Any noticeable differance to 91 octane?
07-24-2008, 12:23 AM
#1
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Any noticeable differance to 91 octane?
I am on my second tank of gas on my bird (no long rides yet, still waiting for my jacket) and I have chosen to run Chevron supreme only. I put that in my car and it has made a dif in how smooth my car runs and my mileage slightly. Will it do the same for my bike, or can I save a couple bucks and put regular in. Im gonna be commuting 80 miles round trip a day and want the best for my baby. Tell me what ya think.
07-24-2008, 03:13 AM
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I've tried 91 in the VTR and can't tell any difference. I've had higher compression bikes that "seemed" to run stronger on premium and did in fact get better mpg, but not the VTR. For commuting especially, I'd stick with the regular.
07-24-2008, 04:20 AM
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I believe the Hawk manual states that you can run 87 octane. (At least my '99). I myself have the 'Hawk and Snowmobiles (those too recommend 87 Octane), but have always run high test (92-93 octane here in NYS) in all my toys. Guess I figured that they're toys, I run 'em hard and might as well give them the good stuff. I'm going to guess a shitpile of guys will respond they're using 87 octane and have been for ever, so go with your gut...
07-24-2008, 04:54 AM
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Lower octane that the motor can burn without detonation is the best, in occurrence 87 octane.
Don't talk of regular as crap because premium in a low compression engine is crap as well, regular has a higher flame propagation speed than premium, to get performance from premium you need to kick the compression up by a full point, that means getting new pistons.
Don't talk of regular as crap because premium in a low compression engine is crap as well, regular has a higher flame propagation speed than premium, to get performance from premium you need to kick the compression up by a full point, that means getting new pistons.
07-24-2008, 05:53 AM
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Lower octane that the motor can burn without detonation is the best, in occurrence 87 octane.
Don't talk of regular as crap because premium in a low compression engine is crap as well, regular has a higher flame propagation speed than premium, to get performance from premium you need to kick the compression up by a full point, that means getting new pistons.
Don't talk of regular as crap because premium in a low compression engine is crap as well, regular has a higher flame propagation speed than premium, to get performance from premium you need to kick the compression up by a full point, that means getting new pistons.
07-24-2008, 06:00 AM
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I can't tell a difference between the octanes in my 98. She's used as a commuter and thrashed more than occasionally.
As long as your bike is constantly being ridden, I wouldn't worry about the internals staying clean. And with your commute, you'll be filling up often! On the other hand, you could add some Seafoam from time to time to give you some peace of mind.
While we're at it, what oil do you use? (sorry, couldn't resist
)
As long as your bike is constantly being ridden, I wouldn't worry about the internals staying clean. And with your commute, you'll be filling up often! On the other hand, you could add some Seafoam from time to time to give you some peace of mind.
While we're at it, what oil do you use? (sorry, couldn't resist
)
07-24-2008, 06:08 AM
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07-24-2008, 07:09 AM
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Piston bore size is a factor, the smaller is the aera the faster it can burn completely, the raising the detonation threshold.
A 600 cc 4 banger will tolerate more than a 1000 cc twin or a 650 cc single.
Chamber design and squish aera makes a more turbulent charge, witch burn faster as well.
Heat absorbtion of the head and cylinder, an aluminium head and Nickasil (aluminium plated bore) will absorb more compression heat than a prehistoric iron head and block engine.
Dynamic compression is a factor too, a one liter engine is not pulling a liter of air, at a VE of 90 % close to torque pesk(best efficiency) 900 cc of air is drawn, add a filter, exhaust and you may increase to 95 % VE you get 950cc of air squeezed in there.
Cam, ports, heads affect dynamic compression, for example an late closing intake drops dynamic compression by allowing some charge to flow back at lower RPM, but will be just right at peak power, lowering the VE at torque peak but increasing it at peak horsepower, an engine with 85 VE @ torque peak and 70 % VE @ hp peak will be less prone to detonnation than a 95 %VE @torque peak and 65% VE @ hp peak.
Sorry for the headache
A 600 cc 4 banger will tolerate more than a 1000 cc twin or a 650 cc single.
Chamber design and squish aera makes a more turbulent charge, witch burn faster as well.
Heat absorbtion of the head and cylinder, an aluminium head and Nickasil (aluminium plated bore) will absorb more compression heat than a prehistoric iron head and block engine.
Dynamic compression is a factor too, a one liter engine is not pulling a liter of air, at a VE of 90 % close to torque pesk(best efficiency) 900 cc of air is drawn, add a filter, exhaust and you may increase to 95 % VE you get 950cc of air squeezed in there.
Cam, ports, heads affect dynamic compression, for example an late closing intake drops dynamic compression by allowing some charge to flow back at lower RPM, but will be just right at peak power, lowering the VE at torque peak but increasing it at peak horsepower, an engine with 85 VE @ torque peak and 70 % VE @ hp peak will be less prone to detonnation than a 95 %VE @torque peak and 65% VE @ hp peak.
Sorry for the headache
07-24-2008, 09:26 AM
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hmmm.. I get it.. but then what is the "lamen" to do... go with factory recommendations? I thought every country might have different formulas for figuring Octane... thereby making .. .. Nevermind.. I've lost interest..
07-24-2008, 10:03 AM
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Thanks for the replies. As for oil I havn't had to change it yet, but I did ask the guy at the local cycle shop and he recomended the red cap stuff they sell there. It had a yamaha label on it but he said it was the same spec stuff for honda. I really dont know cause I'm new to the bike world.
