gathermewool
Site Donor 2023
Originally Posted By: rg200amp
Originally Posted By: gathermewool
If the tune is designed to run on 87, but will occasionally pull timing, then a higher octane is warranted. Using 91 over 87 will provide an engine with a tune designed for 87 plenty of margin to detonation. Heck, maybe they cut it close with the 87 statement, but 89 would be sufficient. In that case, even 91 would be overkill. However, if the engine never experiences any knock and adds full timing using 89 or 91, then 93 would simply be a waste of money, with zero value added.
Yes, but today's computers on todays cars and VVT can also advance timing, over time, to get even better performance and MPG.
I would give 93 a try for a few fill ups and see if there is any gain before I rule it out all together.
They do, but they can only add so much. You're not going to be running 45 degrees of advanced timing or maximum VVT utilization just because you put some 100 octane in. The ECU has a set of values it will run as a base. Timing is added as the ECU sense no knock events, but can only add so much.
For instance, there are some in the STI community who are tuned for 91 octane fuel and run maximum timing on 91 octane fuel. They would not experience any gains if they decided to switch to 93 fuel, unless they were tuned right to within a gnats butt of knock and occasionally, during certain situations, knock would occur. To be conservative, 93 octane might be used, but the benefit would only be during those few instances where knock might occur, but not any other time.
Based on what some of you posted, this 2.0T is tuned pretty aggressively, seemingly too aggressively for the minimum 87 octane rating. If it were the case where knock were occurring frequently while heavily loaded and using 87 octane, but never while using 89 octane, then the ECU would add max timing, and no gains would be seen using anything higher. If, however, knock still occurred while using 89 octane, even if only during certain high load situation, then 91 might provide some gain.
Based on the above assumptions, I can't see anything higher than 91 being necessary for an engine tune for 87, even if aggressively so. I most definitely could be wrong, but it would seem that if 93 were required to prevent all knock, then just about all of those who are using 87 would be experiencing major detonation and engine damage. I know my STI wouldn't last very long if I decided to fill up with a tank full of 87 with how I drive. Even at wastegate boost, I'd still be knocking like crazy I think.
Originally Posted By: gathermewool
If the tune is designed to run on 87, but will occasionally pull timing, then a higher octane is warranted. Using 91 over 87 will provide an engine with a tune designed for 87 plenty of margin to detonation. Heck, maybe they cut it close with the 87 statement, but 89 would be sufficient. In that case, even 91 would be overkill. However, if the engine never experiences any knock and adds full timing using 89 or 91, then 93 would simply be a waste of money, with zero value added.
Yes, but today's computers on todays cars and VVT can also advance timing, over time, to get even better performance and MPG.
I would give 93 a try for a few fill ups and see if there is any gain before I rule it out all together.
They do, but they can only add so much. You're not going to be running 45 degrees of advanced timing or maximum VVT utilization just because you put some 100 octane in. The ECU has a set of values it will run as a base. Timing is added as the ECU sense no knock events, but can only add so much.
For instance, there are some in the STI community who are tuned for 91 octane fuel and run maximum timing on 91 octane fuel. They would not experience any gains if they decided to switch to 93 fuel, unless they were tuned right to within a gnats butt of knock and occasionally, during certain situations, knock would occur. To be conservative, 93 octane might be used, but the benefit would only be during those few instances where knock might occur, but not any other time.
Based on what some of you posted, this 2.0T is tuned pretty aggressively, seemingly too aggressively for the minimum 87 octane rating. If it were the case where knock were occurring frequently while heavily loaded and using 87 octane, but never while using 89 octane, then the ECU would add max timing, and no gains would be seen using anything higher. If, however, knock still occurred while using 89 octane, even if only during certain high load situation, then 91 might provide some gain.
Based on the above assumptions, I can't see anything higher than 91 being necessary for an engine tune for 87, even if aggressively so. I most definitely could be wrong, but it would seem that if 93 were required to prevent all knock, then just about all of those who are using 87 would be experiencing major detonation and engine damage. I know my STI wouldn't last very long if I decided to fill up with a tank full of 87 with how I drive. Even at wastegate boost, I'd still be knocking like crazy I think.
