What kind of gas do you use/how much octane ?
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I've always used the highest at the pump it's like 91/92 octane. It's only a few galons so what the heck.
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We're having this very debate in another thread (the one about the new Honda TRX450R)... and in fact it sorta went off-topic in that we're talking about the very high compression ratio on the YFZ450, which is I think 11.9:1 or something like that, and some are insisting that 91 is fine for it, and I say it isn't.
The Predator has 10.8:1 and I say for that you really need 91 octane to be safe, and for anything over about 11.5 you'll have to go to 94, 96 or higher octane race gas.
Rob
The Predator has 10.8:1 and I say for that you really need 91 octane to be safe, and for anything over about 11.5 you'll have to go to 94, 96 or higher octane race gas.
Rob
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235 Posts
I dont' know much about that, but I saw that thresd and yes it got a bit off the topic. I know that the higher the compression the higher the octane, that's for sure. I don't know about the word "have" to have that higher octane to run. You do to run clean, the lower the octane you will get carbon buildup on the valves I think. It will run but not very good or as good as it is designed for. What does Yamaha recomend for the YFZ450?
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235 Posts
If you search www.google.com about "Compression ratio to Octane" you get lots of info about this subject. It really looks like it's not just the compression that determines the octane level you need, there are many other factors, like cam, exhaust, valves, etc... really the entire engine setup. Here is one web page with some explanations about the subject.
http://cochise.uia.net/pkelley2/DynamicCR.html
Basically almost all the articles state read the owners manual and use that as the guide. Because they have setup the engine to use the octane they specify.
But generally the higher the compression the higher octane or you get premature detonation. Something probable many men on this site are use to hearing.....LOL no just kidding, coudln't resist putting that in....hehehe
http://cochise.uia.net/pkelley2/DynamicCR.html
Basically almost all the articles state read the owners manual and use that as the guide. Because they have setup the engine to use the octane they specify.
But generally the higher the compression the higher octane or you get premature detonation. Something probable many men on this site are use to hearing.....LOL no just kidding, coudln't resist putting that in....hehehe
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63 Posts
Can higher octane fuels give me more power?
On modern engines with sophisticated engine management systems, the engine
can operate efficiently on fuels of a wider range of octane rating, but there
remains an optimum octane for the engine under specific driving conditions.
Older cars without such systems are more restricted in their choice of fuel,
as the engine can not automatically adjust to accommodate lower octane fuel.
Because knock is so destructive, owners of older cars must use fuel that will
not knock under the most demanding conditions they encounter, and must
continue to use that fuel, even if they only occasionally require the octane.
If you are already using the proper octane fuel, you will not obtain more
power from higher octane fuels. The engine will be already operating at
optimum settings, and a higher octane should have no effect on the management
system. Your driveability and fuel economy will remain the same. The higher
octane fuel costs more, so you are just throwing money away. If you are
already using a fuel with an octane rating slightly below the optimum, then
using a higher octane fuel will cause the engine management system to move to
the optimum settings, possibly resulting in both increased power and improved
fuel economy. You may be able to change octanes between seasons ( reduce
octane in winter ) to obtain the most cost-effective fuel without loss of
driveability.
Once you have identified the fuel that keeps the engine at optimum settings,
there is no advantage in moving to an even higher octane fuel. The
manufacturer's recommendation is conservative, so you may be able to
carefully reduce the fuel octane. The penalty for getting it badly wrong,
and not realising that you have, could be expensive engine damage.
What do you think? Geoff.
On modern engines with sophisticated engine management systems, the engine
can operate efficiently on fuels of a wider range of octane rating, but there
remains an optimum octane for the engine under specific driving conditions.
Older cars without such systems are more restricted in their choice of fuel,
as the engine can not automatically adjust to accommodate lower octane fuel.
Because knock is so destructive, owners of older cars must use fuel that will
not knock under the most demanding conditions they encounter, and must
continue to use that fuel, even if they only occasionally require the octane.
