Tuning for E10 vs. ethanol-free
 

Kids are getting older and I'd like to take them for some road trips in my GTO. In the past I've run ethanol free gas just to avoid issues with the gas going bad over the winter. But I only ever drove about 30 miles from home, and always filled up at the same place because I knew they had non-ethanol.

But now, I'm thinking I want to be able to pull into any gas station I want without worrying about trying to find non-ethanol gas. I'll run fuel stabilizer instead. So what I'm wondering is how big of a change I'll see on the tune when I start running "regular" premium gas (92 octane) instead of ethanol-free premium?

Searched to verify my math and assumption. Found the below quote is consistent. You shouldn't notice any difference unless your tune is already very lean.

"Ethyl alcohol contains only 2/3 as much energy per gallon as gasoline hydrocarbons do, so the more alcohol you add to motor gasoline, the leaner your mixture becomes. With E10, the lean-out effect is 1/3 of the 10% ethanol, or 3.3% - easily covered by the safely rich condition of most street-operated carburetion"

Gotcha, thanks!

Pretty much how I tune all my cars since I drive them everywhere.
Stoich for 10 percent ethanol is 14:1
So basically what I do is tune them a bit rich on real gas and then don't worry about it, or tune it on the ethanol and let it be a little rich if I use the real stuff, either way.

You aren't talking about a huge difference. In fact the cars still return good mpg this way.

yeah i am just sick of worrying about finding pure gas ...

I hear ya. It's all but extinct around here and the one station that has it is so far away it doesn't make sense to go fill up. On top of that it's only offered in 87 octane so I can't use it anyway.

It basically takes about 5 percent more of this new fuel to make things happy. I made it standard ops in the shop to add a little fuel to idle, off idle and the cruise part of the fuel curve when setting up carburetors here and never had a single issue sticking to that plan.

Matter of fact I was STOOPID enough to let one customer talk me into keeping the carb 100 percent completely "stock" for his late 70's Corvette restoration. I wasn't comfortable with it, but followed orders. Sure as chit the phone rings as soon as he put the carb in service and he's busting my balls that it's not idling all that great and his "mechanic" claims it's sucking air at the secondary shaft and needs bushings put in it.

So I had him send it back. I opened up the IFR's by .002", replaced the 49K primary rods with my .045" full tapered rods, and sent it back. Didn't even look at the secondary shaft as the huge throttle plates seal tight in the bores and no bushings are needed back there.

Never heard another word from him, which in this business is ALWAYS a good thing because if you do good work 99.9 times out of 100 you don't here a thing. Mess something up and you'll hear about it 100 times before you get a chance to correct your mistakes!.......

Yep Ive found making things just a pinch richer makes the engine happier and doesn't affect mpg anyway.

We really don't need those factory lean calibrations, even with real fuel. Especially if the combo isn't super happy with compression and cam choice. Those are always the most fun to set up, lol.

I was told not to mix ethanol and ethanol free fuel...something about gumming things up? I assume that's BS??

Here is the article I was referred to.

I've mixed them before without issue ... the only issue I've found is letting gas with ethanol sit for a long time. Sta-bil makes a couple fuel treatments to address that issue.

No issue there. What do you think the ethanol is mixed with to get e10...pure gasoline.

Back when I was running the #62's on my 462, I had to mix pump gas with 100 octane pure gas to keep it from pinging. No issues at all with anything gumming up etc.

As already mentioned, the ethanol will evaporate out of the gas over time and this can create varnish. So if you're not going to be using the car for a period of time, put some stabil in it.

So what does a AFR gauge read on E10 vs straight gas? Does the gauge read richer on E10 if lambda isn't calibrated to E10? Meaning the gauge may read 12.0 AFR, when the actual AFR is about 12.6?

If the gauge is reading gas scale, you have to know where your stoich numbers are and calibrate it in your head and you need to command the carb or EFI to give you what you want.

