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502 Questions

Where is your temperature sensor located? How far from the mating surface? On any engine we run about 1.5 to 2 inches from the flange and we like to see 1250 to 1300 maximum. With all the different fuels and specific gravity, temps can go up or down with every tank full. In summer, they add alky to fuel to help reduce emissions (or so they say) during heavy driving months, plus the air is hotter and you can get by with crappier fuel like in higher elevations. In the winter, the air is denser and requires a higher spec. gravity. to do the same job. Sounds to me like a shiner cutting the stuff with cheap fill for more profit.
 
Some good avvice above. I'd also like to add here in hopes it covers the questions posted in some other threads. I personally don't like to see anyone use EGT readings as anything other than a comparitor based on a given well tuned engine. Every engine is different and sees different EGTs. There are too many thing affecting EGTs for there to a very reliable/dead nuts #, just a rule of thumb for a basic/conservative tune in my opinion. As stated about location of the thermocouple...It's distance as well as whether on the inside or outside radius of the pipe will make a very big difference. Also ignition lead, fuel used and whether it's N/A, N2O Supercharged or Turbocharged make big differences. All you are reading is the exhaust temperature at that point in the exhaust system, it by no means it dirrectly correlative to chamber temp. A couple good examples are timing and fuel mixture. late ignition lead (retarded) will send EGTs up, and the tricky one is mixture. Most people think that a lean condition shows more heat. It does tend to and lean definitely sends chaber temps up, but in the case of an overly rich condition the chamber will run cooler, but EGTS will go up due to flame in the pipes in some instances. So the way I do it..Get a tune and read your plugs..Once you have what you want, note the EGT readings that you can use as a baseline/comparitor. Now when you see it go out of range, you have a good indicator to go by....JMO

Felber
 
Mike I had a bunch of people tell me you shouldn't tune a motor by the plugs They said it was not technical enough so I gave up on the last EGT thread. In my opinion is what both treads above say. Fuel, and several other things can throw a wrench into the EGT's. Heck I was using a dyno and tried three different thermocouples in the same cylinder and all three gave me different numbers I looked at the plug and it was dead on so I went by the plug instead of the EGT's. I always go by the plugs nothing else is as reliable or accurate as far as I'm concerned! Fuel, EGT sensor distance, power adders, engine load and a bunch of other stuff will all change the EGT's however a plug will always be telling you what is going on no matter what is going thru the motor!
 
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