OBD 2 question,

[Dan The AMG Man]

Talked to my service writer today and asked him to switch over my car to the RON 91 thing.. he said my car can not do this due to it being a OBD2 unit.. it is a 1996. Is the telling it true or the giving me the brush off..

[speedybenz]

Dan,

He is giving you the Brush off. My 1999, OBDII car has the fuel setting set to RON93. Took some time for the ECU to adjust but after it did the car runs much snappier.

Jeff

[Renn 208]

I still don't quite understand what setting the car to 93 RON would do for performance. Wouldn't it retard timing even more than normal? Isn't 93 RON usually equivalent to 89 US pump octane (assuming that it's 85 MON)?

Could it be possible that say you set your car to 93 RON...the computer retards timing...performance suffers initially. Then the computer then realizes that it can advance timing without getting knock...in adapting it does so, thus giving you back your snap?

If changing the fuel setting can really advance timing, shouldn't we be looking for a setting like 95 Ron or higher?

[KLEEMANN]

"Baseline" setting gives the most IGN advance, all other settings are for REDUCED octane values which will RETARD timing. If you read the screen on the DAS machine it will say something to the effect of: "Ignition correction for countries with sub-standard fuel". Your vehicle will make LESS power at any setting other than "baseline"- if anyone thinks they feel a performance increase, its all in your head. We advocate going to the 93 setting in warm climate states with max 91 (R/M2 method) fuel with our 4 cylinder boost kits if there is a timing retard problem due to incipent knock. Otherwise, leave it alone. This applies to ME SFI vehicles. For HFM and CIS-KE vehicles there are "pills" that are essentially plug in resistance buttons that determine the IGN advance. All USA delivery cars of this vintage all are quite retarded. Using a EU part number for these "pills" will allow a significant increase in timing which leads to higher combustion chamber pressures and therefore higher TQ production.

[Renn 208]

Thanks for the clarification B.

[ThreePointsix]

Originally posted by KLEEMANN
"We advocate going to the 93 setting in warm climate states"

MB Greenway here in Houston initially told me they want $195.00 to hook up to the star computer & see. Sound reasonable anybody? I've had it hooked up for free at another dealer & I'll probably pursue that option. It sounds like it should be an extended/free warranty correction to anybody with an AMG handbuilt on the order of only several hundered a year with performance as the main objective?

[Renn 208]

Originally posted by ThreePointsix
MB Greenway here in Houston initially told me they want $195.00 to hook up to the star computer & see. Sound reasonable anybody? I've had it hooked up for free at another dealer & I'll probably pursue that option. It sounds like it should be an extended/free warranty correction to anybody with an AMG handbuilt on the order of only several hundered a year with performance as the main objective?

Is your computer already set to RON93? and what you want is to set it back to normal? Or do you actually want to retard your timing? I'm a bit confused.

[KLEEMANN]

Originally posted by ThreePointsix
MB Greenway here in Houston initially told me they want $195.00 to hook up to the star computer & see. Sound reasonable anybody? I've had it hooked up for free at another dealer & I'll probably pursue that option. It sounds like it should be an extended/free warranty correction to anybody with an AMG handbuilt on the order of only several hundered a year with performance as the main objective?

No, this sounds insane- its a diagnostic tool. If you actually CHANGE something, thats different.

AMG makes way more than several hundred anythings per year- and I can assure you profit is the objective.

You left out the most important part of my "quote" - with our boost kits on M111 SC engines. Your C36 should be at baseline or standard correction, ANY other setting will REDUCE performance.

[ThreePointsix]

Kleeman,

I am assuming that you are saying - don't mess with the Ron setting at all in my C36 based on your proven performance background. A little clarification on the MB STAR values and what they mean would be great & informative. IE; there is a bit of confusion on what european RON93/RON91 means to us all since there is some type of Euro conversion & we are used to understanding 93,91,89 US methods. So if assuming my car is currently set to Ron91 right now, Ron93 will make my ECU give less advance & a poorer performer? People like me on other threads pertaining to this subject are still confused a little based on the replys.

