tiger 6

Has anyone had experience using 100 octane fuel in their GT 3 RS? If so, any noticeable performance improvements? Did[or does] the ECU automatically adjust itself for the higher octane gas? Any potential negatives resulting from trying this?
Thanks.

sasportas

The ECU will compensate - however, you do risk "frying" your cats if you're on the track and any unspent fuel gets through to your exhaust.

Nordschleife

why?

R+C

1999Porsche911

The ECU WILL NOT adjust for the higher octane. All the ECU can do is respond to the knock sensors. The engine timing, etc, is optimized for a specific quality of fuel, including octane. If your timing is not being retarded due to engine knock, there is no performance benefit gained from using a higher octane.

However, a higher octane fuel will provide a small increase in the level of protection in the engine when running hot and hard.

Nordschleife

the Bosch ECU is a fairly clever bit of kit. It does adjust, as anybody who has driven Turbo cars at high speeds will know. The gains in horsepower being most notcable at high speed. The adapation process is not instant. There are various 'tricks' for speeding it up.

Motec (heard of them?), who have no particular axe to grind, have published an analysis of the power gains to be derived from using higher octane fuel. It reinforces what many of us have known for years.


R+C

1999Porsche911

So, exactly what is this magical device that is able to determine that you have a higher octane fuel in your tank than the ECU is set for? Maybe it smells the octane, or does an analysis of the fuel as it passes through the lines?

Your computer is set. If timing is not being pulled on your engine using a 93 octane fuel, adding a higher octane will provide no performance benefit. Higher octane fuels allow for adjustment in timing and other engine variables, but the octane itself plays no control of these variables except when too low of an octane causes engine knock.

So, what you have "known for years" is WRONG. EXCESS OCTANE does NOT add to performance.

See......these forums can be educational for you.

Nordschleife

Don't be an arsehole.


If I run a modern car on 102 RON octane, the Bosch ECU does indeed 'adapt'. Read the Bosch Blue Book if you do not believe me.

as I have said, Motec ran a series of tests , and I quote

and from a tuner's simple explanation of what happens.....

R+C

1999Porsche911

Sorry, but you are still wrong. Yes, you can tune the ecu to provide better performance using a higher octane, but using an octane higher than the ecu is tuned for will provide no improvement in performance. Octane alows for improved performance but does not contribute to improved performance. There is no ecu adaptation for octane, upwards....just downwards and that is due to knock sensors, etc.

Educate yourself on what exactly octane is and maybe you'll understand a little better.


If you are getting better perfomance from your car using a higher octane than the ECU is set for, then you have a problem with your engine to begin with or your ecu is tuned to use the higher octane fuel. Do not confuse bad and good gas with low and high octane. They are unrelated.

Nordschleife

Quite obviously, you have never read any of the Bosch documentation, either the Yellow Books or the Blue Book,s or attended any of their excellent courses.

Changing octane causes the system to behave differently. This difference is measured by the ECU using a number of different sensors, the ECU 'adapts' to the new readings. After adaptation to a high octane fuel designed for automobiles the engine will be generating a higher torque value than it had previously.

Now, you may believe that the earth is flat, or was created 6,000 years ago, but blindly reiterating your belief that the ecu does not adapt to higher octane fuel is not helpful, 'throttle body' adfaptation is a well recognised phenomenon and has been recognised for years.

R+C

1999Porsche911

Just what are these sensors that can measure octane level?

It's obvious you have your mind set on believing false information. There is NO document from Bosch or any other control manufacturer that states it will increase peroformance if you use a higher octane gas than the computer is set for.....PERIOD. OCTANE CANNOT BE MEASURED BY A BOSCH ECU. Octane does not provide power.

Once again, and I will type slooooooowly: An ECU or sensor CANNOT determine what octane level your engine is running. It cannot tell whether you have too low or too high of an octane in the fuel. If your octane level is below what is required by the ECU and causes knock, sensors will instruct the ECU to pull timing and decrease you performance. These same sensor will tell the ECU to pull timing even if the knock is not caused by too low an octane level. If the knock sensors do not detect a knock, your timing will be set to the default ECU settings. ANY increase in octane level above what prevents knock will provide no benefit to performance.

