Lowering octane of gas?!?!?!
11-10-08, 12:00 AM
#1
Lowering octane of gas?!?!?!
From what I've heard and experianced the rotary engine runs MUCH better with lower octane fuel. Now what I've also heard is that some of the track cars were running fuel as low as 83 octane?!?! I would love to see how my 7 runs on that low of octane fuel but how do I go about lowering the octane? What do I mix with it and how much? Thanks guys!
Eric
Eric
11-10-08, 12:29 AM
#2
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interesting ........ Im puting 91 on mines is that back it aslo has a camden ??? thought higher the octane the better, I definitely want to see what rotary gurus have to say
11-10-08, 12:50 AM
#3
During the combustion stroke, a rotary engine's combustion chamber expands much faster than a piston engine does. A higher octane gasoline reacts slower.
The slower reaction gives the piston engine's combustion chamber the needed time to expand.
On the other hand, rotary engines combustion chamber expands faster, hence a faster reacting lower octane fuel is better for the rotary engine.
The slower reaction gives the piston engine's combustion chamber the needed time to expand.
On the other hand, rotary engines combustion chamber expands faster, hence a faster reacting lower octane fuel is better for the rotary engine.
11-10-08, 12:51 AM
#4
NA Rotary runs great on regular. Boosted Rotaries however should use higher octane to prevent detonation. Early rotaries were designed to run on lower octane than is used today so a 12A car should run fine, if not a little better with lower octane fuel
11-10-08, 05:44 PM
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i wouldnt bother trying to lower octane, just tune it better on 87, if its NA.
a boosted car needs as much as it can get
a boosted car needs as much as it can get
11-13-08, 08:00 AM
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The more oil you pre-mix into the gas, the lower the octane. Oil has a lower octane than gasoline, so it lowers the overall mixtures octane rating.
For naturally aspirated 12A motors (stock, street port, and PP motors) I have had good performance using 87 octane gasoline. My street port daily driver 12A has uses the oil metering pump, with the lever arm cranked up much higher than stock. I road raced a 12A PP for 7 years, using premix oil at 100:1 into 87 octane fuel. the 12A PP motor did not run as well using 93 and higher octane gasoline. In 2004, I switched my race car to a 13B PP motor with the high compression rotors. That particular high compression motor dynos out better with 93 octane gasoline pre-mixed with 100:1 oil.
Again, for a naturally aspirated 12A motor, I would recommend the 87 octane gasoline.
Rotary 84: for any kind of supercharged or turbocharged applications, the higher the octane, the better.
For naturally aspirated 12A motors (stock, street port, and PP motors) I have had good performance using 87 octane gasoline. My street port daily driver 12A has uses the oil metering pump, with the lever arm cranked up much higher than stock. I road raced a 12A PP for 7 years, using premix oil at 100:1 into 87 octane fuel. the 12A PP motor did not run as well using 93 and higher octane gasoline. In 2004, I switched my race car to a 13B PP motor with the high compression rotors. That particular high compression motor dynos out better with 93 octane gasoline pre-mixed with 100:1 oil.
Again, for a naturally aspirated 12A motor, I would recommend the 87 octane gasoline.
Rotary 84: for any kind of supercharged or turbocharged applications, the higher the octane, the better.
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11-13-08, 01:37 PM
#8
djessence
No. Becuase on boost, the quicker/shittier the burn (ie lower octane) results in detonation. Detonation results in blown motors whether piston or rotary. Most high performance cars run on 91 or higher octane. And for some reason i think ethanol is even higher octane, thats why if tuned properly you can get more power out of ethanol powered vehicles.
11-13-08, 04:32 PM
#9
ethonols octane is 100 because it is the base that all other fules are rated against. all octain is in fererence to resistance to knock compaired to alcohol than rated against it's 100 rating. adding 2 stroke premi or kerosene will lower your octane. carefull though kerosene burns much hotter than gas. more power but it waers the engine faster and a na can detonate on kerosene. the old mazda race cars ran on a gas kerosene blend.
11-13-08, 07:22 PM
#11
Ethanol’s octane is 100, because it is the base that all other fuels are rated against. All octanes are in reference to their specific resistance to knock then compared to alcohol and rated against its 100 rating. Adding 2 stroke premix or kerosene will lower your octane. You have to be careful though kerosene burns much hotter than gas. It will yeild more power but it wears the engine faster and a NA engines can detonate on kerosene. The old Mazda IMSA race cars ran on a gas kerosene blend.
11-14-08, 11:58 AM
#13
djessence
To add to hyper/fix a bit, it is the resistance to knock but i had thought the number is the ratio/percentage of octane to pentane or heptane (cent remember which) so if you have 87 "octane" it means its 87% octane and 13% of the other one.
Not overly sure how you get stuff like avgas which is what 120?
Not overly sure how you get stuff like avgas which is what 120?
11-14-08, 03:29 PM
#14
Yes it's it's resistance to knock, which is detonation. **** I totally forgot about iso-octane and heptane, you're right. Methonol is 113 and ethonol is 116 though. That might be what they use to get numbers over 100. Don't forget there is RON and MON octane and in the US the number we use is the average of the two numbers. Some aftermarket fuels sell just by the RON number, so you might think you're buying a RONMON 116 when just the RON is 116 and maybe the MON is 100 giving you a mean 108 RONMON octane.
hexadecane < -30
n-octane -10
n-heptane 0
diesel fuel 15–25
2-methylheptane 23
n-hexane 25
2-methylhexane 44
hydrogen* RON > 130; MON very low[4]
1-heptene 60
n-pentane 62
1-pentene 84
n-butanol 87
E10 gasoline 87–90
n-butane 91
t-butanol 97
cyclohexane 97
iso-octane 100
benzene 101
propane 103
E85 gasoline 105
methane 107
ethane 108
methanol 113
toluene 114
ethanol 116
xylene 117
hexadecane < -30
n-octane -10
n-heptane 0
diesel fuel 15–25
2-methylheptane 23
n-hexane 25
2-methylhexane 44
hydrogen* RON > 130; MON very low[4]
1-heptene 60
n-pentane 62
1-pentene 84
n-butanol 87
E10 gasoline 87–90
n-butane 91
t-butanol 97
cyclohexane 97
iso-octane 100
benzene 101
propane 103
E85 gasoline 105
methane 107
ethane 108
methanol 113
toluene 114
ethanol 116
xylene 117
Last edited by Hyper4mance2k; 11-14-08 at 03:31 PM.
11-14-08, 03:47 PM
#15
Originally Posted by teh wikithing
The octane rating of a spark ignition engine fuel is the detonation resistance (anti-knock rating) compared to a mixture of iso-octane (2,2,4-trimethylpentane, an isomer of octane) and n-heptane.By definition, iso-octane is assigned an octane rating of 100 and heptane is assigned an octane rating of zero. An 87-octane gasoline, for example, possesses the same anti-knock rating of a mixture of 87% (by volume) iso-octane and 13% (by volume) n-heptane. This does not mean, however, that the gasoline actually contains these hydrocarbons in these proportions. It simply means that it has the same detonation resistance as the described mixture.
Pure ethanol is 116 octane AKI. E85 is 105.
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