Yet another octane thread. Wut? Twist: + stoich

[WildHorse]

Well not really, haha.

Prelude:
Since the demise of the only source of 94 octane E10 in my area, I had no choice but to go with Shell 91 V-power E0.

Observations:
Shell 91 V-power E0, ignition timing is fine, AFR, not so much. Does a yoyo from 14.7-13.4 at idle, always, never settles into a groove. Idles erratic. ZERO vac leaks. So, the last tank of shell I ran down to near empty, then put 40 bucks of 91 E10. After 10 miles, totally different feel, AFR settled, idle settled.

Seem either my car, or my tune, does not like Shell 91 v-power E0. Tune calls for 14.08 stoich so that be for e10 correct (even though technically it's 14.13) ? Asking cause E0 stoich is 14.70. I understand that the O2 sensors read measures the ratio of oxygen to fuel vapor in the exhaust exiting an engine. (So it's akin to looking at your piss the next morning to figure out how much beer you drank.) Would a E10 stoich cause that much havoc while running E0 gas ? Or am I way way off base here ?

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[Cory S]

Is this repeatable?

 

[WildHorse]

Is this repeatable?

I'll let you know.

 

[Nuked]

Fuel trims will account for the 10% difference, however if the trims were already adding/subtracting fuel it will compound the issue.

 

[Brian@BMVK]

Well not really, haha.

Prelude:
Since the demise of the only source of 94 octane E10 in my area, I had no choice but to go with Shell 91 V-power E0.

Observations:
Shell 91 V-power E0, ignition timing is fine, AFR, not so much. Does a yoyo from 14.7-13.4 at idle, always, never settles into a groove. Idles erratic. ZERO vac leaks. So, the last tank of shell I ran down to near empty, then put 40 bucks of 91 E10. After 10 miles, totally different feel, AFR settled, idle settled.

Seem either my car, or my tune, does not like Shell 91 v-power E0. Tune calls for 14.08 stoich so that be for e10 correct (even though technically it's 14.13) ? Asking cause E0 stoich is 14.70. I understand that the O2 sensors read measures the ratio of oxygen to fuel vapor in the exhaust exiting an engine. (So it's akin to looking at your piss the next morning to figure out how much beer you drank.) Would a E10 stoich cause that much havoc while running E0 gas ? Or am I way way off base here ?

If your tune doesn't have octane adjust (aka Flex) enabled it'll take quite a lot of miles for it to adjust trims based on downstream O2. Otherwise, you put in a fuel that has target AFR of 14.7 vs 14.1 for E10.

 

[K4fxd]

Put in your E0 and do a KAM reset.

 

[K4fxd]

Drive 20 miles before you do the reset to get rid of the e10 in the fuel lines.

 

[WildHorse]

Fuel trims will account for the 10% difference, however if the trims were already adding/subtracting fuel it will compound the issue.

15% E. But I get what you're saying. LTFT are around 2%

If your tune doesn't have octane adjust (aka Flex) enabled it'll take quite a lot of miles for it to adjust trims based on downstream O2. Otherwise, you put in a fuel that has target AFR of 14.7 vs 14.1 for E10.

Shouldn't matter ? The PCM compensates up to 15% E. Been using Shell 91 V-power since March.

Put in your E0 and do a KAM reset.

Did that in March.

Drive 20 miles before you do the reset to get rid of the e10 in the fuel lines.

Like I said, with E10 was the first 10 miles I noticed. No KAM reset.

 

[Brian@BMVK]

Drive 20 miles before you do the reset to get rid of the e10 in the fuel lines.

That's a bit excessive, but good point. 3-5 miles is more than enough.

 

[Brian@BMVK]

Shouldn't matter ? The PCM compensates up to 15% E. Been using Shell 91 V-power since March.

13.8 is a lot closer to 14.1 than 14.7. It does compensate but not instantly.

 

[WildHorse]

Is this repeatable?

Yep repeatable.

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