Flex fuel questions for those with flex fuel kits and Hondata.

[ebatr24]

Thanks I see my mistake I was figuring e-85 as pure ethanol so would have messed up the percentages. My plan is to get the kit, im just talking all angles to get as much info and knowledge as possible from those who have run it and have the kit.

Also what is the other 15 % in the e-85? just gas? what oct? or something else?

Correct, the other 15% is going to be just gas. Octane is a good question and something I have never really looked into, I have never had an issue with my fuel trims or knock cont running Flex Fuel though which is something I would expect when running lower octane fuel.

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[boosted180sx]

Thanks I see my mistake I was figuring e-85 as pure ethanol so would have messed up the percentages. My plan is to get the kit, im just talking all angles to get as much info and knowledge as possible from those who have run it and have the kit.

Also what is the other 15 % in the e-85? just gas? what oct? or something else?

E85 is 85% ethanol hence the 85 after the E. 15% gas, 85% ethanol. The octane rating i am unsure but i wouldn't be surprised if its mixed with 87 lol.

You don't need a flex fuel kit if you are going to run a strictly E25 tune.
The problem with that is like i have mentioned, ethanol content value at the pump varies from pump to pump. I know it's labeled as E85 but unless your sitting at the pump calculating the actual content every time you fill up, you will not be accurate.

Why it is important to have an accurate value is that ethanol requires more volume to make the same amount of energy as gasoline.
For example, E85 usually requires about 35% more volume to have the same amount of energy. Which means the stoichmetric ratio of ethanol is a lot more rich than pump gas.

So if you run a strictly E25 tune but messed up on calculations and added more, you need to increase the amount of fuel. If you run a E25 tune but actually have E40 in the tank, you'd be running lean. The ECU will compensate for a few % but thats it.

With a flex fuel kit, the ecu would automatically adjust all parameters to the content that the sensor is reading so you don't need to worry about anything.

 

[toddrhodes]

I found that post of mine. I was off on my numbers, it's been awhile:

https://www.civicx.com/threads/flashpro-flex-fuel-support.35679/page-5#post-601188

I just did a Dragy run on mine after filling up with E85, flashed the off the shelf flex fuel w/ DP tune, and modded it like my other tunes.

30-70 times decreased by 10% from 3.89 to 3.52 seconds
50-80 times decreased by almost 20% from 3.67 to 2.91 seconds

Car feels great.

Low Fuel light came on literally as I hit the gas pump. Added 5.002 gallons of E85, 5.5 gallons of 93, and I think there was 1-1.5 gallons of 93 still in the tank #nailedit

I haven't run as high as E40 since then, but that's what that mix above produced. I stick closer to E25 which, I think, is about 2.5-3-ish gallons of E85 to 93 octane, roughly speaking.

 

[Harlaquin]

Correct, the other 15% is going to be just gas. Octane is a good question and something I have never really looked into, I have never had an issue with my fuel trims or knock cont running Flex Fuel though which is something I would expect when running lower octane fuel.

awesome. I am on a pure gas 93 tune. I haven't had any knock issues or even heard a knock or ping. I am using a base map. I need to do a data log and have someone who knows what they are looking at look it over for me just to make sure everything is good. It runs great though. Cant wait to try flex fuel But worried after reading so many post of people with codes after installing them.

 

[Harlaquin]

I found that post of mine. I was off on my numbers, it's been awhile:

https://www.civicx.com/threads/flashpro-flex-fuel-support.35679/page-5#post-601188



I haven't run as high as E40 since then, but that's what that mix above produced. I stick closer to E25 which, I think, is about 2.5-3-ish gallons of E85 to 93 octane, roughly speaking.

So what is optimum percent for these cars? is it the 25 / 27ish area? And thanks so much for your replies and time.

 

[ebatr24]

awesome. I am on a pure gas 93 tune. I haven't had any knock issues or even heard a knock or ping. I am using a base map. I need to do a data log and have someone who knows what they are looking at look it over for me just to make sure everything is good. It runs great though. Cant wait to try flex fuel But worried after reading so many post of people with codes after installing them.

You won't audibly hear knocking, I've never been a fan of running base maps particularly Hondata ones in the past. The variation in fuel quality and atmosphere can sometimes effect how a tune runs, even with IAT compensation. That is why a generic basemap kinda scares me off, but at the same time they are not very aggressive either for that purpose. If you don't purchase Flex Fuel, then a good dyno/street tune would not be bad idea from a reputable tuner. It should also net you a considerable amount more power than a basemap, numbers from bolt on Type Rs I've seen are quite nice.

