Recently I've really been considering getting a flex fuel kit for my w204 c63. Before I do anything however, I want to hear about other owners experiences with E85 in terms of reliability. The one thing I want for my car is to make sure its as reliable as possible, I love this car and I wanna make sure it can last. And also is it worth it.

 

Lots of threads on power gains vs less mpg

But less mpg = more spg ( smiles per Gallon)

I did recently read a post on how it caused earlier than average need to change spark plugs. I'm also concerned about long term effects although I wouldn't use it often and would mostly still be regular fuel

 

I had it for a while and removed it recently as was planning on selling.
I found little difference “feel wise”. Took longer to start , then I had to wait approx 5 minutes to warm the car up as it would splutter without the warm up. Was advised this is normal . Running non e85 fuel I was told maximum half throttle which I followed. What I missed was the bark at cold start running e85 as this was removed to protect something ( can’t remember what).

Had the flex fuel kit with 600cc injectors, also mbh headers, W204 2010 459rwhp

Happy it’s been removed as was not for me .

 

Good info

 

all because of back yard tuning and piggy backs. i'm not going to lie...after SO MANY people here talk so highly of things, you know I took the plunge myself in the past. does it work...yes...does it work well...no...not at all.

the proper way to apply a flex fuel kit is to first have your vehicle retuned for the injector size you plan to run. custom tuning would be preferred. from there, you then install the flex fuel kit. what this does not do is...allow for correction to cold start or utilize increased ignition timing for the added octane of E85. all this does it allow for the piggyback to adjust fueling for the ethanol content it senses. even with that they do it VERY poorly. literally your fuel trims will swing +/- 18 clicks in either direction during the same drive cycle. then to attempt to resolve this, they released 1,600 dollar "tunable" flex fuel computers...does it solve the problems i've stated...no. its a piggy back, you'll never drive perfect, there will always have some quirk. whats the point in running E85 if you cannot harness it in its entirety and throw in all the ignition timing it would safely take to maximize power output? you're just throwing money down the drain at that point unless you're actually flashing your map back and forth for the matching ethanol content to the correct ignition timing map.

all in all, you'll never have the power output, engine response, or throttle response from a dedicated tune specific for the fuel that is in your tank. there is no way around it. for my e85 maps i'm dumping in over 10 additional degree's of ignition timing. some area's over 18 degree's of ignition timing. and i'm just using the term dumping loosely. its all calculated and precise since i'm using time versus outcomes to bell curve the appropriate pathway to build a custom map. don't forget the full rebuild of starting maps, temperature compensation maps for the fuel as it holds a different BSFC versus gasoline. do i recommend flex fuel kits...no...do i support them...yes if i must but they will require the vehicle owner to understand, you'll never ever have the same engine response or performance potential of a dedicated e85 tune. literally losses of 15-25% in throttle and engine response because fueling has to pass through a piggyback to make adjustments, and those adjustments in most cases are way off.

 

So Barry, what about simply forgoing the Flex Fuel option; just run larger injectors, would an E85 map would work just fine? Assuming I consistently test E85 at the pump? Here is SoCal, I have yet to see E85 test less than 80%.

 

I had the kit for just over 3 yrs and did not have any of the stated issues. Started fine in 3 Degree weather. I just wait for idle to set (2-3 Mins), then just drove. I regularly switch between 93 and e85, full,mix no issues. I do keep on top of regular maintenance. The only issue which I will be resolving shortly is a call to Barry as I have had an off the shelf tune and missed the last time EC came to NY. I am ready for a custom tune :-).

 

although it is more work...what is a high performance car without a little bit of effort. I personally run an innovative ethanol sensor and gauge. for the most part i only flash the appropriate map when having to switch between 91 octane and then over to an E85 blend...if i'm unable to fully run the tank down to the last drop, i may end up with ethanol at 60% or so...i'd flash that appropriate map until i'm able to fill up with E85 once again. by the 2nd tank i'm usually within 3 points of max ethanol percentage matching the pump. here in northern california, i see 79-80% ethanol. when I lived in san diego i was seeing 82% always. the ethanol percentage doesn't fluctuate in california for the most part. i'd assume the same for the warmer states as well, arizona, texas, new mexico, etc. its much cheaper for them to give you as much ethanol as possible than to blend in gasoline. since the warmer states don't see snow or very rarely do, they generally stick with the same blend throughout the year. so for me, flashing a map every few months when i cycle back over to gasoline to allow for degunking or for road trips is not a problem.

a dedicated e85 tune will run as reliability as any gasoline map and have amazing throttle response without any issues to your spark plugs or oxygen sensors. that's the first thing i noticed once i pulled that flex fuel kit off and began building my first e85 map way back then, the throttle response i was missing when utilizing the flex fuel kit. if you're seeing oxygen sensors or spark plugs go out, its either your tune, or the fact that the flex fuel kit is unable to correctly correct quickly enough. over time this will cause oxygen sensors to fail due to fuel bunching or spark plug fouling if your fueling is wayyyy off the mark. oh yeah...and without misfires.

with a "shelf tune" and a flex fuel piggy back, i always thought my car ran best with that setup at 60% ethanol...well, that is the only percentage it ever ran without having ridiculous misfires. if i ran any more ethanol, it'll run but would be slow and 50% of the time misfire like crazy. now, with my own dedicated tunes, i'm able to fully utilize higher blends to their absolute potential. my 82% ethanol map kills my 60% ethanol map everywhere. the "shelf tune" i purchased would misfire like crazy on 91 octane as well. the tune felt stock. basically paid $1000 for having my rear o2's disabled. if anything maybe gained 10hp, but that was it. 10hp for massive misfires, no thanks. barely even noticeable power. hell, my 87 octane map out performs the previous shelf tune i purchased. yeah, for those of you who don't follow me on instagram, i have developed an 87 octane tune as well. lol. it is fully safe, and faster than the factory tune of my E63 which is rated at 507hp.