does it matter what octane level to use in a 7? Also does it matter if it is a turbo or non-turbo?

 

Yes.....and.....

Yes.

Naturally aspirated, the lower the better.

Force-fed, now you have to know how much boost and timing tricks you're making the ECU perform before a good choice between cost-per-pump and engine danger can be known.

Mario III

 

Sorry to cut in but just wondering Is av gas too hot and dry to use on a natural rotary or could it be done for short very hard runs?

 

Wow running aircraft fuel to run your car. That seems like some hardcore stuff

 

Not in a car 2 wheeled dirt races for about 300 meters

 

that's still hardcore.

 

So do you just think that it is not necessary or needed to burn high octane or will it do harm to the engine

 

so i shouldnt run special gas in my NA? and should just run regular cheap gas?

 

I'm guessing that the reason for this is the low compression on a natural

 

Av gas lacks the additives normally seen in street use gasoline. Because of that, it tends to be rougher on all of the parts outside of the actual combustion chamber. For short runs, I'm not seeing a problem....for a turbo or boost situation. There's no need for a stock NA engine at all.


If you could find 83 octane, your ignition system would love you...most places have 86 or 87 octane and that's all you need. Once in a long while, hit a Shell station for their additive package. I just get the horrible Kroger gas and it's perfectly happy.


Nope, it's the shape of the "combustion chamber" and the fact that it moves in a rotary engine as opposed to being in a fixed circular environment like a piston engine. That's why you also have two spark plugs per "combustion chamber"...the rotary needs all the help it can get igniting the mixture. You don't want the gas to resist igniting in a NA application that has near stock timing and factory compression....which wasn't really that high either...we are talking the 80's, after all.

 

Mario... Thank-you for the good explanation

 

Wait, so lower octane will make a N/A rotary go faster?

 

This is an urban myth that has some good legs.

Octane of a gas is irrelevant to horsepower. That is to say, if you run 87 octane and then 113 Sunoco, you're not going to see a change in horsepower in the 12A or 400 cid Pontiac engine, if they are still stock.

It's how you tune to the octane that you get horsepower.

However, since pre-ignition will come earlier in the lower octane mixture almost by definition, you're going to have a better chance to burn more of the fuel mixture up, even if the ignition system is on its last legs. It's mainly an emission thing. If the ignition system is tuned up but mainly stock, you're not going to see a difference in horsepower between 93 and 87....so why buy 93?

 

I mainly thought you burned a higher octane in rotaries so you get a cleaner burn and less change of carbon lock in the long term.

 

A "cleaner" burn is strictly a function of the additive package put into the gasoline by the end vendor...what goes in at the end for a Shell pump is different than what you get for a Valero pump or a Kroger's pump though they are all using the same basic stock/wholesale gasoline batch from the Texas coast.

 

Sorry to keep picking at this but Is there a so called brand name fuel additive at the auto parts stores that will actually work and help stop carbon build up ?

 

NA RX-7s have higher compression ratios than turbo RX-7s.

 

I know I'm a new guy, but I'm a former mechanic for a dealership that I won't name, and have been working on cars for about 20 years.

Anyway, as far as additives, I can only recommend two brands that I have seen actually work based on running emissions tests before and after treatment. Those two brands are Lucas Oil Fuel Treatment and B&G. B&G is well known in dealerships. I use Lucas Oil because it's easier to find.

As far as gas, someone said the right thing earlier. It's not really the octane (not so much), it's the additives. Do a search for Top Tier Gas and you will learn alot. Shell is the best in my opinion.

 

Thank-you low key yea I like shell fuel or Esso .. when I fill at co-op or fas gas it is just like throwing out an anchor.

 

I'm surprised the chorus hasn't started yet. There's two things out there but one isn't too good for any kind of emissions equipment, think catalytic converters. That's the Marvel Mystery Oil, a derivative of basic tranny fluid. It's great for the engine internals, hard on the cats.

Seafoam put in the gas tank is the other thing that seems to work. I use it once in a long while to clean things up internally. I keep thinking there was actually a rebuilder on this site who documented the protection Seafoam is capable of.

 

^ Was it on 8club maybe? I remember a similar thread.

 

I have never seen sea foam in Saskatchewan but that doesn't mean that is not here .. We use to buy a product called Rizlone top oil that was poured through the intake .. the idea of that product was to pour it in the carb at partial throttle .. you had to keep working the throttle or the engine would stall and then the last 1/3 of a can was poured in fast to stall the engine. then after a few minutes you started up and went for an aggressive drive I don't know if it worked or not.. but it sure did make a smoke cloud ... and I mean smoke cloud .. We use to do it at my buddy's place and I remember the old guy next door would give us hell. I think it was all for nothing I don't think there was 10 young guys in all of Saskatchewan in the seventies that had carbon build up in their engines.

 

Seafoam in the tank? Hmmm, seen it used many ways, but never that way.

 

Ask Kentetsu....he swears by the stuff. If it could be used on a human, he'd tell us it cures cancer.



edit: Here, I found a link where several SeaFoam tifosi discuss its mystical wonderfulness.


https://www.rx7club.com/new-member-rx-7-technical-256/thanks-everyone-carb-rebuild-sucess-one-minor-hesitation-927318/

 

use to use seafoam in my 5 speed sc300 before an oil change (1/3 in gas, 1/3 in oil, 1/3 brake booster) and it worked amazingly, kinda sketched out to use that stuff in a turbo car