 

[boosted180sx]

awesome. I am on a pure gas 93 tune. I haven't had any knock issues or even heard a knock or ping. I am using a base map. I need to do a data log and have someone who knows what they are looking at look it over for me just to make sure everything is good. It runs great though. Cant wait to try flex fuel But worried after reading so many post of people with codes after installing them.

Theres no way to tell if there has been any knock retard without actually data logging it.

The codes that people are getting is due to the pump hitting 100% and the fuel pressure dropping.
IMO the base flex fuel maps runs too much air charge which is why people running into those situations.

 

[toddrhodes]

So what is optimum percent for these cars? is it the 25 / 27ish area? And thanks so much for your replies and time.

I've been hunting around for some pics I posted of datalogged runs on E30 but haven't been able to find them. I saw no knock (but did see some, minimally but some on 93 octane using the same tune), a little less boost, consistent and safe fuel pump duty cycle, and the car feels and is empirically a little faster if I just compare datalog time intervals to VSS readings in the log. That's not a great way to measure, but it works as a general indicator when that's all you have between two setups.

So that said, I'm the kind of person who asked Derek for the safest, best tune he could give me - not the most power, I want some overhead. Bad gas, shitty environmental conditions - I'd like some margin for error. Hondata has communicated that E30 is a very good equilibrium point, so I undershoot that a little to be E25 up to E30. Any less and you're just losing a little power, no biggie. Any more and you might be stressing the fuel system.

So that's how I arrived at "my" number. Everyone's tolerance for risk is different, but at E25-ish (give or take a few percent), I feel like I'm gaining performance and cooling, while not overly stressing the system.

 

[redline]

If you don't have the ff kit you might as well just get a professional 93 tune and call it a day, numbers were be pretty close to the same. Doing a blend manually can be a pain in the ass and you will need to get a e85 tester and test the e85 your using on a regular basis because it will all ways very when you get it and then you will need to get some sort of e85 mix calculator too which there are a few apps out there that can do it for you. Every car will be different I feel and the mods really have a lot to do with it. I have been running 40% blend on my completely stock car and still about to hit 24-25 psi and not run out of fuel but once you start modding you will start to make more power and have to lower the boost and add some timing.

 

[Harlaquin]

If you don't have the ff kit you might as well just get a professional 93 tune and call it a day, numbers were be pretty close to the same. Doing a blend manually can be a pain in the ass and you will need to get a e85 tester and test the e85 your using on a regular basis because it will all ways very when you get it and then you will need to get some sort of e85 mix calculator too which there are a few apps out there that can do it for you. Every car will be different I feel and the mods really have a lot to do with it. I have been running 40% blend on my completely stock car and still about to hit 24-25 psi and not run out of fuel but once you start modding you will start to make more power and have to lower the boost and add some timing.

I have thought about that as well. but due to the fact that the area i live in all these fuels are rather easy to find. I figured why not . I saw people get good gains from e-85 flex fuel kit.

 

[Birxnn]

So I am thinking of getting the flexfuel kit. First which one did you get and why? Also there are 25% tunes and then flex fuel tunes. Difference? Blending fuel, how do you fill your tank? Do you use the 4 gallon e-85 8 gallon 93? and which tune would use that? Can you just fill up full tank e-85 not blended? Would that be the flex fuel tune? I did some research but seemed to have more questions then answers so I figured I would ask people who actually use the kit. and if you fill up with 93 that is 10% can you just leave the flex full tune on or do you need to go back to the ethanol 10% tune? So many questions.... Thanks in advance.

Also if I were to fill up on pure 93 gas and add a fuel oct booster could I run the 100 oct tune? I rather a noob to all this tuning and fuel stuff.

Also if running pure e-85 do you also add e-85 fuel conditioners? as I have read e-85 is more corrosive adds more deposits and typically comes with no detergents of cleaners like regular gas.

flex fuel vehicles also have some component changes to accommodate the e-85 like fuel pump construction fuel line material and injectors. How will this effect longevity of the R since it was not built with e-85 in mine with its materials?

A friend of mine , is currently running a stock engine with tune only and he pump 8 gallons of 91 and 3.5 gallons of 100 racing fuel and it worked fine. It really help the car run smoother and saw a small increase in performance. He thought since his car takes anything over 91 premium why not.

