someone enlighten me on race fuel...
02-29-2004, 04:12 AM
#1
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someone enlighten me on race fuel...
what would you pick for that extra umph on track days?
i assume i want to stear clear of Oxygenated types.
C10 might be decent.
granted i may not see much a of a difference but i've always wanted to try race gas.<ul><li><a href="http://vpracingfuels.com/vp_01_fuels.html?mgiToken=0C15B7C8E35D01B4D8#unlea ded">VP</a></li></ul>
i assume i want to stear clear of Oxygenated types.
C10 might be decent.
granted i may not see much a of a difference but i've always wanted to try race gas.<ul><li><a href="http://vpracingfuels.com/vp_01_fuels.html?mgiToken=0C15B7C8E35D01B4D8#unlea ded">VP</a></li></ul>
02-29-2004, 05:50 AM
#2
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No HP gain
Unless you get into really exotic (as in $25-$50 per gallon) stuff, there is no gain from fuel with one exception. If your engine is tuned for the higher octane then you will see a gain - or more properly you are seeing a loss with lower octane. If your car is a turbo that might be the case, otherwise you are probably wasting money.
02-29-2004, 07:04 AM
#3
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and as a Californian...
on a hot day with a high-compression engine (or turbocharged) you are very likely to get to the threshold of pre-ignition and lose power.
One of the handy things back racing the Honda was the very low compression ratio and therefore ability to race in even extreme temperatures without preignition.
My 996 (11.3:1 compression ratio) noticeably cut timing on "spirited" mountain drives on hot days.
Octane is basically the measure of a fuel's resistance to pre-ignition. SOME engines have a much higher likelyhood of preignition due to higher cylinder temperatures and pressures (high compression ratio and/or turbocharging/supercharging)...so they "benefit" from a higher octane because it allows the engine to make the power it was designed for.
But as Mark says...octane never "adds" power...the engine won't magically produce more HP from very high octane than it would produce from very low octane...as long as that lower octane fuel isn't pre-igniting. Even the 996 became utterly immune from preignition (which wouldn't occur as the ECU would cut the timing to prevent it so more correct would be "loss of power) with 93 octane which could be mixed by blending 100 octane unleaded race gas with regular pump gas. Many folks achieve this by blending Tolulene in their garage but I'm not comfortable mixing hazardous chemicals in my garage.
<img src="http://www.schube.com/images/blend_sm.jpg">
One of the handy things back racing the Honda was the very low compression ratio and therefore ability to race in even extreme temperatures without preignition.
My 996 (11.3:1 compression ratio) noticeably cut timing on "spirited" mountain drives on hot days.
Octane is basically the measure of a fuel's resistance to pre-ignition. SOME engines have a much higher likelyhood of preignition due to higher cylinder temperatures and pressures (high compression ratio and/or turbocharging/supercharging)...so they "benefit" from a higher octane because it allows the engine to make the power it was designed for.
But as Mark says...octane never "adds" power...the engine won't magically produce more HP from very high octane than it would produce from very low octane...as long as that lower octane fuel isn't pre-igniting. Even the 996 became utterly immune from preignition (which wouldn't occur as the ECU would cut the timing to prevent it so more correct would be "loss of power) with 93 octane which could be mixed by blending 100 octane unleaded race gas with regular pump gas. Many folks achieve this by blending Tolulene in their garage but I'm not comfortable mixing hazardous chemicals in my garage.
<img src="http://www.schube.com/images/blend_sm.jpg">
02-29-2004, 08:16 AM
#4
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Doh!
why did i say that? i know perfectly well Octane is just resistance to pre-ignition...not hp gains.
silly me.
since the STi can compensate for higher octane i might try a bit during the peak summer then.
prolly no need to worry about it this spring.
silly me.
since the STi can compensate for higher octane i might try a bit during the peak summer then.
prolly no need to worry about it this spring.
03-01-2004, 05:59 AM
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Wow...
Finally, an intelligent and realistic thread about fuel octane on the web.
I've found that running the lowest octane possible that won't knock or cause the timing to retard (if it does it by itself) is where the best power is. As previously mentioned, unless you're running big compression (Warren's 13:1 motor....umm...is that legal ??!? I won't tell anyone if you let me drive it...) or wild advances, you'll make better power with lower octane. It 'flashes off' faster, burns faster and keeps cyl. head temps down. In an 'unprepped' motor, running too much octane usually just means that the engine runs hotter, and makes less power. Dyno runs on 'control engines' proves this again and again and again. And again.
In the "Dept. of OT" - I was going to spend the weekend working on broken cars, but I got persuaded to dig the ice car out of the snowbank and go play. My 1.5 CRX on Indonesian stud tires (really...) and E-Rock's Miata on Hakka Q's (he's been terrorizing the 'street legal' classes all season in it), bump-drafting all day on Honeoye Lake. Vid is shot from Randy Zimmer's Subie (the Pro Rally-ers will recognize the name).
Will we ever grow up ?<ul><li><a href="http://www.randyzimmer.com/video/cnyira/icemornprac1.mov">Morning practice...me and the E playing on the ice.</a></li></ul>
I've found that running the lowest octane possible that won't knock or cause the timing to retard (if it does it by itself) is where the best power is. As previously mentioned, unless you're running big compression (Warren's 13:1 motor....umm...is that legal ??!? I won't tell anyone if you let me drive it...) or wild advances, you'll make better power with lower octane. It 'flashes off' faster, burns faster and keeps cyl. head temps down. In an 'unprepped' motor, running too much octane usually just means that the engine runs hotter, and makes less power. Dyno runs on 'control engines' proves this again and again and again. And again.
In the "Dept. of OT" - I was going to spend the weekend working on broken cars, but I got persuaded to dig the ice car out of the snowbank and go play. My 1.5 CRX on Indonesian stud tires (really...) and E-Rock's Miata on Hakka Q's (he's been terrorizing the 'street legal' classes all season in it), bump-drafting all day on Honeoye Lake. Vid is shot from Randy Zimmer's Subie (the Pro Rally-ers will recognize the name).
Will we ever grow up ?<ul><li><a href="http://www.randyzimmer.com/video/cnyira/icemornprac1.mov">Morning practice...me and the E playing on the ice.</a></li></ul>
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03-01-2004, 07:21 AM
#8
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It's legal
Stuff in Civic Type R pistons into an Integra block, and you're already looking at 12:1 or so. Throw on a little shaving of the head and decking of the block, and some other legal but not so common stuff 
Requires mega huge cams to reduce dynamic comp.
Warren
Requires mega huge cams to reduce dynamic comp.
Warren
