cht vs. egt

N

na2slow2

Member
So which is a more useful tool for a gx 390 on race fuel. Also what is a normal heat range for them. We have always used the cht, figured we might try something new. Thanks.
 
If you can use egt that is the tool you want. If you are going to egt take the next step and go Lambda.
 
Using electronics and an O2 sensor you can finely graph A/F ratio in relation to load and RPM. Yes EG will do that also but the sensor is quicker and very responsive to minor changes.
 
Kart43 said:
Using electronics and an O2 sensor you can finely graph A/F ratio in relation to load and RPM. Yes EG will do that also but the sensor is quicker and very responsive to minor changes.
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Actually, it's been my experience, only with the two cycle, because detonation occurs with excessive heat and/or pressure, in the lower usable rpm range, because of the pipe, you have to run very rich to prevent detonation. The EGT temperature will go down in the presence of detonation. The trick to tuning with the EGT is to run as high a temperature as possible, or just a little below. Tell me how an O2 sensor would react under those conditions.

How about this scenario; your driving along on the freeway and your O2 sensor is saying the mixture is just right. Then you come to a very steep hill, now the engine is under a severe load, you have to give it more gas to make it up the hill, and at this point you get detonation, we've all heard it, it sounds like marbles rattling around under the hood. What would your 02 sensor say under those conditions? I know what the EGT would do, it would go down in temperature. Almost immediately. I don't know how the speed would compared to an 02 sensor, but it's pretty fast.
 
After a quick look on the web, which will make this answer/suggestion to try proly wrong but? ... :)

I looked up functions of a micron 5 on Aim manufactures site. I found on that Aim's MXS for cars has an ECU connection. https://www.aimtechnologies.com/car...-loggers/mxs-strada/mxs-strada-documentation/

Next the dumb proly wrong part. I'm thinking maybe instead of using a karting micron you could use a a specific car micron on your kart and look at inputs from an ECU. Find the right car ECU and you might get what you want in the way of O2 input, mass air flow input, rpm, temperature sensors and other things which would help.

I read your asking about a honda but it might open up possibilities in open engine karting. Maybe even having a throttle body on a kart where you could dial in from the steering wheel fuel mixture and read instant output from the O2 or other. yeah just another dumb thought on it but that's what I'm here for. ... :)
 
Chevy ECU from the 90's is adaptable throttle body type . It only allows a 10% adjustment with out reflashing to a different parameter .
Friend has one on a fiat spyder and a international scout.
 
Rules state cht or egt, so o2 sensors a computer is not gonna work. Maybe on my open kart if I ever get to race it.
 
flattop1 said:
Chevy ECU from the 90's is adaptable throttle body type . It only allows a 10% adjustment with out reflashing to a different parameter .
Friend has one on a fiat spyder and a international scout.
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If my memory serves me right I think pretty much all you have to do is put a pot on the dash+ a couple of other components to the mass air flow sensor and you can control the voltage output to the ECU from the sensor. It lets you turn a dial on the dash to change how lean or rich you run the throttle body. There's even a kit you can buy but it's an easy thing to make.
 
alvin l nunley said:
Actually, it's been my experience, only with the two cycle, because detonation occurs with excessive heat and/or pressure, in the lower usable rpm range, because of the pipe, you have to run very rich to prevent detonation. The EGT temperature will go down in the presence of detonation. The trick to tuning with the EGT is to run as high a temperature as possible, or just a little below. Tell me how an O2 sensor would react under those conditions.

How about this scenario; your driving along on the freeway and your O2 sensor is saying the mixture is just right. Then you come to a very steep hill, now the engine is under a severe load, you have to give it more gas to make it up the hill, and at this point you get detonation, we've all heard it, it sounds like marbles rattling around under the hood. What would your 02 sensor say under those conditions? I know what the EGT would do, it would go down in temperature. Almost immediately. I don't know how the speed would compared to an 02 sensor, but it's pretty fast.
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The O2 sensor just like the EGT simply tells you the state of combustion. The EGT does not tell you that you have experienced detonation, it simply tells you there has been a change in the combustion chamber. If you really want to be informed about detonation, install a knock sensor wire it to a source and LED now you will be shown knocking you can't here. Al O2 and EGT give you similiar Data but the electronics are more reactive. They are not building cars with EGT feeding the computer, they are using O2 content. To ask you a question Al, detonation will show as a high EGT how do you determine a lean condition or detonation, without an audible clue.
 
Kart43 said:
To ask you a question Al, detonation will show as a high EGT how do you determine a lean condition or detonation, without an audible clue.
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As I suspected, you know as little about the EGT as I do about the O2. The EGT will go down in temperature when you get detonation, and you get detonation long before you can hear it.
 
Thanks w5r that's what I needed to know. Guess I will get it and try some testing. I have seen someone write up a article about staying 2% under peak temp. Thanks
 
na2slow2 said:
Thanks w5r that's what I needed to know. Guess I will get it and try some testing. I have seen someone write up a article about staying 2% under peak temp. Thanks
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That very well could be good advice, but first you need to find where the peak is, it changes. Low octane fuel will start detonating at a lower temperature than a premium fuel. An engine with a high compression ratio might start detonating at a lower temperature (with the same fuel) than a low compression ratio engine. Every time you go racing, because the air density changes, you have to test for that peak. Then if you want to stay 2% under the peak, all's well and good.

One thing to be aware of; if you see a lower EGT number, and the air density hasn't changed, test (richen up) for a lean condition first. The air density gauge is your friend!!
 
alvin l nunley said:
As I suspected, you know as little about the EGT as I do about the O2. The EGT will go down in temperature when you get detonation, and you get detonation long before you can hear it.
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You are correct Al my mistake Engine temperatures, coolant etc. will increase in temp but the Ex Gasses will drop in temp.
 
Well I ended up more then .02 off my max to make the best lap times, might be the wide open throttle thing no on and off throttle where we race. Gonna try a different fuel next time to see the change in temp.
 
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