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Discussion Starter · #1 ·
Notable Mods:
CPE catback
CPE Stage 2 RMM
CPE PSMM
CPE FMIC

I am getting a good bit of -1.50 and higher on pulls. My tuner suggested I work on getting that fixed before pushing the car.


My heat shield near the rear suspension was rattling so I put some foam between the shield and frame to get it to stop. I have Undid and redid the exhaust from the turbo back and made sure nothing was hitting. DP hangers are not hit the subframe and the T bolt for the FMIC are good. Removed the RMM and PSMM....still seeing some big corrections. It helped a bit by going to stock mounts, but I dont believe mounts are the issue. Plugs are good!

Thoughts?

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Notable Mods:
CPE catback
CPE Stage 2 RMM
CPE PSMM
CPE FMIC

I am getting a good bit of -1.50 and higher on pulls. My tuner suggested I work on getting that fixed before pushing the car.


My heat shield near the rear suspension was rattling so I put some foam between the shield and frame to get it to stop. I have Undid and redid the exhaust from the turbo back and made sure nothing was hitting. DP hangers are not hit the subframe and the T bolt for the FMIC are good. Removed the RMM and PSMM....still seeing some big corrections. It helped a bit by going to stock mounts, but I dont believe mounts are the issue. Plugs are good!

Thoughts?

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-1.50% isn't terrible, although any negative correction is not ideal. What fuel are you running? 99% of the time the tune is too aggressive for the fuel being used. Your tuner should be able to make adjustments if you don't have many options gas wise.
 

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Discussion Starter · #3 ·
-1.50% isn't terrible, although any negative correction is not ideal. What fuel are you running? 99% of the time the tune is too aggressive for the fuel being used. Your tuner should be able to make adjustments if you don't have many options gas wise.
-1.50 is not bad true, but going WOT and seeing -2.50 is scary ahahah

93 Shell gas is being used. He has made some adjustments to the fuel trim.

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-1.50 is not bad true, but going WOT and seeing -2.50 is scary ahahah

93 Shell gas is being used. He has made some adjustments to the fuel trim.

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To be absolutely sure the knocks are false I would strongly recommend adding Torco or the Royal Purple additive, both with MMT. Or, some VP Racing 100 or 109 octane street-legal unleaded fuel.

Once you get the octane way up above what you are tuned for, then if you still have knocks, while the knocks might be false, you could also have a bad injector or two.

Probably telling you something you already know, but "knock" by definition means the mixture explodes violently after the spark fires, instead of burning progressively. That progressive burn requires an even spray of fuel inside the combustion chamber. If you have an injector or two which is/are clogged a little, you might be getting the proper amount of fuel into the cylinder, but the spray pattern may be off.

Of course, if the knocks disappear after you get your octane up, then you know the knocks are not false and you just need better fuel (or a less aggressive tune).

Hope that helps,
Mark
 
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Discussion Starter · #7 ·
You can also try "Stage 0" on the Cobb AP and see if you are still getting corrections. With 93 octane or what Mark noted above, you shouldn't have any negative corrections on a Stage 0 tune.
Someone on FB suggested that actually. I flashed it and made a few pulls... -2.50 on a few cylinders :(

Somewhat depressing...sigh

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Discussion Starter · #8 ·
Also try a different top tier gas station. That one might have issues with their tanks letting water in. Also winter fuel sucks. So that can cause negative corrections also.

Sent from another garage.
What's this winter you speak of?
*Lowers A/C*

I'll try a different station, but strangely my corrections are 90% of the time on 2 & 4.

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Discussion Starter · #9 ·
To be absolutely sure the knocks are false I would strongly recommend adding Torco or the Royal Purple additive, both with MMT. Or, some VP Racing 100 or 109 octane street-legal unleaded fuel.

Once you get the octane way up above what you are tuned for, then if you still have knocks, while the knocks might be false, you could also have a bad injector or two.

Probably telling you something you already know, but "knock" by definition means the mixture explodes violently after the spark fires, instead of burning progressively. That progressive burn requires an even spray of fuel inside the combustion chamber. If you have an injector or two which is/are clogged a little, you might be getting the proper amount of fuel into the cylinder, but the spray pattern may be off.

Of course, if the knocks disappear after you get your octane up, then you know the knocks are not false and you just need better fuel (or a less aggressive tune).

Hope that helps,
Mark
Thanks for your detailed response.

I'll make a trip to the track and get some race fuel. I think I have covered all the other places false knock can occur.

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What's this winter you speak of?
*Lowers A/C*

I'll try a different station, but strangely my corrections are 90% of the time on 2 & 4.

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Winter is a season snow or not. LOL. I hate winter blend. You can escape it. It's funny when people in the more southern states think they don't get that blend.

Sent from another garage.
 

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Discussion Starter · #11 · (Edited)
Winter is a season snow or not. LOL. I hate winter blend. You can escape it. It's funny when people in the more southern states think they don't get that blend.

Sent from another garage.
Well I have been tuned since last March and fighting with this issue :(

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Well I have been tuned since last March and fighting with this issue :(

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I still would suggest using a different top tier station to see if that helps. Maybe one with slightly higher elevation so water doesn't run down to it. I went from one to another and had huge positive results after switching.
 
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