Matty's first 1st Gen

Just a quick question, i've got an 83, good shape, i have heard some conflicting viewpoints about different fuel grades, the manual recomends 91 octane, what are you guys using, and what would you recomend?

i_piss_on_hondas

premium in wa is 92... I up my timeing and run octain boost when I race... if your just running a stock motor regular SHOULD BE FINE...

specRX7_22

if your running a stock motor..... as i understand from the 4 page long gas post awhile back, lower the octane the better due to lack of resisting to combustion. but ill let the fuel gurus take it from here...

Matty's first 1st Gen

yea i was leaning towards lower octane, cause of the price factor, and my poorness factor, as a result of my high insurance

smnc

*SIGH*...

Check the search feature... It's been asked many a time...
https://www.rx7club.com/forum/showth...hreadid=22322&

NanaimoRx-7

On an N/A rotary the lowest octane possible. Teams in the 80's were dominating on 80 octane (didn't they hold the IMSA title for 6+ years?) which they were bringing in. Man I wish I could get my hands on some of that stuff, I also wish I knew how much premix can lower octane. For turbo all the normal rules apply.

i_piss_on_hondas

I just got done reading that thread... not once did anyone say anything about IGNITION TIMEING... high octane gas IE 104 isn’t going to give you any better performance on a carberated car... HOWEVER it will when you start messing with the timing... Higher octane gas allows you to advance your timing more without detonation… increasing hp...

mar3

iTrader: (8)

89 octane is all you need,,,,

alien_rx7

Sunoco 86....too bad there are no Sunoco's down here I've got the HPBooks "How to Modify Your Mazda RX-7" that talks about those races and using the lowest octane that could be found even premixing in good ol' two cycle to lower it since every little bit helped.

i_piss_on_hondas

But the question still is why??? You would have to have your ignition retarted ALL THE WAY to run 86 octain on a car with a large port...

Mark S

iTrader: (1)

I understand what you're saying, but if that's how they raced em, I'd be willing to bet that's how the engine made the best power. If getting more power out of the engine were possible by running higher octane/timing advance, i'd tend to think a race team with a huge budet would be doing it. Unless there's another issue involved other than max power.
Since they were winning, I don't think you can fault their choice.

jeremy

iTrader: (1)

stock octane should be 86/87. rotories are actually very resistant to detonation due to the relative surface area and lack of "hot spots". also compression isn't very high. most of us have advanced our timing and run 87 with perfectly fine results. once you get into running lean, you might find detonation occurring but is still something that happens rarely in a na rotary. oil and temp are our evils.

i_piss_on_hondas

Well I have 74 motor ported with a holly 600 and some other stuff and running anything less then 92 without alot of ignition retard causes it to studder like Elmer Fudd...

rotorhead

and i had a 13b ported with a dellorto dhla 48 and racing beat everything. it ran best off of the sunoco 86. the lower the octane, the better. rotaries like low octane. be cheap on fuel grades, spend your money elsewhere on the car. i **** on hondas may have the only n/a rotary that likes high octane.

jeremy

iTrader: (1)

the renesis does, but thats because the compression is 10:1.

smnc

Well...
The following is an excerpt from the owners manual:
"Your Mazda is designed to obtain maximum performance with unleaded gasoline of 91 Research Octane (RON+MON/2=87) or higher"

Octane is basically a pre-detonation resistance measurement. In North America we use the AKI (Anti-Knock Index) scale. It is composed of two different ratings.

The Research Octane Number (RON) and the Motor Octane Number (MON). RON is the fuel's measured resistance to detonation during normal operating conditions and MON is the detonation resistance during heavy use.

The Formula to figure out the AKI of a fuel is:
(Motor Octane Rating + Research Octane Rating) / 2
(M + R) /2 = AKI

If your Fuel has a RON of 91 and a MON of 83, then the AKI is 87.

In other parts of the world (i.e. Japan and most of Europe) they just use the RON #...

i_piss_on_hondas

Well then again the only low octain gas I ever ran in it was am/pm when I was in high school... Doesnt matter... BLEW IT UP... I will have a thread on that later...

NanaimoRx-7

What kind of timing are you running i_piss_on_hondas? I'm running with a total timing of 20* and 12* never had any trouble plus I'm further lowering the octane with premix. Thinking about it, I've never used anything higher than 87 so maybe I can't accurately comment on this. I had a friend with an -SE who claimed the better mileage and performance of higher octane gas outweighed the cost. I would try it out, but a slower burning gasoline that costs more, just isn't my cup of tea.

George *Still looking for that Holy barrel of 80 octane*

i_piss_on_hondas

Who needs a timing light??? I just advance it tell it starts detonating and then move it back a bit

NanaimoRx-7

Well, obviously. I use the light for interior xenon strobe mostly.