ethanol E85 fuel
ethanol E85 fuel
05-22-2018, 06:00 PM
#2
I run E85. I have been doing conversions on cars for almost 15 years now...it doesn't deserve the bad reputation it has and there are a lot of just plain untrue myths floating around about it. It's a vastly superior fuel, frankly, in particular for cars with forced induction or high compression or anything that would require higher octane or more cooling. E85 has 3.3x the latent vaporization cooling potential of gasoline...which translates to about 150 degrees F of additional intake charge cooling at best power AFRs. It's also highly oxygenated, more so than any gasoline-based race gas, has a faster flame speed (requiring less timing advance for the same power), and burns cleaner. I've had zero issues with mine over two years apart from the cold-start situation, which I mention below.
For my conversion on the Mercedes since I don't actually have access to tune it myself, I just went out and bought appropriately oversized injectors. What the computer doesn't know won't hurt it. As a general rule, after compensating for the differences in viscosity and density, the number you are looking for for a no-tune conversion is 34% larger fuel injectors. I did not have my stock injectors professionally flow-tested so I was kind of guessing on the flow rate, but it appears I got it slightly on the lean side most likely as I did have some difficulties starting in cold weather. I have not had my wideband on it to verify what my fueling is actually at, but it runs absolutely incredible at wide open throttle. It looks like what I went with was 450cc injectors, this was on a 2004 S600. I would recommend actually flow-testing some stock injectors and multiplying that by 1.34 to get your new optimal injector size. If you have to round up or down to find an injector, I would go on the rich side instead of lean like I did, if you experience colder weather in your area.
For my conversion on the Mercedes since I don't actually have access to tune it myself, I just went out and bought appropriately oversized injectors. What the computer doesn't know won't hurt it. As a general rule, after compensating for the differences in viscosity and density, the number you are looking for for a no-tune conversion is 34% larger fuel injectors. I did not have my stock injectors professionally flow-tested so I was kind of guessing on the flow rate, but it appears I got it slightly on the lean side most likely as I did have some difficulties starting in cold weather. I have not had my wideband on it to verify what my fueling is actually at, but it runs absolutely incredible at wide open throttle. It looks like what I went with was 450cc injectors, this was on a 2004 S600. I would recommend actually flow-testing some stock injectors and multiplying that by 1.34 to get your new optimal injector size. If you have to round up or down to find an injector, I would go on the rich side instead of lean like I did, if you experience colder weather in your area.
06-18-2018, 03:55 AM
#3
I done the tests and found the info
I do, since a while, random
33% is perfect, 45% fine
you have to go in Xentry - ME-SFI 2.7.1 - correction programming - Enrich
the other way is to get your injectors enlarged 33% by a specialist, then you can run 100% E85
both might get you still run a bit poor, but it is fine, just creates head in the cylinder when poor
even better, re-tune your ecu with the larger injectors
if you have i well tuned, you'll get your engine temp 15 C down with 100% E85
then you can tune your turbos up even more and get lots of more HP
I do, since a while, random
33% is perfect, 45% fine
you have to go in Xentry - ME-SFI 2.7.1 - correction programming - Enrich
the other way is to get your injectors enlarged 33% by a specialist, then you can run 100% E85
both might get you still run a bit poor, but it is fine, just creates head in the cylinder when poor
even better, re-tune your ecu with the larger injectors
if you have i well tuned, you'll get your engine temp 15 C down with 100% E85
then you can tune your turbos up even more and get lots of more HP
06-18-2018, 02:10 PM
#6
I done the tests and found the info
I do, since a while, random
33% is perfect, 45% fine
you have to go in Xentry - ME-SFI 2.7.1 - correction programming - Enrich
the other way is to get your injectors enlarged 33% by a specialist, then you can run 100% E85
both might get you still run a bit poor, but it is fine, just creates head in the cylinder when poor
even better, re-tune your ecu with the larger injectors
if you have i well tuned, you'll get your engine temp 15 C down with 100% E85
then you can tune your turbos up even more and get lots of more HP
I do, since a while, random
33% is perfect, 45% fine
you have to go in Xentry - ME-SFI 2.7.1 - correction programming - Enrich
the other way is to get your injectors enlarged 33% by a specialist, then you can run 100% E85
both might get you still run a bit poor, but it is fine, just creates head in the cylinder when poor
even better, re-tune your ecu with the larger injectors
if you have i well tuned, you'll get your engine temp 15 C down with 100% E85
then you can tune your turbos up even more and get lots of more HP
As far as the tune, the actual mass flow requirement is about 50% more. However, with the differences in density and viscosity, that 34% figure works great as an all around volume-based correction. Part of the problem with really getting it dialed in though is that the viscosity of ethanol changes a lot more with temperature changes than gasoline does. So the correction factor needed is dramatically different cold vs warmed up. At the end of the day it doesn't really matter much except for cold-starts because the computer will adjust to the correct ratio itself while in closed-loop as long as your correction is within a reasonable range. Most vehicle's computers will add positive fuel trims to wide-open-throttle fueling as well...but usually will not take fuel away at WOT if you have negative trims...which is also ok because E85 is just as happy as can be at fairly rich AFRs.
