E634Me

A station near me just started offering E85.

I've seen some threads in other places about special E85 tunes to take advantage of the higher effective octane, but is there any benefit in running it in a stock E63S?

2012 merc amg

Not worth it. You'd need to change the spark plugs to a couple ranges cooler and also hope that the fuel delivery systems in our cars is capable of delivering the extra 25 percent more flow of fuel your going to need especially under full load over gasoline. Plus your fuel economy will drop around 25 percent plus you could risk engine damage on a car like our E63 so just not worth it. I could see you had something like a Chevy with a big block and a carb and simply re-jetted it, but with fuel injection it becomes more complicated. The octane ratings on E85 sure is high, like 105, but too many potential issues with running it.

Not only that, I know you were having that much talked about check engine light issue, I'm hoping since you got the injectors replaced your car is ok, but were you to run E85 the dealer would definitely say that was the cause of your check engine light, just the most simple thing for them to blame it on whereas it sounds like they don't have any real answers for this issue as of yet.

bobblehead

Carac

I don't even run E10 if I can avoid it.

2012 merc amg

I'd also worry about the E85 attracting moisture into the fuel system and messing with injectors and other components.

E634Me

Thanks, I've never run it, even in my Jeep. But was curious.

e65

You can mix e85 with premium gas. You need to monitor your fuel trims, long term trim <20% is fine. >25% you are begging for CEL lean codes, but CEL goes away when u add nonoxygenated fuel. E30 prob will give u 20-25% positive LTFT, straight e85 will definitely set off the light and may not run properly if ECU no longer believes exhaust sensors and stops responding to them, reverting to some predefined fueling table instead.

Your fuel pump should handle the extra 20% fuel flow at stock power level. AF ratio is adjusted hy ECU, keep LTFT <20% and it will run fine. U will get an octane boost, but u might not benefit from that in a stock E63. You could theoretically benefit from the added Oxygen in ur fuel. Bigger turbos, intake etc bring in More O2 from atmosphere, this way u add more oxygen through fuel injectors.

MuffinFlavored

> U will get an octane boost, but u might not benefit from that in a stock E63.

Why not?

aoschadlin

Because the overall fuel tables that are mapped in the stock M177 is to handle fuel around the 91 - 93 octane range. If you start running an E30 mix and thereby boost the octane to something like 96 (spitballing here, don't know what the actual octane ends up as) the fuel tables just can't extend dynamically far enough to take advantage of it.

Now if you get a 96 octane specific tune, that's a different story.

I've decided not to gain that extra power with E85 this time. I used to have a 535i that ran E30 with Meth Injection. Was a beast, but as Murphy's law would have it, hard to find an E85 pump when the fuel light is showing.

I am on a waiting list to add a meth injection setup to my car though. But that comes with it's own headaches. Like the battery is inside the spare wheel well in the trunk, just where you'd normally place the meth tank. Not a good mix. LOL

ronin amg

Just tune it and drive it. If it's not fast enough for ya just take it into the canyons and notice how little time you can keep your foot down before running out of road.

Ralcbah

​​​​​​My meth tank setup.

ronin amg

The best way to blow your engine is to rely on a system that could fail. Zero warrantee with that junk in the trunk.

Ralcbah

Man, you have such strong opinions, without asking questions. Meth/water to be supplemental only...will not modify tune enough to where it requires the mixture. It will be a 50/50 mix, roughly.

ronin amg

I have tuned cars for over 40 yrs and I've never seen a car with meth / alcohol injection not have an engine failure..
Reality sucks...

