Gas to E85 injector calculations

[Bleakley]

What are you guys using? Been trying to nail this down for a little while.
For gasoline requirements I pretty much exclusively use deatschwerks (spelled that bugger right this time) calculator. That thing has pretty much been dead nuts for me.

Now E85, doesn't seem to be as accurate.

Being that our e85 at the pump fluctuates, I just go to the max of 82-84% when calculating.

Anyways. Some people say go by the stoich values and calculate the percentages from there. Other say go 30%, 33%, 35%, 40% more for e85.
There's gotta be a dead nuts calculation for max content you'd get at the pump (which would create highest fuel demand). Curious what you folks use.

 

[import solutions]

Your injector size *.67= actual e85 size
450/actual e85 size= injector compensation

 

[Tigerinstincts]

If you can, get a GM flex fuel sensor so ecmlink can calculate the methanol content from where ever you get your e85 once you figure out the injector values

 

[BaldEagleTalon]

Coming from a guy that knows almost nothing about gas other than it combusts, what's the benefit of converting to e85?

 

[1990TSIAWDTALON]

More timing = more power with E85. Knock is almost nonexistent so you have to watch how you tune since if it knocks it will be too late. On 93 octane I could run about 9-10* timing max, with E85 I was at 21* up top, so a noticeable difference to me.

 

[smbgsx]

Target flywheel HP x .65 BSFC\(duty cycle\ # of injectors)

example for 800 bHP on e85 running 80% injector duty cycle....

800x .65\3.2= 162.5 lb per minute injector. (convert to cc per min by multiplying lb\min by 10.5)

so 800 flywheel hp running 80 percent duty cycle calls for a 1700cc injector.

Best not to run higher that 80% injector duty cycle. yes its done all the time, but its poor practice.

typical BSFC (brake specific fuel consumption)...

e85= .65
pump gas= .55

 

[smbgsx]

Also, in addition to being able to aggressively advance ignition timing to get more pressure on the piston at the ideal time; the fact that the stoichiometry of e85 is around 9:1 means that much of the fuel entering the cylinder is not burned but actually just helps to remove heat from the cylinder through evaporative cooling. This further increases the ability to run higher boost without worrying about the compressed charge air causing pre-ignition. Essentially raising the "perceived octane" of this amazing fuel. When it comes down to it, legit e85 is 100-106 octane

 

[linksys42]

https://www.amazon.com/Quick-Fuel-Technology-36-E85-Sample/dp/B007ZJ749O

Test per tank. And make adjustments per content.

 

[Bleakley]

Why bother with that sh*t / what's the benefit when I can get a sensor to monitor the content?
Double check the sensor after a while to make sure it's still good??..

 

[smbgsx]

maybe I misunderstood, but I'm interpreting the initial question as how to calculate injector size necessary when switching to e85. A flex fuel sensor doesn't have anything to do with that. even if you put in the sensor and have the wrong size injectors your just gonna max out your duty cycle and lean out unless they have the capacity to deliver the larger volumes of fuel needed for e85. I didn't think this was a question about how to adjust say ecmlink or closed loop fuel trim to compensate for fluctuating ethanol content. Although I could be wrong.

 

[jakk220]

There is also a difference in the viscosity of E-85 from 93 octane which causes a change in fuel flow as well. It varies for different size / injector brands. The larger the injector, the less they seem to be effected.

At one point I thought that I was having a fuel issue because my global was so far off from where it should be according to various calculators. So after calculating the loss due to viscosity I was not nearly as far off.

https://www.ecmtuning.com/wiki/injdata-fueltype

 

[smbgsx]

There is also a difference in the viscosity of E-85 from 93 octane which causes a change in fuel flow as well. It varies for different size / injector brands. The larger the injector, the less they seem to be effected.

At one point I thought that I was having a fuel issue because my global was so far off from where it should be according to various calculators. So after calculating the loss due to viscosity I was not nearly as far off.

https://www.ecmtuning.com/wiki/injdata-fueltype

You're referring to "specific gravity" which is a measurement comparing the SG of any fluid to the SG of water. I don't remember off the top what the SG of gasoline or e85 is but you are correct in your statement. Tho I haven't seen any issues personally from it.

 

[Bleakley]

If we're referring to gravity...
gravity for e85 is 0.79
Gasoline is 0.72
Source: Injector Dynamics article on e85

Edit: @jakk220 , Just read that ECMlink post. That's actually interesting stuff to me. Thanks for that.

Weight of gasoline is 6.xx depending on temperature and whatnot. I know where I work (FedEx), jet fuel is 6.7-6.8 this time of year.
I THINK gasoline is around the 6.25 mark with e85 I THINK coming in a little heavier at AT LEAST 6.5 or more, but I'm not 100% sure on that. I can probably find the answer to this. The guys fueling equipment out in the fields usually have charts for different fuels.

@smbgsx , you are correct. I'm pretty familiar with the uhh, MANY ways to calculate flow requirements for e85. While there are plenty of injector calcs for gasoline, FOR ME, deatschwerks has pretty much been DEAD ON in real life scenarios over the years.
However, comparing people's injector duty cycles to the e85 calcs out there I haven't seem to find a calculator with the same repeatable results. Albeit, the varying content at the pump is namely (probably) why that's happening. This was the basis for asking my question.
I was curious. Assuming max content, what do others use to calculate? I've been a big fan of using what import solutions posted. Injector size * 0.66 repeating (or something similar like I posted 0.6, 0.65, 0.66666, etc.) --> which gives you an effective size to aim/shoot for using the gasoline calculators...

