[scotty_miller]

So I was hanging out with a couple of 335 guys this weekend and they were telling me before they ran e85 they ran Sunoco 260gt... another name for 104 octane. My one friend and I can get it at a oval dirt track around my place for a reasonable price from what I hear. He wants to take a trip and get some 112 for his street bike and thought why not go get a couple gallons. So do you think 93 pump with 104 octane cut at like a 5:1 or 7:1 would hurt, benefit, or do nothing at all for our motors?

[justpete]

http://www.racegas.com/fuel/17

Look under Tech Corner in the right frame about mixing octanes.

Won't have any significant effect on engine power at your proposed dilution. Won't hurt it either. But it'd be fun to try...

[scotty_miller]

Originally Posted by justpete

http://www.racegas.com/fuel/17

Look under Tech Corner in the right frame about mixing octanes.

Won't have any significant effect on engine power at your proposed dilution. Won't hurt it either. But it'd be fun to try...

I just said those ratios because I have no idea of the effect on what it would do haha if I can it'd be fun and I probably will toy around with like a 3:1 or 1:1 just to see what would happen. I calculated it out off the example the tech corner gave me. Running a 3:5 ratio of 104:93 gave me an overall octane of 99.6 and at a 3:1 ratio only a 95.75. I wonder what a nice ratio would be...

[justpete]

Any ratio up to full 104 will work but it'll get less efficient with higher octane or so I've been told. Even with a tune the improvement running 100% 260GT isn't going to be much, probably not much more than the margin or error on the dyno, I think. But definitely fun to try and it's something I was thinking of doing for the next HPDE.

[scotty_miller]

Originally Posted by justpete

Any ratio up to full 104 will work but it'll get less efficient with higher octane or so I've been told. Even with a tune the improvement running 100% 260GT isn't going to be much, probably not much more than the margin or error on the dyno, I think. But definitely fun to try and it's something I was thinking of doing for the next HPDE.

I think I'll try a 3:5 ratio just for fun and see if I notice any difference. Doubt I will. My friend emailed the guy to get prices and I mean for just for fun and money to blow why not

[justpete]

Go for it! Won't hurt nuthin' Sure don't cost nuthin' though.

Going to see if I can't get a dyno run after letting it adapt over 100mi or so. Gotta run another baseline first for comparison. Worth it to see how scientifically effectively I've just wasted all that money.

[scotty_miller]

Originally Posted by justpete

Go for it! Won't hurt nuthin' Sure don't cost nuthin' though.

Going to see if I can't get a dyno run after letting it adapt over 100mi or so. Gotta run another baseline first for comparison. Worth it to see how scientifically effectively I've just wasted all that money.

hahaha we'll both do it see how scientifically smart we thought we were. Wonder if it'll help fuel economy

[Dylanize]

Won't Hurt, might notice slightly stronger pull,

[scotty_miller]

Originally Posted by Dylanize

Won't Hurt, might notice slightly stronger pull,

Sweet, I'm just trying it for s&g's but I'm not running a tune yet and planned on doing tune and headers soon. But who knows. I'll try it as a baseline and see if it benefits stock in anyway

[Dylanize]

Originally Posted by scotty_miller

Sweet, I'm just trying it for s&g's but I'm not running a tune yet and planned on doing tune and headers soon. But who knows. I'll try it as a baseline and see if it benefits stock in anyway

Yeah, same here man. All I have is an exhaust and intake, but seemed to pull a bit harder with 104, but who knows... (placebo?)

[Taskmaster]

I have a tune for 10x octane - I can't imagine it making that much of a difference though.

[scotty_miller]

Originally Posted by Dylanize

Yeah, same here man. All I have is an exhaust and intake, but seemed to pull a bit harder with 104, but who knows... (placebo?)

I was thinking placebo, but I'll see when I mess around with it. I can see where it would pull harder because higher combustion gives more efficiency... but I can't vouche for much until I try it

[scotty_miller]

Originally Posted by TheAxiom

I have a tune for 10x octane - I can't imagine it making that much of a difference though.

I honestly have no clue what to expect haha it's not going to be a throw your ass back in the seat. But the question is how much of difference there really is between pump 93 and a 100. (3:5 ratio of 104:93 that gives you a 99.6 ~ 100octane)

[mike-y]

as long as the gas is unleaded, you can try it without harming anything. some of the higher octanes are leaded, which will foul your O2 sensors.

running 104 isn't going to really make a difference when you are running a tune meant for regular pump gas. 104 allows you do do things, like run more timing advance, and more boost on turbo cars, because higher octanes actually burn slower.

the slower burn makes the gas more stable in high heat/pressure situations that would cause normal gas to ping/knock. So unless you've actually done something to the car to take advantage of 104, you can very well end up making your car slower.

if it is very hot outside, and your engine is pulling timing, mixing in some 104 will help restore base timing though. but if your car is running great on 92 octane, putting in 104 won't make more power than the 92 if you don't change the tune.

[Taskmaster]

Originally Posted by mike-y

as long as the gas is unleaded, you can try it without harming anything. some of the higher octanes are leaded, which will foul your O2 sensors.

running 104 isn't going to really make a difference when you are running a tune meant for regular pump gas. 104 allows you do do things, like run more timing advance, and more boost on turbo cars, because higher octanes actually burn slower.

the slower burn makes the gas more stable in high heat/pressure situations that would cause normal gas to ping/knock. So unless you've actually done something to the car to take advantage of 104, you can very well end up making your car slower.

if it is very hot outside, and your engine is pulling timing, mixing in some 104 will help restore base timing though. but if your car is running great on 92 octane, putting in 104 won't make more power than the 92 if you don't change the tune.

Again, too lazy to post this - so thank you.

[smellthebeans]

au contraire!

I have tanked up on Aral ultimate 102 (RON 102 or about 98 Octane). Certainly made a difference. Go for it!

[scotty_miller]

Originally Posted by mike-y

as long as the gas is unleaded, you can try it without harming anything. some of the higher octanes are leaded, which will foul your O2 sensors.

running 104 isn't going to really make a difference when you are running a tune meant for regular pump gas. 104 allows you do do things, like run more timing advance, and more boost on turbo cars, because higher octanes actually burn slower.

the slower burn makes the gas more stable in high heat/pressure situations that would cause normal gas to ping/knock. So unless you've actually done something to the car to take advantage of 104, you can very well end up making your car slower.

if it is very hot outside, and your engine is pulling timing, mixing in some 104 will help restore base timing though. but if your car is running great on 92 octane, putting in 104 won't make more power than the 92 if you don't change the tune.

Wow thanks for clearing that up big time for me. So say you had an aa tune and had it tuned to run at 104, then in that case is really the only time you would see a benefit from 104?

[scott135i]

Sunoco GT260 is 100 octane.

[mike-y]

Originally Posted by scotty_miller

Wow thanks for clearing that up big time for me. So say you had an aa tune and had it tuned to run at 104, then in that case is really the only time you would see a benefit from 104?

pretty much. you have to do *something* to take advantage of the higher octane. A tune with advanced timing can do that. Or if your car is running poorly for some reason (like if it's super hot outside, or you have some crappy gas in your tank), then spiking it with the higher octane may provide a benefit, but that's only because some other factor was out of spec.


in most cases, your car will make the most power with the gasoline it's rated and tuned for. If you change the octane, you need to change the tune to get the best results.

335i tuning boxes have "maps" that adjust the boost levels and tune for higher octane gas, that's why they can get so much more power. we can't change boost like the 335i guys, so the benefits of higher octane are much, much smaller. Even then, most 335i tunes still run on regular pump gas. high octane is only needed for the most extreme boost levels.