If you are already using the proper octane fuel, you will not obtain more
power from higher octane fuels. The engine will be already operating at
optimum settings, and a higher octane should have no effect on the management
system. Your driveability and fuel economy will remain the same. The higher
octane fuel costs more, so you are just throwing money away. If you are
already using a fuel with an octane rating slightly below the optimum, then
using a higher octane fuel will cause the engine management system to move to
the optimum settings, possibly resulting in both increased power and improved
fuel economy. You may be able to change octanes between seasons ( reduce
octane in winter ) to obtain the most cost-effective fuel without loss of
driveability.
Once you have identified the fuel that keeps the engine at optimum settings,
there is no advantage in moving to an even higher octane fuel. The
manufacturer's recommendation is conservative, so you may be able to
carefully reduce the fuel octane. The penalty for getting it badly wrong,
and not realising that you have, could be expensive engine damage.
What do you think? Geoff.
i run vp c12 in my bikes. i found in my 400ex it lowered the engine temp by 7-10 degrees. on my crf450 2 wheeler i run c12 also, when i had the stock pipe on it it was a little rich, after putting a white bros pipe on, the stock jetting with vp race gas is perfect.
i switched to race gas after having to many jetting issues with pump gas. sometimes id get gas from one station and the jetting would be fine, next time the bikes detonating. the gas here in cali varies so much from different makers, fuel milage is also way different from station to station.
i switched to race gas after having to many jetting issues with pump gas. sometimes id get gas from one station and the jetting would be fine, next time the bikes detonating. the gas here in cali varies so much from different makers, fuel milage is also way different from station to station.
The engine will run on lower actane but when you start to rev it, it is probably detenating and you can't hear it. This is also know as knocking which will destroy the engine eventually. Premium gas at your local gas station has enough octane to run well. It will cost you about an extra 35 cents more to fill up. I keep a bottle of octane booster like 104 or something like it in my tool box in case I end up with regular gas for one reason or another.
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4,878 Posts
I was running 10 octane for awhile , yeah it runs cooler and burns slower....I found when I went back to 87 octane I have MORE POWER now.
Can someone tell me why?
Can someone tell me why?
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2,923 Posts
People have argued about this octane issue with you 10.8:1 comp ratio engine. The manual says to run 87, most other say 91 or 92. I have had the big V8's and i know if you have a engine at 10.8:1 you just about have to run them at high octane to not have detanation (pinging).
I have ran 87 and 91 and maybe it was just the weather or my mind but 87 did feels a little better. But i went back on up to 91 just because it will lower the chance of detoanation..but how would you know if this thing was pinging anyway. So should people run the 87 or 91? I know over a while in vehicle engines detonation can do damage to an engine, but will that happen to the predator engine? So has anyone had any problems by going with the 87 that the manual recommends?
I have ran 87 and 91 and maybe it was just the weather or my mind but 87 did feels a little better. But i went back on up to 91 just because it will lower the chance of detoanation..but how would you know if this thing was pinging anyway. So should people run the 87 or 91? I know over a while in vehicle engines detonation can do damage to an engine, but will that happen to the predator engine? So has anyone had any problems by going with the 87 that the manual recommends?
The only reason to go with a higher octane is if you have detonation, the engine was designed to work well (ie, not ping) with 87 octane so that should be adequate. Running 89 or 93 will not hurt anything though and if it makes you feel good then its worth the $0.72 it costs extra per tank.
I have researched this topic on a half dozen different occasions and I heard once that the higer octanes are not as efficient in some way and will not produce as much power as a lower octane, you see high octance gas in a high performance engine because of the compression and the need for the fuel to resist detonation, if they could, they would run a lower octane. I dont know how true this is, I think the theory was based on the higher octane gas burning slower. Any pump gas should work fine though, I stick to mid grade or premium in my predator just to err on the safe side.