07-24-2008, 01:03 PM
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07-24-2008, 01:28 PM
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High octane isn't "the good stuff", its just different stuff. Some cars use 87 octane, some use 91, some use diesel. There is no good or bad, just different uses and different prices.
07-24-2008, 01:32 PM
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Piston bore size is a factor, the smaller is the aera the faster it can burn completely, the raising the detonation threshold.
A 600 cc 4 banger will tolerate more than a 1000 cc twin or a 650 cc single.
Chamber design and squish aera makes a more turbulent charge, witch burn faster as well.
Heat absorbtion of the head and cylinder, an aluminium head and Nickasil (aluminium plated bore) will absorb more compression heat than a prehistoric iron head and block engine.
Dynamic compression is a factor too, a one liter engine is not pulling a liter of air, at a VE of 90 % close to torque pesk(best efficiency) 900 cc of air is drawn, add a filter, exhaust and you may increase to 95 % VE you get 950cc of air squeezed in there.
Cam, ports, heads affect dynamic compression, for example an late closing intake drops dynamic compression by allowing some charge to flow back at lower RPM, but will be just right at peak power, lowering the VE at torque peak but increasing it at peak horsepower, an engine with 85 VE @ torque peak and 70 % VE @ hp peak will be less prone to detonnation than a 95 %VE @torque peak and 65% VE @ hp peak.
Sorry for the headache
A 600 cc 4 banger will tolerate more than a 1000 cc twin or a 650 cc single.
Chamber design and squish aera makes a more turbulent charge, witch burn faster as well.
Heat absorbtion of the head and cylinder, an aluminium head and Nickasil (aluminium plated bore) will absorb more compression heat than a prehistoric iron head and block engine.
Dynamic compression is a factor too, a one liter engine is not pulling a liter of air, at a VE of 90 % close to torque pesk(best efficiency) 900 cc of air is drawn, add a filter, exhaust and you may increase to 95 % VE you get 950cc of air squeezed in there.
Cam, ports, heads affect dynamic compression, for example an late closing intake drops dynamic compression by allowing some charge to flow back at lower RPM, but will be just right at peak power, lowering the VE at torque peak but increasing it at peak horsepower, an engine with 85 VE @ torque peak and 70 % VE @ hp peak will be less prone to detonnation than a 95 %VE @torque peak and 65% VE @ hp peak.
Sorry for the headache
My thoughts exactly! I was going to say all that but I was afraid I'd get a headache. Uh huh.
Seriously, you seem to know what you're talking about so I have a couple of questions. Any idea about the effect ram air has on volumetric efficiency?
I've noticed ram air bikes, the old Kaw zx9r in particular, would turn in better quarter mile ET/speed than bikes with better power to weight ratios based on dyno runs.
What about ignition advance? If you took an engine which ran well on "regular" and began advancing the ignition timing, would you get to a place where it would detonate on regular but run OK on higher octane fuel?
07-24-2008, 03:41 PM
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Seriously, you seem to know what you're talking about so I have a couple of questions. Any idea about the effect ram air has on volumetric efficiency?
I've noticed ram air bikes, the old Kaw zx9r in particular, would turn in better quarter mile ET/speed than bikes with better power to weight ratios based on dyno runs.
I've noticed ram air bikes, the old Kaw zx9r in particular, would turn in better quarter mile ET/speed than bikes with better power to weight ratios based on dyno runs.
An automotive engineer will probably not call it VE, but will use a separate graph called ram charging.
The VE tables are really relying on the ability of the engine to draw air based on throttle opening versus RPM.
Automotive engineers usually aim for max cylinder pressure at 14° ATDC, so ignition is just ahead by the time it takes to get there, but passing by TDC (the smallest combustion volume, the charge need to be lit, but not burnt, if you ignite too soon the higher pressure from the burnt gases will detonate the rest of the mixture outside of the flame front causing a pressure spike 2 or 3 times greater than the normal max cylinder pressure.
Some guys monitor the detonation using a stethoscope, microphones, piezo electric pressure sensors, knock sensors with all the electronic gimmicks to filter the noise and adjust to detonation then take off 3-4°
Another way is the dyno, best power, then it peaks, so just before the curve start to flatten.
Engineers tune an engine by designing the engine and combustion chamber, run a test engine, adjust the max cyl pressure at 14° ATDC with the ignition map, then adjust the compression to the intended fuel.
We build an engine with too much compression, back off the timing to run on premium Or get the timing right and have to stuff ethanol, toluene or expensive octane bottles to our gas since swapping pistons like undies is out of question
If you want to push this even further, there is even a drivability question, with super high compression, the flywheel mass need to be increased for optimal timing to be maintained without the V-twin jerking, to some small gains from higher compression may be losses in weight, rotating weight, ability to dive in corners and the average joe that will stall the engine and fall on the side from the compression hit.
Sorry for the extra headache, but I usually keep this for myself
Last edited by gboezio; 07-24-2008 at 03:54 PM.
07-24-2008, 06:59 PM
#16
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The ONLY time in anything that I notice a difference, is in my Wifes 2000 Blazer ZR2.... when we tow the ATV's with it 91 octane or higer seems to make the engine run a little better and less pingy..
my 2005 silverado could care less when towing
but there there is a big difference in engine and torque between the two vehicles
my 2005 silverado could care less when towing
but there there is a big difference in engine and torque between the two vehicles
07-25-2008, 04:51 AM
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with 93 being 4.17 and 87 bing 3.77, all of your wallet comments are true especially if you commute like me. My ride is 80 miles round trip if I take the 4 lane the whole way. use 87 and save the money for new tires
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