What octane is U4?

NightCrawler

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It seems as if every test I read on the new Busa and '08 ZX-14 has some sort of mention of U4 fuel. I understand its racing fuel, but what is it? Is it a higher octane fuel? If so, I thought higher octane didn't provide any benefits.

I mean, I assuming the new Busas and 14s were made to run on 87 to 93 octane. If (and I say "if" because I honestly don't know) U4 is a higher octane than 93, wouldn't that mean the Gen1 Busas would run best on 93 octane and not 87?

For the sake of an argument I use "plus" fuel which is 89 octane. Not regular nor premium ... just the middle one on my Gen-1. I'm saying that because I don't want anyone to think I'm trying to get others here to use the highest octane at their local gas station.
 
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http://www.vpracingfuels.com/vp_01_fuels.html


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U4TM
Used in stock and modified 4-stroke applications, as well as stock 2-strokes. Makes up to 6% more power than pump gas and any basic nonoxygenated racing fuel. Passes fuel rules for AMA amateur racing, and is also perfect for club level racing, CCS, WERA and AFM.

"¢ Color: Clear
"¢ Oxygenated: Yes
"¢ Motor Octane: 92
"¢ Specific Gravity: .718 at 60° F



NEW! U4.2TM
The latest generation of our U4 based fuels, this fuel is a direct pour-in replacement for U4 with little to no jetting changes required - +2 main jets and +2 pilot jets at the most. Makes power equivalent to U4 with no sticky residue and a less pungent odor. U4.2 passes AMA amateur fuel rules and is perfect for club level racing, CCS, WERA and AFM. U4.2 makes up to 6% more power than pump gas.

"¢ Color: Blue
"¢ Oxygenated: Yes
"¢ Motor Octane: 102
"¢ Specific Gravity: .784 at 60° F



U4e
Developed for those states that restrict the use of MTBE in fuels. Will work well in the same applications as U4, with comparable power increases.

"¢ Color: Pink
"¢ Oxygenated: Yes
"¢ Motor Octane: 93
"¢ Specific Gravity: .718 at 60° F

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Whatever you do, be careful that you get your oxygenated fuel from a FRESH can.
Here's what happens when you get it from a can that has been opened for too long.
Ok,
first off, I know this doesn't apply at every drum, and ever racer doesn't have this luck, but check this out.
A couple of weeks ago, I decided to try some oxiginated fuel, so a local guy had a drum of U 4.
I got 3 gallons.
I emptied the regular unleaded and put about a gallon and a half in on Saturday.
Ok, first, I have a stock Busa with a small box mod and at this point, just an airlid, no filter.
Well, I got a map from Johnny that he had made for a buddy of mine with a 100% stocker.
It had alot of negative numbers in it, to lean out the rich, stock Busa. Mine was slightly leaner because of the airbox.
The U 4 only gave me about .5 mph, and no ET.
I just figured it was because it was trying to lean out and already lean bike???
That wasn't a problem tho. If the bike had a good tune on pump gas, i'll just run pump gas.
Anyway, that was a Saturday. I went again on Sunday to keep practicing. On initial startup on Sunday, I heard a valve train clacking. It sounded like back in the day when a hydraulic lifter had come loose on a car engine.'clack, clack, clack.
I knew it was up top, and not a rod, so I ran it anyway. If something was hurt, i'd just have to fix it.
Well, it ran just fine.
I ended up bringing it to Johnny to check out.
What we found was the fuel had already gummed up the throttle bodies, the intake ports and the valves.
The intake valves were sticking to the head so tight that the clacking noise was the valve breaking loose from the head. I have never seen anything like it. We could roll the motor over by hand, and when the seal broke, it would clack. :grn:
Anyway.
A couple of can's of Berryman B-12, some meduim unleaded, STP injector cleaner and some good old Techron from a guy that I know that works for Chevron  ;), and I am back. Johnny had to take the injectors out and clean them too.
Talk about some nasty ****!
1 day folks.
Put the gas in Saturday, and Sunday it was fuckered up!
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I just ran U4 today at the track (the 93 octane version). I love that smell. Anyway, no real notieable power gains. Nor losses. Well, the power gain is very minimal at best. I was powerwheeling out of several corner. My brother drag races and had 4 gallons left. He wanted me to use it up, which I was able to do in 3 sessions. After that it was back to 91 pump gas to clean her out. BTW-it was a trackday on my 06 Gixxer 1K with Full Yoshi Pipes but no PC and no map.

Yes, U4 (all of them, or any VP racing gas for that matter) is VERY CORROSIVE TO THE GAS TANK, INJECTORS, VALVES, ETC...if left in there for a prolonged period of time. Gotta drain it out after every race and flush with pump gas.

I would imagine it works best if you're custom mapped, running turbos, nitrous, etc.

Club racers use it b/c many have built motors with higher compression ratios.
 
+1 on draining the U4. You cannot leave it in!! It will Fubar everything. I seen what happens over the summer on a bike at Lee's performance. The owner didn't know he had to drain it and the fuel ate the heck out of his injectors. Drain the U4 then run some pump gas alittle bit.
 
Is it a higher octane fuel? If so, I thought higher octane didn't provide any benefits.
The added benefit of higher octane is only noticable on high compression engines. The octane is a rating of how much you can compress the fuel before it spontaniously combusts (like deisel fuel) You can compress (presurize) 93 octane more than you can 89 octane without it igniting. Therefore, if you have a high compression ratio you have to run a higher octane fuel to keep from having pre-detonation issues. As for the U4, you'll have to go on the other guys replies for the benefits of it with a standard busa engine, cause I have no clue.
 
With just a full pipe - large airbox Mod - PC II 87 always-------- I live at 5000' ride up to 8k and down to sea level.. always runs great.. just wish i had sea level HP where i live-- it can be done just need $'s
 
It seems as if every test I read on the new Busa and '08 ZX-14 has some sort of mention of U4 fuel. I understand its racing fuel, but what is it? Is it a higher octane fuel? If so, I thought higher octane didn't provide any benefits.

I mean, I assuming the new Busas and 14s were made to run on 87 to 93 octane. If (and I say "if" because I honestly don't know) U4 is a higher octane than 93, wouldn't that mean the Gen1 Busas would run best on 93 octane and not 87?

For the sake of an argument I use "plus" fuel which is 89 octane. Not regular nor premium ... just the middle one on my Gen-1. I'm saying that because I don't want anyone to think I'm trying to get others here to use the highest octane at their local gas station.
By the way, the k8 Busa, needs 90 or better octane, with the 12/5-1 compression ratio.
 
VP reformulated the U4.2 so that it would not have that residue anymore. The sticker on the fuel can still says to not leave it in the tank, but the guy that runs the dist. center here in town leaves it in his and has no probs.

Personally, I drain the tank after the race day and put pump gas in and run it for a bit to clear the lines.
 
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