Safe to Run 93 Octane??
#26
Rotorhead
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Not such a great way to determine the octane requirement, eh?
A stock RX-7 in average condition will not burn all of the fuel anyway so there is no need for anything over 87 without large boost or porting etc. A rotary engine is fairly wasteful with fuel. That is why you see them shooting flames when straight piped. The unburned fuel is sent out through the exhaust and ignites there.
Yes, it is fine to use 87 because porting does not raise compression. Since none of the RX-7 rotors have all that much compression, the ignition timing is the main factor that could increase the fuel octane requirement in an NA engine.
#27
Former Moderator. RIP Icemark.
Therefore, if I have stock NA engine, racing coil-overs, a full roll cage, racing seats and harnesses, short shifter, nice stereo system, Delrin bushings, competition sway bars, performance brake pads, aftermarket steering wheel and shifter, body kit, cool paint job, aftermarket spoiler, aftermarket wheels, competition radiator and oil cooler, and ricer stickers all over my car, then I must need REALLY high octane.
Not such a great way to determine the octane requirement, eh?
No.
Yes, it is fine to use 87 because porting does not raise compression. Since none of the RX-7 rotors have all that much compression, the ignition timing is the main factor that could increase the fuel octane requirement in an NA engine.
Not such a great way to determine the octane requirement, eh?
No.
Yes, it is fine to use 87 because porting does not raise compression. Since none of the RX-7 rotors have all that much compression, the ignition timing is the main factor that could increase the fuel octane requirement in an NA engine.
#28
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You get a bit better mileage by using 87, because it burns easier. As was said, the lowest octane you can run on your setup w/o spark knocking is what you want, no matter what the setup is. The reason high-compression or high-boost engines run higher octane is because it doesn't burn as easy or quickly, and resists pre-detonation (pinging, spark knock, same thing) and so allows more boost or timing.
#29
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Could you maybe hook up a forum function that shocks anybody who posts anything about octane other than AKI and cost?
Last edited by Evil Aviator; 08-18-08 at 10:23 PM.
#32
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Lol, well what are the correct answers then? And what is the difference between spark knock, pinging, detonation and pre-detonation? I help a lot of people out w/ this kinda stuff on other forums and in person, so I need to make sure I'm giving out proper info
#33
If your car isn't tuned to run 93 octane, then there is no need to run it. I run 85 octane in my seven. they don't sell higher octane like that in higher altitude areas.
#35
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Pre-detonation = A common incorrect term made by combining the terms "pre-ignition" and "detonation".
Pre-ignition = When a hot spot in the engine ignites the fuel-air mixture prior to the initiation of the spark, or otherwise without the spark, such as run-on (dieseling).
Gas mileage has nothing to do with the octane rating.
Also, there are several types of octane ratings. Two fuels could have the same Anti-Knock Index number, but one could have a higher Motor Octane Number. Example:
Brand A "93 Octane" (97 RON + 89 MON ) /2 = AKI 93
Brand B "93 Octane" (94 RON + 92 MON ) /2 = AKI 93
#36
Junior Member
The higher the octane of the fuel, the more compression is can withstand without causing detonation... This is why you can safely turn the boost up in a turbo engine if you are using a premium fuel. Most people should know that it is always advisable to run high octane fuel in any turbo, or high compression N/A motor. I won't fill my tank with anything below 98.
#37
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Yes, higher boost, higher engine load, advanced ignition timing, higher temperatures, lower humidity, higher atmospheric pressure, and engine hot spots will increase the octane requirement. Higher octane fuel will not hurt anything but your wallet.
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