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pmercury (06-18-2018)
06-18-2018, 02:43 PM
#7
I've been doing E85 conversions for over 10 years now on various cars. I haven't found the engine to run any cooler...the thermal mass of the evaporating ethanol functions against the air temps, and is insignificant in comparison to the mass of coolant. Plus, you're ultimately putting slightly more energy into the burn. It does have 3.3x as much vaporization cooling though...which maths out to about 114 degrees F of potential air cooling over what gasoline provides. Of course, actual will be less since you'll have some vaporizing on port/chamber surfaces instead of within the air stream itself, but the difference is still significant.
As far as the tune, the actual mass flow requirement is about 50% more. However, with the differences in density and viscosity, that 34% figure works great as an all around volume-based correction. Part of the problem with really getting it dialed in though is that the viscosity of ethanol changes a lot more with temperature changes than gasoline does. So the correction factor needed is dramatically different cold vs warmed up. At the end of the day it doesn't really matter much except for cold-starts because the computer will adjust to the correct ratio itself while in closed-loop as long as your correction is within a reasonable range. Most vehicle's computers will add positive fuel trims to wide-open-throttle fueling as well...but usually will not take fuel away at WOT if you have negative trims...which is also ok because E85 is just as happy as can be at fairly rich AFRs.
As far as the tune, the actual mass flow requirement is about 50% more. However, with the differences in density and viscosity, that 34% figure works great as an all around volume-based correction. Part of the problem with really getting it dialed in though is that the viscosity of ethanol changes a lot more with temperature changes than gasoline does. So the correction factor needed is dramatically different cold vs warmed up. At the end of the day it doesn't really matter much except for cold-starts because the computer will adjust to the correct ratio itself while in closed-loop as long as your correction is within a reasonable range. Most vehicle's computers will add positive fuel trims to wide-open-throttle fueling as well...but usually will not take fuel away at WOT if you have negative trims...which is also ok because E85 is just as happy as can be at fairly rich AFRs.
thx for your comment
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06-18-2018, 02:48 PM
#9
As far as what size injectors to get, if you have the ability to adjust fueling you should size them based on your power goals and adjust in the tune such that the computer thinks they are 34% smaller than they actually are. If you're not adjusting fueling in the computer, then just go 34% more flow than the stock injectors.
06-18-2018, 02:49 PM
#10
If you need a recommendation on a quality ethanol rated injector supplier, I can give you one (and probably get you a discount, but they are not inexpensive for this particular injector).
02-28-2019, 12:56 PM
#12
I will have to look back and see exactly what part number I needed for my car. I went on the lean side of what I figured would be appropriate, which does present some cold start difficulties...I am on about E40 during cold weather to compensate, so I may want to send in my stock set to get some actual precision flow data for you to better be able to do the math on sizing. The company I use is fiveo motorsports, and yes, I can probably still get you a decent discount.
