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Old 12-28-2020, 09:54 PM   #1
E1
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Join Date: Dec 2009
Posts: 27
Country: United States
Location: Blackfoot, ID
Ethanol-Free Fuel's true tank range benefit

I gave it a try, two weekends in a row. I have some advice to pass on to those with fixed fuel metering systems, like carburetors, i.e. if you have computer controlled fuel injection or direct injection, then the claims may hold true for you. But for carburetted engines and especially ones being run at altitude, keep a close eye on how your engine runs on ethanol-free fuel. It's not a free lunch.

First off, if its economy/tank range you're after and you just fill up without rejetting for ethanol-free, you're going to lose fuel economy. There is no formula where your carburetted vehicle runs on E10, then on E0 without modification where you come out ahead. The reason is pure mathematics. If you have your vehicle tuned to E10 stoich, which is 14.1:1 and you add any amount of E0, which contains no oxygen, you're mixture will run richer than it did on E10 alone.

That's great if you're looking to increase power for a tank or two, but your vehicles efficiency is going to drop. That's a purely mathematical certainty. In my case running a 68/32 mix of E0/E10, mine dropped 4% from E10 alone. Both my cruise AFR and engine coolant temperatures dropped soon after setting out.

The reason has to do with the chemical makeup of E0 and E10. E0 has no oxygen in it, whereas ethanol has one oxygen atom in the ethanol molecule. Without that oxygen to maintain stoich, your AFR will drop and so too will your engine's efficiency.

When you think about it, if you've only run E10 in your vehicle and your carburetors are tuned for best efficiency, the best you can expect is an increase in power from running E0. Conversely, if your engine is tuned on E10 for best power (12.2:1 for E10), adding E0 is a lose-lose proposition for power. You're going to pay a premium on the fuel to end up losing a lot of engine power.

The good news is, you can rejet to take advantage of E0. You just have to get the stoich formula the same as computer controlled fuel injection systems do, get your bike tuned to 14.7:1 on 100% E0. Then instead of losing 4%, you may gain 2, 3, or 4% over your best range capabilities from running on E10 with an E10 tune. I gained 4% running 99% E0 after rejetting my motorcycle specifically for E0, but I had to ride 5 - 10 MPH slower than I typically do with E10 to maintain E0 stoich of 14.7:1 too. I have a UEGO wide-band sensor/gauge on my motorcycle that tells me what my AFR is with pinpoint accuracy, in case you're wondering.

The one word of caution to doing that on a carburetted vehicle however, is that by running 14.7:1, your coolant temperatures will increase over that of E10. Mine did. Why? It's because of two things. Primarily the leaner AFR will produce more heat. And two, because E0 is stoich at 14.7:1, it's going to create more heat than an equivalent mixture of E10 gasoline, which is stoich at 14.1:1, due to the flame front temperatures of gasoline v. ethanol; 100% gasoline being about 115F/47C higher than 100% ethanol. Something to consider during those hot Summer months.

Here's my other words of caution for those with small carb engines running at 2,000' AMSL or above. If your engine appears to run rich (black sooty exhaust pipe) on E10, putting in E0 will just make things worse. Power and performance will drop off just as they would in the earlier examples, for say your lawn mower, generator, or snow blower, simply because if it's already rich on E10 and you take away the oxygen built into E10, your mixture will be even richer; your engine will suffocate on fuel it cannot effectively oxidize. Again, that is a mathematical certainty.

The good news for you high altitude carb users is that you may not have luck rejetting your small ICE engine for altitude, but you can make one simple adjustment that will probably gain you a freebie 100 - 200 RPMs at full throttle. Increase your float-bowl float height. Doing so decreases the fuel level inside the float bowl and subsequently your AFR will be slightly leaner and more than likely more powerful.
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