FlexFuel and Facts

[Shiv@Openflash]

Quick update:

Took a datalog today on the way back to the office from Chipotle. After 3 more days (~200 miles) of driving on E60, you can see that no additional LTFT has been done. In other words, all the learning that the ECU did in the last 200 miles of running E60 (instead of E85) was done within the first few miles after leaving the gas station. And at no time (even during that first WOT run before learning) did the car feel "out of tune". It hasn't felt anything less than perfect since adding gasoline to my E85 tank.

Still goes to show that it's not necessary to be concerned about ethanol % variance in E85. The ECU will handle things effectively and quickly. And without the having to add any more hardware (flexfuel sensor kit) or custom code.

Link to log:
http://datazap.me/u/shivvishnu/stage...3-days-driving

Full log:


Partial log:

[jeebus]

Originally Posted by shiv@vishnu

Quick update:

Took a datalog today on the way back to the office from Chipotle. After 3 more days (~200 miles) of driving on E60, you can see that no additional LTFT has been done. In other words, all the learning that the ECU did in the last 200 miles of running E60 (instead of E85) was done within the first few miles after leaving the gas station. And at no time (even during that first WOT run before learning) did the car feel "out of tune". It hasn't felt anything less than perfect since adding gasoline to my E85 tank.

Still goes to show that it's not necessary to be concerned about ethanol % variance in E85. The ECU will handle things effectively and quickly. And without the having to add any more hardware (flexfuel sensor kit) or custom code.

It's worth noting though, that lowering your ethanol % will improve fuel mileage. So if the car is getting all the knock protection it needs, and running the most timing it can with only around 100 octane requirements, then is there any reason you couldn't regularly run a 65/35 mix of e85/91? Assuming e10 gas, that gives you e58 and an effective octane of 100 even.

In "theory" you'd get a 12.5% improvement in fuel mileage over straight e85.

[RickyB]

I thought the whole reason for flex fuel was to make it easy to pull up to any pump and fill the tank with whatever was available without having to switch between a gasoline vs. an E85 map.

[Shiv@Openflash]

Originally Posted by RickyB

I thought the whole reason for flex fuel was to make it easy to pull up to any pump and fill the tank with whatever was available without having to switch between a gasoline vs. an E85 map.

That is correct. But the purpose of this thread was in response to those who are now claiming that a flexfuel kit was necessary for those running exclusively on E85 due to the ethanol content variance that is typical from station to station and from season to season. The point of this thread was not to suggest that a static non-flexfuel tune can handle flexfuel duties. But rather that a static non-flexfuel tune can indeed handle even the widest reasonable ethanol variance found in pump E85

[Luckrider]

The proof is in the logs. I myself really wanted a full flex fuel setup, but the more I have seen the e85 tune being run from various members (with various setups, ethanol content, and temperatures), the more I am convinced a quality tune is all that is needed.

[R/T Tuning]

Originally Posted by shiv@vishnu

lol thanks guys. I have a couple other pet peeves (ie, using Mustang dyno results to "calculate" Dynojet dyno results) but I think that's enough for today. But serious, is it really that hard to take the car to a Dynojet after you tune it to get actual authentic Dynojet results?

our take it to a shop that has both a mustang and dynojet like us

we had a bimmer here for some oulls running your flexfuel set up and tune, i forget the exact numbers somewhere in the mid 500's iirc...very cool

[RickyB]

Originally Posted by shiv@vishnu

That is correct. But the purpose of this thread was in response to those who are now claiming that a flexfuel kit was necessary for those running exclusively on E85 due to the ethanol content variance that is typical from station to station and from season to season. The point of this thread was not to suggest that a static non-flexfuel tune can handle flexfuel duties. But rather that a static non-flexfuel tune can indeed handle even the widest reasonable ethanol variance found in pump E85

A conservative tune targeted to an 85% ethanol mixture should run the engine pretty well with any mixture between 60% and 95% (give or take) since the lambda changes are well within the authority range of the closed loop system. The only area where it will not function as well as a true flex fuel system is in the cold start domain. The reason for this is that below 50F, the ethanol is basically useless and only the gasoline fraction plays a role in starting. This means that from E60-E95 you are dealing with gasoline content in the 40% to 5% range, which is an 8:1 variation . Essentially, you will need about 8 times as much cranking fuel to start the car cold on E95 as you will on E60. Lambda sensors don't work unless the engine is already running, so on cold cranking without a flex fuel sensor, the ECU is running blind.

