Hi thanks for the comment, No I haven't burned down the piston ... yet when I saw the high temp I backed off quick ( I did a compression test and all still 127 PSI. The probes are about 6 inches from the piston. The plugs lookm OK to me But then that is why I put in EGT's because I have no experience in reading plugs !!. I am using synthetic oil and the "pump gas" here is 96 Octane so they burn pretty cleanly which doesn't help reading ?.
GlennM, those temps. are a little high, with your compression, and if your motor is stock. You should also put your probes about 8"-9" from piston face or 6" from cyl. flange for most accurate temp. reading (hottest). I've also had difficulties reading plugs unless they are at the extremes (black/rich&oily or white/lean). I do however like reading piston wash with a cyl. light (see attached pic. of my piston wash which is safe and I had egt. temps. of 1250-1270 F for that wash, with probes at 8" from piston). The more clean piston you see and the less carbon you see, means you are running richer, the more carbon (black) and less clean piston (shiny metal), the leaner it is running. Also, wash has to be measured with a long wide open stretch (at least 1200'- 2000'
then shut down and stop quickly to measure wash.
Hope this helps!
Use the piston wash methond to get your baseline jetting. This will give you a baseline for correct jetting. Then you can calculate the approx. jet for the day. You can use the EGTs as a SECONDARY indication of engine condition/ performance.
I have always said. I have only burned up one motor since I have been sledding, and it had gages on it. Since then, I have gone by wash. EGTs are needed on a engine that is very picky or finecky.
This is right out of the race manuallace probe 100mm from piston: Detonation=720 celcius(1330 farenheit) (E.G.T's are not absolute.Engines have siezed with EGT's in the allowable range) I would use piston wash to verify my jetting and use the EGT's as a safety measure.
if your running above 1300 and still not burning down, then your probes must be too close to the pistons. i would do like everyone else says and find a baseline for your sled using traditional techniques and then go from there. also, i find the bigger triples(800 and up) like fuel. Also, i have not noticed any gain from running these engines at 1250 rather than 1170 or 1150. a lot of the times I have found the sled sort of falls off at the end of a drag race when you run higher temps. try a few different things with your sled and see what happens.
also what sort of gauges are you running, analog or digital?
The engine is quite new and still less than 5 hours on it, so mI guess that may be the compression hasn't come up yet ?. I looked in the service Manual and it explained when to do a compression test but didn't give a reccomended PSI ?. So what is correct compression ??
As to the gauges they are digital so quick response
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