Wonder what this could be?
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Joined: Aug 2005
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From: Cabot, Arkansas
Rawson glad to hear your package has safely arrived.
Yeah that is why I want to have nothing but 93 octane in my truck so I can data log ASAP.
My plan with my selected tunes would be to mostly run the 93 perf tune and if I needed to tow just switch down to the 87 tow. Maybe I am reading too much into something Mike posted the other day but I am starting to wonder if you can use the 87 octane tow tune with 93 octane in your tank.
i want to believe the 93 performance IS the most aggressive we could've gotten
the 93 tow woulda been a wasted tune for me, i'd never use it.
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From: Florida Panhandle
Please correct me if I am wrong. Octane is the rating given to gas to indicate the gases ability to resist igniting at a given temperature (without spark). the higher the octane rating the higher temp it takes to ignite the gas. You also get the better additives in higher octane (premium) fuels. There should not be any problems with running an 87 ocatane tow tune with 93 in the tank. 
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From: Monroe, Michigan
Originally Posted by 05SilverFX4
Please correct me if I am wrong. Octane is the rating given to gas to indicate the gases ability to resist igniting at a given temperature (without spark). the higher the octane rating the higher temp it takes to ignite the gas. You also get the better additives in higher octane (premium) fuels. There should not be any problems with running an 87 ocatane tow tune with 93 in the tank.
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From: Cabot, Arkansas
I hope you are right o5silverfx4. That is exactly what I thought. Again I don't know if I was reading too much into this statement from Mike
Now going the *opposite* way, say if you are switching from premium back to 87 octane tuning, then you can run it down to about 1/4 tank or so and fill it up with 87 octane, and immediately install your 87 octane tuning - that won't be a problem.
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Joined: Mar 1998
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From: Virginia
Hey Rawzon,
Your post cracked me up - now I know you're a South Park fan, too - "my precious" indeed, I busted a gut laughing, thanks!
For 05Silver - Not exactly - there's much more to octane than just a higher octane number having a higher resistance to one form of detonation (pre-ignition). While what you said in that vein is correct, more octane gives higher resistance to pre-ignition, you do NOT want to run premium gas on an 87 octane tune, as that will result in making less power and dropping the fuel mileage, as the fuel does not have enough time to burn properly.
See, the higher you go up in octane, the longer it takes to *initiate* the combustion event, in terms of real time and thus in terms of degrees of crankshaft rotation - thus when running higher octane, there MUST be more spark advance (additional timing) in order to allow more time to get that mixture lit and to burn as much of it as possible, enough to make proper power, etc. Now once it's lit, then the flame front propagates itself across the combustion chamber at about the same rate with either 87 or 93 octane, all else being equal and the ignition system being up to the task.
Running 93 octane on an 87 octane tune, you will not have enough time to burn enough of the air/fuel mixture, thus power will actually drop starting at about 4000 rpm at full-throttle in the 5.4 3V, and can do so even earlier on part-throttle - trust me, we've tested this, as a number of our customers have found this out on the dyno the hard way, calling us to complain why their engine stopped making any more power at 4000 rpm instead of peaking at at least 4800+ rpm - it was because they made the mistake of running premium gas on an 87 octane tune.
Always run as close as possible to the octane level the engine is actually tuned for - 1 point of octane HIGHER really isn't going to matter much, but much more than that, and it quickly hurts power. So you definitely want to run the same basic octane level that the engine is tuned for in order for the engine to run properly, and at it's best.
My earlier comment was simply predicated on the fact that when going from premium to 87, it's not quite as important to run the tank down as low as when changing from 87 to 93, as i that case you don't' want to invite detonation - so you want to run the tank down as low as is reasonably possible without running out. When going the opposite way, from premium gas back to 87, you could do that with as much as say, 1/4 tank of premium still in the tank, though most people aren't going to do that, as they want to get every bit of power & performance from even drop of premium they pumped in.
Just FYI.
Your post cracked me up - now I know you're a South Park fan, too - "my precious" indeed, I busted a gut laughing, thanks!
For 05Silver - Not exactly - there's much more to octane than just a higher octane number having a higher resistance to one form of detonation (pre-ignition). While what you said in that vein is correct, more octane gives higher resistance to pre-ignition, you do NOT want to run premium gas on an 87 octane tune, as that will result in making less power and dropping the fuel mileage, as the fuel does not have enough time to burn properly.
See, the higher you go up in octane, the longer it takes to *initiate* the combustion event, in terms of real time and thus in terms of degrees of crankshaft rotation - thus when running higher octane, there MUST be more spark advance (additional timing) in order to allow more time to get that mixture lit and to burn as much of it as possible, enough to make proper power, etc. Now once it's lit, then the flame front propagates itself across the combustion chamber at about the same rate with either 87 or 93 octane, all else being equal and the ignition system being up to the task.
Running 93 octane on an 87 octane tune, you will not have enough time to burn enough of the air/fuel mixture, thus power will actually drop starting at about 4000 rpm at full-throttle in the 5.4 3V, and can do so even earlier on part-throttle - trust me, we've tested this, as a number of our customers have found this out on the dyno the hard way, calling us to complain why their engine stopped making any more power at 4000 rpm instead of peaking at at least 4800+ rpm - it was because they made the mistake of running premium gas on an 87 octane tune.
Always run as close as possible to the octane level the engine is actually tuned for - 1 point of octane HIGHER really isn't going to matter much, but much more than that, and it quickly hurts power. So you definitely want to run the same basic octane level that the engine is tuned for in order for the engine to run properly, and at it's best.
My earlier comment was simply predicated on the fact that when going from premium to 87, it's not quite as important to run the tank down as low as when changing from 87 to 93, as i that case you don't' want to invite detonation - so you want to run the tank down as low as is reasonably possible without running out. When going the opposite way, from premium gas back to 87, you could do that with as much as say, 1/4 tank of premium still in the tank, though most people aren't going to do that, as they want to get every bit of power & performance from even drop of premium they pumped in.
Just FYI.
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Joined: Aug 2005
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From: Cabot, Arkansas
What about when you data log? You go to the dyno and make 3 pulls witht your most aggressive tune so you have 93 octane in your tank and you other tunes are lower octane tunes. Mike I don't know where I am on the list. I sent my papers in 11/11 but I need to talk to you to help decide which tunes are going to suit me best. I will call you Monday.
Senior Member
Joined: Aug 2005
Posts: 140
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From: Cabot, Arkansas
the 93 tow woulda been a wasted tune for me, i'd never use it. all i wanted was better shifting/shift points mainly for my tow, and i believe i'll get that with just the 87 tow tune.