It is not the octane level that determines the engine's performance but the various parameters in the engine, timing, fueling, etc. All octane does is provide an added level of protect to allow for more aggressive engine settings.

BTW: You will not find any Bosch documentation that is in conflict with what I stated.

MarekN

Please, don´t stop, I just finished microwaving the popcorn.

Just to chip in a little bit, back in my Impreza days resetting the ECU was a favorite past time.

I am with Nordschleife on this one. On the GT3 fuel cap, it says 98 octane. I think we can all agree that using 98 or more octane (V power racing here is called 100 octane gas, but it is not the only one on the market with this rating) gives the engine more possibilities in terms of timing and fueling to reach the best numbers. I also think that there is an upper limit here, using 104 octane AVGAS for example, will not, in my opinion, give you more power than 100 octane gas.

1999Porsche911

So, by your statement, you agree with me? It requires additional tuning to take advantage of a higher octane than is required. Smart guy.

gt2r

I am agreeing with MarekN and Nordschleife as well. To low of octaine reduces power by retarding the ignition and timing. In the USA most of us can only get 91 octaine at the pump. If you go to say 93-100 octaine you will get an advance in timing and more power (how much is the question). If you go to 86 octaine you will loose power by the ECU reading there is detonation and it will retard the timing. ...If you go to 110 octaine there is no gain in the HP because the parameters of the ECU do not allow it to go that high, and there would be no effective increase in power any way.

This is especially true in high temperature areas and with boosted (turbo) cars..It does give added protection from knock or detonation and when we are at the track the temps are usually pretty high to start with..

Nordschleife

1999Porsche911

I don't think you have the slightest idea what a Bosch ECU can and cannot do. But you are a happy ignorant bunny, just stop fluffing your tale]sic] at me.

If you bothered reading my last post, you will see that I said - "Changing octane causes the system to behave differently. This difference is measured by the ECU using a number of different sensors, the ECU 'adapts' to the new readings. After adaptation to a high octane fuel designed for automobiles the engine will be generating a higher torque value than it had previously." Which is rather different to measuring octane directly. However, you yourself said - "There is no ecu adaptation for octane, upwards....just downwards and that is due to knock sensors, etc" Well, the etc bit of what happens adapts the ecu settings to take advantage of the higher octane fuel, just as it winds the engine back when the fuel is poor.

Now, don't patronise me by typing slowly, go back and read my original post. When you have digested that, you might just understand exactly what I said. If you have any difficulty, ask a Grade School teacher, only a couple of fairly simple statements.

If you read the Bosch documentation, you will discover exactly how smart the Motronic unit is. I am not surprised you are having difficulties, not even the Mercedes engineers have figured out how to use all its features. For that small group of engineers who do understand the ecu, the possibilities are boundless, in fact these guys don't even have to use the Mororsport ECU on their race cars.

R+C

1999Porsche911

You still are wrong. There is NO documentation that states that the ECU will adapt to any octane level higher than what the ECU is set for. That is a fact. You can end this debate by simply giving us a link or a scan of such a document.

The ONLY way the ECU can adapt to a higher octane level is if the engine is knocking with a specific octane fuel and you fill it up with a higher octane fuel. In this case, the higher octane will stop the octane knock and the engine timing will revert back to the targeted setting. Timing CANNOT advance higher that the established maximum, no matter what octane you add to the fuel. Using any fuel that has an octane level higher than that which stops the knocking will provide not further engine adjustments and therefore no further performance improvement.

This fact is not only scientifically sound, but has been proven over and over again by all the major car magazines and other testers.

You told the OP, that his ECU will adjust from the factory setting that requires 93 octane to his use of a 100 octane fuel. This is absurb and, did I say, incorrect.

Once again, the ECU determines the maximum advancement of timing, NOT the octane level.

The adaptation you speak of is a result of engine tuning where the settings of the ECU are changed manually, which might include advancing the timing. This change would require a higher octane fuel. However, that is not what we are discussing.

I now see why Porsche is able to convince people like you that it is normal for your engine to burn as much as 9 gallons of oil between scheduled changes. Simply amazing. You'll believe anything you read, even if it is not supported by the facts.