Custom tune question

[Riceball1]

I have custom tunes on my Gryphon and love them (Thanks Bill) but I was wondering if you can just change the octane setting to run 93 octane on the 87 performance tune. Are there other things that need to be changed? Just wanted to see if there was a difference in performance.


Thanks
Bob

[Jackpine]

Originally Posted by Riceball1

I have custom tunes on my Gryphon and love them (Thanks Bill) but I was wondering if you can just change the octane setting to run 93 octane on the 87 performance tune. Are there other things that need to be changed? Just wanted to see if there was a difference in performance.


Thanks
Bob

Bob, your question is probably best answered by Bill, but I don't see how you change the octane setting in a tune. I don't recall that being a custom setting option. You COULD advance the spark timing on any of the tunes if you ran with higher octane, of course, but this would probably not give you the full benefit of using the more expensive stuff.

I'm 99% sure you need a specific, custom tune for 93 octane if you intend to use it. Bill can put that tune on any of the levels though.

- Jack

[Riceball1]

Originally Posted by JackandJanet

Bob, your question is probably best answered by Bill, but I don't see how you change the octane setting in a tune. I don't recall that being a custom setting option. You COULD advance the spark timing on any of the tunes if you ran with higher octane, of course, but this would probably not give you the full benefit of using the more expensive stuff.

I'm 99% sure you need a specific, custom tune for 93 octane if you intend to use it. Bill can put that tune on any of the levels though.

- Jack

yea I meant to say advance timing. I was just trying to see if that was an option now that gas is so cheap

Bob

[Jackpine]

Originally Posted by Riceball1

yea I meant to say advance timing. I was just trying to see if that was an option now that gas is so cheap

Bob

No worries, Bob.

But, you might consider this: I recently looked at the difference in price per gallon between 87 and 91 (which is what we have here in Tucson) and found it was 22 cents. Now, where I buy gas, I get 87 for $1.499, so the difference in price is roughly 16% to go to the premium stuff. To break even, I'd have to see an increase in MPG of 16% by using the higher priced blend, which for me would be about 1.94MPG (using 15MPG with 87 octane as a baseline).

Here's where my memory is fuzzy though. Back when 87 octane gas was near $4.00 per gallon, I never even looked at the price of 91. If it was still only 22 cents higher, it would only cost a bit over 5% more to use it and at that price spread, I'd only need to improve my MPGs by about 0.75MPG.

So, it's possible that if the cost of gas DOES go up again (and it probably will), we all might do better running hi octane tunes.

It's something to think about.

- Jack

[Corey Cohron RIP]

Don't do it...

The answer is that TECHNICALLY you can run 93 octane with an 87 calibration. However, you run the risk of detonation even with retarding the timing. Also, your 87 calibration was written with a particular timing curve. By backing off the timing of a 93 octane program, you are affecting the whole timing curve and will be sacrificing fuel economy.

Ask yourself, "Self, is it worth it? Am I feelin' lucky?"




Yay! I knew the answer!

[Northern Supercrew]

well...that didn't make me happy i'm doing the same thing...running 91 octane on my 87 perf tune...just cause wifee f'ed up and put that in, i raised the timing 2 adjustments and everything seems good, but.........i better put 87 back in or run the canned 93 tune i guess.

[Jackpine]

Originally Posted by Groovy Chick

Don't do it...

The answer is that TECHNICALLY you can run 93 octane with an 87 calibration. However, you run the risk of detonation even with retarding the timing. Also, your 87 calibration was written with a particular timing curve. By backing off the timing of a 93 octane program, you are affecting the whole timing curve and will be sacrificing fuel economy.

Ask yourself, "Self, is it worth it? Am I feelin' lucky?"




Yay! I knew the answer!

Corey, respectfully, I'm not sure you're right on this and I think we need an opinion from the Mad Doctor.

I believe you can ALWAYS run higher octane fuel in a low octane fueled vehicle. (OK to run 93 octane in an 87 octane tuned truck). And, since the octane is higher, you should be able to bump the timing a bit to at least recover most of what you would lose by using the higher octane fuel in a lower octane tuned vehicle.

The reverse is probably not true. I wouldn't try to stick 87 octane into a 93 octane tuned vehicle, because, as you say, you still run the risk of detonation under certain conditions (unless you backed the timing WAY off).

But, he won't get the full benefit from using high octane fuel unless he has a custom high octane tune - we agree on that - 100%.

- Jack