What colour for inside exhaust pipe?

[sawood12]

On every car i've had until until now i've always used the colour of the inside of the exhaust pipe as a very rough guide as to whether the engine is running rich or lean. I look out for a dark brown deposite. A black sooty deposite denotes a rich running car and a light brown deposit denotes a lean running car. By this rough guide my 944 Turbo appears to be running rich. I also noticed a black sooty deposit on the iside of my wastegate when I recently changed it.

Am I running rich?

Cheers,
Scott

 

[Guest]

ORIGINAL: sawood12

On every car i've had until until now i've always used the colour of the inside of the exhaust pipe as a very rough guide as to whether the engine is running rich or lean. I look out for a dark brown deposite. A black sooty deposite denotes a rich running car and a light brown deposit denotes a lean running car. By this rough guide my 944 Turbo appears to be running rich. I also noticed a black sooty deposit on the iside of my wastegate when I recently changed it.

Am I running rich?

Cheers,
Scott

Forget the exhaust pipe and check you plugs, better still get it onto a dyno with an exhaust gas analyser.

 

[jr2015]

Hi Scott,
Before doing the above go out when its quiet and drive like you stole it for 100 miles,do the above then repeat regularly.Not getting an engine stinking hot from time to time does it no good at all.
works for mine!
jr.

 

[Diver944]

ORIGINAL: sawood12

I also noticed a black sooty deposit on the iside of my wastegate when I recently changed it.

Well both the inside of my wastegate and exhaust have black sooty deposits. I've never heard of this method for gauging the mixture but it is impirtant for Turbos to be running correctly. Too lean and you will have head gasket problems, too rich and it will lead to piston wash and early engine wear.

The only cast iron way I know to check your mixture is either with a wideband O2 sensor or a Dyno run on a rolling road that can also measure the air fuel ratio and boost pressure against RPM.

I won't hijack this thread, so see the other one about this years 944 Dyno Day

 

[Fen]

When I saw the subject I thought you were going to paint the inside of your exhaust [8D]

A grey colour is what I always thought was correct (although browny grey is near the mark) but if I cast my mind waaaaaay back my Turbo used to be sooty too. I think maybe after a remap it was better but then it was running pretty close to maxing out the injectors just to keep the fuelling right by then.

 

[John Sims]

A grey colour is what I always thought was correct (although browny grey is near the mark)

On "normal" cars this was my experience if you got them good and hot, and gave them a damn good thrashing. I'm not sure this holds true with the Turbo though and Beaky seems always to be black, even after Wayne thrashed him to within an inch of his life.

Having had a similar discussion with someone a year or so ago we did conclude that it was very unusual to see a grey exhaust on any car these days. The last one I remember was on one of my 944's after a track day, but I am pretty sure it was my Lux not the Turbot.