Just need a little guidance. Any help will be greatly appreciated.

Twin turbo 6.0.

Made 7 passes last weekend. The last two passes put out a cloud of smoke from both sides. I had no idea. The car ran great and there was absolutely no degradation in performance. In fact, I broke out on the last run.

Any help at all on what to look for will be greatly appreciated.

 

What color was the smoke? Afrs on decel? What’s your oil drain setup from the turbos consist of?

 

Thank you for the reply.
Hard to say the color. Let's say blueish gray like oil.
I was not capturing AFRs that night. Had a soft proven tune in it. Probably should have been.
Drains are #10 straight down to the pan.

 

Here is a video. Hard to see much, but explains it.

 

Decel may cause high vacuum which sucks oil into baffles, past valve seals, through intake seals on some engines, can even pull oil up from the crankcase into combustion chamber through rings and rip the rod bolts apart.

My recommendation is
1. Don't strongly decelerate at high vacuum, leave the throttle open enough to keep such high vacuum from forming
2. monitor crankcase pressure, if using a vacuum pump you will monitor the supplied vacuum. If not, considering logging a 1 or 2bar map sensor on the crankcase into ECU so you can see when pressure rises over atmospheric which drives oil out of the engine creating smoke like that.
3. Consider washing out the baffle system, valve covers and valley cover or wherever they are depending on the engine. Get a fresh start and monitor the crankcase pressure from that point.
4. Use decel fuel cut to rule out fuel issues

 

Thank you for all of the information.

I will monitor crankcase pressure, let off easier. Did a leak down test this past weekend rule out ring problems.

Everything checked good. Have a little bit of oil showing up on the compressor side of one turbo. I'm afraid that I might have a compromised seal. Will investigate.

Thank you for taking the time to respond and give advice. I will check all that you suggested.

Thanks again!

 

The PCV system determines crankcase pressure. On wet sump application without a vacuum pump the target pressure for performance applications is 0.75"Hg to 2.5"Hg usually I try to hit at least 1.0" Hg or 1.25" Hg at wide open throttle.

The crankcase vent should be tied into the compressor inlet. Oil is beneficial to the compressor wheel, a tiny film of oil is protective, will help trap debris, will lubricate the ferrous materials (e.g. compressor hardware and shaft) and will help seal the wheel. All OEM Original Turbocharged engines use this PCV system- the venting is done into the air filter tube which feeds the compressor wheel in order to provide a slight oil film to the wheel and drop the crankcase pressure at wide open throttle.

The other side of the engine PCV system is the PCV valve which connected to the intake manifold.
The OEM Chevrolet pcv valves will leak boost into the crankcase. I do not know which engine you have but this is a common trouble spot. You must use a high quality PCV valve worthy of forced induction such as Toyota Supra 1998 Twin turbo PCV valve. I use one in-line with the chevrolet PCV Valve on my engine for example. The high quality PCV Valve will shut tightly under boost and prevent boosting the crankcase.

If you have not done so already, all forced induction engines require a pressure test. I will show you how to pressure test and how to measure crankcase pressure with these videos




If you pressure test, it will show the weaknesses in the PCV system and intake plumbing which can be corrected.
Then the crankcase pressure test will show you whether you have PCV at wide open throttle, or not (Pressure below atmospheric is PCV). once you dial these crankcase pressure and fix all the pressure leaks, the engine will run like a factory engine, no smoke, no smell, no burning oil, etc... if the setup is capable of it, e.g. no oil line return issues, no windage issue on the oil return, no oil sump issues derived from aftermarket pans, the basics must still be covered.