I know 93 octane fuel will tolerate more advance in a 'performance' engine than 91 or 89

Also as a side note off the subject a little,

My car was purchased new in TX and shipped over & used in Mexico City by the previous owner for 5 years & also the engine temp gauge & climate control reads metric not standard? I was told that these settings cannot be changed by the Star computer also. Maybe that was user error by the tech? I'll post this in a tech forum on Mercedesshop I guess.

[Renn 208]

Originally posted by ThreePointsix
Kleeman,

A little clarification on the MB STAR values and what they mean would be great & informative. IE; there is a bit of confusion on what european RON93/RON91 means to us all since there is some type of Euro conversion & we are used to understanding 93,91,89 US methods.

here:

Originally posted by KLEEMANN
"Baseline" setting gives the most IGN advance, all other settings are for REDUCED octane values which will RETARD timing. If you read the screen on the DAS machine it will say something to the effect of: "Ignition correction for countries with sub-standard fuel". Your vehicle will make LESS power at any setting other than "baseline"- if anyone thinks they feel a performance increase, its all in your head. We advocate going to the 93 setting in warm climate states with max 91 (R/M2 method) fuel with our 4 cylinder boost kits if there is a timing retard problem due to incipent knock. Otherwise, leave it alone. This applies to ME SFI vehicles. For HFM and CIS-KE vehicles there are "pills" that are essentially plug in resistance buttons that determine the IGN advance. All USA delivery cars of this vintage all are quite retarded. Using a EU part number for these "pills" will allow a significant increase in timing which leads to higher combustion chamber pressures and therefore higher TQ production.

3.6: it's not a "Euro Conversion" per se, but a difference in how we view octane. You have the answer in your post "we are used to understanding 93,91,89 US methods" The US method is to use an average of two Octane tests: Research Octane (Test) Number (RON) and Motor Octane (test) Number (MON). The results are the Pump Octane Numbers PON that we know and love. That's why on US pumps you always See the ((R+M)/2).

In Europe (and within Stardiagnose) the Standard is just to quote the RON number. A RON 93 fuel is most likely equivalent to 89 at a US pump. That's why Brandon states that setting the car to anything other than baseline (i.e. 93 RON) would retard your timing as you are telling the computer that you are going to feed it lower octane fuel. In CA the most common premium fuel we have is 91 PON. That is equivalent to 95 RON (assuming 87 MON), hence to get more advance we'd have to have a setting for 95 RON or higher in Stardiagnose.

My question is however, even if you set say a 91RON in the car, but continue to feed it high octane fuel, will the computer realize that it can advance timing without knock, and eventually adapt? If so, that would explain the situation that Jeff has experienced.

[ThreePointsix]

I think a more detailed look at the ECU's ability to correct and modify the existing fuel/spark tables would be great knowledge here. PowerChips actually re-burns these ECUs and states actual HP claims for $600. They claim 30hp increase on my car w/ 93 octane fuel maps. Someone who engineers these maps may be able to in depth let us know how the MB ECU in the 202 'thinks' and adjusts without us guessing and assuming.

[Renn 208]

Originally posted by ThreePointsix
Someone who engineers these maps may be able to in depth let us know how the MB ECU in the 202 'thinks' and adjusts without us guessing and assuming.

And that's my standing question as well.

[KLEEMANN]

There is no guessing going on here, and you dont have to write the tables to know whats going on. Each of the settings has an operational window. Each window has a "basement" and a "ceiling". The basement is the total amount of retard, the ceiling is maximum advance. Choosing 91, for example, will limit the ceiling to 16 deg BTDC. Using 100 octane fuel will not allow advance past this value. What would be the point of a set point if the ECU could just go past it? This is an adaptive system, not one that "thinks". The ECU will allow as much as 100% of it base map timing, no more. If the KS detects incipent knock the ECU will retard timing 2 dergees at a time until the knock is mitigated. The amount of total advance used depends on the operating circumstances of the engine (load, speed, temp etc).

