I just bought my first Rx7 (an '83) three weeks ago.
I could definitely use a clue. Several questions, actually. The car is stock (at least for now!). What octane gas should I use? Will spending extra for 93 octane make the car run better? Also, about tires. Need new ones (dry rot). Should I stick with 185/70HR 13's on the original (slightly messed up) wheels, or get a whole new wheel/tire combination? If I decide to stay stock, what brand of tires is good performance for price?
Lastly, I understand that exhaust is the best first performance mod. Please point me in the right direction. Brand name, cost, where to find it. Thanks to anyone who takes the time to help me out. These forums just may save me!

 

Best octane is 80.

Since you can't generally find that, get the lowest-octane you can find.

 

Fuel octain doesn't have that great of an effect on the NA rotary. Maybe for the sake of keeping the system clean run quality gas.

New rims and tires are the way to go if you want street performance. If you must remain on a budget I am sure someone still makes a perfromace tire that will fit your rim size and width properly.

www.RacingBeat.com

I have shopped there for years for all of my exhaust needs. They have what you need to do it. And it seems to last longer than any of the other exhaust products.

 

80 octane is the best for performance according to Yaw... he says that it's a quicker burner and that somehow helps the rotary. I am not making this up... he said it.

 

For tires go to www.thetirerack.com I got a full set of 13" tires from them delivered right to my house all for a VERY reasonable price!

 

i read that mazda won the lemans 24 back in like 82 with 80 octane gas.

 

Actually it was the Mazda-backed race teams who were trucking 80-octane in to the IMSA races...

 

that'd be it...

 

i will only run premium,
all my custom gauges say "premium fuel only"
instead of "unleaded fuel only"

cheap gas makes 7 sad
premium makes 7 happy

 

I cant tell a difference. In my 88 vert or in the 85 (when it ran) for that matter

 

Preimum fuel just makes less power and makes the exhaust hotter...

 

I agree, save your money and buy 87 (the lowest you can get from a normal gas station I think) Back when I first got my 83 rex I experimented with different octanes and found no difference, other than a slightly lighter walet.

 

I once read that the rotary runs better with lower octane fuel as it burns it faster and more efficiently.

 

this was beat to death in the 3rd gen forum and seems to be misunderstood down to marketing octane booster. octane is only the gases rating against detonation. that is it folks. that is why turbo and high compression engines run premium. due to the higher compression the gas will try to detonate early and ping, boom. of course if its a rotary, there goes an apex seal and your compression. the downside is the additives they use to do this will also cause the gas to be harder to ignite and burn. so running premium in a car that doesn't need it will lower gas mileage and performance. run what gas you need to keep your engine from detonating. go with the lowest safe octane. since these engines are not high compression or turboed there isn't really any reason to run premium, unless you are tuning and trying to keep it from pinging if you run too lean (to an extent of course). this is why i laugh everytime i see some octane booster marketed as a performance gain. its a crock of marketing ****. bigger is better so to speak.

as for tires, go with tire rack. if you want performance go with either 195/60-13 or 205/60-13. which is better is still a debate. someone here is running 195s in front and 205s in rear. not sure if that would cause understeer or not? the sumitomos are good and cheap. you get stick without worrying abou burning money everytime you light the rear tires.

 

i am using LRP in my s3 rx7.

 

low compression+low octane makes better power

High compression needs high octane.

Stay with the regular unleaded and just get good stuff instead of the local pump"n"go cheapo station.

There is a station in thown that was closed for family reason for almost 3 months. When they opened back up they sold the gas for $1.00 a gallon. People were lined up! I just drove by thinking how bad the gas might be from sitting in their tanks unused.

 

Sure I would go with what your custom gauges say over the manufacurer any day, LOL

 

What's the best fuel for my rotary car?

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 normally aspirated (NA) rotary, the highest octane you should use is US pump (AKI - anti-knock index) 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 the 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, 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"

From Felix Miata's FAQ

 

definitely check out tirerack.com and tires.com and look around. personally, if i had the $$$$, i'd get some nice 15 or 16 inch wheels ($100-150 each at tire rack) and put some kumho ecsta 712s (under $100 each). if you have the money, i think that'd be an excellent set up for street performance and FUN!!!

as far as exhaust, i'd vote for racing beat's dual pipes all the way back to the muffler if you don't have to deal with emissions laws. but check out racingbeat.com and mazdatrix.com.

enjoy the 'new' 7!!!!!!

 

I just want to point out that all the gas in Washington comes from the same two refineries. I know this because my Mom works for the company that engineers their fuel lines for the two refineries. So no matter where you go to buy your gas, it all comes from the same place .

~T.J.

 

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