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Old 06-02-2009, 12:47 AM   #1
gling
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Default Help - Weird temporary CEL under boost and at high rpm.

The symptoms

A constant CEL between ca. 6500 and 8000 rpm under 22.5 psi of boost that disappears when the throttle is let off. There is no knock detected via logging and the A/F ratios are mid 10s to low 11s when this occurs. There is also no appreciable change in which the car runs within this rpm range. Upon driving a bit longer after the last flash for the day, I get a regular CEL (constantly lit regardless of anything). I was going to pull the code after I had dinner but when I started the car again (without resetting the ECU), the CEL disappeared!

Background

I'm running a Version 8 STI motor (everything but the stock twin-scroll turbo and TMIC setup) with a rotated GT30R turbo and a rerouted TXS FMIC setup. I have AVCS hooked up and am running the JDM ECU. Right now, we (my tuner and I) have idle and cruising dialed in (MAF and A/F ratios) along with a decent fuel table and boost set at 22.5 psi. Timing is severely retarded and the AVCS tables have not been touched yet.

The MAF was tuned with stock STI Pink injectors and when that was done, we swapped them out for 860 cc injectors and compensated for that. I have a CAI and am fully catless. I also have a GM three-port BCS and a 44 mm EWG plumbed back into the downpipe. Spark plugs are NGK one-step colder iridiums (BKR7IX or something like that). I'm not running anything else but plain 93 octane gas.

Thoughts thus far

1. I'm having misfires due to fouled spark plugs/coil packs. The plugs were replaced when my motor went in about two weeks ago and the car was running rich at idle due to the different intake (skewed MAF; injectors were stock and should have not been a factor).

2. I'm having "fake" misfire codes due to a lightened flywheel (STI-specific ACT streetlite flywheel; ca. 15 pounds). I doubt this is the problem as it ran fine with my previous setup although I'm using a different ECU now. Also, nothing in the logs point to it being misfire.

3. Boost threshold limit? Don't know if that is what it is called though. Basically, I am using a USDM WRX MAP sensor that apparently has a limit of 22.68 psi (am running 22.5 psi). The JDM one that came with the motor pegs at 18 psi as we found out (or could just be a faulty unit). Could the ECU be throwing a CEL because the boost is too high considering the stock MAP sensor is only supposed to read only up to 18 psi?

We've tried looking (briefly) in the CEL tables to disable such a CEL but the relevant options are grayed out. Also, I find this a bit strange as peak boost comes in at 4400 rpm (3rd gear; JDM six-speed) at the moment but the CEL only kicks in at 6500 rpm until redline. ¿Que?

4. The timing tables are messing things up. Timing throughout the entire range was pulled at least 5 degrees before we even started tuning under boost since we planned on starting out conservatively and the fact that the stock timing/tune is catered for higher octane JDM gas.

Don't know if this is related but we've yet to be able to make the A/F ratio leaner than 10.5 above ca. 7500 rpm even after pulling some fuel within that range a couple of times.

Closing remarks

Having said all that, I would appreciate any thoughts or suggestions on the "phantom" CEL I am observing. I'm tired and sleepy now so forgive me for not proof-reading my post. Also, I plan on getting an aftermarket MAP sensor that reads higher so that I can boost to at least 24 psi and perhaps solve this CEL issue (if it is related).

Cheers.

Gerald.
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Last edited by gling; 06-02-2009 at 01:08 AM. Reason: Forgot to mention I am running a TXS FMIC with rerouted piping.
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Old 06-02-2009, 01:29 AM   #2
gto7419
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Default

check under "boost"


- "boost limit (cel)"
- "boost limit cel delay"

If you see a number that is close to the max psi you are hitting, chances are, your boost limit (cel) needs to go higher

Also check to see what "boost limit (fuel cut)" is...
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Old 06-02-2009, 01:43 AM   #3
gling
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Quote:
Originally Posted by gto7419 View Post
check under "boost"


- "boost limit (cel)"
- "boost limit cel delay"

If you see a number that is close to the max psi you are hitting, chances are, your boost limit (cel) needs to go higher

Also check to see what "boost limit (fuel cut)" is...
Thanks for the quick response.

