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0 360 - Lean fuel, EGT question

C

Canuk

Well-known member
Reading another post got me wondering if it is possible for EGT's to get hot enough to melt a piston if running a too lean fuel/air mixture at WFO.
My engine experience is mostly on two strokes.
To be safe, and to produce max power, I usually tune the high speed fuel/air mixture so that EGT's never exceed 1300 degrees....above 1340 pistons melt.

Can a lean fuel/air mixture drive EGT's to the point of melt down on these engine technologies?
 
Yes, you can run a mixture so lean that it will burn a hole in the piston like a blow torch would. I did that on a 1600 CC VW engine once. I was trying to get just a little more power. I did too, for a short while and then lots of smoke. I had to replace the piston and the cylinder wall. The new parts were less than $100. Cheap little engine to work on.
 
Can the tip of the spark plug (white) be used an indicator or will it always be a bit black from the oil blow by?
I couldn't even begin to count how many times I have done it on two strokes....they too are quick and cheap to fix, unlike this beast.
 
Is it fairly easy to install an EGT sensor and gauge? I've seen they are suggested for my powerstroke too, but I've never gone past reading. Seems like drill and tap exhaust headers, and put a sensor in, and wire to gauge?
 
Thanks, I have installed a number of them on my performance two strokes. Given the unit I have has been running for a few years with the current set up I'm going to assume it is safe. If I hear a lean popping after it has been warmed up it may change my mind.

On two strokes we adjust the fuel/air based on the colour of the spark plug tip...ie black is too ritch, white is too lean, light tan is perfect. It also has to be checked at various temps as they run much leaner at -30 than +30. I suppose the 0-360 would be the same.
I don't seem to be able to get much info from the plug tip as I suspect blow by is changing the colour to black.
EGT's are kind of like measuring things after the fact, only good as a general indicator, spark plug tip colour is instant and more accurate.

I also just installed an air box over the K&N air filter to keep snow out and to reduce icing, I'm sure it is making it run slightly restricted and therefore richer.
 
o2 sensor is what you need to monitor air/fuel. A pyrometer is nice also but the o2 sensor will tell you how your mixture is.
 
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