The adpation for fueling is very simialr. The "apaption" that happens is +/- a value of 1.00 where 1.16 represents the addition of 16% to the base map and .84 represents the subtraction of 16% from the base map. 1.00 would represent using no correction from the base map. Allowable deviation from 1.00 is +/- .30 or 30%, at this point a MIL will light for reaching the maximum allowable correction. There are three ranges for fuel adpation, idle, lower part load and upper part load. These adaptions are constantly taking place with the last adjustment being the basis for the next operating window. If the "goal" (in this case lambda value at the leading O2) is not met the next cylinder firing will have an addition or subtraction from the existing "adpation". This system allows for the degradation of fuel componenets while maintaining precise tail pipe emissions.

A chip tuner will make maps for "93 octane", this has nothing to do with the MB nomenclature. Its their way of stating that their claims are based on using 93 octane fuel. You really cant (why would you want to) write the safety retard feature out of the system you can only change it. So a tuner will write a hex decimal file that allows a X% over the max advance and it wont touch the "basement". If you dont run 93 octane you wont get the claimed result, but you wont kill the engine either because it still has the baseline shift to -X degrees advance.

If you want to change any of the existing data tables used for *whatever* inside the ECU, of course you have to "re-burn" the EPROM, there is no other way to do it.

[CoryU]

:werd:

[Vodka G]

so basically you are saying that for example my car bought in CA should be set to 95RON (which should be the baseline setting)setting in the comp. and it'll be fine running 91 R+M/2 fuel

what about if i were to put in 93 R+M/2 fuel in canada?? is there a need to set it to something diff.....and will it help

[Renn 208]

Originally posted by Vodka G
so basically you are saying that for example my car bought in CA should be set to 95RON (which should be the baseline setting)setting in the comp. and it'll be fine running 91 R+M/2 fuel

what about if i were to put in 93 R+M/2 fuel in canada?? is there a need to set it to something diff.....and will it help

They are saying that changing the settings won't help as the system at baseline only pulls timing in response to knock.

All of the alternates to baseline (93RON, 91 RON, etc) artificially retard timing.

And until someone comes up with a good argument/proof otherwise, setting the ECU to 93 RON is not a performance enhancement.

The only question I still have is if one were to say set the ECU to the lowest setting (reduce the ceiling to 91 RON), will the ECU eventually adapt and advance timing beyond the user selected setting? (Effectively overriding whatever is set because knock will not be detected past the ceiling).

[KLEEMANN]

The ECU will not advance timing past the set point determined by the "setting". The ECU will run 100% of the map selcted if the fuel being burned will allow it without knock. The ECU will not run 105% of the selected setting.

Let me try to explain why one would want to use a lower octane setting than baseline. On a M111 engine (230 SC) if you use a boost pulley you are increasing discharge temps over "stock". On a very hot day with 91 octane fuel you could have incipent knock. Once a knock event has occured in the cylinder the temp spikes upward immediately. The ECU will pull out 2 degrees at a time until the knock event ceases. The temp remains elevated in the previously knocking cylinder for a several seconds. The ECU may have taken 6 degrees out (retard) to mitigate the knock. This retard will say active for as long as you have the throttle depressed. This means on a long accel (dyno or hill or straight away etc) you will loose power for the entire time you are pressing the throttle. If you remove 2 degrees of advance by using 93 octane setting the knock event may never occur. Therefore you will never suffer the power loss of 6 (or more?) degrees of retard, ultimately making more power.

If you dont have a knock problem, dont change the setting, leave it at baseline. This is the setting for maximum advance. A "normal" C36 (for example) may actually be able to run 2 to 4 degrees MORE advance than BASELINE even in the Arizona desert with 91 octane gasoline. You would need to re-write the ign tables in the ECU to do this.