RE: "boost limit (cel)"

I believe that that is one of the few options that is grayed-out; hence, not being able to modify it. However, I am not completely certain and will check on it when possible.

RE: "boost limit cel delay"

I have not looked into that; I will when I am able.

RE: "boost limit (fuel cut)"

I don't think that is an issue since I am not hitting a fuel cut and that is one of the existing parameters we can, and have, changed accordingly.

Cheers.

Gerald.
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Old 06-02-2009, 05:46 PM   #4
gling
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Bump; anyone else have any ideas?
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Old 06-02-2009, 08:56 PM   #5
gto7419
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you need to change your user level to access these...

Im not saying the boost limit fuel cut is the issue, I want to know from a reference standpoint to see if it needs to be changed as well...

If you send me your rom, I can check/change these for you...
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Old 06-02-2009, 09:03 PM   #6
Tea cups
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your "grayed out" tables is because you have the "show invalid tables" setting in Ecuflash's options selected which shows you tables that are found in other ECUs but NOT applicable to your vehicle. That option should not be selected and has no useful purpose whatsoever. Not all ECUs have a boost limit (cel) table.

If you have an actual code set, you need to pull the code. No sense in trying to guess what it was. There are temporary and there are memorized codes. Temporary codes will be cleared when turning the ignition from off to on if the condition is no longer present. Memorized codes are codes of a more permanent nature (code history). Make sure whatever you using to read the codes will read both (may be called something different, like current/history).

Also, the CEL will flash upon a misfire. Next time, do not turn the ignition completely off after turning off the motor - then read the code.
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Old 06-02-2009, 10:18 PM   #7
gto7419
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hes right ^ - my v7 maps dont have boost limit and boost limit cel delay tables...
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Old 06-02-2009, 11:19 PM   #8
gling
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Quote:
Originally Posted by gto7419 View Post
you need to change your user level to access these...

Im not saying the boost limit fuel cut is the issue, I want to know from a reference standpoint to see if it needs to be changed as well...

If you send me your rom, I can check/change these for you...
Thanks. I'll look into that when I meet my tuner next; the maps are with him.

Quote:
Originally Posted by Tea cups View Post
your "grayed out" tables is because you have the "show invalid tables" setting in Ecuflash's options selected which shows you tables that are found in other ECUs but NOT applicable to your vehicle. That option should not be selected and has no useful purpose whatsoever. Not all ECUs have a boost limit (cel) table.
Thanks; good to know.

Quote:
Originally Posted by Tea cups View Post
If you have an actual code set, you need to pull the code. No sense in trying to guess what it was. There are temporary and there are memorized codes. Temporary codes will be cleared when turning the ignition from off to on if the condition is no longer present. Memorized codes are codes of a more permanent nature (code history). Make sure whatever you using to read the codes will read both (may be called something different, like current/history).

Also, the CEL will flash upon a misfire. Next time, do not turn the ignition completely off after turning off the motor - then read the code.
This part I am aware off. However, the CEL only comes on steady (not blinking) from 6500 rpm to 8000 rpm. No misfire or knock was detected either by "butt dyno" or in the logs. This is reproducible but does not stay on once the pull is complete.

I was not expecting the other (constant) CEL to disappear the first time so I was kind of bummed when it did since I would have liked to know what it was. However, a CEL appeared today out of nowhere and it was P0130 or something (high MAF voltage). I cleared it, mentioned it to my tuner, and it has not returned; though, I've not done any pulls since.

I'm going to use ECU explorer to try and log that code as it occurs the next time.

Thanks again for all the suggestions guys.

Cheers.

Gerald.
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Old 06-07-2009, 07:23 PM   #9
JSarv
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Could it be a "gear change" cel - I know Hondata S300 has an option to make the CEL come on right before redline as a shift light...

^^? Haven't looked through a V8 rom before..

-Jerod
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Old 06-07-2009, 07:51 PM   #10
gling
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Figured it out guys; it was a high MAF voltage CEL. The limit was set at 4.6 V and we were hitting 4.9 with a Big MAF. After changing the max value to 5 V, we were all set. Thanks for all the suggestions and help.

Cheers.

Gerald.
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