Thread: E-85
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Old 08-02-2020, 06:48 AM   #12
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You never want to run any methanol in a car not designed for it. Ethanol is not nearly as bad and it won't kill anything anywhere near as soon as methanol but there's more to doing a full conversion than changing injectors. The fuel pump is submerged in the fuel in addition to pumping it and needs to be specifically designed for ethanol. You'd want to check with Walbro on the compatibility. There are also a lot of seal and other system component changes when a vehicle is designed for E85 compatibility. The few people running it in their SRT-4 right now probably won't see any issues but give it time. Especially on a big turbo car relying on fueling you don't want something to die under high boost.

The ethanol does have a much higher knock resistance rating but the energy content per gallon is pretty poor which is why you need to dump a lot more fuel in. Most of the OEM systems have a sensor in the tank that is used to measure the alcohol content and tell the PCM what the content of ethanol to gasoline is so it can compute how much fuel to run. Some of the new GM systems have figure a way to remove that sensor which is probably one of the main reasons they're added the capability to so many cars (i.e. very cheap with little extra cost and can be used as a selling point and to appease the environmentalists).

Let's say you went through the fueling system and upgraded all components as needed. Our engines are going to behave a little differently than a naturally aspirated Neon in that we have boost to deal with, and how much boost will determine how much fuel needs to be injected while a n/a car is a lot more linear in its fuel needs.

Originally Posted by punkrokdood
i know the SRT-4's NGC tries to maintain a stoichiometric 14.7:1 a/f ratio for gasoline at idle/ part throttle.... when running E-85 stoichiometric is more like 10:1, and the PCM will NOT let you run that rich, bigger injectors or not. at WOT, it can be tuned like you would tune any other big turbo set up, but you'd need to run a LOT richer than you do with gasoline... tuning to lambda here is a good idea to make things easier. .75-.85 lambda is generally considered a "Safe" full boost A/F ratio

i guarantee, if you run straight E-85, bigger injectors or not, you'll never see a lambda of 1 with the stock PCM
I'd have to think about it a little more, but the stock PCM should be looking only at Lambda when trying to maintain stoich at idle and light cruise. All O2 sensor measure in Lambda and that's probably what the NGC uses in it's calculations. A/F or AFR is nothing more than taking that Lambda number and multiplying it by a conversion factor to give the ratio for a specific fuel type. Lambda is Lambda and if the NGC is using that you can burn whatever you want and it will always remain the same (Lambda of 1=stoich=all fuel burnt and essentially no leftover oxygen). The AFR is just a number to make it easier for us humans to grasp how much air to fuel an engine is using.

The problem does come down to tuning. Like mentioned converting a naturally aspirated car is much easier since you might be able to just mechanically increase the fuel flow with injectors or fuel pressure. On the SRT-4 it's still going to need more fuel at idle and it will also need the extra fuel under load but you would need some tuning solution to maximize the gains. Another thing to consider is how readily available it is in your area. If you travel to a lot of areas that don't have ethanol/E85 you'd have to be able to switch fuel maps and mixing different amounts (such as refilling on gasoline while still having a few gallons E85 in the tank) might cause issues if you go into boost.

Eric H.
'04 eBlue SRT-4 + four other turbo Dodge's + a turbo GM + some truck... and a few other cars
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