Another Fuel Question: Sunoco Purple 110 v. VP U4

Been running a stock-motored MZ since I started racing, using pump gas.

A couple months ago, I picked up another MZ with a little motor work: +2 piston, welded crank, new rod, cam, Ti valves, flat-slides.

The guy i got it from was buying what they sold at the track at Summit (I think Sunoco.) I have a local shop that keeps Sunoco Purple 110 for $5.50/gal., or I can get the U4 at the track from Cindy.

I know the U4 is appx 2 times the cost. It also has lower octane, but O2 added. Is the U4 OK for high-compression big singles? Has anyone done comparative testing for power on these two fuels?

Thanks,


Trent

 

OK, is anyone willing to speculate on the jetting differences necessary between these two fuels?

Thanks.

 

U4 isn't high octane, I know that much. I remember reading the brochure and I "think" it was around 87.

 

Trent:

I have run all kinds of gas in my bike, including Sunoco 110 race fuel from the track, Klotz, etc. It doesn't seem to matter. And generally speaking, the bike does not seem to be sensitive to jetting, once you get it right. Ask Tim Barker for guidance on this, it sounds like you have a setup very close to mine. I have never once changed the carbs, other than to speed up the idle a little.

Andy Weiss did do some comparative fuel testing, and buys VP as a result of a small bump in HP on the dyno, but I don't know which VP it is. It wasn't enough of an improvement to me to justify the pain of buying the fuel.

 

pretty sure your wasting money on high octane gas that is not going in a high compression motor (but i have been wrong, maybe)... I DO know that simply pouring in VP u4 will increase on 3 600cc bikes i have had on a dyno by 5+HP.. Remapping smoothed things out a bit but did not get much higher peak hp than originally just pouring it in. U4 is 92 octane, oxygenated and leaded (dont run in a bike with cat. converter)..

 

if you want oxygenated with high octaen theres U2 101 octane the octane is the only diff between it and U4

 

I did the same thing on an '02 GSXR 750. Ran the bike with U4 on the dyno at almost empty, and then filled it up with 93 pump gas, and dropped 5 hp right off the bat. It took tweaking the map all day just to get it back to the peak hp it had by just pouring in U4.

 

Thanks, guys.

Melk, I tried to return your PM, but your box was full.

My choice is not between U4 or Pump, though - my new motor will require some kind of race gas and I was trying to decide between U4 or Sunoco. I wasn't sure that the U4 would be good in a high-compression single...

Bruce - glad to hear that the jetting is pretty stable. Pulling jets is the last thing I want to be doing on race morning

Since the Sunoco is easier to get, cheaper, and has already been used in this motor, I'll probably start with that, then maybe try the U4 later...

 

U4 may not be the choice in a high compression single, there may be better VP choices for that application..Here is the site..
http://www.vpracingfuels.com/vp_01_fuels.html?mgiToken=0C15B7C81E44AC4A873

 

Go with the Sunoco. It has the octane you need for your hi-compression single and it is oxygenated. Plus it's way cheaper. If you can win races with it then that's it right? Nobody else in your class is spending/wasting money on U4 or equivalent. My .02

 

Trent:

I have an oxygenating additive I'd be happy to add to your tank next time we're at the track together.

It only LOOKS like sugar!

 

Ha ! ... So THAT'S why you miss so many races...

 

If the bike worked properly, how could I explain not winning????

And how did you get a double-digit WERA number????

 

Just clean livin', I guess...

Thanks for the ideas.

 

Does Sunoco have an alternative to U4 that is designed for modern supersport style motors, with the 4 horsepower bump over pump gas you normally see with U4. I might have a source for some sunoco, but don't know if they have a similar fuel.

Thanks,

dk

 

Have you ever seen the show Myth Busters?

They busted the sugar myth, the big caddy ran with a five pound bag dumped into a couple of gallons of gas. Then they let the sugar set over night and tried it again. Caddy ran like a champ.

 

They make a 104 oxygenated unleaded.

 

Have you used it in comparison? What's it called by the way.

dk