A non-flex tune will probably be set up to expect 65-75% ethanol below 50F since that is your average winter mix across most of the nation. With higher ethanol mixtures, the engine will probably start, but take much longer or many tries before it does. If the tune is set up to expect 85-90% ethanol, it may easily flood the engine, again requiring longer cranking times and more retries to successfully start.

Is a flex fuel sensor absolutely required to run E85? No. Is a flex fuel sensor always a waste of money? Not if you have the electronics and tune to properly use it and you value the flexibility of never having to worry about what's in the tank enough to offset their cost. It's a personal choice.

[jamesm]

i've never tuned a flex-fuel system, as i'm not a real tuner. i'm just a nerd, and they don't let us nerds play with the cool toys (edit: i guess they do now). to me though it just doesn't seem like a great idea unless you have lots and lots of time to dial it in.

it's like electronic boost control. it's a wonderful idea. solves all of our problems. it's automagical! but then, it isn't. it's a bitch to tune, you have spiking and creep and tailing and all sorts of stuff to deal with that you don't have with an mbc. i'm sure it could be great, but in 99% of the installations i've seen, the user would've had better boost control with a cheap ball and spring. keep it simple...

in the same way, ethanol content analyzers are great. you can adjust boost and timing and fuel by eca, it's automagical! except i'm sure it's not. someone has to tune the thing. and if past experience (and that of the collective internets) is any indication, getting a car tuned right via email is hard enough just getting the basics right.

one perfect example: a buddy of mine has flex-fuel (i won't name names). his tuner accidentally mixed up the boost maps, so he was running 16psi on pump and 10 on e85. Not great for long-term reliability. this can't happen with an mbc. sometimes, manual human intervention is a good thing. he's running a hallman pro and loving it now, fwiw.

the other risk is that people will assume that because they have flex fuel and a 'good tuner', they've got nothing to worry about. that's insanity. of course you do. have you read other people's logs? there are people driving around with very, very bad tunes who either don't know enough to realize it or just have blind faith that their email-buddy will keep everything together for them. there are people driving around in tuned cars that don't even own a cable to log with, and vendors promote this practice! this also is insanity. blind faith is not warranted here. 'trust but verify' as they say.

point is, some view flexfuel as a 'fool-proof' way to run various blends of e85 without having to do boring tuner-y stuff like log and tweak maps. but the truth is nothing is fool-proof, and e-tunes generally suck big donkey balls even without the added complication of flex fuel. by adding it, that's one more thing your tuner has to get right. in my experience, it's unlikely that they will. so in any case, you're back to reviewing logs. or you remain oblivious and just take whatever comes your way. kinda like before you bought the flex fuel setup lol.

[bfrank1972]

Originally Posted by jamesm

i've never tuned a flex-fuel system, as i'm not a real tuner. i'm just a nerd, and they don't let us nerds play with the cool toys. to me though it just doesn't seem like a great idea unless you have lots and lots of time to dial it in.

it's like electronic boost control. it's a wonderful idea. solves all of our problems. it's automagical! but then, it isn't. it's a bitch to tune, you have spiking and creep and tailing and all sorts of stuff to deal with that you don't have with an mbc. i'm sure it could be great, but in 99% of the installations i've seen, the user would've had better boost control with a cheap ball and spring. keep it simple...

in the same way, ethanol content analyzers are great. you can adjust boost and timing and fuel by eca, it's automagical! except i'm sure it's not. someone has to tune the thing. and if past experience (and that of the collective internets) is any indication, getting a car tuned right via email is hard enough just getting the basics right.

one perfect example: a buddy of mine had flex-fuel (i won't name names). his tuner accidentally mixed up the boost maps, so he was running 16psi on pump and 10 on e85. Not great for long-term reliability. this can't happen with an mbc. sometimes, manual human intervention is a good thing. he's running a hallman pro and loving it now, fwiw.

the other risk is that people will assume that because they have flex fuel and a 'good tuner', they've got nothing to worry about. that's insanity. of course you do. have you read other people's logs? there are people driving around with very, very bad tunes who either don't know enough to realize it or just have blind faith that their email-buddy will keep everything together for them. there are people driving around in tuned cars that don't even own a cable to log with, and vendors promote this practice! this also is insanity. blind faith is not warranted here.

point is, some view flexfuel as a 'fool-proof' way to run various blends of e85 without having to do boring tuner-y stuff like log and tweak maps. but the truth is nothing is fool-proof, and e-tunes generally suck big donkey balls even without the added complication of flex fuel. by adding it, that's one more thing your tuner has to get right. in my experience, it's unlikely that they will. so in any case, you're back to reviewing logs. or you remain oblivious and just take whatever comes your way. kinda like before you bought the flex fuel setup lol.

