Race gas

[don250r]

was just wondering how many people cut their race gas with pump gas?
half and half is what i use(112 w/ 93 pump).
been told simple math doesn't apply here, but i'm not so sure.
would this not be 102.5 octane in the end?

[Derrick Adams]

We all run it 50/50 in our race bikes. Makes for easier start up, faster warm up, and never foul plugs.

[GPracer2500]

I run 50/50 of 91 pump and VP110. Mixing fuels insn't ideal but I do it for cost savings and to standardize my fuel across several engines (some need more octane than pump, some don't).

There's a couple things to consider when mixing fuel and trying to estimate the final octane rating. The first is the initial ratings of the two fuels--what type are they? MON, RON, or R+M/2 ?? I dislike the R+M/2 system our pump fuel uses. MON is a better indicator of deto resistence in our engines. For that reason I always try and use MON ratings to keep everything apples to apples. You can estimate the MON rating in pump fuel by taking the R+M/2 and multiplying by 0.95. It won't be exact, but it should be close.

Once you're using the same octane rating type for the fuels consider leaded vs. unleaded. Mixing MON 86 unleaded with MON 108 unleaded 50/50 will give you about 97--just what you'd expect. That is not the case when mixing unleaded fuels with leaded fuels. Leaded fuels are not simply unleaded fuels with TEL added. The hydrocarbon mix in unleaded fuels is formulated to react favorably with the TEL. If you throw some unleaded fuel into the mix, you may have just introduced hydrocarbons that do not have a favorable reaction with TEL. Some unleaded fuels could actually have a negative lead response (unlikely but possible with all the "boutique" pump blends around the country). The result is that you will never know exactly what you're ending up with when mixing unleaded and leaded fuels.

Mixing oxygenated fuels throws another wrench in the works. Avoid mixing an oxy fuel with anything whenever possible.

Mostly, I don't worry about what the final octane rating of a mix actually winds up being. I go with a pass/fail evaluation as to whether it meets my engine's required octane rating. I find conditions tailor made for detonation and if my engine shows no signs of deto then I know that mix is good to go.

[Dammit!]

The pump gas in AZ sucks in general (imo). I just bought some AV fuel (100 octane, low lead) before my last dune trip but didn't use any of it yet. I still have a little of my old 50/50 mix to burn through. The AV gas I'm going to run straight and see how that works.

[GPracer2500]

I'm with you on AZ gas being junk--it is.

As much as I'd like the octane ratings on the pump to be the final word on detonation resistence, that is just not the case. With R+M/2 we don't ever really know the MON rating--and that's the one I really want to know. Also, (and this goes with any fuel, not just pump fuel) the distribution of the higher octane components of the fuel is not reflected in the octane rating. If the higher octane components are crammed within a narrow range of the distillation curve then certain running conditions can cause deto when the octane rating would suggest it should not occur. In other words, one particular 91 fuel might not perform the same as another 91 fuel in real world conditions.

Lots of people talk smack about 100LL and how it's not good for anything but aircraft engines. This is not true. 100LL has a minimum MON of 99.5 (that would be ~105 in pump fuel terms, i.e. R+M/2) and a fine looking distillation curve. Is it as "good" as a premium leaded racing fuel? No, but it's way better than straight pump fuel from both a octane rating perspective and a distillation curve perspective.

[Dammit!]

With a 50/50 mix of 110 race fuel and 91 pump gas, I still get just a little pinging at the dunes under a heavy load at lower RPMs. I'm hoping the 100LL gets rid of it completely.

[250r'en +TCB]

yeah I run 50/50 leaded 110 and 93 in my 310R. I notice a difference and besides I have to run 100 octane, but that's with a 20:1 mixture lol. I'm sure if I ran 93 octane with a 32:1 mix I'd be fine, but I want to be more than OKAY.......

[Yamahondaman]

I Was ALLWAY'S Told that when you Mix Pump Gas with Race Gas is that it ONLY WEAKEN'S the Octain of the Race Gas But..........................
Also some people Mix it because of Money and some Motor's only need that Little Bit More for Detonation Purposes because also i was told NEVER to use a Fuel Additive such as Octain Booster in Pump Gas for 2-cycle Motor's... "they" say it messes with the life of the seal's and the Reed's .... PLUS....................
AV Gas and race Gas SMELLS G@@D !!!! :naughty:

[don250r]

well guys i took it out after work yesterday.
i thought i heard a tiny bit of detonation with my mix.....
gonna really try out this weekend(i have a 4 day weekend:w00t: ).
if it still detonates with the blend, might try straight 112 octane race gas.
The AV gas i'm really leary of.
back in the 70's my dad ran an NHRA Super Stock drag car.
he tried running straight AVgas but one week later it melted a piston.
sent it to the lab, of course they said it was the straight AVgas.said AVgas HAS to be mixed half and half with pump gas.
Don't know if this is true of 100LL(don't think it was available, then).

[dufrain]

I read before thAT the problem with the airplane gas is the anti iceing additives that can cause the problems.Anyone else ever heard that.

[GPracer2500]

I read before thAT the problem with the airplane gas is the anti iceing additives that can cause the problems.Anyone else ever heard that.

