good AFR, good timing, and no knock BUT higher EGT's??
EGT are far from useless. The problem is people dont know how to use and understand whats happening. When you have a good safe tune your egt will be at 825-850.
There could be many things causing this.
1 probe could be failing. doubtful though as usually go way off scale or just die.
i'm sure the probe is still working ok, it's just somewhat inaccurate. this is the email i received from zeitronix themselves since it's their probe:
"It's a compromise between the fast response of the probe and the life span. An open junction gives you a very fast response but it will burn out faster.
We will offer in about 2 months a closed junction probe. It's also quite fast but it will last much longer."
2 timing is too retarded. if burn cycle is retarded that means more heat will end up in exhaust manifold.
timing is set pretty good. i upped the timing a degree at a time until i saw knock, then backed off on the timing till knock was gone. if you look at my timing map, you will see that my timing is set pretty conservatively for 91 octane.
3 fuel is lean. are you sure your a/f is not going leaner above 7000 in 4/5 gears? injector duty should always be less than 85%. after that injectors are static. you get no additional fuel after 85%. dont be smarter than simple math. if see 85% at any time during tuning it time for more fuel.
AFR is not going leaner in the higher gears, if anything a tiny tiny bit richer. besides, these higher temps are in 3rd gear. also my IDC goes no higher than 65% throughout the pull so i think i'm good with fuel.
There could be many things causing this.
1 probe could be failing. doubtful though as usually go way off scale or just die.
i'm sure the probe is still working ok, it's just somewhat inaccurate. this is the email i received from zeitronix themselves since it's their probe:
"It's a compromise between the fast response of the probe and the life span. An open junction gives you a very fast response but it will burn out faster.
We will offer in about 2 months a closed junction probe. It's also quite fast but it will last much longer."
2 timing is too retarded. if burn cycle is retarded that means more heat will end up in exhaust manifold.
timing is set pretty good. i upped the timing a degree at a time until i saw knock, then backed off on the timing till knock was gone. if you look at my timing map, you will see that my timing is set pretty conservatively for 91 octane.
3 fuel is lean. are you sure your a/f is not going leaner above 7000 in 4/5 gears? injector duty should always be less than 85%. after that injectors are static. you get no additional fuel after 85%. dont be smarter than simple math. if see 85% at any time during tuning it time for more fuel.
AFR is not going leaner in the higher gears, if anything a tiny tiny bit richer. besides, these higher temps are in 3rd gear. also my IDC goes no higher than 65% throughout the pull so i think i'm good with fuel.
85% IDC is not max fuel... 100% is... that's "simple math".
I run 20-21psi @ redline with AFR of 10.9 and IDC of ~95%. I can tell you that there is headroom to run richer than 10.9. Obviously not much, but my point is, 85% IDC is not maxing out the injector by any stretch of the imagination.
EGT are far from useless. The problem is people dont know how to use and understand whats happening. When you have a good safe tune your egt will be at 825-850.
There could be many things causing this.
2 timing is too retarded. if burn cycle is retarded that means more heat will end up in exhaust manifold.
4 knock. knock sensors are just microphones. they are far from perfect at detecting all kinds of knock. egts skyrocket when knock is bad. and they go up small amounts for small knock events.
5 preignition. hots spots in the chamber (spark plugs too hot) can cause combustion within the cycle no where near TDC. this causes egt to go up as well. there will be no knock on your knock sensor. simple rule of thumb. one heat range colder for every 100hp.
the first thing I would try is a colder plug. and prep the electrode correctly. file the sharp edges off.
There could be many things causing this.
2 timing is too retarded. if burn cycle is retarded that means more heat will end up in exhaust manifold.
4 knock. knock sensors are just microphones. they are far from perfect at detecting all kinds of knock. egts skyrocket when knock is bad. and they go up small amounts for small knock events.
5 preignition. hots spots in the chamber (spark plugs too hot) can cause combustion within the cycle no where near TDC. this causes egt to go up as well. there will be no knock on your knock sensor. simple rule of thumb. one heat range colder for every 100hp.
the first thing I would try is a colder plug. and prep the electrode correctly. file the sharp edges off.
Oh yes ..make sure the 'knock' you're picking up is not some chassis noise .. my experience is these phantom knocks caused alot of issues and PITA troubleshooting
Sorry I have no sense of what is 91 octane, but on 98 RON .. the Evos here typically run 17-18 degrees at higher rpms
I'll also add that if the probe is at / near the collector rather than closer to the cylinder head, it will be alot higher higher than normal.
Lastly, cam timing .. if you're willing to go for a compromise
FYI, I have auto-Xed with the engine at fullbore for 15-20mins with EGT's hovering around 880-900C and spiking to 930 during shifts ... daily driven .. (Probe at collector .. maybe that's why it's higher)
Last edited by gunzo; Sep 20, 2007 at 04:30 PM.
