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Old 11-30-2005, 05:15 PM   #1
KitchenerWRX
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Default high egt's from running rich?

I know when you are lean you get high egt's but i just heard that you can also get high egts from running way too rich? can some one explain this?
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Old 11-30-2005, 05:39 PM   #2
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bump.
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Old 11-30-2005, 05:58 PM   #3
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I don't know what a rich condition would do to your EGT, but I do know that high EGT's are often a sympton of running lean. Evaporating fuel helps cool the engine. Therefore, when you don't have enough fuel, your EGT's go up. I would assume that running rich would do the opposite, but I don't know for sure.
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Old 11-30-2005, 06:06 PM   #4
KitchenerWRX
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dude i know that already!
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Old 11-30-2005, 06:09 PM   #5
boxerboy
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what are you saying?
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Old 11-30-2005, 06:10 PM   #6
KitchenerWRX
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read the first post
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Old 11-30-2005, 07:22 PM   #7
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Quote:
Originally Posted by KitchenerWRX
I know when you are lean you get high egt's but i just heard that you can also get high egts from running way too rich? can some one explain this?
i don't think this is possible. it all depends on what load point you're referring to. running rich is a way to suppress detonation due to high cylinder pressure or in other words too much of a bang. as a reference, at 7K my egt's are at/around 800*C and i know i'm dumping a whole lot of fuel (running rich). so i guess yes, you can still run rich and have high egt's, but this is in reference to load point. at a less load, i don't think it's possible to run rich and have high egt's, unless it has something to do with timing, but that would just contribute to the loss of power in most cases.
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Old 11-30-2005, 08:35 PM   #8
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Quote:
Originally Posted by KitchenerWRX
I know when you are lean you get high egt's but i just heard that you can also get high egts from running way too rich? can some one explain this?
Your exhaust gas temperature will be hottest at some point slightly "richer" than the stoichiometric point because that is where you are burning the most gasoline (for gasoline, that is 14.7).

You have to realize that "rich" and "lean" are relative terms, meaning simply "more" or "less" fuel than desired at a particular point. If you should be running 14.7 (low load highway cruise) and for some reason you are actually running 14.0, chances are your EGTs will be high.

Another thing that drastically affects EGT is the timing. If the spark is too 'retarded' (meaning happens too late), the mixture will be burning much later in the engine cycle and some of this later burning will make your EGT gauge read higher.

Now, if you consider the normal "turbo tuning" use of the words "rich" and "lean", you might consider "rich" to be somewhere in the range of 10:1 and "lean" somewhere in the range of 12.5:1. If this is your frame of reference, running richer will NOT make you run hotter. All that extra fuel is soaking up the heat and making your EGT gauge read lower.
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Old 12-01-2005, 12:28 AM   #9
KitchenerWRX
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thanks for the responses guys but they keep insisting that the more fuel the more combustion and then the more heat???

the only thing i can think of is an antilag system that dump fuel in - but when the throttle is closed....
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Old 12-01-2005, 12:43 AM   #10
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I've also heard of this... iirc, it was being said that if you go way too rich, ie further than 10 afrs, you can also get high egts...
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Old 12-01-2005, 01:40 AM   #11
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The reason hot rodders put in lower temp thermostats is so that the ECU will run in "warm-up" mode and fatten up the motor(richen the mixture). So, following logic, if the computer richens the mixture to warm up the motor, more fuel will give you a warmer motor.

But more commonly, high EGT's mean a lean motor.
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Old 12-01-2005, 02:19 AM   #12
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100% possible, and happens all the time. Although its USUALLY lean that does it, it can still happen when rich.

One common cause is when the timing is too far retarded causes the mix to not be far enough into the burn when the exh valve opens, which = higher EGTs

The reason that happens is people see some knock, and instead of figuring out what is going on, they automatically throw fuel at the knock, when the entire reason they saw knock was a rich misfire condition. So then the extra fuel doesnt fix it, so they start yanking timing. But it still misfires, and they see the flash, which makes them think knock (it CAN be knock as well) so they yank MORE timing.

Or it could just be that the map is a poor match for that car, and has a combination of too much fuel and too little timing...
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Old 12-01-2005, 02:35 AM   #13
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Sounds like a good recipe for pre-ignition.
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