rotax fuel

[Joe Ricard]

Doesn't Arizona have like one lake?

But there are race tracks and lots of hot rod shops.
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Arrow AX-8/ Rotax Sr.

[Bill Wright]

I'm going to hijack this thread a bit. I was told that the U.S. Nationals and the Pan Am event were run on "pump" gas. Does anyone know for sure exactly what fuel was used, and what the results were?

It seems very difficult for me to believe they actually ran "pump" (from a station) gas, considering the differences in alcohol content, and the oxygenators used by many "pump" fuels. It seems to me it would make for some really interesting jetting issues.

Not that I wouldn't love to have pump fuel prices. It's no secret I've been feeling "violated" by VP/Race Fuel pricing for many years, and have looked for a cheaper/viable alternative every year for many years. All the lower cost options posed big question marks about performance and tuning.

It's important that you're not guessing about this. If you were there, and know exactly what it was, tell us what it was, and if there were any issues.
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Bill Wright
Formula Kart Productions, Inc "SERIOUS FUN!"
Exclusive Promoter / Owner of the Florida Winter Tour
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[Andre Eriksen]

I was NOT there, but I think this thread is running a bit academic. I think the key is that be it race or practice that you run from the SAME (brand) gas station.

For example at Infineon Raceway there is a Sunoco gas station at the facilities where they also have 91. That could be used in a race no problem, as they could calibrate tech accordingly and ask people to buy the gas there.

For practice it is more a question about convenience in jetting. I bought from the same lowest cost provider for years and never had any issues. Also I never faced any performance issues. End of Saturday practice I would always swap to VP as mandated in the race. No change in lap times.

Had I bought from 10 different gas stations I may have had to play around with jetting more - don't know...
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2012 Formula Car Challenge Vice Champion (Pro Formula Mazda)
2011 Rotax DD2 Masters National Points Champion
2011 NorCal DD2 Masters Vice Champion
2010 NorCal Rotax Masters Champion
www.viking-racing.com
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[Scott Falcone]

Bill,

At Nationals they ran pump fuel. Not sure where they got it. I believe trucked in. I asked twice and was told that.

At Pan Am they ran Shell 91 from a gas station down the street. Right out of the pump. I blew up my motor twice that weekend because of fuel issues and ended running a very bad back up motor.

I really don't want to go on a rant about this crap pump fuel we are now using more and more. (Rotax Nationals, Pan Am, Joke!) Maybe just a little rant.

As far as I'm concerned any International, National or Max Challenge Rotax Series race should be ran with a spec race fuel. As in the past. This Bs of buy your fuel at a gas station and come run it at one of these races is unacceptable. I complained about this to Josh and it went in one ear and out the other.

For the Karter who just wants to go out and have some fun with his buddies for a weekend god bless you and run whatever you want but, a Rotax affiliated race needs to be a race spec fuel.

This is what I do know. In one month I ran 4 different fuels at 4 different races 3 of which were pump fuel. (Dallas,Denver,Southbend, Utah) You want to talk about a complete debacle this is a joke and something needs to be done its out of control. Jetting is all over the place, contamination in the fuel line and tanks is an ongoing issue in tech, rebuild cost through the roof and detonation is a problem more than ever, just to name a few issues.

More importantly I'm having to rebuild my motors 70% sooner than when we were running ms93. This is a fact. I have been dealing with a Rotax National Tech Advisor whom is very involved with the rebuilding of Rotax motors. He is finally agreeing with me that the pump gas, at least in Denver is absolutely hurting are motors and causing re-builds sooner. I have been complaining about this for two years and now he has finally admitted that there is certainly and issue with the pump fuel at least in Colorado with the Rotax motors breaking down sooner than usual. He used all these big tech words an theories of why. I really don't care why it's doing it. I just know it is! Hurting our motors sooner.

So what!!! You save a little money on some gas! Big deal! Is the savings of pump prices worth the off-setting of the rebuilds? (NO) Are the savings worth loosing a great cylinder or motor in general like I did at Pan Am? In my opinion NO!

