drifter

just normal pump fuel as well?

relisys190

damn good run time. That's a quick little first gen. my guess was close..lol



And you'll sure as hell kick the crap out of my car! lol

'79rx7

the lowest octane, conoco pump gas... I'm pretty happy with the way it runs, but you always want more (speed that is)

Racer X

Need to run it on 94 pump gas and see how it goes.

Directfreak

It will be slower, and less efficient.



What's the best fuel for my rotary car?



ANSWER:



It depends. If your rotary Mazda is equipped with a turbocharger, all the normal rules about octane apply. Use the highest available octane premium fuel for best power and best protection against the ravages of detonation. You may find slighly better fuel mileage using lower octane, but you need to be very careful about using the available power on lower octane. If you are good at exercising restraint, you can save a little money on a long trip using regular, but it's probably best to stick with premium for normal use.



With the NA rotary, the highest octane you should use is US pump (AKI) 87, typically RON 91 outside the US, no matter how heavily your engine is modified. Octane in excess of any engine's actual requirement is always wasted. The issues of purity and additives in more expensive fuels are entirely separate issues. There's no reason not to want either in a NA rotary.



The rotary engine's high turbulence combustion chamber provides a very high resistance to detonation. Its duration of combustion is also longer, remembering that the rotors turn at 1/3 of the tachometer reading, and the slow burn* of high octane is undesirable in it. Pump 80 octane is more than sufficient for most of them. Best power and mileage is usually produced with the lowest available octane.



Many serious rotary racers bring their own low octane gasoline to tracks that supply only racing gasoline. From "How to Modify Your Mazda RX-7", by Dave Emanuel and Jim Downing, HP Books, 1987, ISBN 0-89586-383-9, p 47-8:



". . . the best results are obtained with conservative spark-lead calibrations provided the engine is fed a diet of low-octane fuel. The fact that both 1985 and 1986 IMSA Camel Lights championships were won with low-octane fuel is a rather definitive statement . . . ."

So if you want best performance from your NA rotary, you want lowest octane. The lower cost of it is a nice bonus.



* Note - the time allowed for combustion at high RPM is measured in ten-thousandths of a second. Some literature ascribes lower volatility rather than a slower burn as the characteristic of a higher octane value. In contrast, consider the following: From "14-to-1 compression", By David Green, NASCAR Winston Cup Scene:



"One problem that has developed in the 9.5-to-1 engine is high exhaust temperatures, due to a less-efficient burning of 108-octane gasoline in the lower-compression combustion chamber." (emphasis supplied)

For more information on octane/antiknock characteristic:

Octane Determination, by Gregory Travis

The autos/gasoline FAQ, by Bruce Hamilton, or its mirror.

Chevron's "A Consumer's Guide: Gasoline Octane for Cars"

Mobil's "Gasoline Product Knowledge"

Shell's Fuel "Properties"

relisys190

Finally the window of what type of fuel to use comes into play...



I've never used anything above 87 in my N/A Acctually i did once.



Any my dyno Readings were 4 HP lower with the 93 pump gas. 3 consecutive runs the lower octane fuel made the engine pull harder. I'm tellin ya. If your all motor.. your better off with low octane. (LOWER PRICE!!!)



my 7 cents

Smog Fighter

That's great news!!



Raul

Racer X

Thanks DirectFreak.

rx7machine

Good times and nice info on pump gas.

walshb6413

Awesome...