This is supposed to be a global forum

I certainly accept that 98% of membership is probably American

 

I don't think that is the case for my car in particular. There is settings in STAR for gas and E85. I am not 100% positive, maybe Glyn can comment, but I believe their are separate maps for gas and E85. I would love to dyno to prove it, but I definitely feel a difference. Also, I keep extensive records of every tank of fuel I have used since day 1, and the car can obviously adjust for E85, as E85 has 30% less BTU's than gas, but my average difference between E85 and gas is 21% less on E85.

 

No, 2007 2.5L C230's are flex fuel capable, so no modifications needed. Just fill with E85 and go.

 

Have you ever used it? I see you are in Portland. The cheapest, and best place to get E85 is Bob's Gas on 82nd near Johnson Creek. Just paid $2.23/gallon on Saturday.

 

Benz have not been consistent in this regard in my experience. Some have broad maps & depend on the O2 sensors & knock sensors to correct timing & AF ratio etc. Some have switchable maps with Star. I like this approach because the map is optimised.

However - from a Benz perspective I think they would like a Flex fuel car to be just that. Put a broad range of fuels in the tank & it will run on them without issue. This I fully understand.

 

my car states i can use either premium or e85 so i found a gas station around me and filled her up! just like what john says.. gas mileage is not as good but my car does feel much better! and i do feel gains as well

it was kind of a far drive (well not really 10 miles away from home) it was kinda of fun to try something different!
wish there were more gas stations with e85 =( it is soo much CHEAPER!!!
i should've took more photo's but yeah it was 2.69 a gallon!

 

What is the price of premium in your area? I average 21% less mileage, so as long as it is at least 22% cheaper for E85, it will save you money.

 

I would think that there is a fuel map and timing variation between the two fuels.
I've been bouncing between E85 and premium for two reasons:
1) I'd like to think the properties of E85 and it's volitility might actually have some cleaning benefit to the fuel system and it's parts
2) When the price scale tips in favor of E85, I find it a great opportunity to be frugal and the above comment.
3) There is a definite increase in seat-of-the-pants throttle response and low end torque when I use E85 over premium. I just dislike getting under 270 miles per tank.

 

$2.69/gal ..WHAT.............. ..out here in NJ the regular we can get for $2.42/gal CASH(cheapest) avegrage hess is @ $2.45/gal CREDIT regular (which I use).......OMG........

 

Even that is too expensive. Last week it was $2.15/gallon here.

 

John, just a few times. I ran about 2 tanks last year. I too was about 20% less on fuel economy. At the time the price diff in fuel cost vs. MPG was roughly a wash. At ~2.23 per gallon it is somthing i may consider again however.

I live in NW Portland, but work is in SE, so 82 and JC is not too far. Are you in Portland ?

 

I actually live in Camas, WA, but work in Wilsonville, OR, so Bob's is conveniently located along my daily commute. The difference in price between premium and E85 fluctuates a lot here in the NW, but lately E85 has been quite a bit cheaper than premium. Seems as premium goes well into the $3/gal range and above, E85 isn't much less than premium. But, when premium is ~$3.30 and under E85 is usually much cheaper. December 2008, Bob's had E85 at $1.65/gallon

 

Well, I know the car can adjust! It has to! But what most likely happens is that when using E85, the car will initially run on the gas maps and the O2 sensors will determine that it is running too lean, so it will enrich the fuel mixture. Once it reaches a certain threshold, it will switch over to the E85 maps. It can do this because there is a huge difference in the proper AFR for the two fuels that it won't be mistaken. But I just don't see getting extra power over gas from E85 as the engine is not optimized for E85. All you really have is that timing can be advanced, and the cooling effect, and I don't know if that can really account for an increase in performance. If it did, wouldn't you think all the auto mags would be using E85 for testing for better numbers? I could be wrong, but I think its all in your head.

 

I WANT E85! I've been trying to find it, but the only time I came across it was driving through Atlanta... and I'd just filled up! I'm heading up to Atlanta tomorrow, though, so I will try to seek out E85!

 

^^ Stop lying

 

^^About??

 

About how you're heading to Atlanta...you told me you, Trey and Matt are coming down to SoCal...so stop lying.

 

If all goes well I'll be meeting up with Drew on Sunday. I won't, however, be filling up with E85. I don't think my car would appreciate that at all.

 

Have you checked here: http://www.e85refueling.com/location...tate=flFlorida

There appears to be many E85 stations in FL. Not sure if any of those are close to you.

