Antler87

When I get a baja 5t I plan on running 91, that's the highest octane pump gas we can buy around here. If I ever go to a bigger engine I was thinking about running race gas. You can buy 112 octane race gas around here for $12 a gallon. Is this a good Idea? Would I see any gaines on say a 30.5 race engine. Any gains on the stock engine?

Lars from Norway

I have heard the higher octane gas itself will not give any gain in power, but maybe if you raise the comp a bit and some other things it will. Here in Norway we have 98 octane as the highest pump gas. But there is no difference between that and 95 as we also have.

sheograth

There is no benefit from using higher octane fuel in these kinds of engines, some would say lower is better in fact. In any case I just use standard 87 octane pump gas mixed with oil.

extremeaudi

Thats exactly what I did, I ran standard 87 with the crappy stock engine and when I got my stroker engine I now run 100 octane with blue marble in all my rc cars and snowmobiles. The higher the octane fuel, the better your engine will run. 2 strokes just run better on high octane. Plus the smell is so intoxicating!A local track I go to I seen a few people using 108 octane, but thats a little pricey.

My latest project >

Croozer

My Feedback: (1)

High octane is a waste, these engine are designed to run on 87 octane fuel, some people even run 55 octane Coleman fuel.

clubin

I run 110/130 Av Gas. THe blue colored stuff, leaded with no ethanol. It doesn't cost me anything, so I am not complaning.

extremeaudi

Unless you have a much higher than stock compression ratio the higher octane fuels will not give you any extra performance except an addicting smell. In one of my Bajas I have a full mod motor I get bad detonation on 87 and I can tell a big difference with using 100 octane. The higher the octane, the higher the flash point or the temperature it takes to burn, which is why it is less detonation prone.

hndaman1

My Feedback: (6)

I was running 110 leaded, never seen any diference.. I also have a 27.2 race port (813 carb) and HAD a GBe side pipe.. going back to good ole 91 octance..

badd_maxx.25

i run camp fuel with 8oz of oil to the gallon

logon69

Try using that in a 15:1 compression engine. You cant! If you are running a low compression (Stock) engine it will work but you do sacrifice power.
8oz of oil? Can you see with all that smoke?

BKNate

Very true indeed about using low octane fuel in high compression engines, it just won't work at.

mecano

The octane rating in fuels indicate how much the fuel can be compressed before it ignites spontaneously. Raising the octane level may even reduce the ignition point at "stock" compression ratios, and thus could reduce performance. Diesel fuel has a very high octane rating, allowing diesel engines to run at much higher compression ratios. [sm=49_49.gif]

Johnnysplits

Everything sounded good until you got to the diesel fuel. I think your confusing octane for cetane.

mooman007uk

indeed, diesel has an octane rating of 20-25 but combusts in a totally different manner, it's rating is in cetane.
but mentioning diesel that would be an interesting engine for a largescale rc, nothing like loads of torque and black smoke

here's something interesting i found

also my echo weedwacker and stihl leafblower both recommend 89 octane or higher (the stihl came with a zen 27.2 in it) . i generally use premium, which is 91 here, for my rc's, i was going to start using avgas but if there is nothing to be gained then it's pointless...the gas here is still ethanol free...as soon as they start chucking that stuff in i'll start using avgas

JCBaja

clubin,

I was running av gas for a short while (I am on an airport, so avgas is also free for me), and my spark plugs would become lead fouled. How have you been able to keep this from happening in your engines?

-JC

clubin

Interesting I have not had any issues yet. I should tear down one of my engines and see. Plugs look fine.. I am mixing with Polaris Gold maybe that has somthing to do with it?

SAVAGEJIM

I too would be very interested in seeing a very high compression ratio diesel RC engine. I would however prefer it to be a 4-stroke or at the very least a valved 2stroke with the intake ports set very low in the cylinder walls so you get much more of a trapped compression ratio (the closer to a geometric compression ratio, the better). The much much higher torque of diesel would allow you to turn very very high gear ratios, and even though the engine turns very slowly, even as slow as 8K RPM maximum, the taller gears could even more than make up for the loss in engine peak RPM.

I would prefer as close to geometric compression ratio as possible for the specific reason that you get more torque created from each combustion because if the sleeve ports were high enough, you would lose so much more potential torque from fuel that goes unburnt even after the ports open (thus that much potential chemical energy being wasted) and also the quote you mentioned that the cylinder pressure drops drastically towards zero at the instant the sleeve port opens.

Aviation gasolines? I am not to sure of those. It totally depends on their content. From what I remember, aviation-grade gasolines still have tetra-ethyl lead additives to create those much higher octane ratings. I cannot remember, but I believe you would have to seek plugs that are intended to burn leaded gasolines. (If someone knows the correct answers and reasons why, please post; it has been years since I learned about this sort of thing.)