RX-7 Gasoline FAQ

Last updated: April 24, 2000

Date: Thu, 21 May 98 07:38:27 -0500
From: "Linthicum, Sandy" (linthias@sandy-ntws.usps.gov)

Premix 2 stroke with oil is allways advised. About 4oz per 12-16 gallons of gas is about right for a car with the oil meter injection still functional.


Date: Fri, 21 Apr 2000 22:55:36 EDT
From: SuprProbe@aol.com

Here's my $3.95 contribution (sportrider magazine) to the list this week. I'm only going to quickly summarize the article.

Basically they test 93 octane gas against 104+ "enhanced" gas, along with various types of race gas availible. VP and Powermist were the two companies willing to submit their "brews" for testing. Many companies refused, interestingly.

The test subject was a Suzuki TL1000R, chosen because it's fuel injected and they had access to a Dynojet Power Commander (just think of it as a Power FC) to change ignition and fuel points. The compression ratio is 11.7:1 on this motor, a big bore twin, where flame propogation and burn properties come into affect. The 7 of course, has a much larger combustion chamber that necessitates two plugs. So there's a bit of relevance here :-)

The results:

104+ Showed no appreciable gain in performance. They comment that stock 93 octane gas has enough octane for a street bike like this with an 11.7:1 compression ratio, which is possibly why no gains were seen. Duh. Like Suzuki's going to ship a TLR mapped for J-market 103 octane fuel...

VP Motorsports 103 -Street legal unleaded with an (r+m)/2 rating of 103. Intended for motorcycles and high perf street cars. Meets California's RFG. $4.75 a gallon. Showed a small gain (maybe 1-2hp) down low and up top. Nothing in between. Again, stock tuning.

VP C-SP-Unleaded, non-street legal, 102.3 Octane rating. Recommended for compression ratios up to 12:1. Contains additives to boost oxygen content. $5.25 a gallon. With higher oxygen content, there's the potential for more hp, so they say. At stock "jetting", they saw a loss. 10% richer returned them to stock power levels. Richer yet caused a loss. They failed to advance the timing any.....

Power Mist RFG- Non-street legal unleaded with a six percent oxygen content and an octane rating of 108. $7.72 a gallon! Best of the unleaded fuels tested. Provided a whopping 2hp jump over pump gas in the entire rev range. They felt the additives in the fuel as opposed to the octane rating. They felt tweaking the fuel tables would have provided more hp. I guess the Power Commander doesn't change timing as I first thought....Hence they would have been smart enough to vary the advance using each type of gas. Right?

VP-MR #4 What was used for Supersport racing in the past. Leaded, oxygenated race fuel with 2.5% oxygen content, 104 Octane rating. A bit more power everywhere, more so if they'd have increased the mixture. $10/gallon.

VP C-12 Apparently smells like race gas. Leaded, UNOXYGENATED, with a 109 rating. Good for 14:1 compression ratios. No appreciable gains. Probably due to the fact it needs a higher output engine to achieve more hp, closer to 14:1 than to 11.7:1 I'd guess...

VP-MR #3- Just replaced the #4. Leaded oxygenated race gas for supersport bikes. 2.5% oxygen content, but uses a new compound to provide said oxygen versus the #4 Overall octane is actually less than the #4 as well. Apparently contains more calories of energy and burns quicker (is this conducive to rotaries?). They call this stuff brutal. Major gains over the entire rev range, with 5.5 peak hp over pump fuel. Big power changes without changing fuel. $25 a gallon. Damn.....

While all the info is of course specific to bikes, it's still somewhat interesting. On a daily basis, running a medium level of mods on sane boost levels, I doubt we'd need anything much over 93 octane with the proper tuning. But come race weekend, I'm willing to bet a highly tuned steed would indeed see big gains in hp and safety by using such gasses. Sounds like an interesting article for SCC to do, huh? Heck, Shiv could even use the 7 for testing :-) Of course he'd have to swap out the M2 remapped ECU in favor of a "tunable" solution.


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