Need help white/gray smoke... but only with 3" cat-less exhaust
 

Hi I am just finishing up my 944 Turbo project which I built myself. I received the car in peices having never owned a 944 Turbo or driven one I am often times curious how one should drive and behave. Here is what his happening...

I am getting white/gray smoke out of the back tail pipe of my lindsey 3" exhaust but only after about 20 seconds of sitting and idleing but there is a twist keep reading....

Here is what happens: Come back from a drive around town and pull into driveway. It idles great and sounds great. About 20-30 seconds after sitting and still running it makes a breif regurgitating/quieter rummble sound and then I know what is coming next the white/gray smoke out the exhaust pipe. I can repeat this time after time. I do not see any smoke when I am driving and the car seems to run and idle great to me otherwise...but again never driven one before I rebuilt this one and modified it.....Dont jump to conclusions now.....Here is the catch. I put on the Stock 2.5 exhaust with Catylitic converter and no more smoke no matter how long I drive around and let it sit in driveway running...No Smoke! Kept the stock exhaust on for a few weeks until I recently passed emissions (the first time I took it in!)......Well guess what I just put the
3" lindsey cat-less exhaust back on yesterday took it for a drive brought it back home and yes once again the Smoke has returned after sitting and running for 20-30 seconds in driveway. ??? WHY???
Additional Info: Car seems to be running rich with dark black deposit on tailpipe...

Here is what I have on car: 1987 951 ,Rebuilt 2.5 Longblock, Tial 38mm WG, Lindsey/Garret medium sized turbo (not currently watercooled), Full 3" Exhaust Cat-less), MBC, New Vacuum Hoses, alluminum BOV medium spring, Adjustable Fuel Pressure Regulator, brand new 55# injectors, Max Chips, Lindsey Quad-MAF, Currently running 15PSI

You guys have been a wealth of information thanks for your help!

Can you take a video of the smoke? Big difference in potential causes if white vs. gray....

Have you installed a new O2 sensor? I had a car doing a similar thing and ended up being a bad O2. And another car that was bad seals in the turbo.

"(not currently watercooled)"

What do you mean? is it a water cooled turbo with out any waterlines connected to it? is the turbo DBB?

Isn't white smoke usually mean H20? ..water not sure what gray is?

not sure on the smoke, but just out of curiousity let me know if you want to get rid of the lindsey 3" exhaust, i can test it on my car and see if it smokes ;)

Thank you for your replies. I can take video just not sure if I can post video. The O2 Sensor has not been replaced but that sounds like a good place to start. Thanks PorscheDoc.

I just am wondering why aftermarket exhaust would smoke and the stock one does not?? It is not a DBB and has ports for both water and oil but currently is just Oil cooled. I had a problem wrapping the coolant neck around the large turbo and still clearing the intake manifold.....so left it off and converted to oil only. I am thinking the smoke is more white than gray but my gut is telling me it is not coolant but it may be running rich.

As far as grey smoke goes that would be fuel I think. Ive seen a 964, I believe it was, that had a bad cylinder head temp sensor (not coolant temp but cylinder head temp) and it was running very rich and smoking light grey/blue/white smoke. It smelled exactly like unburnt fuel though so have you smelled the smoke?

**Edit: but since yours only smokes with the aftermarket exhaust and we don't have cylinder head temp sensors (or do we?) my experience doesn't really help you. Unless its running rich enough that the catalytic converter burns the excess fuel with the stock exhaust and without the catalytic converter the excess unburnt fuel is not burnt and would create a grey smoke...

Thats an interesting theory about the Cat burning the excess fuel, but do cats burn any fuel? Anyone live in Connecticut want to stop by and check this car out. I am at a loss sometimes because I dont know how it should feel and have a million questions. The car feels fast but I dont know what stock feels like either. I just am amazed I put the thing together myself and it drives down the road...one step at a time I guess...

As slapsalot suggested, what does the smoke smell like? Burnt coolant, oil, and fuel have distinctly different smells.

How do you know he slapsalot? Anyway...I can smell the smoke but not sure what either smell is supposed to smell like. I am not a mechanic and this is the only car I have ever owned that smokes. Any tipps?

Hahahahahahahah :roflmao: no comment on that.

The job of the catalytic converter is exactly to burn excess fuel and other byproducts of combustion. And I don't know if I could describe the smell of unburnt fuel vs. water vs. antifreeze but someone else might be able to chime in on describing the smells...

The best I can do is, antifreeze smells slightly sour/sweet and unburnt fuel smells like fuel and **** mixed together.

They all taste like chicken!

Any sign of coolant levels going down?

