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Registered 2005 SLK350
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Do you think I can run e85 on my stock 2006 slk 55 Amg[/QUOTE]

I'm surprised that our more knowledgeable members haven't responded so if I misspeak here, feel free to correct me.

In answer to your question, unless your SLK was built as a flex-fuel vehicle (which I highly doubt), burning E85 would be highly ill-advised. Ethanol attacks and deteriorates rubber items in the fuel system unless they are designed to be compatible with ethanol. And there's a real possibility that your ECU would have to be re-mapped and your compression ratio changed in order to get any appreciable increase in performance if that is what you are after.

I drive a flex-fuel vehicle and my experience has been a dramatic reduction in mpg with no noticeable improvement in performance. I used E85 for the first two years of ownership simply because my home state subsidized my usage. If it were not for that, even though (at the time) E85 was cheaper than the lowest grade of gasoline, it would have been more costly to use because of the reduction in miles per gallon. When the subsidy went away, I no longer used E85. And yes, I know that race cars run on pure ethanol but their engines designed specifically for that.
 

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E85: lowering fuel economy (see above testimony), putting farmers on welfare (increased dependence on subsidization), and raising the cost of animal feed (and your dinner).

Not good for anything but those who produce it. I wouldn't use it in my lawnmower, and especially not my Mercedes.

My two scents......
 

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I personally remap ECU for using E85 with flex-fuel mode. So you can use unleaded to, and mix with E85 as you wish. There is no problem with rubber items in the fuel system because all european vehicles has been designed to accept ethanol mixed with gasoline since late 90's. But your ECU software is not designed for more than 40% of ethanol although you injection system is big enough. So, a "simple" flex-fuel chiptunning will allow you to use E85. That's my job.
 

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Premium Member 2001 SLK320/2000SLK230
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OK here is the problem and is threefold. First e85 is about 110 octane which means it burns very slowly and you need more advance to get close to stoic. Second you need about a 20% richer mixture so the pulse width of the injectors needs to be fattened up (assuming the stock injectors/fuel pressure can flow enough - Duke says it can be and I will defer to him). Third, what to diddle so that the ECU recognizes it as a legitimate program.

Unless you have a method to determine whether gas or E85 you also need a double memory and a switch on the top address line

Can be done but really takes a professional or a very knowledgeable amateur. (I do not know enough. Yet.)
 

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You don't need 20% richer mixture for E85 but 35% ! The way i use to determine whether gas or E85 or a mix of both is in the car is very simple : AFR exhaust captor (Lambda). Your ECU is able to adjust AFR yet. But not enough for 80 percent of ethanol. About 40% with stock program. I can change some datas in your ECU program file to increase this capability (with some other parameters to increase performance if you want). So my SLK 55 AMG 2005 works perfect with 100% E85 AND 100% SP98 gas AND any mix. See my facebook page to have exemples of what i do. I tunned A 45 AMG few days ago for athletic french champion by example. I work in chiptunning since 2003, and develop Flexfuel program for 6 years. So i can confirm you that there is no problem with using E85. You just have to tune ECU program file in the good way.
 

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And yes, i adapt ignition advance… of course!

For R172, i can make real dual-map automatic switch to increase performance when E85 is used. For R170 and 171, you will have same performance with 98 RON gas and E85. So for my 2005 R171, i have "stage 1" 98 RON power as usual + E85 compliant. An dall is automatic. I use E85 all days but, if i can use 98 RON gas to.
 
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