I have researched this topic on a half dozen different occasions and I heard once that the higer octanes are not as efficient in some way and will not produce as much power as a lower octane, you see high octance gas in a high performance engine because of the compression and the need for the fuel to resist detonation, if they could, they would run a lower octane. I dont know how true this is, I think the theory was based on the higher octane gas burning slower. Any pump gas should work fine though, I stick to mid grade or premium in my predator just to err on the safe side.
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3,009 Posts
Jetting changes with the octane of the fuel ??
I just ran into a curious problem.
Bike info, 03 predator with white bros slip on pipe and Hardrock air box mods w/ new jetting. Air box mod consists of a K&N filter with a 1.5x6 cutout in air box covered by a oiled Pre-filter
I was setting up my bike for my trip to the dunes last week after installing air box mods and a new pipe. Jetting went from a 150 main to a 172.5 main with no changes needed in the pilot or the fuel screw. Bike ran real strong through-out the rev range even though she was a little rich on the top end. My testing area is dirt and paved roads so I left her a little rich and was going to do the final testing/ jetting on the sand as sand needs higher jetting plus it was going to be colder than when I tested.
(ALL TESTING to date was done with fresh 87 octane Sunoco UN-leaded gas of know good quality bought at the same time and from the same pump. I buy all of my fuel at this store and have never had any problem with it, not a fuel quality issue in my opinion)
All of my testing was with the K&N filter, but the day before leaving my uni style foam filter arrived in the mail and I put it in the bike but did not test it much, just started it and ran around the yard.
I know that the uni filters don't flow as well as the K&N, but I feel that they filter our SL sand better, and knew the filter would make the bike a little richer because of the flow restriction but I was going to do final jetting anyways so that was not a concern.
Now the weird stuff, I had just bought 10 gals of Sunoco 110 leaded race fuel for my other bike and decided to take this fuel with me as I had it on hand and was not planning on running the other bike in the near future, so why not use it up! Plus it just smells SO GOOD !!! lol
The bike had less than a half tank when we got to the dunes so I just topped her off with the 110 and went out for a ride nothing real radical just having fun and getting used to how it rides the dunes and what not. No real dragging or super long full throttle pulls. Bike was running real strong and seemed to be spot on as far as jetting was concerned. No lean cut outs or popping and no ,rich, black smoke marks on the bumper.
After running through the first tank of gas I went in a filled her back up and went out for some real fun, as the dunes were now getting busier with people to run and what not.
Once back out I lined her up for a few runs and she started to lean out and pop out of the pipe, a sure sign of being lean. I double checked all connections to rule out spark loss and ran a few more times but still the same thing upper rpm cut out/popping through the pipe.
Back at trailer I put in the biggest jet I had, 175, and went back out to test further. Lean out and popping lessoned but she was still showing signs of being lean. I'm thinking to myself WTF why is she so lean now she was fine before and at home? DAR shop didn't have any bigger jets so I just ran her the way she was and just didn't beat on her as much.
I got back home and called my guys at Hardrock to run it past them as they have been testing this combo for almost a year and they told me that they have seen this on the dyno and on the track where a switch to higher octane fuel ,with no other changes, needed bigger jetting. So my choice was to run bigger jetting for the 110 or drop back down to 87-89 octane fuel and jet for that. Seeing how the bike doesn't "need" the race fuel I just planned on running out the fuel I had and run the normal stuff in the future.
Last night I was working in the garage and decided to put the K&N filter back on as the uni needed cleaning, I had been running the bike off and on that night showing the bike to some friends that had stopped by and had not seen her yet so the bike was warm and all that. Well any ways,after swapping out the filters I started her back up and now she is popping back and spitting through the pipe and it won't even idle worth a crap and I think WTF again?? So for shits and giggles I drain the rest of the 110 out of the tank and put in some of the 87 I was using before and she is running like a dream again smooth idle and just a touch rich on the top end!!
