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Old 10-04-2019, 11:08 AM   #1
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AFR on E85?

Hey everyone, so I recently had my blower/ snout ported and put on a 102mm throttle body along with some other little things and I datalogged the car last night and my AEM wideband was reading just over 9.0 at WOT. I know my tuner likes to keep the car safe, but does that not seem unnecessarily rich? Even for E? I sent my tuner the log so hopefully he can take a look at it and address any changes that need to be made but I just wanted to hear your guys’ input. Thanks!
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Old 10-04-2019, 11:29 AM   #2
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I would have actually expected a little under 9 at WOT, but I'm a noob to this stuff so my input isn't worth much lol
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Old 10-04-2019, 12:05 PM   #3
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From what I've seen about 7.6 - 8 under boost and 9.5 cruise/idle is "ideal".
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Old 10-04-2019, 12:13 PM   #4
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I'm sure you're aware that Gasoline stoich is 14.7 and E85 stoich is 9.7. So, obviously, you're going to have a much lower AFR (if you're AEM is only setup with gasoline) when cruising (those stoich) and WOT. I like running lambda because it removes the AFR confusion, so, I like 0.76 which is 7.3 equivalent AFR at WOT with E85. The 9.0 AFR you're getting appears very lean to me.
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Old 10-04-2019, 12:18 PM   #5
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Quote:
Originally Posted by dreksnot View Post
I'm sure you're aware that Gasoline stoich is 14.7 and E85 stoich is 9.7. So, obviously, you're going to have a much lower AFR (if you're AEM is only setup with gasoline) when cruising (those stoich) and WOT. I like running lambda because it removes the AFR confusion, so, I like 0.76 which is 7.3 equivalent AFR at WOT with E85. The 9.0 AFR you're getting appears very lean to me.


I’ll have to take another look at the log this evening. The tuner is a pretty well known guy in SoCal so I’m sure he’ll make it all right if anything’s wrong
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Old 10-04-2019, 12:43 PM   #6
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Quote:
Originally Posted by dreksnot View Post
I'm sure you're aware that Gasoline stoich is 14.7 and E85 stoich is 9.7. So, obviously, you're going to have a much lower AFR (if you're AEM is only setup with gasoline) when cruising (those stoich) and WOT. I like running lambda because it removes the AFR confusion, so, I like 0.76 which is 7.3 equivalent AFR at WOT with E85. The 9.0 AFR you're getting appears very lean to me.
AGREE 100%.
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Old 10-24-2019, 08:43 AM   #7
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"E85" varies at different pumps and times throughout the year. Can be E51 to E85. So the stoichy will change depending on the percentage of ethanol. Thus your afr will change too. Is a flex fuel sensor installed to monitor the amount of ethanol and is it accessible to read? If not, you can pick up a test unit to measure the ethanol percentage when you fill up. They are cheap and easy. You can even do it with a graduated cylinder, used in chem labs. Then calculate the stoichy for that blend. Then multiply that stoichy by .78 to get your afr at wot. Then account for stoichy that is programmed into your afr gauge. Or just use lambda on your wideband. Normal cruising lamda will be about 1. For boosted, it will be roughly .75 to .78. Which AEM do you have? It may have a fixed stoichy for straight gas, that may be the reason for 9.0 afr. If all the values are not known and accounted for, your afr is meaningless. That's why lambda is the best route. Also, if you have no flex fuel sensor, the factory narrow band O2 sensors will try to adjust for the different blends by changing the long term fuel trims, LTFT. Which may cause issues when at wot and open loop. Different blends also will affect the amount timing. Not sure how your tuner tunes and ecm tuning is definitely not a strong point for me. Can you switch your gauge to lambda?
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