Tephra map switching and E85 Q?

[Jim in Tucson]

We know that E85 needs approx 30% more fluid volume than does gasoline. I'm using the Tephra Alt Map functionality for the E85 tune and the normal map is the 91 tune. Both sets of maps have separate injector scaling so the 30% volume difference is compensated for adequately.

My question is, since there is only one Accel Enrichment map would the car potentially run better if I increased those values by 30% when switched to the E85 tune?

[scheides]

I do not believe so, those should be scaled by the injector scaling, which you have already done with your +30% alt-map.

[mplspilot]

You may wanna do some reading here:
ECUFlash accel enrichment table not really accel enrichment?

[Jim in Tucson]

Originally Posted by mplspilot

You may wanna do some reading here:
ECUFlash accel enrichment table not really accel enrichment?

That was a very inconclusive thread, to say the least. I would think that someone with a wideband could tell very quickly if the Accel Enrichment works as expected or not.

[mplspilot]

Maybe you should get one and enlighten us? I know i'd like to know what the table does.

[mrfred]

Originally Posted by Jim in Tucson

That was a very inconclusive thread, to say the least. I would think that someone with a wideband could tell very quickly if the Accel Enrichment works as expected or not.

Its most definitely a barometric pressure based compensation to IPW. It has no direct connection to acceleration. The only indirect connection is that when you step on the gas, the baro pressure at the MAF will drop somewhat. Using larger values in the table will cause AFR to be more sensitive to changes in air pressure at the MAF. Since baro for the most part is relatively constant, the main effect of increasing the values will be to make a global increase in open loop AFR. I'm sure that in the dark ages of tuning Evos, many tuners used this table to compensate for inconsistencies between AFR listed in the fuel table and actual AFR across the RPM range. Some might still do it.

So, if you were to increase the values, what you'd see is a generally richer AFR, but if you then brought the AFR back to the desired value by tuning the fuel table, what you'd see when stepping on the gas is that you'd lose some acceleration enrichment because of the greater sensitivity to baro.

[ohthree]

I was considering doing the same, keeping my current 93 oct map and tuning to E85, let me know how you like it, Jim.

[Jim in Tucson]

Originally Posted by ohthree

I was considering doing the same, keeping my current 93 oct map and tuning to E85, let me know how you like it, Jim.

I love it. The E85 tune is awesome. But, if I ever need to leave town I can easily switch to the 91 tune. My Scot Gray tune review.

[Jim in Tucson]

Originally Posted by mrfred

Its most definitely a barometric pressure based compensation to IPW.

Did you see this question?

[Smogrunner]

Sorry for the thread jack, but if you guys don't mind, please take a look at my new thread: Getting ready for first tank of E85

[Jim in Tucson]

Originally Posted by Jim in Tucson

We know that E85 needs approx 30% more fluid volume than does gasoline. I'm using the Tephra Alt Map functionality for the E85 tune and the normal map is the 91 tune. Both sets of maps have separate injector scaling so the 30% volume difference is compensated for adequately.

My question is, since there is only one Accel Enrichment map would the car potentially run better if I increased those values by 30% when switched to the E85 tune?

My original question still has not been answered with certainty: Do we presume that the Injector Scaling and the Alt Injector Scaling also scale whatever Accel Enrichment functionality the ECU provides? Or is this simply an unknown at this point?

Asked another way, has anyone on E85 with a wideband noticed any lean tip-in issues? Thereby indicating the possible lack of adequate Accel Enrichment.

It is fairly easy to see the Accel Enrichment happening in this graph. So, if an E85 car had a graph with the opposite effect, that might be evidence of lean tip-in.

[mrfred]

I didn't think you had asked that question originally. All fueling adjustments are based on injector scaling, so injector scaling is a global fueling adjustment. The only reason for possibly needing to mess with accel enrichment would be if E85 had much different accleration enrichment needs than pump gas (beyond the need for 30% more fuel). So far, no one has had any issues like that. Its kind of hypothetical discussion at ATM because the true accel enrichment routine is not currently available to anyone but Bez and anyone with a USDM IX who has tried to implement the accel enrichment tables that mixmastermatt posted.