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Old 07-05-2009, 12:40 PM   #1
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Default can 11.5:1 AFR produce high egt?

I discussed my warped turbo manifold with someone and he seems to think that too rich of an AFR can brun slowly enough to cause a high-egt espescially with the output levels I'm at on a 4-cylinder.

I run 25-28* advance from 4k-redline at 15psi so I don't think its a spark advance issue. Does anyone agree with the logic on this?

I'm about to buy water injection regardless, but still would love the advice.

edit: Unless I have detonation, spiking EGT. Maybe I should pull the head and have a look at things so I can sleep at night.
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Old 07-05-2009, 01:15 PM   #2
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hmmm...am I looking for problems? I should have put water on this car a long time ago just for pizza mind.
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Old 07-05-2009, 01:52 PM   #3
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Yes you can have high EGTs despite 11.5:1 AFRs.

Read up on konck and EGT on efi101.com.
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Old 07-05-2009, 01:59 PM   #4
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Quote:
Originally Posted by JasonC SBB View Post
Yes you can have high EGTs despite 11.5:1 AFRs.

Read up on konck and EGT on efi101.com.
I've trolled the forums there and most say EGT drops when detonation occurs due rapid / multiple flame fronts. I'm tempted to pull the head...but that's going to be a bitch. I need a little camera.

I can look down the sparkplug holes and see nothing of course, I need to see the edges of the pistons.

I like this quote:
Quote:
A quick adjustment will restore the power and save that expensive rebuild. Even with just EGT, it's alot easier to get the most out of your engine without burning it down. EGT should climb as the RPMs come up on the straight, then drop when you lift for the corner. If it drops when you're pulling off a hard corner, or under acceleration, you're on the detonation expressway back to the shop for a rebuild.
I tuned the car with det cans, tuned to MBT, then backed off 2* all the way around. I don't think I can heat-soak my big BEGi #3 intercooler, but now I'm curious of the clt/iat ratios in MS. Then again, I'm chasing a problem that doesn't indicate detonation so I probably should stfu, get my car back together, look at EGT on each cylinder, then spray water above 10psi just for longevity.
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Old 07-05-2009, 02:19 PM   #5
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install the EGT gauge before you pull anything.
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Old 07-05-2009, 06:44 PM   #6
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install the EGT gauge before you pull anything.
yeah...I worry about **** like this when I'm locked in an apartment, out of town working. I need to move home again and drive this car. I could be on the track today if it weren't for that god damn manifold/turbo hardware ****.
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Old 07-05-2009, 09:29 PM   #7
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I messed about trying to drop my EGT's before i fitted a IC, i found that the AFR really made very little difference to EGT's and the richer i went from a AFR of 13 the less of a difference it made.

WI made absolutely no difference at all to the EGT's on it's own.

Timing made a huge difference thoughWhat i did find though was that the timing i managed to claw back with using WI significantly dropped the EGT's.

I was seeing 980c on a long WOT pull.
I'm using a piggyback (EMU) so i'm on the stock timing curve then what ever i decide to set the EMU to.
Before WI on a 14 btdc base timing curve i was pulling 6 degrees at 11psi, this gave the 980c EGT's.

After the WI i managed to run 100% on the stock timing curve (i.e. pulled no timing with the EMU) i saw my EGT's drop to 930c.


The other thing is anything richer than a AFR of 12 is not going to burn the entire charge anyways, all your really doing is using the extra fuel as a expensive WI, so i can't see a AFR of 11 burning any slower than a AFR of 12.


Where did the manifold warp?


Cheers
Mark
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Old 07-05-2009, 09:55 PM   #8
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Quote:
Originally Posted by eunos1800 View Post
I messed about trying to drop my EGT's before i fitted a IC, i found that the AFR really made very little difference to EGT's and the richer i went from a AFR of 13 the less of a difference it made.

WI made absolutely no difference at all to the EGT's on it's own.

Timing made a huge difference thoughWhat i did find though was that the timing i managed to claw back with using WI significantly dropped the EGT's.

I was seeing 980c on a long WOT pull.
I'm using a piggyback (EMU) so i'm on the stock timing curve then what ever i decide to set the EMU to.
Before WI on a 14 btdc base timing curve i was pulling 6 degrees at 11psi, this gave the 980c EGT's.

After the WI i managed to run 100% on the stock timing curve (i.e. pulled no timing with the EMU) i saw my EGT's drop to 930c.


The other thing is anything richer than a AFR of 12 is not going to burn the entire charge anyways, all your really doing is using the extra fuel as a expensive WI, so i can't see a AFR of 11 burning any slower than a AFR of 12.


Where did the manifold warp?


Cheers
Mark
Thanks for all that advice. Here's the warpage thread. I need to get the EGT in there to help explain this problem.
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