Ralcbah

I respect your experience man, but there are many, many folks out there with street cars (myself included) running safe mixtures/tunes with healthy motors. Regardless, your past is your past, and if that's been your experience, then, yeah, I see where you are coming from.

ronin amg

They weren't my cars that failed.
Unless it is a system designed like the BMW M4 with individual injectors for each cylinder you are not flowing the same amount of water vapor to each cylinder.
The Mercedes intake manifold is not designed to flow water vapor.

e65

One thing I wonder, the O2 sensor feeds the ECU and tells it to cut 20% fuel when both methanol injectors are going full blast (-20% shirt term fuel trim at WOT). This is based on the exhaust from all eight cylinders. If the methanol is not evenly distributed and yet 20% fuel is being cut from each cylinder, some of them might end up running lean. As far as I know my engine is still intact but this thought has crossed my mind now that the season is over.

aoschadlin

How are you determining the ECU cuts fuel by 20% when meth is being injected? All my cars that have run meth, it was a supplemental injection. Also how "uneven" can the meth being injected be when it is sprayed as a fine mist into the air intake?

e65

short-term fuel trim is close to 0% under normal driving conditions. When methanol is being injected during quarter mile run it's -20% it fluctuates a bit but it's around that number. 2 big aem nozzles.

when the methanol injection is off short-term fuel trim remains close to 0% during the quarter mile plus or minus a few percent fluctuation.

kponti

A -20% fuel trim by the ECU does not equate to 20% less fuel compensation by the injectors. I couldn't exactly tell you the ratio (been a while), but from my tuning days STFTs do not illicit such wild changes in injector duty cycles or durations. You start seeing LTFTs going that high, then yes fuel is being cut that much

chiromikey

e65

Short-term fuel trim adjustments are practically instantaneous. Long-term fuel trim takes several hours even days to reach a steady level. Long-term fuel does will not change during methanol injection that occurs for 10 seconds. The only adjustment that can take place to fuel delivery is by the short-term fuel trim. This is what I have seen.

If I put M15 into the fuel tank while your long-term fuel trim is +5, I will see short term fuel trims jump to ~ +15% even more. As the long-term fuel trim creeps up to 10% the short-term fuel trim will come down to ~10%. This adjustment keeps going on until the short-term fuel trim is close to zero. At which point the long-term fuel trim will be ~20%. If you go back to premium fuel while your long-term fuel trim is +20% your short-term fuel trim will become negative. As the long-term fuel trim comes down towards or +5 the short-term fuel trim will increase towards 0 and that takes a couple of days. The long-term fuel trim does not have time to adjust during methanol injection, the graph shows a flat line for LTFT.

When you go full throttle the ECU will command a pre-programmed amount of fuel + whatever the long-term fuel trim is + whatever the most recent short-term fuel trim is. If your long-term fuel trim is + 10 and your short-term fuel trim was + 10 then the ECU will add 20% to whatever it is programmed to deliver. Then during the run if you are a bit rich or lean the ECU will find tune adding or subtracting a little bit of fuel reflected in the short-term fuel trim which fluctuates a bit throughout the run. The initial WOT initial fuel delivery is calculated from the pre-programmed value + LTFT + STFT.

If the long-term fuel trim is negative this will not automatically be subtracted at wide open throttle for safety reasons. As a result you end up running rich initially but the short-term fuel trim will adjust.

For 2 WOT runs with identical long-term fuel trims you can compare the short-term fuel trim with and without methanol injection. In my case it was 0% short-term FT without methanol and - 20% short-term trim with methanol. My long-term fuel trim for both runs was +20% because of the oxygenated fuel I had in the tank. Pre programmed fuel amount + 20%LTFT with no injection. Preprogrammed amount +20% LTFT - 20%STFT with 2L/min meth injection. As soon as I run is over stft comes right back down ~0.

Vic55

Chiro and Ronin, you both have given much to this community- I have erased the comments that clearly are not part of a fruitful discussion in this thread. Keep it civil and please agree to move on with no further off topic/insults.

Back to the thread please.

aoschadlin

Even with the goal of octane boost, isn't the *amount* of boost proportional to the risk? eg I want to boost from 91 oct to 93 oct. Low risk. I want to boost from 91 oct to 98 oct. High risk. ???

chiromikey