08-08-2018, 03:08 AM
I try to avoid recommending a "max" for any type of temp measuring instrument for the simple reason that they are all reference devices and should not be used to dictate the temp you run your engine. The readings on both EGT and CHT are going to be different for every engine/driver combination based on atmospheric conditions, track layout, driving ability, handling characteristics and so on.
For example, my Mc 101 powered Bug Sprint typically shows 375-385 each year at Adams in early February when the engine is tuned to run clean all the way around the track and produces a nice medium brown plug color on the porcelain. The same exact package runs at 435 at NCMP in the middle June tuned to produce the same plug readings. The gauge should not be allowed to dictate the way you tune the motor. Feel and sound are both more important than the temp reading from any type of gauge. I always recommend starting the day with the gauge turned off, the jets set very rich and a new plug. First session should be devoted to tuning the carb to get it so the engine breaks into a four cycle right before you lift at the end of the longest straight. Once that setting is found the kart should be driven hard all the way to the pit entry and then slowed quickly and the engine shut off as soon as possible..... a procedure often called a "plug cut". The engine should not be allowed to load up or idle. Once off the throttle to leave the track stay off and get the kart stopped push it back you your pit and remove the plug to get a look. If the plug looks close to right then the next session you fine tune to get rid of the four cycle and once the tuning is done turn on the gauge and see what it shows. That reading is now your reference point for additional fine tuning. The number may be a lot higher or lower than you expect to see yet you will not let the gauge dictate where you run the motor as you sorted out the tuning the correct way before turning the gauge on. Once you have the reference number you can use it to creep up on possible performance gains, be warned if the temp begins to climb faster than you normally see and so on.
Steve O'Hara
For example, my Mc 101 powered Bug Sprint typically shows 375-385 each year at Adams in early February when the engine is tuned to run clean all the way around the track and produces a nice medium brown plug color on the porcelain. The same exact package runs at 435 at NCMP in the middle June tuned to produce the same plug readings. The gauge should not be allowed to dictate the way you tune the motor. Feel and sound are both more important than the temp reading from any type of gauge. I always recommend starting the day with the gauge turned off, the jets set very rich and a new plug. First session should be devoted to tuning the carb to get it so the engine breaks into a four cycle right before you lift at the end of the longest straight. Once that setting is found the kart should be driven hard all the way to the pit entry and then slowed quickly and the engine shut off as soon as possible..... a procedure often called a "plug cut". The engine should not be allowed to load up or idle. Once off the throttle to leave the track stay off and get the kart stopped push it back you your pit and remove the plug to get a look. If the plug looks close to right then the next session you fine tune to get rid of the four cycle and once the tuning is done turn on the gauge and see what it shows. That reading is now your reference point for additional fine tuning. The number may be a lot higher or lower than you expect to see yet you will not let the gauge dictate where you run the motor as you sorted out the tuning the correct way before turning the gauge on. Once you have the reference number you can use it to creep up on possible performance gains, be warned if the temp begins to climb faster than you normally see and so on.
Steve O'Hara