Redneck in training
Elite Member
Because high octane fuel burns slower there is a danger that the fuel is still burning when the exhaust valve opens. If that is the case then you need to advance spark little more to prevent exhaust valve damage.
Will mixing Sunoco Racing Fuel hurt my 825i Gator?
- Thread starter jcmseven
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tomd999
Platinum Member
Hiya,
My 2 cents would be that putting a few more degrees of timing into the engine wouldn't be worth the effort. The octane rating of the fuel is not the only factor of burn rate. (Although one SAE paper on E15 fuel said that flame front travel was significantly higher in port vs direct injected spark ignition engines)
Sunoco racing fuel as the OP said he is using, (Although I don't think it's the 116 blend as that one is dyed red and he said the one he is using is blue which I think is the 110 blend) are fast burning fuels as they are designed for complete burn in engines turning past 7500RPM. If I remember right, Sunoco says the 116 red fuel blend is the fasest burning racing fuel they have.
The "high octane gas burns slower" got it start when people used to run AV-Gas in auto engines. If you think about it, aircraft engines operate at one RPM for most of their life, "cruse". Aircraft fuels are blended for cold temps, low air pressure and slow turning engines with more often than not, terribly shaped combustion chambers. They have the ability to vaporize well at freezing temps, the highest resistance to vaporlock as well as high resistance to detonation. Add all of this up and you have a very slow burning fuel which suited the radial engines that these fuels were initially blended for.
Tom
My 2 cents would be that putting a few more degrees of timing into the engine wouldn't be worth the effort. The octane rating of the fuel is not the only factor of burn rate. (Although one SAE paper on E15 fuel said that flame front travel was significantly higher in port vs direct injected spark ignition engines)
Sunoco racing fuel as the OP said he is using, (Although I don't think it's the 116 blend as that one is dyed red and he said the one he is using is blue which I think is the 110 blend) are fast burning fuels as they are designed for complete burn in engines turning past 7500RPM. If I remember right, Sunoco says the 116 red fuel blend is the fasest burning racing fuel they have.
The "high octane gas burns slower" got it start when people used to run AV-Gas in auto engines. If you think about it, aircraft engines operate at one RPM for most of their life, "cruse". Aircraft fuels are blended for cold temps, low air pressure and slow turning engines with more often than not, terribly shaped combustion chambers. They have the ability to vaporize well at freezing temps, the highest resistance to vaporlock as well as high resistance to detonation. Add all of this up and you have a very slow burning fuel which suited the radial engines that these fuels were initially blended for.
Tom
Redneck in training
Elite Member
When I was younger (in sixties) we used to have 92, 96 and 100 octane fuels. We used to install thinner head gasket or machined the head to get higher compression. That in turn required 100 fuel. If the spark was not retarded enough the exhaust valves would burn. The fuels were standard gas pump stuff and there was no information about burn speed. We had just empirical experience. I guess the situation is different today. I didn't know that you might have high octane fast burning fuel.
BleedGreen
Gold Member
FYI the 825i Gator absolutely has an O2 sensor. I cannot say if the race/street fuel blend you are using will do anything to it, but it is there.
Thanks for the advice. My main concern is that I do/did not do anything to harm the engine or injection system. I have burned very little of this mix (only about 10 gallons TOTAL so far) and my perception is that the Gator runs better, and it definitely used less fuel, by not an inconsequential amount. My main reasons for trying it were not related to a desire for more power. With the spec'd compression ratio and 87 octane limit, I knew there was no real reason to do it, other than 1. to eliminate the ethanol and 2. I like the smell (I know, sounds silly). The fringe benefit was that the Gator does seem to get better economy also. I am very particular about my equipment, and do not wish to damage the machine. I remain confused about why JD specs 1/8-1/4 tank of racing fuel in their machines when shipped other than what we already discussed in my original post. Seems as though, given the sheer number shipped, that this could be an expensive thing to do if not needed, and I would suspect they have good reasons for doing it. I do not know if their fuel is leaded or not. Interestingly, VP fuels answered my tech question by recommending their 94 octane fuel without ethanol (unleaded). Is this pretty easy to order?? Also, Tom was correct, it was blue 110, not 116 as originally stated. Sorry for the confusion.
John M
John M
tomd999
Platinum Member
Hiya,
I use the VP Fuels SEF94 in all my small engines. I know the 94RON is a little overkill for the modern engines but I have several 30+ yearold Onan, Kohler and Wisconson that were designed when "Regular" was 92 RON back in the 60's so 94 is just about where they need to be.
The SEF is unleaded so you can run it in the Gator and not have to worry about any O2 issues. It's easy to get around here, the local Bobcat dealer in the next town has it or I can get it from a few different places close to the race tracks that sell VP. It comes in 5G cans.
Tom
I use the VP Fuels SEF94 in all my small engines. I know the 94RON is a little overkill for the modern engines but I have several 30+ yearold Onan, Kohler and Wisconson that were designed when "Regular" was 92 RON back in the 60's so 94 is just about where they need to be.
The SEF is unleaded so you can run it in the Gator and not have to worry about any O2 issues. It's easy to get around here, the local Bobcat dealer in the next town has it or I can get it from a few different places close to the race tracks that sell VP. It comes in 5G cans.
Tom