It has to do with insurance, the insurance my boss has covers only the employees of the station, who are *professionals* who are trained with proper use and safety when using hte pumps. in a state with self serve the station would have to insure everyone, and some people are idiots and could potentially **** **** up, so insurance would be more, and that in turn raises the prices. Thats little help when I look at my bill everytime I fill up, but whatever.

 

Ok here we go. Lower the octane, the least demanding the engine is in a way. Lower the octane, the more easily the fuel is ignited, but there are drawbacks to having such a easily ignited fuel.

Heres what I mean by this: A normally asperiated engine that has reasonably moderate compression will have no problems what-so-ever unless you have it too far advanced and improper air/fuel mixture. A rotary is hard to get to a compression ratio that will nessessiate anything above 87octane. I am uncertain what the renesis engine will need, since its supposively a higher then previously N/A rotaries. But it will probably still be a 87octane engine.

Some V8's or any piston engine with above 10:1 or 11:1 will need higher octane since lower octane will pre-ignite like a desiel engine. Most automakers want higher compression if possible since its more effiecent at using the fuel and making more power.-why high hp pistion engines usually need it and operating cost isn't a major concern to the buyer. But a lower compression engine is a cheaper operating engine since its requires a fuel that is slightly cheaper to make.

Have you ever heard a carb'd rotary have run-on/desieling after shutting it off like a pistion engine does? I think not! Its design makes that pretty much impossible.

Anyway, when it comes to igniting a mixture. All the gasoline out there whether it is 87 or 110octane will run about the same on a normally asperated engine with compression below 10:1. Which all rotaries are right now with no boost at least. Now when we are considering the higher compression engines and boost and putting a fuel in with lower octane then recommended, you risk making it a deseil engine and detonation by igniting the mixture before the spark plug ignites the mixture and then igniting the rest of the mixture by the spark plug causing the two combustion starting points running into each other(detonation). Deseil fuel is much lower then 87octane for the reason it is ignited by just compression heating and is given really high compression ratios for this reason to make certain its ignited by compression heat.


It has to do with cylinder of a piston engine or chamber pressure generated in a rotary being above a certain compression PSI and temp(before ignition) which is what determines what type of fuel will be required. In a rotary, realisiticily the only time a psi will be too high for 87octane is when usable boost is appied.

 

Nicely done

 

so its awast to fill up with premium ?


and what about STP octane booster? i got a bottle for christmas, will that do anything >?

 

Only one way to find out.

 

so basically i am waisting my money on 91 when i should be useing 87 witch if better for the car, **** ! i wish i known sooner. as long as i have NA i use 87? what if my engine was fully built, and still NA would i still use 87 or a higher octane??

 

If you've got a stock 12A, like I do, I would recommend using 87 octane, which is what's recommended in the Mazda Owner's manual.

 

Okay, a complete noob here. I just started to get into cars when I bought my 82 last month Got a few questions for you guys.

The dreaded numbered list!
1)What is n/a?
2)What models were out in 82? (do I have a GSL?)
3)Doesn't it "run cleaner" to use a higher octane? Wouldn't that be a reason to use higher octane?
4)Does anyone know what octane Premium gas at Chevron is?

Thanks

EDIT- oh yeah, and what is the number included in the model? (maybe that doesn't make sense...

 

Premium here, but Id like to run higher octane when i go racing

 

Well, I run a 12a bridgeport, and no knock or detonation. No need for premium in rotary unless boost is the bottom line.

N/A = normally asperated engine. Meaning the engine draws air/fuel in using vacuum. Were as turbo engine forces air/fuel into the engine with pre-compressed air under moderate to full load.

 

HERE YOU GO.

 

hehe must be a noob, thinks im the best guy to ask lol
i mean come on, look at my avatar
just kiddin
all i can say is read and read and read, ive been readin since before i joined and im just now starting my turbo project
have fun
gamble

 

so i was completely off? wow, what one can learn on this board. lol

--eric

 

My RX-7 is turbo'ed and I ALWAYS use anything higher than 94 octane to resist detonation. This is a must have for ANY turbo car. Everybody should know that by now..jeez.

 

here in Colorado we can get 85 octane, what about that?

 

No Alcohol here at the 'ol corncrib, or in the corral. Only have the cleaning, disinfectant kind. In other words, we only burn Shell fuel as it's the last brand left that isn't mixed with alcohol since Marathon took the plunge.

Denny,
From the 'ol corncrib..

 

Absolutely. That is why they sell it. I am sure some of us could use it in lower altutides too.

The reason they make a even lower then 87octane for the mountains is the lower RAD - Relative Air Density. The higher you go up into the atmphere the less there is and thus the lower your max PSI you will reach before igniting the mixture. And that max PSI will undoubtibly be below the threshhold of detonation/knock problems then it would be 5000ft lower, so your even farther away from detonation so lower octane is fine and will ignite with less work and uses more of the cheaper components of gasoline.

OFcourse at 5000ft, you will make less power ofcourse unless you have a turbo that will force positive PSI into your engine. If you measure the RAD at sea level its 100%, were as at 5000ft, its about 79%. So at really high places like 10,000ft, you get RAD's below 70% which is why you make less then 70% of what you'd make at a much lower altitude. So if you went REEEAALLY high up a gas below 85octane would probably work also.

Oh, some of us are using carbs instead of a EFI, don't forget to lean it out as you go higher or you will be too rich as you go higher and higher or you will make even less power.

 

Yep, 85 works fine for us high-altitude boys, and would probably be fine for you guys at sea level.... I have used 85, 87, and 91 (thats the highest they sell, until race gas...)

 

really? out here we can get 94 from a pump. strange how it varies so much.

 

94 octane is unheard of in Colorado (and I'm sure Utah as well).

 

Actually, a naturally aspirated rotary is designed to run on 83 octane at sea level. You guys remember all those IMSA 7s that won all those races in the 70s, 80s and early 90s? They did it on 83 octane fuel. They tell about it in that history of the RX7 book, by what's his name... Damn. Anyway, it said the mazda teams would bring their own 83 octane "race gas" because the tracks didn't cary anything that low.

And, if I remember correctly, the 787b also ran on 83 octane.

So in reality, we'd all be better off running lower octane fuel than is comercially available. (NA only)

 

What causes this.... my timing was way off and I was on 87 and mine did this a few times. (V8)

 

My bro's GSL-SE ran better with 85 while in CO. At sea level it didn't run as well, even with 87. I use 87 because it's the cheapest and lowest octane available here.

 

The RX-8 has a N/A engine, I wonder what runs best in it ???

 

i use whatever billy bob sells on the side of his convenient store/barn.