Originally Posted by 94AWDcoupe;
EGT are far from useless. The problem is people dont know how to use and understand whats happening. When you have a good safe tune your egt will be at 825-850.
There could be many things causing this.
1 probe could be failing. doubtful though as usually go way off scale or just die.
2 timing is too retarded. if burn cycle is retarded that means more heat will end up in exhaust manifold.
3 fuel is lean. are you sure your a/f is not going leaner above 7000 in 4/5 gears? injector duty should always be less than 85%. after that injectors are static. you get no additional fuel after 85%. dont be smarter than simple math. if see 85% at any time during tuning it time for more fuel.
4 knock. knock sensors are just microphones. they are far from perfect at detecting all kinds of knock. egts skyrocket when knock is bad. and they go up small amounts for small knock events.
5 preignition. hots spots in the chamber (spark plugs too hot) can cause combustion within the cycle no where near TDC. this causes egt to go up as well. there will be no knock on your knock sensor. simple rule of thumb. one heat range colder for every 100hp.
the first thing I would try is a colder plug. and prep the electrode correctly. file the sharp edges off.
There could be many things causing this.
1 probe could be failing. doubtful though as usually go way off scale or just die.
2 timing is too retarded. if burn cycle is retarded that means more heat will end up in exhaust manifold.
3 fuel is lean. are you sure your a/f is not going leaner above 7000 in 4/5 gears? injector duty should always be less than 85%. after that injectors are static. you get no additional fuel after 85%. dont be smarter than simple math. if see 85% at any time during tuning it time for more fuel.
4 knock. knock sensors are just microphones. they are far from perfect at detecting all kinds of knock. egts skyrocket when knock is bad. and they go up small amounts for small knock events.
5 preignition. hots spots in the chamber (spark plugs too hot) can cause combustion within the cycle no where near TDC. this causes egt to go up as well. there will be no knock on your knock sensor. simple rule of thumb. one heat range colder for every 100hp.
the first thing I would try is a colder plug. and prep the electrode correctly. file the sharp edges off.
There is alot more to tuning than just AFR and timing.
I am surprised by some of the comments, that EGT is an old trick.
It is far from a trick, but another useful piece of information to use when PROPERLY tuning an EFI system.
Especially a forced induction application that may be seeing track use.
HP = EGT, adding fuel drops temps because less power is produced. EGT will increase with leanining until power starts to fall and in that case - so will egt
Severe knocking will show a decrease in the EGT before going higher.
I think temp probes are more useful in diesel (pyro) and drag racing applications, the latter used as an indication since temps will steadily increase until the 1/4 mile is finished.
Timing will change the way egt is read in ways beyond the math of this lesson (or in my case - arithmatic)
Just my perspective or opinion if you will, whether different from others or not - I do not give a poop. But I hope someone may find it useful
Severe knocking will show a decrease in the EGT before going higher.
I think temp probes are more useful in diesel (pyro) and drag racing applications, the latter used as an indication since temps will steadily increase until the 1/4 mile is finished.
Timing will change the way egt is read in ways beyond the math of this lesson (or in my case - arithmatic)
Just my perspective or opinion if you will, whether different from others or not - I do not give a poop. But I hope someone may find it useful
Last edited by C6C6CH3vo; Sep 21, 2007 at 02:49 PM.
People use 85% as a safe point so when picking injectors for an application, you don't pick something that's already maxed out (ie 95-100%) as this would give you no head room to modify further, nor is it safe to always run 95-100% IDC.
85% IDC is not max fuel... 100% is... that's "simple math".
I run 20-21psi @ redline with AFR of 10.9 and IDC of ~95%. I can tell you that there is headroom to run richer than 10.9. Obviously not much, but my point is, 85% IDC is not maxing out the injector by any stretch of the imagination.
85% IDC is not max fuel... 100% is... that's "simple math".
I run 20-21psi @ redline with AFR of 10.9 and IDC of ~95%. I can tell you that there is headroom to run richer than 10.9. Obviously not much, but my point is, 85% IDC is not maxing out the injector by any stretch of the imagination.
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On the standard Evo injectors I found that control was good to about 94% IDC when there was a rich step upwards in wideband AFR which seemed insensitive to further increments from 94-100%. In other words I believe this supports them going static at 94%.
If we are to follow the rule of swapping injectors once they hit 85%, then every Evo 9 owner who has a stock Evo must swap their injectors.
I have logs on my stock Evo 9 and they show an average IDC of 85% by 6500 rpm and 96.5% by 7000 rpm. The max IDC for the same rpm was 88% and 100%.
Going by the 85% rule, this is too damned high.
I have logs on my stock Evo 9 and they show an average IDC of 85% by 6500 rpm and 96.5% by 7000 rpm. The max IDC for the same rpm was 88% and 100%.
Going by the 85% rule, this is too damned high.
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