Author Topic: Question for COBB Gurus  (Read 1134 times)

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Offline lst_coz

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Question for COBB Gurus
« on: August 31, 2019, 08:54:42 am »
So I recently put an EJ207 in my 12 STI (build thread on its way eventually). Anyhow, I needed to install a COBB accessport in order to delete the secondary air pump that the 207 doesn’t have. I took it to Lakeview (Max is amazing!!) and got everything tuned up and re mapped. They tuned it for 91 octane and everything for the first week was running great. The difference between the 207 and the 257 is noticeable.
So last night I was down to about a half tank, so I stopped and topped up with 94 octane for the first time since the engine swap. I got her out to Stoney and managed a WOT pull in sport sharp mode and for the first time my DAM pulled back to 0.841 and my knock feedback went to -4.2 and the fine knock learn started to twitch around as well. It all settled down about 15 seconds after the pull, but my DAM is staying down at the 0.841 mark (I know it takes a bit of time to come back to 1).
It’s got brand new plugs, filters, a fresh tune, and a belly full of half 91 and half 94 fuel. Any idea why this is happening at WOT? I know the pistons and bearings are good. I just spent bucket loads on this swap but there’s nothing I can think of to cause this. With just 91 I tend to get some knock feedback at hard acceleration, but the DAM was always a solid 1 and the fine knock learning never moved.

Offline lst_coz

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Re: Question for COBB Gurus
« Reply #1 on: August 31, 2019, 10:14:15 am »
I can post AP logs if anyone can interpret them. I’m still trying to learn  :-\

Offline RockThePylon

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Re: Question for COBB Gurus
« Reply #2 on: August 31, 2019, 02:08:14 pm »
Knock is usually attributable to weak fuel, seems most likely given your timeline. Where did you buy the 94 octane?

I tuned my car on Safeway 91 octane, and it's happy on just about any swill that I can find. But a half tank of Chevron 94 gave me enough knock to drop the DAM.
I may scream like a dainty lady, but I punch like a fairly strong 11-year-old.

Offline lst_coz

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Re: Question for COBB Gurus
« Reply #3 on: August 31, 2019, 04:34:02 pm »
I bought the 94 from the Petro down by Seaton. I mean I always had a bit of low RPM knock in the 91, and since putting the half tank of 94 I noticed the low RPM knock has almost gone away completely but then everything else is shifting now. I noticed fine knock learning twitching about this morning even at low RPM putting around my neighborhood. Could I really have gotten that bad of 94? How long did it take for your DAM to stabilize? Should I reset ECU?

Offline RockThePylon

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Re: Question for COBB Gurus
« Reply #4 on: August 31, 2019, 06:25:49 pm »
I bought the 94 from the Petro down by Seaton. I mean I always had a bit of low RPM knock in the 91, and since putting the half tank of 94 I noticed the low RPM knock has almost gone away completely but then everything else is shifting now. I noticed fine knock learning twitching about this morning even at low RPM putting around my neighborhood. Could I really have gotten that bad of 94? How long did it take for your DAM to stabilize? Should I reset ECU?

Petro 94 is generally regarded as "meh". But you can get a bad tank anywhere, anytime. That's what knock sensors are for.

The ECU has responded to knock, so a reduced DAM is a good thing. Less timing advance for more safety. Resetting your ECU will usually return DAM to 1, which is a bad thing if you really do have a bad tank of fuel.

For the DAM to return to 1, you need to meet a few operating parameters. Generally, easy driving and highway cruising will not cause the DAM to change.

If I were you, I'd let the ECU do it's thing for now. Drive around with the reduced DAM, burn through the fuel you have, drop the tank as low as your patience allows, then refill with the fuel you were tuned on. Keep an eye on knock, and assess.

If boost is lower in Sport than Sport#, leave it in Sport. Don't be scared to accelerate, but avoid long hard pulls.

And always, if you want more assurance, contact Lakeview.
I may scream like a dainty lady, but I punch like a fairly strong 11-year-old.

Offline lst_coz

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Re: Question for COBB Gurus
« Reply #5 on: August 31, 2019, 09:19:06 pm »
Thanks dude. Good advice