Bill, I sure hope we run ms93 at FWT this year and many more to come.

[Chris McGinley]

[Michael D Jones]

I've been racing Rotax since the day the engine was introduced to the US. I've never had engine problems like I've had since we started the XPS oil and "pump" gas. I ran the Nationals in Indiana and experienced excessive detonation using their "pump" gas. I too, was told it was Shell 91 fuel which was trucked in. I lost two engines early in the week due to rod bearing failures. Then, ran the Pan Am race in Colorado and lost another engine (rod bearing failure) in one of the heat races. I personally, have NEVER had these types of problems, especially with the Rotax engine.
If I had a vote in the matter, I would say stick with the VP MS93 fuel and go back to Motul oil.
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www.thekartshop.net

[Dave Harrington]

[Bruce Woodrow]

[al nunley]

Octane is a measure of a fuels ability to resist detonation. Nothing more!! It’s not hotter, it’s not more powerful, not by itself.
If you have high compression ratio, you need high octane, but if you have a lower compression, you can run less octane.
If you run low octane, and you get no detonation, you will most likely get more power verses running a high octane. Nothing bad will happen if you run “too” high an octane. If you run “too” low an octane, bad things can happen.
Detonation is the spontaneous explosion of the fuel, caused by excessive heat and/or pressure. It is not “pre ignition”, the starting of the burn process before the ignition spark. Mostly caused by a “hot spot” in the combustion chamber.
So even though you might be able to run a fuel with less octane than say VP98, (it’s not going to hurt anything but the engines power out put.) you have to be very careful with the detonation.
Things is, be aware that detonation starts long before you can hear it. I’ve found the best way to detect detonation, short of pulling the head, (it looks like sand blasting around the edge of the piston or head) is by using the EGT gauge. If the EGT reaches a peak, and drops down a little, or a lot, it’s a sure sign of detonation. Same for the top end and the low end. If you start out and the EGT is reading some number coming out of the slowest turn on the track, and then later, that number get’s lower, it’s a sure sign of detonation.
Detonation can start with a change in air density. More air, more pressure, means a good chance of detonation. Not always, it depends on what the mixture was before the increase in air density. If you are little rich before the increase, you just get a little leaner, but it you are right on the edge, higher air density can push the engine into a lean condition.
There’s a lot to learn.
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If the data does not support the theory, get a new theory. (Al Nunley)
All else being equal; Compression is the Holy Grail.
45 years, in and around karting

[Chris McGinley]

[Brent Harper]

If the concern is saving racers money then they should reduce the price of D2's and D3's not change to crappy fuel. ALL of my practicing is done on MS93 even though I have to drive 6 hours to DKC to get it.
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SWISS HUTLESS SWISS I/CMC ROTAX

[Todd Renaud]

Coming into this a little late - but found out today Pump fuel is now required by Rotax (switched before the Nationals). I am prepping to start racing RotaxMax races for 2013 for my son - how do I keep track of all these little changes because they aren't on the Gorotax.com site anywhere.

I know my local Distributor should do that (and he does when we speak) but I'd rather be able to find out myself.

Thoughts?

[al nunley]

It’s been my experience, with the KT100, that we could run any octane, even regular, if we just watched the EGT and tuned accordingly. No, you can’t get the EGT up as high as you can with race gas, but we were fast, (in the lead most of the race) and came really close to winning. Long story. This was at Sears point in the no body work sit-up class. With good tuning, I’m going to guess you can do the same thing with a Rotax. All you need is an EGT and an air density gauge.
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If the data does not support the theory, get a new theory. (Al Nunley)
All else being equal; Compression is the Holy Grail.
45 years, in and around karting

[Harj Singh]

Just curious as to how much oil you guys are mixing with XPS, I thought 4 ounces to a gallon was rule of thumb for this mix with no matter what gas / Ron type you are using.

Thanks

[Todd Renaud]

Doesn't Rotax now also require only between 2oz/4oz per gallon and nothing more or less?