I think flex fuel is cool, but seeing how flexible the ECU is makes me think it's not worth tapping into my factory fuel system. We've seen in many different posts how not doing that properly can go HORRIBLY wrong.

[s2d4]

Originally Posted by jamesm

i've never tuned a flex-fuel system, as i'm not a real tuner. i'm just a nerd, and they don't let us nerds play with the cool toys. to me though it just doesn't seem like a great idea unless you have lots and lots of time to dial it in.

it's like electronic boost control. it's a wonderful idea. solves all of our problems. it's automagical! but then, it isn't. it's a bitch to tune, you have spiking and creep and tailing and all sorts of stuff to deal with that you don't have with an mbc. i'm sure it could be great, but in 99% of the installations i've seen, the user would've had better boost control with a cheap ball and spring. keep it simple...

in the same way, ethanol content analyzers are great. you can adjust boost and timing and fuel by eca, it's automagical! except i'm sure it's not. someone has to tune the thing. and if past experience (and that of the collective internets) is any indication, getting a car tuned right via email is hard enough just getting the basics right.

one perfect example: a buddy of mine had flex-fuel (i won't name names). his tuner accidentally mixed up the boost maps, so he was running 16psi on pump and 10 on e85. Not great for long-term reliability. this can't happen with an mbc. sometimes, manual human intervention is a good thing. he's running a hallman pro and loving it now, fwiw.

the other risk is that people will assume that because they have flex fuel and a 'good tuner', they've got nothing to worry about. that's insanity. of course you do. have you read other people's logs? there are people driving around with very, very bad tunes who either don't know enough to realize it or just have blind faith that their email-buddy will keep everything together for them. there are people driving around in tuned cars that don't even own a cable to log with, and vendors promote this practice! this also is insanity. blind faith is not warranted here. 'trust but verify' as they say.

point is, some view flexfuel as a 'fool-proof' way to run various blends of e85 without having to do boring tuner-y stuff like log and tweak maps. but the truth is nothing is fool-proof, and e-tunes generally suck big donkey balls even without the added complication of flex fuel. by adding it, that's one more thing your tuner has to get right. in my experience, it's unlikely that they will. so in any case, you're back to reviewing logs. or you remain oblivious and just take whatever comes your way. kinda like before you bought the flex fuel setup lol.

C'mon you amateur tuner, logging is for pussies.
I had my car dyno tuned by a master tuner and it looks good.

[jeebus]

speaking of flex fuel...I just swapped back to 91 from e85 for the first time since I went e85. I got my tank down to 45 miles past the fuel light, filled up, drove 1.5 miles slowly and started seeing my trims go rich rich rich...parked and shut car off. Flashed gas map. Started up and saw my trims lean lean lean...let idle for 2 mins and watched trims clean up. Drove slowly for 1/2 mile...got on freeway and watched trims fix themselves over the next 15 miles. Trims look perfecto now.

So yeah, if you don't want to do that you need flex fuel. I don't mind it.

[vgi]

Originally Posted by jamesm

there are people driving around with very, very bad tunes who either don't know enough to realize it or just have blind faith that their email-buddy will keep everything together for them.

some of them don't drive anymore. at least not their brz/frs.

[andrew20195]

Originally Posted by FRSFirestorm

I've always understood however that AFR's while running methanol/ethanol fuels should be somewhat richer? Which tuning and commanded AFR's won't account for since tuned to run regular fuels?

The air/fuel sensor doesn't care what the stoichiometric ratio of your fuel is, it only cares about lambda. Lambda = 1 is always stoichio., whether you're running gasoline at 14.7:1 or pure methanol at 6.8:1 (IIRC). As long as your fuel system has the capacity to supply the required amount of fuel, the ECM will adjust fuel trims to reach that point in closed loop.

That's obviously an unrealistically extreme example, but hopefully it makes sense.

[garfull]

Great point! Just wanted to add for e85 stoichiometric ratio would be 9.7:1

Originally Posted by andrew20195

The air/fuel sensor doesn't care what the stoichiometric ratio of your fuel is, it only cares about lambda. Lambda = 1 is always stoichio., whether you're running gasoline at 14.7:1 or pure methanol at 6.8:1 (IIRC). As long as your fuel system has the capacity to supply the required amount of fuel, the ECM will adjust fuel trims to reach that point in closed loop.

That's obviously an unrealistically extreme example, but hopefully it makes sense.