January 23, 2015 at 1:09 pm #40955
Is one better than the other? If so what do you recommend? I have been using 93 octane and thought about testing with higher Octane. Any thoughts?January 23, 2015 at 3:03 pm #40958
A. Recommend MS 93.
B. Contact Nick Weil, located in Orlando
LAD Specialties customer / tony kart / rotax / kt100January 23, 2015 at 7:32 pm #40968
Lowest octane you can get away with without knocking; I like 91 pump gas. Lower octane fuel ignites faster (the reason it detonates in high compression motors). MS93 smells better and keeps your carb clean, but Rotax motors love pump gas with ethanol. It’s also much easier to tune with pump gas; the ethanol makes your carb less sensitive to weather, so jetting doesn’t need to be as precise. There is a scientific explanation for this, but I don’t know what it is. If you are going to run at a national event where they mandate MS93, plan to go one jet leaner than you would on pump (no oxygen in race gas).January 24, 2015 at 1:14 pm #40995
how do you find out if your knocking with a 7 year old driver?
we can only get 9900 rpm on 98 octane fuel, will try some 93 pump tomorrow.January 24, 2015 at 3:18 pm #41001
Well, he’s 10, and he’s been known to say “Dad, my motor sounds weird.” Honestly, you could probably get by with 89, As Rotax are pretty low compression engines. I like the idea of race gas; consistency, smell (not important, but nice), and doesn’t leave your carb sticky with ethanol residue. I’m sure it’s easier on the motor, too. But we’ve always had much better performance with pump gas, so pump gas it is when we can use it.January 24, 2015 at 7:43 pm #41007
what kind of rpm do you see with the various fuels? and to clarify, my guys 7 and if i can’t hear it from the sidelines i probably won’t get that kind of feedbackJanuary 25, 2015 at 4:45 am #41015
You really should be able to get the same rpms with either; it’s just going to be easier and take much less time with pump gas. The tuning window is just broader. We can get above 10k with either, but it just takes more trial and error with race gas. When I wrote that we always get better performance with pump I really should have written we get better performance with much less tuning. Your carb tuning can be a little off and it won’t affect your performance, whereas race gas isn’t as forgiving. I’ve never used any race gas other that MS93, so I don’t have any info on 98 octane fuel.January 25, 2015 at 5:58 am #41017
9900 RPM is fine for micro. 93 octane is just right. Check the plug to determine jetting. Stay far away from ethanol if you use pump gas find non ethanol 93. Do an internet search for non ethanol gas in your area and see who’s got 93. For karts ethanol destroys everything it touches.
BrianJanuary 25, 2015 at 5:57 pm #41050
I’ve got to disagree with you on ethanol Brian. If you keep your carb clean after every day at the track, you won’t have any problems. Rotax motors are tanks, and they are designed to handle 10% ethanol fuel. Guys here in the northeast run 93 pump almost exclusively and never have any ethanol related issues. The person I trust most in the karting industry loves pump gas for Rotax and thinks race gas is just a way for events to make a little extra money.January 26, 2015 at 4:06 pm #41125
Ethanol carrys moisture which causes corosion on aluminum. It’s widely known and there are a whole aray of products on the market to try to combat it. If you left non ethanol gas in your engine and let it sit for six months odds are strong you would have no problems. If you did the same whith ethanol not a chance. Yes you drain drain and clean and make it work but why bother?
One of the thousands of studies done on the problem http://www.mossmotors.com/SiteGraphics/Pages/ethanol.html
BrianJanuary 26, 2015 at 9:52 pm #41139
I have easy access to 93 e or non e, any tuners care to chime in?January 27, 2015 at 5:54 am #41148
Brian, of course you are correct about ethanol attracting moisture. But regardless of what fuel we use, we will drain the fuel and clean the carb after every race day at the track. We don’t consider this a bother, just standard operating procedure. I never use fuel more than a day or two old anyway. You will never have any ethanol issues if you do this. Karting is so time consuming and expensive I don’t take any chances with the fuel or fuel system. This is less of a hassle than tracking down ethanol free fuel or race gas, especially when I like the tuning ease of pump gas with ethanol anyway. My leaf blower and weed whacker are a different story; they’d run better if I treated them like my karts instead of throwing them in the barn when I’m done with them.
And Mark, if you have easy access to both, why not test it? There is no magic bullet fuel. Any 91-93 octane gas, with ethanol or not, will eventually give you the same performance, it’s just a matter of how much tuning it takes to get there.January 28, 2015 at 5:44 pm #41301
My last comment. Unless your buying your fuel from the refinery you really don’t have and idea how old it is.
Your fuel passes through your crank case. So unless your dissasembling the engine and drying it out you’ve got ethanol sitting inside.
It may not matter or you may tear that engine down one day and wish you had stayed away from ethanol. As you said everything in karting is expensive and time consuming which for me is a reason to stay away from it.
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