 

[GotCTR?]

I have been doing hondata e30 tune for 10k miles on my 2018 and now 3k miles on my 2020 and never had a check engine light. I just put 4-5 gallons of E85 and then 91 octain

probably already had my hondata paid for with gas savings . I save about 5 bucks every fillup, Not concerned what people think about logs and crap . i know how my car runs and feels , i am sure the flex fuel kit is a better tune. Id rather save my money and upgrade my 2020 in a few years vs wasting it on more mods. Hondata is all i need. I have run straight 91 octain on the hondata regular e tune and never had an issue. Ethanol runs better IMO , 1.99 gallon here

dont leave your car outside in cold weather ethanol will gum up, might make the car have a rough start, i have an insulated garage with a heater so my garage stays 60 degrees+ all year round, even when it is below 0

Cold weather brings humidity up and E85 fuels are very receptive to this. They tend to attract this extra moisture and you will most likely end up with water in your gas tank that participates in rust formation and also can choke your engine if you're running on carbs or even damage your fuel injectors.Mar 6, 2018

 

[ayau]

E85 is 85% ethanol hence the 85 after the E. 15% gas, 85% ethanol. The octane rating i am unsure but i wouldn't be surprised if its mixed with 87 lol.

You don't need a flex fuel kit if you are going to run a strictly E25 tune.
The problem with that is like i have mentioned, ethanol content value at the pump varies from pump to pump. I know it's labeled as E85 but unless your sitting at the pump calculating the actual content every time you fill up, you will not be accurate.

Why it is important to have an accurate value is that ethanol requires more volume to make the same amount of energy as gasoline.
For example, E85 usually requires about 35% more volume to have the same amount of energy. Which means the stoichmetric ratio of ethanol is a lot more rich than pump gas.

So if you run a strictly E25 tune but messed up on calculations and added more, you need to increase the amount of fuel. If you run a E25 tune but actually have E40 in the tank, you'd be running lean. The ECU will compensate for a few % but thats it.

With a flex fuel kit, the ecu would automatically adjust all parameters to the content that the sensor is reading so you don't need to worry about anything.

The problem isn't stoich.

The ECU runs in full time closed loop, which will automatically add/subtract the necessary fuel trims to hit the AF target. Supposedly +/- 25% per Hondata. Never tested this myself. For example, if your tune was tuned for E25 and you put E40, your ECU will still hit its AF target. The only reason why you won't hit AF target is if the ECU runs in open loop during WOT, which this ECU doesn't but other cars do (eg., STI).

The main problem when ethanol is off by too much (+/- 10% for example), you may see knock or your fuel pump will be maxed. Engine knock being worse. Imagine the following scenarios.

Scenario 1 - too much ethanol
You run the E25 tune and you actually have E40 in the tank. Fuel trims increase to compensate for the extra ethanol. Now your fuel pump has to add more fuel, which means you may max out your fuel pump during WOT and throw a CEL.

Scenario 2 - too little ethanol
You run the E25 tune and you actually have E10. Fuel trims will decrease since you have less ethanol than what the tune calls for. However, your tune is running more timing/boost than basemap since it was tuned on more knock resistant gas (E25). Your engine may knock and begin to start pulling timing in order to protect itself.

The benefit of a flex map is that the tune will automatically adjust the timing/boost/fuel trims based on the ethanol in the fuel tank. The more important piece are timing/boost as that has impact on the reliability of the engine.

 

[ayau]

So what is optimum percent for these cars? is it the 25 / 27ish area? And thanks so much for your replies and time.

You mean what ethanol percent allows you to run the most boost and timing?

It's right around E30-E40 but you'll need to custom tune it. You can run more timing than what the E25 basemaps are calling for.

 

[kefi]

Not concerned what people think about logs and crap . i know how my car runs and feels

You really don't know how your car runs by how it feels. These ECUs can have a lot going wrong even if it 'feels' right. You can't feel the difference when the AF ratios are swinging wildly or when there's a ton of knock or even if your fuel pump is being occasionally tapped out. I test drive my R daily with different configurations and 95% of the time what I'm looking to fix or change cannot be 'felt' in any way whatsoever.

Your engine could have a major problem with it and you wouldn't even know because you don't check your logs or have someone else check them. The ECU will fix things to make it work but it doesn't mean it's ideal.

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