 

I think it is all in spark advance. Most aftermarket ECM tunes are mostly spark advance. E85 is 105 octane, so that is a large amount of advance over 93. Even my wife feels the difference, and she doesn't notice anything when it comes to cars. Plus, as you see from this thread, several others with the 2007 C230 notice a difference. It is possible, but I doubt it is all in "our" heads. Too bad your 2005 wasn't flex capable, so you could try it for yourself. Like I said, if I ever get a chance to dyno it for a reasonable price, I will.

 

Earth shattering differences I don't buy but an increased peppiness out of the engine on E85 is possible. The camshaft arrangement on the 2.5l M272 is excellent & it has an 11.4 to 1 compression ratio. It breathes well & has good volumetric efficiency. With tuning it should show some benefit on E85 - albeit not optimised.

Power output of an engine as relates to fuel is mainly driven by fuel density & fuel volume that can be completely combusted by that engine. Octane rating per se has nothing to do with power output - it is purely a rating of resistance to knock of a fuel, however it does allow higher compression ratios & more advanced timing.

In the case of the baby M272 the standard base line tuning map is very conservative so that it can run on crap fuel without any danger to the engine. It is not tuned for maximum power output.

When running on the oxygenated fuels map, pumping in more fuel at corrected AFR & advanced timing (which would be dangerous on the standard map with crap fuel) it could well show some meaningful benefits in responsiveness & increased power output. I believe one could feel this in normal driving because the basic profile of the engine is actually quite good for alcohols - high CR, capable of injecting & combusting sufficient fuel, capable of timing advancement & good breathing. Breathing is less of an issue with alcohols because of the oxygen molecule in the fuel, but when you are pumping in a whole lot more fuel you still need enough air for roughly 9 to 1 AF ratio.

I don't think that John is trying to make unrealistic claims here or that the engine is "perfectly" optimised for E85. As a flex fuel car it is certainly capable of making better use of alcohols than any "standard" vehicle with narrow tuning parameters.

We can go into cooling effects & what that does for max air density/cylinder filling & flame front propogation with alcohols etc. but the basics above make John's reasonable claims likely.

 

Thanks Glyn, you are right absolutely right, it is far from an earth shattering difference and I have never claimed that. It is a subtle increase in throttle response and eagerness to rev.

I have been researching some tuners as of late, and trying to get one willing to tune the engine for premium AND E85. I think there quite a bit of room for improvement as far as power and economy on E85. As, you pointed out, MB never bothered optimizing E85 maps because, frankly, the percentage of owners running E85 is REALLY low, so it wasn't worth it. That is why sometimes I have some minor drive-ability issues on E85.

Honestly for me personally, the driving force in me using E85 is pure economics, and nothing else.

 

To further back this claim, I can attest to the difference of the base conservative mapping to the higher octane mapping. My dealer explained that the M272 when driven mildly will run quite well on 89 octane and only AMG motors require 92+. I begged to differ but humored them and ran regular a few times in cooler weather. It actually did run fine at the expense of reduced power (through the entire powerband though!). Once the weather heated up and I got down on the throttle I heard what any car enthusiast is repulsed by... pinging. I immediately filled it up with E85 to at least get the octane rating up. Since then, I've personally banned all octane under 92. I have also found the mileage to be better with 92+ octane fuel. The performance without a doubt has increased significantly and slightly more with E85.

In short, my findings through trial and error:
1) 89 Octane (aka "Cheap Hooch")
PRO: Good gas mileage, decent price
CON: Lowered performance & Risk of detonation in warmer weather or spirited driving

2) 92+ Octane (aka "Top Shelf Libation")
PRO: Normal performance, greatest gas mileage and no detonation.
CON: Highest gas price

3) E85 - (aka "Grain Alcohol/Moonshine")
PRO: Highest performance, no detonation & best price
CON: Decreased gas mileage and due to the lower energy rating (E85 < 92+), it can be a wash based on pricing.

 

Yep! - I'm surprised you actually detected pinging, knock, detonation, pre ignition by whatever name you know it. It must have been real "cheap hooch". High speed knock is the most dangerous for an engine & difficult to detect (by hearing not sensors)

Benz use amazingly good knock sensors & will retard the timing in a flash at the onset of knock. This is why the Diesotto works.

 

I agree with your mapping intentions - you are never going to run your car on "cheap hooch" - love it! - irrespective of economics. Why run with the timing permanently retarded & it's adverse effects on performance & fuel consumption.

When it comes to the odd drive-ability issue - I'm not surprised & the E85 might be a little variable. I'm sure these drive-ability issues are nowhere near what the Brazilians tolerate with their mainly hydrous alcohols with real crap distillation curves.