Air Fuel Ratios with Ethanol Gas Mix

mca · 02-01-2009, 08:07 AM

Curious ... the LM-2 user manual shows 14.7 stochiometric AFR for Gasoline and 9.0 stochiometric AFR for Ethanol.

Given that our gas generally has 10% ethanol these days shoulldn't we target a richer AFR?

I don't have my O2 sensor hooked up which allows me to set mine where I like. But what if I want to use the sensor in the future?

RoninLB · 02-01-2009, 08:26 AM

don't know if this helps?

I monitor EGTs digitally within 2deg accuracy.

I've never noticed any difference in EGTs with 10% al gas and 100% gas.

mca · 02-01-2009, 09:50 AM

Okay. Thanks.

Just wondering b/c I have my hands on a LM-2 right now. Did some runs this morning and think I liked what I saw.

I set the idle AFR at 13.3 (roughly 3.5 CO). At cruise it is 14.7 steady.

In second gear WOT the richest I saw was 11.92.

In third gear WOT the richest I saw was 12.58.

In third gear WOT the richest I saw was 12.26.

Steve W · Steve W's Garage

change the display to lambda. Stoichiometric under lambda is equal to 1.0, regardless if it's pure gas, alcohol, or a mix of anything in between.

HarryD · 02-01-2009, 12:14 PM

This thead can be enlightening: Effects of Ethanol in gas

Quote:

Originally Posted by HarryD

Hate to burst your bubble but E85 requires a significant change in the air fuel ratio to be at stiochiometric (exact amount of fuel to use all the air). E10 is close enough to straight gasoline that these changes are not needed. FWIW, at Stoichiometric you get max power at lowest emissions.

For gasoline, the optimum air:fuel ratio is 14.7:1, for E10 the stoichiometric air:fuel ratio is 14:1, and for E85 the stoichiometric ratio is 9.8:1.

Unless you do some serious tweaking to your CIS Control pressures and springs in you other control devices, I doubt you will be able to get the car to run poorly if at all.

E85 is an adequate fuel but the car needs to be specifically designed for it. This includes the materials that touch the fuel and the controls that meter the fuel.

Interesting reading: http://www.allsafe-fuel.org/TechPaper.pdf

dvkk · 02-02-2009, 12:30 AM

Quote:

Originally Posted by mca

Curious ... the LM-2 user manual shows 14.7 stochiometric AFR for Gasoline and 9.0 stochiometric AFR for Ethanol.

The thing you have to remember is your LM-2 does NOT measure AFR. It only measures oxygen. The AFR is calculated based on the amount of oxygen that is read.