Combustion Temps

[fixmyevinrude]

I read in a post from Dhadley that he would not use OE Pistons in a 90 degree looper unless he was sure the Combustion Temps were correct. How does one check the Combustion Temps?

 

[Dhadley]

Re: Combustion Temps

We use an EGT (exhaust gas temp) gauge. If your ring locating pins have come loose or out, the combustion temp is too high.

 

[fixmyevinrude]

Re: Combustion Temps

What causes the combustion temps to be high and how do you correct it? Engine running to lean and perhaps needs larger carb jets? Just out of curiosity could you tell me a little more about the EGT gun and how you use it? Is it done on the water and if so how? Is it infra red? Where do you point it? As far as I know my exhaust comes out thru the prop hub in the water. I am finding these engines extremely interesting but I am also finding out how little I know everyday.

 

[Dhadley]

Re: Combustion Temps

Combustion temps are effected by many things - octane, timing, lugging, dirty carbs, air leaks, fuel restriction, spark plug heat range, air density & temp and so on. An EGT gauge has sensor(s) that are placed in the exhaust passage as close as possible to the combustion chamber. There are several styles.

On a stock production recreational motor the best thing is to make sure you're running the motor as it was produced with fresh 87 octane and a quality TCW III oil. That includes making sure it's propped out (set up) to turn at or near the upper rpm range, the carbs are clean and assembled correctly, you're running the correct Champion plug (2 stroke carb'd) and the timing is correct.