I got to thinking today about temperatures on water cooled 2 cycles today. I have a motor on alcohol and have leads for all 3 temps (CHT, EGT, H20), but you can only have 2 with any tach out there. Water temperatures are no doubt important. But what if water was getting low, and the probe was picking up air pockets instead of water? Wouldn’t a CHT tell you if the motor is running hot or cold and definitely start telling you if there was water loss or water getting too hot by rising temps once you’ve established a baseline temperature it typically runs at? EGT will always be used in my setup, but I’m just wanting an opinion when it comes to CHT vs H20.
CHT vs Water Temp
- Thread starter mtk1977
- Start date
flattop1
Dawg 89
Good question . That scenario seems correct . Steam may come in too play .
I have burnt up a couple auto engines the temp gauge was always pegged .
Low water , no water or no anti freeze and frozen radiator .
How fast it registers vs how soon its damaged would be a concern also .
I have burnt up a couple auto engines the temp gauge was always pegged .
Low water , no water or no anti freeze and frozen radiator .
How fast it registers vs how soon its damaged would be a concern also .
I did this with a CR125 when I didn’t have an H20 lead and it seemed to be pretty responsive. I had an in-line QRC water gauge with that motor but it was never readable even under caution. One night my radiator dropped down and kissed the track and started leaking, I had no idea it happened but from the beginning of the heat to the end, my CHT went from 120-130 (advised water running temp, which matched the water gauge give or take a few degrees) to 170 and climbed up to 200 when I shut it down and water was able to sit in the cylinder. That CHT/analog gauge combo was a quick fix when I didn’t have the option of running more than 1 lead, but I never thought about asking if it’s truly improper, or actually better.
Dan Brown
Member
We run water temp and exhaust temp. We have our Mychrons set up so that the water temp light stats red until the engine hits 110degrees and the thermostat opens. It stays green unless it gets too warm, we have that temp set at 160. The light starts flashing red at that point. With the aftermarket radiator kits we run, and sell, over heating is never a problem unless we have a water pump belt fail which had happened before. The 2nd temp lead we run exhaust temp and use that to tune our high speed setting on the carb.
On alcohol in a two cycle, I’m thinking not really. I’m yet to hit above 110 with an 8x10” double core radiator that’s half taped. On gas, definitely. That 125 I mentioned above was on gas and it never took any time to get to 130 and keep climbing if there were excess cautions. Mind you that also had the largest champion radiator you can get and it still ran crazy hot.
Theshadow05
Member
I am a fan of head temp. My thoughts on water cooled heads. Is that they should all come with a purge port on top. This will help or aid in getting any air pocket out. Water temp gages are ok but by the time the gage spikes to give you an indication of an apparent issue; the damage has been done or started. EGT is the way to go, but I have not had great success on say big 500cc engines due to blowing the probes out on more than a few occasions. This is also better suited for fine tuning of carb/s. I would recommend whatever works the best for you and use the second as a reference or back up. Always top off liquids, use good fuel/mix and run em as fat as you can!
alvin l nunley
Site Supporter
Water temp is good, (kind of slow to react) CHT is worthless, almost, (also very slow to react) but the quickest and most accurate way to tune the engine is with the exhaust gas temperature gauge (EGT).
I’m yet to hit above 110 with an 8x10” double core radiator that’s half taped.
110 degrees? Do you think you are flooding the motor and leaving horsepower not burnt?
I say this because with my micro600 the target is 212 degrees water temp for methanol to get max power. In our open methanol 2s Parillas (all air cooled) we are looking for 990 exhaust and 180 head.
DK
110 degrees? Do you think you are flooding the motor and leaving horsepower not burnt?
I say this because with my micro600 the target is 212 degrees water temp for methanol to get max power. In our open methanol 2s Parillas (all air cooled) we are looking for 990 exhaust and 180 head.
DK