tuning, timing, fuel??? Mileage discrepancy
02-04-2006, 11:47 PM
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tuning, timing, fuel??? Mileage discrepancy I've notice about a 3 mpg difference between using Sunoco Ultra 94 gasoline and Shell V-Power 93. This is around town tire spinning action by the way
I get the better mileage using the Shell gasoline and the T/A pulls noticably harder as well with Shell. I'm running a LS2 402 with the SLP stroker kit 11:1 compression, cnc'd LS6 heads 63cc combustion chambers. 
So my question actually relates to this thread. I would think that I would have better milage and power using the higher octane fuel unless my engine is at the point were I'm not getting a good burn out of the Sunoco 94. Could this be a tuning issue that a little more timing would cure. My car has a conservative mail order tune of which I have no idea of the parameters or could this a gassoline quality issue? By the way cruising on the highway I get 24mpg with Shell and like 23.3mpg with Sunoco. 
Any ideas????
I get the better mileage using the Shell gasoline and the T/A pulls noticably harder as well with Shell. I'm running a LS2 402 with the SLP stroker kit 11:1 compression, cnc'd LS6 heads 63cc combustion chambers. So my question actually relates to this thread. I would think that I would have better milage and power using the higher octane fuel unless my engine is at the point were I'm not getting a good burn out of the Sunoco 94. Could this be a tuning issue that a little more timing would cure. My car has a conservative mail order tune of which I have no idea of the parameters or could this a gassoline quality issue? By the way cruising on the highway I get 24mpg with Shell and like 23.3mpg with Sunoco. Any ideas???? 
02-05-2006, 08:12 AM
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V-power is somewhat oxygenated so it should burn
leaner (in open loop). If it makes you more power it
means your spark tune is not aggressive enough.
Thing is, you probably can't be optimized for both;
I think you want to pick a flavor and stick with it,
but Sunoco 94 seems like a fairly limited-availability
fuel and I'd say a standard 93 octane basis would
be the way to fine-tune. Though if you can make it
on V-power, any other 93 should be well tolerated.
leaner (in open loop). If it makes you more power it
means your spark tune is not aggressive enough.
Thing is, you probably can't be optimized for both;
I think you want to pick a flavor and stick with it,
but Sunoco 94 seems like a fairly limited-availability
fuel and I'd say a standard 93 octane basis would
be the way to fine-tune. Though if you can make it
on V-power, any other 93 should be well tolerated.
02-05-2006, 12:29 PM
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Thats interesting. I knew there had to be something more distinguishing between the two fuels than 1 point of octane. I planning a cam swap in the future followed up by a full dyno tune and honestly I would have never considered what brand of gas to use. Thanks guys.
Maybe this is the wrong forum but we are sorta on the topic of fuel, so which is better considering my future tune. My choices in my neiborhood are:
Speedway 92,
Sunoco 93-94,
BP 93,
Shell V-Power 93
Amoco 93-94?
Maybe this is the wrong forum but we are sorta on the topic of fuel, so which is better considering my future tune. My choices in my neiborhood are:
Speedway 92,
Sunoco 93-94,
BP 93,
Shell V-Power 93
Amoco 93-94?
02-05-2006, 04:38 PM
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You get best part-throttle mileage with 87 octane.
the more watered down the fuel is with additives to raise octane rating, the less power you get per volume of fuel, unless the density of the fuel increases.
the more watered down the fuel is with additives to raise octane rating, the less power you get per volume of fuel, unless the density of the fuel increases.
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02-05-2006, 09:53 PM
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If I were going on a long road trip across the flat countryside (ie. no mountains or serious grades) would you suggest filling up with the cheap stuff like 87 to get better mileage? Would I see any knock retard on partial throttle even with 11.1:1 compression? If the engine did pull some timing, would it overcompensate for or remove the benifit of a lower octane fuel?