Very interesting I suppose the cat may be burning the excess fuel. No sign of the coolant going down so far but have not driven it enough yet as I just got it registered. I may also try replacing O2 sensor. Thanks for your help guys. If anyone else has thoughts please chime in.

Is it using oil or water ? However sounds like a turbo leaking oil into the exhaust side . Need to do leak down test or just a compression test to see the cylinder condtion. I had one doing this a few years back ended up being a turbo .

Yes I agree the turbo may also be causing the smoke. I really do need to run some cylnder tests soon. The turbo was a used Garrett unit and not sure the condition before I put it in allthough there was no shaft play and upon taking it apart it looked in great condition. How did you determine your turbo was smoking anyway. Is there anyone way without replacing the unit first? C Anderson: Where did you get that front splitter?

See if you can see the Turbo Exhaust pipe. Either from above or below. You might be able to see oil seeping down the pipe or around the gasket. I had a similar problem and it was the rear seals in the turbo.

The splitter is from Texas Performance , He usually has them on E-BAY or look Texas Performance on line. He does a real nice glass job and sends with brackets to mount at the rear and the holes are pr-drillled .

Clifton

Well I don't know what happened but took car out for drive yesterday and allmost immediately major smoke began pouring out the exhaust. I could also see it when I drove the car and not just at idle. It was quite embarrassing and I felt like I was laying down a smoke screen like in that old game Spyhunter! I have been afraid to take it out since. I think there is just too much smoke for it to be coming from the turbo alone. I think the head must be blown. What u guys think? I just put a brand new headset on before putting engine in car but fear I may have over torque the bolts or folded the cylinders with fuel trying to get the car started after I put engine in. I do remember hearing a loud bang or backfire sound upon finally getting the engine started...thanks for the info on the front splinter I will check him out. Think i saw him on eBay but then he was no longer listing them....

Headset = headgasket

Folded = flooded

Sorry stupid auto correct on phone.

Check the inlet pipe to the throttle body to see if it is the cool side. if it's the turbo on the hot side will be hard to find. If its the hot side will most likely not smoke untill warmed up. is it consuming water or oil ?

Does not appear to be consuming either, water or coolant, then again I just have not driven it enough to tell. I might drain the oil to see if it mixing. Coolant looks good no milkshake mixture that I can tell.

Don't drain the oil, pull the dipstick and look at the bottom first.

Oil on the dipstick looks very clean. I know this engine originally had coolant mixing into the oil but I replaced the headgasket and oil cooler seals before putting it into my car. Hope there is not a crack in the head or case.

Sounds like turbo seals.

Any idea the shape or mileage on the turbo when you rebuilt the engine?

No I have no Idea how many miles were on the turbo. It is a Garret hybrid turbo I picked up used. No shaft play and it looked very clean. I even took both housings off and did not see any problems although I admit I am not really sure what it should look like inside. Could turbo seals leaking oil really give off that much smoke? The last time I took the car out it was smoking quite a bit...I felt bad for the guy behind me who had his window down at the stop light...!

New development: I just started the car in the garage it has been 48 hrs since I pulled the car in on Friday with it smoking out of control. Upon starting the car, cold, I noticed droplets of fluid coming out of the tailpipe and hitting my lawn tractor which is parked behind the car. After hitting the tractor it ran down the tractor tire and formed a puddle of liquid. This liquid had a green tint and I think it is safe to say that it is coolant coming out the tail pipe?? I picked it up in my hands and it did not have a strong odor eitehr way but I am leaning towards coolant and not fuel. Well I let it run for 10 minutes and it never smoked one time. The car did reach normal operating temps because the radiator fan turned on. How could water or coolant be entering the exhaust?? I am now thinking the exhaust burns the water/coolante in the exhaust when it become really hot and maybe steams? What you guys think?

Yea sounds like you are burning coolant for sure. Sounds like blown head gasket or crack in block. Taste some of the liquid then taste your coolant and compare. Coolant is very bad to consume though so just lick your fingers don't drink any!

Well I just took the car out again around the block and it is smoking again like crazy. I am tired of working on this thing after 3 months of putting it together and just got it registered now this. I am not looking forward to replaceing the headgasket with the engine in the car this time!!

When you did the head gasket last time did you check the head for flatness?

If you do repair it again i would suggest having the head both checked for flatness and pressure tested for leaks. Most automotive machine shops will do it for about an hours worth of labor. Well worth it for a engine that has blown one maybe two headgaskets.

No I did not have the head checked before I put it on and the gasket looked wet but no breaks in metal when I took the head off the engine last time. I think I might have over torqued the bolts down this time. I figured that the oil cooler seals were the culprit last time since the coolant was in the oil. I have a spare head maybe just use that one this time just as added security.