Remember the sensor itself doesn't know what you're pumping through the engine, so lambda is always 1 and it delivers a reading based on voltage variance away from 1. You gas scale calibrates from there.

This really only becomes a concern when you're going very far away from gasoline, like all the way to E85 where your stoich numbers are significantly different.

What I do on my FiTech system is to command a couple points richer everywhere and leave it be. Instead of running around 12.8:1 at WOT, I commend closer to 12.5:1 and at idle and cruise I command closer to 14.1:1 instead of 14.6:1.

As with any type of tuning, listen and smell what the engine is telling you. Don't just worry about that number on the wideband. My engine likes around 14 to 14.4:1 at idle and at cruise will happily tolerate close to 15:1. Outside of WOT, it doesn't like to be richer than about 13.6:1 anywhere. This is all with e10. There's very few gasoline only places in Colorado and when you do find it, it's typically lower octane, meant for small engines.

Does ethanol free fuel have the same considerations?

A mechanic friend of mine told me that my 389 with stock 77 heads, intake and a Carter 750 carb would “run like it never did” if I used it 100% of the time.


Thanks
Mike

It's not just the stoich that changes, your timing requirements will also change. I find when I tune EFI flex cars I need to pull timing out in the mid range (around 4-6 degrees) all the way to the top otherwise the knock sensors start working or you can hear it rattling when driving through a tunnel etc...

Just something to look at if you're wanting to use E10. BTW all of my cars are flex because I run E10 in everything. It is such a good fuel for the $$$. Even my fuel injected 400 Pontiac. It loves it! My turbo LS3, just cap the boost at about 7-8psi and it'll turn about 550hp wheel on e10 but will go 635 on non-ethanol 98 fuel (93 over there) on 10psi. On e85 it should go around 800 wheel at 13psi.

The math is really quite easy.

According to a number of sources:

Gasoline has 117,600 Btu/gallon
Ethanol has 67,000 Btu/gallon

Thus for E10:

Btu = [(0.9 x 117600) + (0.1 x 67000)]
= 105,840 + 6,700
= 112540

Difference = 117600 - 112540 = 5060 lost Btu/gallon

Percentage = 112540/117600 = 95.7 %

But the AKI of ethanol is 116 which is too high for most street driven IC engines, so some of the ethanol goes out the tailpipe unburned.

Like Cliff posted, when I was still doing carbs, I added about 5 percent fuel to all circuits for E10

Jon

If you are tuning with a wide band I think you will probably see more variation tank to tank using 10% gas week to week, season to season as the fuel blend changes.

Yes and the E10 is not consistent either.

Years ago when this stuff started becoming more prevalent you could buy test kits on the internet, maybe you still can. Anyway I was finding some stations at the time were as high as 17% so it was a mixed bag of fuel at that time, and I haven't seen any reason why that would change today. In fact with the push in some states to increase ethanol content to 15% or more I have to wonder how much over that amount it will fluctuate since I've already seen more than that with the 10% mix.

This is why I said I simply tune my cars on the rich side of things, similar to what Cliff posted. Better to be safe since you never know what you're getting tank to tank. Keep it fat and happy and then you don't have to worry about it. I've been running the ethanol fuel in the classics for the last 20 years or so consistently, and 2 of them are daily driven. Never an issue, even with the bigger HP stuff.

I've found a number of times, that you're likely to encounter ethanol free fuel at stations near lakes. Ethanol fuel is one of the worst things in the world around marine engines, especially 2-strokes. Where we go at Lake Ouachita in Arkansas, ethanol free is available in all grades. Probably a 10% cost hike, but worth it for piece of mind and fuel mileage. My BMW X5 with direct injection loves it.

Your assumption is correct. Total BS.

All I can get is E-10. Been that way for the past 15 years at least. When I drove my '67 to Colorado last year, it sure liked the real gas. I'm running the original Q jet that I haven't touched in 30 years. Runs great, but likely could use richening up a hair. (I'm at close to sea level and it's HOT and arid here in the summers). Attachment 633421