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Flex Fuel Blending, COBB.

Ethanol & Flex Fuel Tuning

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Discussion and questions related to the course Ethanol & Flex Fuel Tuning

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Hello everyone,

I'm looking for some insight what I should look at to rich'n my AFR.

Followed Cobb's guide for flex fuel tuning to the T and the Flex fuel tuning course here. Car is running great, 93 map is dialed in and over all blending is working great. Except during high load/WOT. I'm targeting 11.5AFR for now, but I'm seeing lots of 12-12.3 during pulls. My timing is conservative so no knock yet (love this e85). Ethanol blend is around 67%.

What my map looks like:



Boost =23 and tapering

93AFR = Target 11.1

E85AFR= 11.5-11.7

From what I understand, and could be very wrong here, I should not have to adjust the my SD VE table as its suppose to blend. I only have the 1 SD VE table unlike in the course, the standalone EUC has 2 that blend. If I adjust that table then my 93 AFR will be off. So I'm guessing I have to adjust the Fuel Injector scale blending table to add more fuel/blend more.

Here is an image of the stock blending table vs what I think I need to do.


Or am I on the wrong track and there are other things I should adjust.

Thanks for all the help,


what you are proposing should work very well

As high E value fuels use considerably more fuel volume, I would also check the fuel pressure is also stable - no point chasing mapping if there is still a problem elsewhere with the fuel supply.

Since this post, I have made a few changes.

- Aeromotive a1000 FPR

- 6AN lines all around from hard lines from tank and back to hard lines

- Running in series for fuel flow.

- FPR set at 43.5psi

- AEM 340LPF and hardwire kit ordered.

This change alone had caused me to redo a lot of my fuel tuning. MAF was off (Hybrid MAF/SD tune), idling needed correction, TIP-IN needed adjustment. I guess I had the stock FPR dialed in pretty well and now with "proper" fuel flow, it needs adjustments.

At the moment I'm using up the last of e85 in the tank and will go back to 93 to tune the new AFPR and start over. I did adjust my VE table to about 104-106% to get an AFR of around 11.8, so I think I did the other parts correct, if that is all I had to do to hit that AFR.

Fuel pressure is much more stable now with the AFPR.

Thanks for all the help, more to come!

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