Gas to E85 injector calculations

linksys42 · Apr 5, 2018

I started using E85 back in 2007 to 2008. Back then it was a new fuel to a lot of people and definitely to me. And also I was tuning on a safc with 650cc injectors. And experimenting with mixing different ratios of 93 and E85 mix because of the limitations I had with the 650 injectors. Hence the reason for the Excel calculation I have. once the content tester came on the market that I could get a hold of I never had to worry about leaning the engine out with a ton of timing and destroying my engine. I was just putting my experience and information out there in the community so a new guy (seems like there's a lot of them nowadays) doesn't throw a full tank of E85 in his tank drive off and do a WOT pull and Destroy his engine. I'm just of the school of thought measure twice and cut once. I don't want to have to do unnecessary work for a stupid mistake that I can prevent. Cheers

bastarddsm · Apr 5, 2018

Gotcha, and that makes sense. You had sort of a unique deal going on and you were well aware of the effects the changed you made would have.

I guess I should expand that my "looseness" comes from starting with it the same time you did, and it's basically all I've ran since. Once you've ran it a bunch you start to get a feel for what's going on and realize you really can play fast and loose with it. For the beginners it's best to cross that t and dot that i.

If your new check your fuel when you get it. if your unsure check it. All you need is a water bottle infact I'll be a nice guy and make a video of it.

Anyway the take away from my post is basically don't get too wrapped up in that single percentage point change. You don't need to retune the car because it went from 80% to 79.6%, or 74%, but if it goes down to 65% then yes you probably need to take a couple degrees out and change the global a bit. Or just leave it and don't romp on it until you get the percentage up. E85 is easy you just gotta use your head, don't fill up at an unknown and immediately go 40psi. Watch your wideband, if the fuel is that much different it'll show up in the wideband long before you blow an engine up. Datalog! Datalog! Datalog! If you don't know how, or can't tell the percentage work up to the big boost every time you get fuel.

Anyway typically I would run somewhere around 12:1 GAS-AFR, and typically we get about E75 around here in the summer. Say I magically get a batch of E85, being tuned on E75, it'll only lean out about a half a point, so 12.5 GAS-AFR. That's still plenty safe, back in the day I used to run 13.5 GAS-AFR, and never had an issue, besides not making as much power as 12AFR does. Get a batch that's like 65, and you only richen up half maybe a full point. The timing really doesn't change as there isn't much of a change in octane, unless you are a big compression high boost setup, and then you wouldn't be asking these questions anyway.

Bleakley · Apr 5, 2018

bastarddsm said:
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.

Uhh no, they don't... Injector Dynamics flow tests their injectors with GASOLINE. And THE flow rate changes are due to the basic fact that there's a higher demand with E85..
Static flow rates as pointed out, yes, change due to the viscosity, gravity (science babble sh*t), etc "physical characteristics" of the two different fuels.

bastarddsm said:
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.

And no. Lol. It could matter in an example: you're getting e85 by the barrel and then have to switch to the 70% content you get at the pump. That COULD matter.
That's about an 18% change! If you're ramped out by the barrel that's enough to cause some issues, w/o doubt.

bastarddsm said:
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.

I agree with what you're saying about tuning conservatively. And maybe this is my own personal opinion, but:
I do not believe that's good enough...
I think e75 covers you for +/- 75% and up.
If I tuned on e70, then yeah, I would consider high 60's on up.

bastarddsm · Apr 5, 2018

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Bleakley · Apr 5, 2018

bastarddsm said:
Gotcha, and that makes sense. You had sort of a unique deal going on and you were well aware of the effects the changed you made would have.

I guess I should expand that my "looseness" comes from starting with it the same time you did, and it's basically all I've ran since. Once you've ran it a bunch you start to get a feel for what's going on and realize you really can play fast and loose with it. For the beginners it's best to cross that t and dot that i.

If your new check your fuel when you get it. if your unsure check it. All you need is a water bottle infact I'll be a nice guy and make a video of it.

Anyway the take away from my post is basically don't get too wrapped up in that single percentage point change. You don't need to retune the car because it went from 80% to 79.6%, or 74%, but if it goes down to 65% then yes you probably need to take a couple degrees out and change the global a bit. Or just leave it and don't romp on it until you get the percentage up. E85 is easy you just gotta use your head, don't fill up at an unknown and immediately go 40psi. Watch your wideband, if the fuel is that much different it'll show up in the wideband long before you blow an engine up. Datalog! Datalog! Datalog! If you don't know how, or can't tell the percentage work up to the big boost every time you get fuel.

