E50 tune leaner than pump gas.. why?

[Speed3kid93]

Hey guys,

A little confused,

I recently switched from a pump gas tube to e50 tune both from the same tuner. However my 93 octane tune targeted a 11.3 air to fuel and my e50 tune is targeting 11.8.

Why is the e50 tune leaner?

When you use E85 you need to use more fuel because the btu is lower.

More fuel should mean a richer air to fuel..

So why is it leaner?

[Hoyoman]

Because that's what the tuner is targeting. Why not just ask your tuner..

[Fstrnyou]

Bad tune?

Target AFR of ethanol has nothing to do with BTU's.

[phate]

Originally Posted by Speed3kid93 Hey guys, A little confused, I recently switched from a pump gas tube to e50 tune both from the same tuner. However my 93 octane tune targeted a 11.3 air to fuel and my e50 tune is targeting 11.8. Why is the e50 tune leaner? When you use E85 you need to use more fuel because the btu is lower. More fuel should mean a richer air to fuel.. So why is it leaner?

O2 sensors read in lambda, and then convert to AFR using the gas scale of 14.7:1 (this scale isn't able to be modified in the ECU). Technically, you are putting in more fuel with the eth blend, you're just running at slightly higher lambda. Fairly common method, as you don't need to run such a low lambda when you have such high octane fuel.

[g00s3y]

It's leaner to even out the weight distribution with you in the car