Nevada and Utah only have 91 (93 is not common) octane as well, which is pretty much normal across the US. However, I requested the chip programmer modify the timing maps to increase power which consequently requires that I run a 94/95 octane level to avoid pre-detonation when at WOT.

To acheive a 94 octane level I mix 100 octane (you have to locate a store that sells race gas or get it at the track) with 91 and arrive at 94+. Store octane boosters will not even come close to increasing above 94.

 

Unfortunately, the thread to which you so generously provided the link actually undercuts your argument, as in it people w/stock ECUs reported performance gains from switching from 91 octane to 93 octane gasoline, which if true would support my argument that Mercedes optimizes their ECUs for octane ratings > 91.

Nicely done.

Readers and responders, please do not accept undocumented, unproven, baseless claims that stock 208 timing *is* optimized to a maximum of 91 octane gasoline when no evidence whatsoever has been presented, by anyone, to prove this claim.

ashutt seems to have some ulterior motive here, don't know if a financial interest is involved or if it's just sheer stubbornness on his part, but clearly he is trying to get people to ignore objective, published facts, and clearly he very actively promoted this chip in both this forum and the W208 CLK forum. I would also point out that, as shown by the threads he started I quoted above, when it served his interests, he was showering me (and wikipedia) with flowery praise, up until I disagreed with him, when suddenly I was magically transformed into a know-nothing, and Wikipedia became worthless.

I, otoh, have no motive other than the airing of objective facts on this matter, in response to which ashutt has resorted to repeated personal attacks, and a refusal to engage in any dissemination of facts supporting his arguments.

The fact is that 93 octane gasoline is widely available in the US, and even higher octane (up to 95) is available outside the US, in Europe, where Mercedes designs and builds their cars. There is no motive for Mercedes not to optimize the timing to octane ratings higher than 91, and again not a shred of proof has been presented that they have done so.

In fact, I invite any and all interested parties to simply contact Mercedes AMG AG and ask them yourselves about this matter.

 

I've been told over and over, the damn cars are optimized for 93. Cali cars all limp around with LESS power as a result, not optimal.

 

Yup, it sucks. The most ridiculous thing is some people put 89 or even 87 (both these pig-swill grades have long been outlawed in Europe where our 91 *95euro* is their worst) in the S85. Of all the production engines on the planet, a V10 that spins to 8,250 is the worst place to try and save $3/tank.

 

That's the thing: with antiknock sensors, the way these things work is to simply run as much timing advance as they can without getting detonation. This is a complicated feedback and control system, not some arbitrary "hey, let's set the timing advance to 20 degrees and call it good" type like in the old days.

The optimum timing varies not only with octane, but with temperature, humidity, load, etc...the maps are set to account for all of this, and would also in all likelihood be set to have the capability to operate up to the maximum octane rating they're likely to hit--worldwide, meaning that they're probably set to even higher octane ratings than we get here right out of the box.

Fifth Gear examined this phenomenon in this test with three diffferent cars, and found that the base, entry-level, cheapie econobox gained nothing from using super-octane fuel, while a Golf GTI and Scoobie WRX STi gained horsepower with each increase in octane, the Scoobie doing the best at +14 hp (+6%), the VW picking up more like five (+3%).

To make sure everything was done correctly, they reset the ECU after each fuel type was used, and completely drained each vehicle's tank.

 

Exactly impro, there's really nothing more to say here.

 

Yeah, but you know me!

I did want to add two more pieces of data to the mix. The first is the folllowing, quoted directly from my W208 owners' manual:

Kind of added a bit of emphasis there, but the key word is "min". This means "minimum", not "exactly", "only', or "exclusively"...i.e., they are saying that the fuel requirement is not 91 octane, but 91 octane and above.

Which, again, makes sense given that 91 octane is by no means the highest octane of premium unleaded available in the US, let alone outside it.

Also, have a look at this article from Hot Rod magazine. They took a 360CI V8 with a 10.5:1 compression (same CR as ours if memory serves), and tested its horsepower/torque output with several different octane fuels (87 octane, 91 octane, 91 octane plus "octane booster", and 100 octane race fuel. They also varied the timing to try and optimize it to the fuel rating, recording horsepower numbers at several different timing settings for each octane rating.

Guess how much extra horsepower using 100 octane fuel with optimized timing netted them over 91 octane with optimized timing?

