Of EGT questions and such
12-14-2006, 01:53 PM
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Of EGT questions and such
I’ve been doing a lot of research on EGT’s lately and have some unanswered questions as to how they react:
Now from what I understand to make the most power you want to be in the optimal AFR range just under your peak EGT which start at Stoich, and from what I’m reading that’s 15:1? But if the EGT is supposed to range from 13:1 to 15:AFR and a temp of 1250F to 1800F, which is supposed to make the most HP, what’s more important here: EGT range or AFR?
I already know there are a lot of factors as far as burn rate, fuel type, advance/retard timing. If you retard too much timing isn’t it true that the more fuel you add the higher your EGT’s would get? But in place of the less timing using a different type of fuel with higher octane the burn rate will go down which causes EGT’s to go up right? So this is where it gets confusing….If you add more timing with a higher octane fuel EGT’s will go up but until the temperature flattens out or is does it go past this point until detonation. So again what is more important now? EGT or Detonation? I know that EGT’s will melt stuff but what about detonation….This is where I get really confused
So far this is what I’m understand:
Lower octance will burn fast = dropped EGT but a higher octane fuel has a lower burn temp which will make it burn slower which causes EGT’s to rise?
A leaner mix will burn slower = raised EGT’s….But how lean of an AFR mix are we talking here? Would this be 15:1 or less?
Another question I have is on the EGT placement, now I know you’re supposed to always tap into the leanest cyclinder but is it ok to tap into the down pipe? I understand that there is about a 200F difference from placement but why is that?
I’m just trying to understand the basic principles of what causes EGT’s to raise/lower and what range I should be looking for in general.
Any good info is appreciated
Now from what I understand to make the most power you want to be in the optimal AFR range just under your peak EGT which start at Stoich, and from what I’m reading that’s 15:1? But if the EGT is supposed to range from 13:1 to 15:AFR and a temp of 1250F to 1800F, which is supposed to make the most HP, what’s more important here: EGT range or AFR?
I already know there are a lot of factors as far as burn rate, fuel type, advance/retard timing. If you retard too much timing isn’t it true that the more fuel you add the higher your EGT’s would get? But in place of the less timing using a different type of fuel with higher octane the burn rate will go down which causes EGT’s to go up right? So this is where it gets confusing….If you add more timing with a higher octane fuel EGT’s will go up but until the temperature flattens out or is does it go past this point until detonation. So again what is more important now? EGT or Detonation? I know that EGT’s will melt stuff but what about detonation….This is where I get really confused
So far this is what I’m understand:
Lower octance will burn fast = dropped EGT but a higher octane fuel has a lower burn temp which will make it burn slower which causes EGT’s to rise?
A leaner mix will burn slower = raised EGT’s….But how lean of an AFR mix are we talking here? Would this be 15:1 or less?
Another question I have is on the EGT placement, now I know you’re supposed to always tap into the leanest cyclinder but is it ok to tap into the down pipe? I understand that there is about a 200F difference from placement but why is that?
I’m just trying to understand the basic principles of what causes EGT’s to raise/lower and what range I should be looking for in general.
Any good info is appreciated
12-14-2006, 03:12 PM
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Re: Of EGT questions and such (wickedEFguy)
lemme see if I can help.
AFR is much more important than EGT, being both lean or rich can also cause EGT's to rise. You know why lean would, but rich can also cause unburnt fuel will enter exhaust mani and burn there because it is so hot, this will cause temp to rise.
on a honda, cyl #3 is the best cause it runs the hottest.
It is important to put the EGT about 2 inches away from the head, in cyl #3 as you will get the quickest response/most accurate reading.
The reason EGT temp is lower in the downpipe is the heat from the motor had time to cool slightly.
My usual EGT's are in the 850-900F range, getting on it, it gets up to 1250F but not much more than that. If you see 1400F, that a little too high, 1600F, metal stuff will be melting.
AFR is much more important than EGT, being both lean or rich can also cause EGT's to rise. You know why lean would, but rich can also cause unburnt fuel will enter exhaust mani and burn there because it is so hot, this will cause temp to rise.
on a honda, cyl #3 is the best cause it runs the hottest.
It is important to put the EGT about 2 inches away from the head, in cyl #3 as you will get the quickest response/most accurate reading.
The reason EGT temp is lower in the downpipe is the heat from the motor had time to cool slightly.
My usual EGT's are in the 850-900F range, getting on it, it gets up to 1250F but not much more than that. If you see 1400F, that a little too high, 1600F, metal stuff will be melting.
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