnt and wet oil buildup in the exhaust port around the end of the valve guide after removing the headers... and you will be able to rock the exhaust valve spring retainer sideways a little with a screwdriver gently used as a prybar against the inside of the cam tower while the lower rocker cover is off.
Be gentle so you don't bend the valve stem when doing that.

If it was rings it seems the oil smoke would be more consistant. When intake valve guides or seals leak oil the oil deposits are usually more on one side of the spark plug and on the side next to the intake valve.

Smoke from a rich fuel mixture is usually black or gray and yours looked more whitish like oil smoke... and I don't know what fuel you're using here.
Oil smoke is usually a faint blueish white but that shop is under flourescent light which has a weird funky color spectrum that may not show the smoke as blueish white on this low rez auto white balance video.

IMR-Merlin · 04-09-2011, 12:32 PM

Just watched it again, looks like oil or something in the intake tract. It comes out of both sides of the exhaust at the exact same time.

drmatera · 04-09-2011, 01:00 PM

yeah, the engine pulled smoothly thru, I'm thinking it may have been fuel..

also did some back pressure testing today. We built a make shift exhaust pressure gauge out of copper tubing and a cheap oil pressure gauge. We had a feeling back pressure was high on this turbo and confirmed it today. At 1 bar of boost i'm seeing 38psi of BP. Thats a PR of around 2.6:1 which is not acceptable. I think 2:1 is just tolerable and 1.5:1 to be a good target. I don't think a larger exhaust housing will help much as the wheel is most likely the culprit.