1.4 horsepower.

Wow.

It is also illustrative to note that their maximum horsepower numbers at **all** octane ratings, from 87 octane all the way up to 100 octane, came with the **SAME** setting of timing advance: 36 degrees. Deviating from this setting in either direction, regardless of the octane of the fuel being used, resulted in lower measured horsepower and torque. The only octane level that benefited from a different level of timing advance was 114 octane, wherein maximum power was reached by retarding, not advancing timing, to 31 degrees of advance.

Their conclusions:

 

I've seen the octane setting in the STAR/DAS be set to lower octane fuel.

I've also seen Euro E55 timing maps compared to USA E55 maps, and there are timing differences-especially up top.

 

How can you determine from a timing map what octane it's optimized for? As evidenced by the HR article, a different octane rating in and of itself doesn't necessarily require timing changes for max power. Do they spec this somewhere?

Makes sense--on a forced induction car running 14psi there is a much higher chance of detonation than on a normally aspirated car.

But with n/a motors, it's a different story.

Can you get, and post, the info for a 208? Tia....

 

There's a spec in the variant coding area of the system. I'll try to get some screenshots up for you soon.

WRT power production, that depends on the car's compression ratio, head material, cooling ability, etc.

In the article, they were running 10.4:1 CR with 36 degrees of total timing.

Your car most likely runs under 29 degrees total.

 

I wouldn't think it would be set that low....my car has a 10.5:1 compression ratio, and in the article they ran 36 degrees using 87 octane gasoline without any detonation (which is also the point at which they got the max power at that octane rating)...it took a full 38 degrees to get detonation w/87 octane.

Using 91 octane they were able to run 38 degrees w/no detonation, *but* it got them no additional power; max power came w/36 degrees timing--as it did with 100 octane, even though they were able to run it as high as 40 degrees with no detonation. In fact, w/the 100 octane, although their max of 403.5 hp came at 36 degrees, the motor produced above 400 hp at settings of 31, 34, 36, 38, and 40 degrees.

What was really interesting was the 114 octane. With that octane, their max power of 408 hp came using 31 degrees; it actually lost power at the higher settings.

In fact, the total variance in hp from 87 octane to 114 was 12 hp. Here are the peak results for each octane, given as octane/peak hp/degrees timing at which peak hp was achieved:

87/396.0/36
91/402.1/36
100/403.5/36
114/408.3/31

As you can see, going from 91 to 100 octane picked them up 1.4 horsepower, so it's kind of doubtful that they would pick up 22 going from 91 to 94.

 

All i can say is that... Evotech is a virus that infected sleepers perfectly running RennTech P5 11.5 car... as soon as we started putting that garbage in his car is where it was over....

the icing on the cake was when alex sent a modified AMG speed**** to me thru sleeper... that he had no idea how to hook up.. we hooked it up as he told us to... threw all types of malf... then he said do it a diffrent way.. still no good... then sent it back to him.. oh it was the wrong one or something? then we got another one... then this one appeared to do absolutly nothing.. so im thinking what could of been done to the car when i had it hooked up the wrong wire the wrong way twice? Then the his ecu flash and the other stuff... i dunno... seems like a nice friendly guy, but doesnt know alot about cars... seems like a middleman that sits in a room somewhere slinging parts he doesnt know about...... and yes, some of his stuff is cheap... but you get what you pay for.... I take this very personaly because this is the only car out of 100's that i ever had a issue with, and it was my favorite....



(i have some deep nested issues with this)

 

Chappy attached is the mileage and performance on the way back. A straight run from Greenville SC. to Dallas (no adventures :-), with a breakfast stop in Atlanta and misc gas stops etc..

Can't say if tune affected mileage or not. Curious to see what other 208 owners have experienced and if this MPG rate is inline with expectations.

 

Glad you made it back safe. My average is a little higher for highway...26-27mpg, but my cruising speed is closer to 70.

 

A 77MPH average over 12 hours? So you were doing 90+ most of the time, right? Great mileage at those speeds.

 

I get about 24-25 on a 2 hour interstate trip.

 

lol.....on his way up to Greenville from Dallas, Zal called me from the road and I kept hearing his V1 in the background. Yep - Zal makes excellent time on road trips!

 

How was the driving school?