Generally, icing inhibitors are not added to aviation gasoline at the time of manufacture. If it's used at all, it's added by the end user. Isopropanol and di-EGME are both approved for use. Di-EGME is the preferred choice when an icing inhibitor is desired by the owner/operator of the aircraft.

It's a non-issue because there is an excellent chance 100LL at your local airport contains no iceing inhibitors. Even if there where iceing inhibitors in the fuel (added by the distributer or retailer), I'm not aware of it causing any performance issues (except for higher concentrations of isopropanol lowering octane rating--one reason di-EGME is preferred). Whomever you buy the fuel from can tell you if they've included any additives in the fuel. Unless they primarily serve a specialized customer, chances are low they do anything to the fuel.

[Bryan Raffa]

AV gas,,,,has no lead in it witch is needed in our trikes it also attracts water and holds water in it! It has been noted for this!
race gas has lead in it designed for the use in our bikes!and leaded machines,Thus this is why we buy it.

stay away from AV gas.....

[GPracer2500]

Avgas does have lead in it.

[Bryan Raffa]

verry little not nearly as mutch as race gas or pump gas, and yes your correct but its verry minamal.

[3Razors]

All this talk about AV gas being bad is nonsense. Other riders including myself have run it for 17 years now in all my machines and never once had a mechanical breakdown. Dont be scared to try it! Plus its half the cost of race gas.

[GPracer2500]

verry little not nearly as mutch as race gas or pump gas, and yes your correct but its verry minamal.

100LL contains 2 grams of lead per gallon. Most racing fuels we're likely to use have about 4 grams per gallon, maybe a little more depending on exactly which fuel we're talking about. Sure, that's twice as much but it's not like 100LL barely has any lead in it.

Also, I'm not sure what pump gas you're refering to. In the 70's, leaded pump gas typically contained 2-4 grams per gallon. Current pump fuels in most parts of the world contain virtually no lead whatsever.

The lubricity benefits of lead are less applicable to 2 strokes anyway. Aside from what lead does for octane rating, the largest benefit to leaded fuel is as a cushion between valves and valve seats. Unless your engine was built in the seventies or earlier, the metalurgy of those compenents has improved to the point where I believe is would be difficult to measure any increased lifespan of those parts by using leaded fuel.

[Yamahondaman]

i was told that "Lead" also is Lube for the 2-cycle...they like that....
Lube is Carbon....Burnt Well Makes HorsePower.....
Duncan Racing Doesn't like it when people use 100LL AV-Gas..
i have had no Problem's with it when Jetted Right..."back in the day when my bike was stock" ...
Now ....with the Compresion i have ....I Can't use it..Just Cam-2

[Bryan Raffa]

the lead now a days is replaced with ethanol.... yes they do like lead ronnie!

[Yamahondaman]

Smells GOOD TOO !!!
i also was told that back in the day "they" put "Dryer's" in the AV-GAS....and....
they don't do that no more and ....................
When Mixed with a GOOD 2-Cycle Oil "KILL's" the additives in AV-Gas ...
RUN IT PEOPLE !!! :beer

[phil53]

I've used both avgas & 50/50 mixed, VP C-12 & 93 pump. I tend to stick with
the 50/50 mix though. A friend buys VP fuel in 50 gallon drums and is easier for me to get. I don't have to change jetting too much between the two.
maybe my *Edited**Edited**Edited**Edited**Edited* dyno likes the 50/50. No huge differences.
I wouldn't run avgas in any 4 stroke.

[Yamahondaman]

When we ran it in our 400ex we put 1 oz. of Maxima 927 per gal. so it wouldn't dry out the valves.... smelt funny too ... made people wonder what we were running... :naughty:

[Pete]

why would our trikes need lead in the fuel? Stock they are designed to burn UNLEADED PUMP GAS. Lead is not needed in any modern engine for lubrication, detonation resistance only.

[Yamahondaman]

"WE" Don't need nothing for "our" Motor's if we want to stay at the BACK OF THE PACK...........
Lead is Lube........
Lube is Compresion........
Compresion is Horse Power.....
it's what some People Want and Need.....
and when EveryThing is Right it all blends in NICE....
For on "RACE DAY " when "WE" Run the Rice...
Air is GOOD,Gearing is ON ,Traction is Perfect for the" NEED FOR SPEED" !!!

[Pete]

if I want to be at the front of the pack, I run methanol :) I've tried alot of fuel in my trials and tribulations with the 250R and I've never noticed a lick of difference regardless of lead content. The biggest differences are oxygen content.

But you know how the disclaimer goes...to each their own..

[Yamahondaman]

Oxygenated Fuel ................. YES !!! :naughty:

[Pete]

its too bad it likes to leave nasty things behind, kind of like a good time on prom night.

[Yamahondaman]

Yup ..... i heard that Brother !!!!

[don250r]

well guys,
pretty much made up my mind to run straight 112 race gas.
took it out the other day, and i THOUGHT i heard a little pinging close to the top end of 6th(with 50/50 mix). don't know what my actual compression is(will find out this weekend).somebody told me about settling ocurring in mixed gas(pump+race).
does this happen quickly?
my gas isn't around long enough to settle(i'd like to think).

[Fox250R]

I get topend pinging with pump, but when i run 50/50 ping goes buhhbye!! :)