What does the turbine soot color tell us?
 

TLDR: My friend is in the process of rebuilding his turbo (TD04H-15G, from a greddy kit) and the turbine is white, bordering on a little tan. Curious what this tells us? My feeling is that we may be running it a hair leaner than we think/should be?

I have searched and can only find info on diesel stuff, which I am assuming doesn't really apply to this...

Specs on car:
1.6 BNC
Greddy TD04H-15G
Aretech Greddy replacement manifold
Flow Force BYOI kit
ebay intercooler
ebay BOV
2.75" divorced down pipe to 3" with big magniflow resonator
90-93 FM Link ECU (Yeah, yeah, I know. It works, not as good as MS)

tune lands it in the 10-11afr range up top, boost level has been around 13psi. Timing map is the base map on the Link.

Reason for the rebuild is that the bearings finally went in this old turbo and let the compressor wheel start to lightly contact the housing.

https://cimg0.ibsrv.net/gimg/www.mia...1ff60e748b.jpg
https://cimg3.ibsrv.net/gimg/www.mia...7d60af8c25.jpg

Was the engine/turbo consuming any oil?

It did occationally give a puff on shifts. But not always. No major signs of oil consumption. It leaked though.

PCV system is just a 323GTX PCV to the intake manifold and then a breaker on the other side.

My turbine tends white also. However, at tailpipe, all is black.

White or light gray is Ash. Ash is product of soot being raised to a temperature above 1000 degrees Fahrenheit in the presence of available oxygen. 1000 degrees Fahrenheit is well within the normal operating temperature of exhaust gases of a gasoline engine. Soot is a natural byproduct of the combustion of gasoline but excessive soot can indicate a rich condition. Excessive soot can also be indicative of the burning of oil.

That's precisely why I asked about oil, given the AFR readings are correct. Another culprit might be EGTs (timing?) but then again something needs to be burned off to leave that residue.

Super lean would suprise me since the way tha carr is treated, it would have melted by now.

Oil burning or rich rhnning is the likely culprate. It was run stpud rich for a while (to where you could smell the gas in the oil after a bit, and the plug would foul). Once I got that sorted for him it ran in the above AFRs. That likely turned it white. I figured you guys would have the answers here.

I would be surprised if the O2 sensor was that far off to be lean (innovate).

I don't know, I'm too weirded out over that picture of his hands in those gloves. Anyone else reminded of old episodes of Dexter?

It looks normal to me.

Doubt you can take any real info from the color, turbos see all conditions, lean off the throttle, periods of rich, tons of heat, etc.. Like with plugs you'd have to do a WOT pull on a new turbo and then immediately kill the motor to get an ACTUAL reading. Which is pointless on a modern engine.

Me too.

IMHO, if you want to know if the engine is running rich or lean you use a wideband -- that's what it's designed to do. Trying to infer that kind of information by looking at the color of the spark plugs or the turbine wheels is like predicting the future by reading chicken entrails or tea leaves.

--Ian

:rofl:

It was more I have never seen one this color and wanted to make sure it was in the range of normal.

looks normal to me. pretty much all turbos I have looked at on gas engines have looked similar. It gets real hot right there.

Hey, sometimes predicting the furture is useful. :P

We've actually caught issues that could have destroyed high dollar engine builds by pulling the spark plugs immediately after some dyno pulls.

Let's say the plugs on cylinders # 1, 3, & 4 are good, but cylinder #2 plug shows it is running lean. Despite this, engine is running 11.3-11.5 AFR on the wideband and the dyno sniffer shows the same.

Well, the injector in cylinder #2 wasn't flowing correctly, so it was around ~13-14:1 AFR. Cylinder #1, 3, & 4 is running richer at a ~10:1 AFR. This is hard to catch, since most builders put a single wideband post turbo. I've only heard of top dollar builds running individual cylinder widebands.