Has any one else seen this kind of thing before, jetting changing that much just from fuel changes or is this more of a 4 stroke thing??
I just ran into a curious problem.
Bike info, 03 predator with white bros slip on pipe and Hardrock air box mods w/ new jetting. Air box mod consists of a K&N filter with a 1.5x6 cutout in air box covered by a oiled Pre-filter
I was setting up my bike for my trip to the dunes last week after installing air box mods and a new pipe. Jetting went from a 150 main to a 172.5 main with no changes needed in the pilot or the fuel screw. Bike ran real strong through-out the rev range even though she was a little rich on the top end. My testing area is dirt and paved roads so I left her a little rich and was going to do the final testing/ jetting on the sand as sand needs higher jetting plus it was going to be colder than when I tested.
(ALL TESTING to date was done with fresh 87 octane Sunoco UN-leaded gas of know good quality bought at the same time and from the same pump. I buy all of my fuel at this store and have never had any problem with it, not a fuel quality issue in my opinion)
All of my testing was with the K&N filter, but the day before leaving my uni style foam filter arrived in the mail and I put it in the bike but did not test it much, just started it and ran around the yard.
I know that the uni filters don't flow as well as the K&N, but I feel that they filter our SL sand better, and knew the filter would make the bike a little richer because of the flow restriction but I was going to do final jetting anyways so that was not a concern.
Now the weird stuff, I had just bought 10 gals of Sunoco 110 leaded race fuel for my other bike and decided to take this fuel with me as I had it on hand and was not planning on running the other bike in the near future, so why not use it up! Plus it just smells SO GOOD !!! lol
The bike had less than a half tank when we got to the dunes so I just topped her off with the 110 and went out for a ride nothing real radical just having fun and getting used to how it rides the dunes and what not. No real dragging or super long full throttle pulls. Bike was running real strong and seemed to be spot on as far as jetting was concerned. No lean cut outs or popping and no ,rich, black smoke marks on the bumper.
After running through the first tank of gas I went in a filled her back up and went out for some real fun, as the dunes were now getting busier with people to run and what not.
Once back out I lined her up for a few runs and she started to lean out and pop out of the pipe, a sure sign of being lean. I double checked all connections to rule out spark loss and ran a few more times but still the same thing upper rpm cut out/popping through the pipe.
Back at trailer I put in the biggest jet I had, 175, and went back out to test further. Lean out and popping lessoned but she was still showing signs of being lean. I'm thinking to myself WTF why is she so lean now she was fine before and at home? DAR shop didn't have any bigger jets so I just ran her the way she was and just didn't beat on her as much.
I got back home and called my guys at Hardrock to run it past them as they have been testing this combo for almost a year and they told me that they have seen this on the dyno and on the track where a switch to higher octane fuel ,with no other changes, needed bigger jetting. So my choice was to run bigger jetting for the 110 or drop back down to 87-89 octane fuel and jet for that. Seeing how the bike doesn't "need" the race fuel I just planned on running out the fuel I had and run the normal stuff in the future.
Last night I was working in the garage and decided to put the K&N filter back on as the uni needed cleaning, I had been running the bike off and on that night showing the bike to some friends that had stopped by and had not seen her yet so the bike was warm and all that. Well any ways,after swapping out the filters I started her back up and now she is popping back and spitting through the pipe and it won't even idle worth a crap and I think WTF again?? So for shits and giggles I drain the rest of the 110 out of the tank and put in some of the 87 I was using before and she is running like a dream again smooth idle and just a touch rich on the top end!!
Has any one else seen this kind of thing before, jetting changing that much just from fuel changes or is this more of a 4 stroke thing??
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249 Posts
bob - i'm not familiar w/ the sunoco fuel, BUT some racing fuels are oxygenated. oxygen will "fuel the fire" - i've had conversasions with VP and with certain fuels they recomend jetting up thru the whole range. hope this may help?
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