E85 burn speed

[Tachyon]

Over the past few weeks, I've been looking more into the relationship between AFRs and timing advance. Specifically for E85, I've always understood that it burns slower than gasoline. To reinforce this, I've found DSMs to be a bit flat under acceleration after converting them to E-fuel, until I dial in a bit more timing on a dyno.

Recently, I've been reading more and more, from a general sampling of Google results, that ethanol actually burns faster than gasoline. Various figure were posted, but given the historically inaccurate nature of the internet, I've taken the results with a grain of salt.

I did, however, run across a paper published by the EPA. In this paper they had a chart graphic the burn speed of both Gas and ethanol. See below:


According to this data, when over an AFR of ~.8 lambda, ethanol burns faster than regular gasoline. I am slightly confused as this chart does seem to go against tangible results.

What are everyone's thoughts on this?

[carltalon]

From what I undarstand. E85 burns faster then Gasoline but is harder to Ignite. So you'll need a little more timing advance to get the burn started at the same point.

[Tachyon]

Originally Posted by carltalon

From what I undarstand. E85 burns faster then Gasoline but is harder to Ignite. So you'll need a little more timing advance to get the burn started at the same point.

Ok, that makes complete sense. Thanks!