Searched for this, didn't find anything, maybe I just didn't get the terms right, anyways...

CLIFFS: the car just doesn't like doing 75+mph for an extended period of time, which isn't a big deal as it rarely happens, but I would really like to know what causes this so I can fix it. Any ideas?

Went for a drive on Saturday, going to Omaha (I'm in Lincoln, about an hour apart) and I'm on the interstate doing 75-80 mph for about 5 minutes or so, I've already been driving for twenty or so, when I start seeing smoke coming up from the transmission tunnel. I start thinking oh **** an oil/coolant leak, pull off to the shoulder, get down and check it out, looks like something is leaking onto the downpipe/catless midpipe. It looks clear, but I'm not getting any smoke from the engine. Well I have to go another ten miles or so before I hit an off-ramp to turn around and since it stopped smoking and I have my fire extinguisher I keep going. Doing 75-80 again (damn no cruise control) and it starts smoking again, so again I pull off, but now I don't see anything leaking.
I still have a few miles to go and the speed limit has dropped to 65, so I get back on the interstate (no traffic luckily) and doing between 65 and 70 I don't get anything. I call one of the guys I'm meeting up in Omaha (who also has an FD and has been through just about every problem we seem to face) and he says that it's probably a coolant leak from the turbo coolant line. He says if I feel comfortable going the rest of the way I should try to make it and we can take a look when I get there. Well it hasn't started smoking again as I'm cruising around the 65 mph mark so I tell him I'm turning around if it smokes again. I get back to a 75 zone so I speed up, and I've been doing 65 for ten minutes or so, but I hit 75 and within 3 minutes, I start getting a little smoke, I've come to an off-ramp and as I'm going up it, the second my speed drops below 70 the smoke is gone, I pull off, and get under, once again, NOTHING!
At this point I have no clue, but I'm closer to Omaha now than Lincoln, and I've noticed the trend that it only smokes when I've been doing 75 for a bit. So to test this theory I get back on the interstate, proceed to do 75, and sure enough, 5 minutes or so later, smoke. I get to an off ramp, let it cool down, and just get back on, cruise around 65 the rest of the way (about 30 minutes) no smoke.
I get to where we're meeting, he checks it out, looks like some oil at one point was dripping onto my downpipe, but I knew this as I had changed the oil feed and return line gaskets on my stock turbos shortly after I bought the car because I KNEW those were leaking, and I also know now they're not.
Travelling around 65 for the rest of the time I can not get it to start smoking again. However we do a few short little bursts to 100 or so and it doesn't smoke. This also happened to me the last time I drove the car up to Omaha (late August), but it hasn't smoked since (about 600 miles of driving and some really hard driving too).
My theory is the car just doesn't like doing 75+mph for an extended period of time, which isn't a big deal as it rarely happens, but I would really like to know what causes this so I can fix it. Any ideas?

and I know driving a car that is smoking is a bad idea, which is why it's currently sitting in my garage. Mods are non-sequential, FMIC, efini y-pipe, PCV delete, full exhaust, no cats, PFC, EBC, wideband and boost controller. 15k on current motor, 65k on the car.

I do not know the condition of the clutch/flywheel.

Sorry about the length, but I figured I should tell you guys as much as possible to help you help me.

 

this is strange. maybe its coming from your transmission? change the fluid, might help? i really dont know.

 

Did you check your fluid levels after all of this? If the coolant level is low, then you will know it is a coolant leak. Doing a pressure test on the cooling system should recreate the leak, if it is a coolant leak.

 

I'll check these, I've got Saturday free. Any other ideas?

 

Kyle,
Not sure I understood you correctly but if it's from a leak in the area of the transmission, the only source I can think of off-hand (on the exhaust side) would be from the shifter reservoir or the shift-select spindle. I guess it could be leaking from btwn the transmission and tail-shaft housings, but I've never seen one do that.
Speculation...but the speed variable may just be related to blowing whatever is leaking onto the exhaust. At lower speeds it's just dripping onto the ground and missing the exhaust.
At any rate, I know it means another drive but if you wanted to come here we can put it up on the lift to look. Give me a call.

 

yea, i really dont know, just throwing an idea out there. but he did say that the smoke is coming from the transmission tunnel so it could be more then just something leaking onto the exhaust.

 

thanks Jim, I'll have to keep an eye on the weather and find a weekend that is nice to come up and we can figure it out.

 

I had a similar problem when I bought my car where it would smoke around the transmission tunnel after driving extended periods of time. Turned out to be a loose banjo bolt on one of turbo oil inlet lines. Oil would ooze out of the gasket and eventually drip down the downpipe and burn off. Sounds like you'll need to remove the y pipe and the inlet piping to the turbos in order to find the source of the leak.

 

thanks goddard, I don't wanna pull that **** off again, but seeing as how I just replaced the oil feed and return line gaskets and ****, this wouldn't surprise me in the least.

 

update: I haven't been able to drive the car in a while, popped the motor last April. However while removing the motor I noticed that the split air pipe was still in place. The previous owner removed the emissions system, or most of it, as this was still connected to the LIM but open at the other end, right beside the midpipe, and right beneath the hole in the transmission tunnel where the shifter is located, and the smoke came from. I believe this was the culprit, but since there's no way to find out if this is correct at the present time and when the car goes back together I'll be using an excessive LIM I won't be testing this theory. If someone else wants to they are more than welcome.

This also may have explained my continuing idle problems and low power at 13 psi with full bolt ons (259 rwhp) plenty of pressure could've been lost through here.