Anyway typically I would run somewhere around 12:1 GAS-AFR, and typically we get about E75 around here in the summer. Say I magically get a batch of E85, being tuned on E75, it'll only lean out about a half a point, so 12.5 GAS-AFR. That's still plenty safe, back in the day I used to run 13.5 GAS-AFR, and never had an issue, besides not making as much power as 12AFR does. Get a batch that's like 65, and you only richen up half maybe a full point. The timing really doesn't change as there isn't much of a change in octane, unless you are a big compression high boost setup, and then you wouldn't be asking these questions anyway.

^^^This though^^^ :thumb:

bastarddsm · Apr 5, 2018

Bleakley said:
Uhh no, they don't... Injector Dynamics flow tests their injectors with GASOLINE.

Ok so I wasn't sure about ID flowing with gasoline, do you have a flow sheet from ID that actually shows what fluid they test with? Still doesn't change the fact they do not use a dsm driver to drive the injector, and that does change the effective pulsewidth, which has a great effect on flow when not static.

Bleakley said:
And THE flow rate changes are due to the basic fact that there's a higher demand with E85..
Static flow rates as pointed out, yes, change due to the viscosity, gravity (science babble sh*t), etc "physical characteristics" of the two different fuels.

The viscosity and SPECIFIC GRAVITY of the fuel most certainly changes the volume flow rate when under dynamic conditions. Do you own an injector bench that can test this? Or are you just riding on the coat-tails of science babble shit. If you can't write scientifically on a subject how can we trust your statements?

Bleakley said:
And no. Lol. It could matter in an example: you're getting e85 by the barrel and then have to switch to the 70% content you get at the pump. That COULD matter.
That's about an 18% change! If you're ramped out by the barrel that's enough to cause some issues, w/o doubt.

Clearly you can't read, I did not say tune on 85 and expect to run right on 60. I said tune on 75 and be pretty good from high 60's to low 80's. Yes I would expect that if you have a setup that requires the octane of E85, and you are tuned to the edge you could have problems trying to run E70, but then again that's not the subject of this thread.

Bleakley said:
I agree with what you're saying about tuning conservatively. And maybe this is my own personal opinion, but:
I do not believe that's good enough...
I think e75 covers you for +/- 75% and up.
If I tuned on e70, then yeah, I would consider high 60's on up.

Reading your comments I have to ask how much E85 you have actually ran and tuned. I have to ask if you have real experience, or are just quoting some HP academy videos.

I mean really it doesn't change that much. On my car for example, it is well setup, and I run over 40psi. I do not see any difference from 85% down to 70%. Now yes if it dips down to 50%, it does go pretty rich and pick up some knock counts, but you need to consider how aggressive the setup is. It's 40+psi and upper teens for timing on a HE351 with a 9cm exhaust side and I'm putting a 3300lb car in the 9's with it. That's 700hp through a 60mm turbo with a tiny exhaust side. If I don't have an issue with 85 vs 70 vs 50 really I don't anyone who has to ask will have an issue. To further my point, I run a cheap felpro composite head-gasket - if I had any detonation at this power it would toss that thing instantly. I've gotten 2 seasons out of them before.

Bleakley · Apr 5, 2018

Mate, I just didn't want somebody possibly getting bad info.
I do not have a flow sheet. I just called.
I can't prove that, and am just going by what they said. Hopefully I wasn't lied to, or hopefully I didn't misinterpret something.
Edit: question I want answered - why would their flow rates be stating 'using gasoline' or 'using iso-octane?' Possible that this is based off of calculations then? Instead of the actual parameters being stated?

And I'm definitely riding on science. Lol. Those variables mean something to us. We're saying the same thing here / on that one I think.
I readily admit I'm still learning. Probably always will be.

Woah. Yeah, I can definitely read man. Your statement left things on the table that someone could misinterpret and foul up. What works on your setup may not work on someone else's.
It's def not the subject of the thread, but we went there.

Bleakley · Apr 5, 2018

I feel reluctant to answer the last question, as if the lack of high power experience would somehow discredit the statements I made.

But for clarity. I have only dabbled in e85. Most everything I've ever done has been on gas ONLY because there was no real benefit for me switching over. No point when you've been sub 400 crank hp.
I'm a welder, but am also back in school at 25 finally doing cars because I've been doing it like everyone else who's probably on tuners (since they were like 13). I also have begun watching hp academy and do plan on messing with tuning solo and would not mind attending efi university in the near future.

And in closure, i just wanna state for the record. I think the only reason I DON'T have a sub 11 second car is because I currently don't make the bank. Hahahaha

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