Megasquirt flex fuel tuning e85 with ethanol sensor. – turbobricks forums gas pains or contractions

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I am trying to work through a decent flex fuel tune on my daily driver 240. I have done plenty of E85 tunes on red blocks over the years. But on my daily driver car I wanted to experiment with true flex fuel automatic tuning. I bought the sensor and plumbed it into the return fuel line near the fuel rail and wired it up. I get realistic readings from the %ethanol gauge in Tunerstudio. Everything seems to be working OK. I was getting 12% reading on my standard pump gas 91 octane. I have heard and read the signs at gas stations in Colorado that standard fuel blends contain about 10% ethanol. So that 12% reading seems about right. I added a couple gallons of E85 to my 3/4 full tank of gasoline and the reading climbed to 21% ethanol. Good enough. The sensor reads in a somewhat useful way matching the fuel I added. I think I can tune with that.

I open up Tunerstudio and find the screen for the flex fuel sensor and activate it. And I have to say that I’m somewhat surprised with the basic settings available. I was hoping I could have a totally different set of maps for fuel, ignition, and boost for e85 and gasoline. And some sort of blending between the pairs depending on the ethanol percentage. But below is what I see. I guess it could do the trick buuuuut.

Is a simple linear multiplier for the fuel map and spark map really good enough? It seems overly simplified. My motor is a high compression NA motor with a turbo. The gasoline tune is really tricky and conservative in the timing to make it survive with 12psi boost. It’s a funky set of maps especially in the positive pressure parts of the maps. High octane E85 should allow me to set up a more optimum spark map. But all I get is a "distributor twistin" adder of X degrees? Really?

I know My old MS1 setup wouldn’t have done anything at all like that, or even what you had. All I could do with it was (mis)use the Nitrous switching functionality to swap spark and fuel tables from gas to E85 with a dash switch. You just had to run it really low on one fuel before refueling on the other and flipping the switch. And cold starts were a bit iffy because it didn’t change any of those settings.

On the MS3X system the only trick I ever needed was to turn all the flex fuel stuff off when doing tuning/autotuning. You obviously can’t tune two tables at once, so I’d just do a similar thing to the old (run it super low on one fuel, switch to the other) and then do some tuning. And even then, only really do E85 tuning if the tank read as close to 70% or more Ethanol. I would occasionally get some very weak E85 fuel out of pumps. It’s ‘up to’ 85%, and at times (especially in the winter, presumably for cold starts) they drop the percentages way down. I’ve never seen it, but I’ve heard that occasionally they’ll just go ahead and put normal E10 gas in the E85 tanks.

I am trying to work through a decent flex fuel tune on my daily driver 240. I have done plenty of E85 tunes on red blocks over the years. But on my daily driver car I wanted to experiment with true flex fuel automatic tuning. I bought the sensor and plumbed it into the return fuel line near the fuel rail and wired it up. I get realistic readings from the %ethanol gauge in Tunerstudio. Everything seems to be working OK. I was getting 12% reading on my standard pump gas 91 octane. I have heard and read the signs at gas stations in Colorado that standard fuel blends contain about 10% ethanol. So that 12% reading seems about right. I added a couple gallons of E85 to my 3/4 full tank of gasoline and the reading climbed to 21% ethanol. Good enough. The sensor reads in a somewhat useful way matching the fuel I added. I think I can tune with that.

I open up Tunerstudio and find the screen for the flex fuel sensor and activate it. And I have to say that I’m somewhat surprised with the basic settings available. I was hoping I could have a totally different set of maps for fuel, ignition, and boost for e85 and gasoline. And some sort of blending between the pairs depending on the ethanol percentage. But below is what I see. I guess it could do the trick buuuuut.

Is a simple linear multiplier for the fuel map and spark map really good enough? It seems overly simplified. My motor is a high compression NA motor with a turbo. The gasoline tune is really tricky and conservative in the timing to make it survive with 12psi boost. It’s a funky set of maps especially in the positive pressure parts of the maps. High octane E85 should allow me to set up a more optimum spark map. But all I get is a "distributor twistin" adder of X degrees? Really?

I know My old MS1 setup wouldn’t have done anything at all like that, or even what you had. All I could do with it was (mis)use the Nitrous switching functionality to swap spark and fuel tables from gas to E85 with a dash switch. You just had to run it really low on one fuel before refueling on the other and flipping the switch. And cold starts were a bit iffy because it didn’t change any of those settings.

On the MS3X system the only trick I ever needed was to turn all the flex fuel stuff off when doing tuning/autotuning. You obviously can’t tune two tables at once, so I’d just do a similar thing to the old (run it super low on one fuel, switch to the other) and then do some tuning. And even then, only really do E85 tuning if the tank read as close to 70% or more Ethanol. I would occasionally get some very weak E85 fuel out of pumps. It’s ‘up to’ 85%, and at times (especially in the winter, presumably for cold starts) they drop the percentages way down. I’ve never seen it, but I’ve heard that occasionally they’ll just go ahead and put normal E10 gas in the E85 tanks.