02-06-2006, 08:21 AM
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Originally Posted by squealingtires
If I were going on a long road trip across the flat countryside (ie. no mountains or serious grades) would you suggest filling up with the cheap stuff like 87 to get better mileage? Would I see any knock retard on partial throttle even with 11.1:1 compression? If the engine did pull some timing, would it overcompensate for or remove the benifit of a lower octane fuel?
02-06-2006, 11:52 AM
#10
I have seen noticeable differences in milages in the three brands of gas I use.
Shell V-power 93. decent power ok milage
BP(amoco) 93. best performing, decent milage
Phillips 66. 92, power, eh, best milage by far.
I stick with BP fuel, my car runs great on it, combustion chamber and plugs are always clean as a whistle, never had dirty injector problems either.
Personally i'd never put anything below 91 in my car. Don't forget only some of our cars "adjust"(I copied and pasted my high table to my low) and by adjust this means your motor suffered so much excessive knock it started to lower its timing to the low octane timing table. The way I see it as you paid a premium to buy a fast high compression car, if your going to be so cheap as to buy the incorrect gas(87), then sell it for a civic.
Shell V-power 93. decent power ok milage
BP(amoco) 93. best performing, decent milage
Phillips 66. 92, power, eh, best milage by far.
I stick with BP fuel, my car runs great on it, combustion chamber and plugs are always clean as a whistle, never had dirty injector problems either.
Personally i'd never put anything below 91 in my car. Don't forget only some of our cars "adjust"(I copied and pasted my high table to my low) and by adjust this means your motor suffered so much excessive knock it started to lower its timing to the low octane timing table. The way I see it as you paid a premium to buy a fast high compression car, if your going to be so cheap as to buy the incorrect gas(87), then sell it for a civic.
02-06-2006, 12:17 PM
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Originally Posted by SmokingWS6
I have seen noticeable differences in milages in the three brands of gas I use.
Shell V-power 93. decent power ok milage
BP(amoco) 93. best performing, decent milage
Phillips 66. 92, power, eh, best milage by far.
I stick with BP fuel, my car runs great on it, combustion chamber and plugs are always clean as a whistle, never had dirty injector problems either.
Personally i'd never put anything below 91 in my car. Don't forget only some of our cars "adjust"(I copied and pasted my high table to my low) and by adjust this means your motor suffered so much excessive knock it started to lower its timing to the low octane timing table. The way I see it as you paid a premium to buy a fast high compression car, if your going to be so cheap as to buy the incorrect gas(87), then sell it for a civic.
Shell V-power 93. decent power ok milage
BP(amoco) 93. best performing, decent milage
Phillips 66. 92, power, eh, best milage by far.
I stick with BP fuel, my car runs great on it, combustion chamber and plugs are always clean as a whistle, never had dirty injector problems either.
Personally i'd never put anything below 91 in my car. Don't forget only some of our cars "adjust"(I copied and pasted my high table to my low) and by adjust this means your motor suffered so much excessive knock it started to lower its timing to the low octane timing table. The way I see it as you paid a premium to buy a fast high compression car, if your going to be so cheap as to buy the incorrect gas(87), then sell it for a civic.
It picked up power on 87 octane and runs faster than ever.
Why not try some (non-ethanol added) 87 octane just to see what it does for you mileage. I think you will be surprised and pleased.
You probably wouldn't make good power on the 87 though.
The PCM doesn't need terrible spark knock to adjust. It usually adjusts before you can even hear any knock. You would still get knock retard no matter if your SA tables are the same.
The C5 had the KR turned off and a little over 30* advance at WOT.
It saved a lot of money on gas just driving it around everyday.
02-06-2006, 07:14 PM
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This is all great advice. Thanks guys! I certainly didn't buy this car for its gas mileage but the old, "You would if you could" saying comes to mind when considering squeezing as much efficency as possible out of the engine. Certainly none of you would scoff at another enthusiest who gets awesome mileage out of a stroker motor in addition to loads of power? Most modern gasoline engines are only about 33% efficient anyways. Wouldn't it be nice to get 30mpg out of a 3600lb, 500hp power plant?