Just for clarity, I wouldn't necessarily say a flex fuel sensor doesn't have anything to do with any of this. But for the raw basis of calculating flow requirements to pick an injector size based off of the max requirement, obviously a flex fuel sensor is not required for that.
And while this depending on the ethanol content, the required flow demand from the fuel system as a whole is going to change. Focusing on the injectors, and I'm sure you know this, but for the sake of clarity --> the flow requirement is higher with e85 than regular gasoline (up to e10)...
Another way of saying it... The flow requirement is higher with max content out of the pump (82-84) than with the winter blends (65-75) we've been seeing out of the pumps.

Out of curiosity i addressed linksys42's post as to why i would need something like that when we have a fricken sensor to do that for us. Idk, maybe I'd learn something....

 

[linksys42]

Out of curiosity i addressed linksys42's post as to why i would need something like that when we have a fricken sensor to do that for us. Idk, maybe I'd learn something....

I must have misunderstood the questions and the thread. In the calculation I use the specific gravity of blend is 0.78465. I use the tester to get the ethanol content so I can make adjustments based on the percentage of ethanol from tank to tank. I also mix e85 and 93 because of the limitations of the size of my injectors. I Tune for Target air flow and Target air fuel ratio.
Example of Excel file.
Good luck.

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[Bleakley]

Interesting.
Thanks.

 

[linksys42]

Was wondering if you were just doing research to figure out what injector you were going to need to run e85? Because i saw in your profile you are still using 450's. What kind of tuning device/software where you planing to use? Link?

 

[Bleakley]

No. Just seeing what everyone else is doing. More information up on the boards, the better.
If funds ever come in and if my build ever progresses, I plan on going with Link for tuning and ID1050's for injectors (highest turbo I plan on running is a 20G). and I will def mess with E85 (Edit --> "IF" I think there will be a benefit at the time).

Right now I'm in school, and paying for it solo. So I'm pretty broke. It sucks. Lol.

 

[bastarddsm]

I'm not sure what was going on in this thread, but for me it has typically worked out to multiplying the injector flow by about .75. We get anywhere from 70-78% around here. I just put it in and run 9's. I ain't got time for all this measuring the content, changing the tune and shit. Keep the timing safe and run it. It's really not all that big of a deal.

You can theorize and calculate all you want but here's the rub, all the injector guys flow tests are with test fluid. Way different viscosity and density than both gasoline and E85. The injectors have different flow rates for gas and E85 due to the change in viscosity, but the good news is that E85 is denser, so you still get close to the same mass flow. Also keep in mind that the injector companies do not test the injectors with a dsm ecu driving them. Believe it or not that has an effect on the flow rate.

 

[Tigerinstincts]

Figuring out what injectors to run on e85 is easy. Getting a base tune from that calculation is easy. The ethanol testers linksys42 linked will allow you to get an even more precise tune like he has shown since you can account for all the variables once the ethanol content is known.
I only suggested the flex fuel sensor so you don't have to keep changing your timing/fuel map because of the varying percentage of ethanol content. Ecmlink will do it for you with that sensor.

 

[1990TSIAWDTALON]

I drove to the station, tanked up with E, crossed fingers and prayed to the DSM Gods, reset my stoich, fired her up and drove home. Now it wasn't "perfect" but it didn't take much tweeking to get it really running at what I think was close to peak for what I have. Just my O2.

 

[c2ypt1c]

I ain't got time for all this measuring the content, changing the tune and sh**

Same here. What's worked well for me is locking in open-loop at idle and adjusting until my o2 starts cycling (narrowband sim)...

edit: and for anyone thinking to themselves - "WTF c2ypt1c, stoich is 9.2343434238498573452234234234 on e85, your ecu targets 14.7 on gas!!"
To this I say, your wideband measures lambda so we still target 14.7, even on e85

 

[bastarddsm]

Figuring out what injectors to run on e85 is easy. Getting a base tune from that calculation is easy. The ethanol testers linksys42 linked will allow you to get an even more precise tune like he has shown since you can account for all the variables once the ethanol content is known.
I only suggested the flex fuel sensor so you don't have to keep changing your timing/fuel map because of the varying percentage of ethanol content. Ecmlink will do it for you with that sensor.

Unless you drop to E50 from dead nuts E85 tune you don't need to touch a thing. Timing is not that sensitive, neither is AFR. Find some E75, tune on that. Your covered from high E60's to Low E80's. Good enough.

 

[Tigerinstincts]

Unless you drop to E50 from dead nuts E85 tune you don't need to touch a thing.

So very true... An Evo friend of mine threw a rod through his block precisely because of this. I thought he was either ignorant or the gas station changed the e85 content earlier than normal for the seasonal change but it ended up costing him his motor. He had a very aggressive tune and never had problems with the e85 he got from Shell. This was before the GM flex fuel sensor was a thing, so he went to the station the next day to test the e85...ended up between 45-50%..way lower than the normal winter blend for california and it shouldn't have changed to the winter blend for another month.
Sometimes you get a bad batch of fuel and that's when you don't want to push your turbo to it's limit

 

[bastarddsm]

If you run E85 enough you can smell a weak batch.

 

[jakk220]

If you run E85 enough you can smell a weak batch.

I frequently use my nose as a "content tester" . If I question the ethanol content, ill test it with my little glass vial that I keep in my glove box. I get mine from speedway and that stuff is almost always dead on E85.