I own a race ported 12A Mazda Rx-7.
I'd like to pick your brain a bit about the car. More specifically; fuel.
(Quick stats about the car)
Race Ported 12A
Mikuni PH44 Carb
Dual 6AL MSD Ignition
Holley Red Fuel Pump

What type of fuel do you think I should be using?

I understand that the higher octane means it's harder to combust. (added benefits of cleaning the engine, etc.)

I've looked online, and I find answers; but not to my issue.

Now the engine is race ported; meaning the ports are ginormous. It takes in a lot of air.

Would this be the same effect, (not methodically) as having a turbo force in air?
Turbo forces air in, giant ports give it tons of air. Same effect?

Now, I'm not sure if race porting ups the compression like a turbo does under boost.
If it doesn't, I'm completely off and I apologize.

So, would running higher octane fuel help performance in my case?
Would it compress more air/fuel before combusting; yielding more power?

Thanks guys
-Lucas

 

its not the same effect , turbo FORCES air in , while even large ports can only gulp as much air as atmosphere, the larger ports allow more air in , but a turbo compresses the air which builds boost and compressed air is always going to be more .

An NA , large port application relies on compression , and vacume to suck in the air .

while a turbo application uses both compression vacuum , and the turbocharger .

 

Larger ports on rotary motors = less vacumn that is used
Race port what does that mean? J, Bridge, Semi-p, Full Peripheral, Half bridge. their lots of port work that can be done and effect timing and different characteristics of the motor. But to make you answer simpler I believe that rotarys in NA love the high octane looking from timing gains and preventing detonation and hp gain stand point.

 

basically octane is a measurement of a fuels resistance to detonation.

for a given engine, like a 12A, the more power you make the more likely it is to detonate. if we were engineers, we would express this with combustion pressure, more power = more pressure. there are other things that factor in, like intake temperature. compression ratio matters too, but you can't change it.

that being said a stock 12A is very far from detonation, so even increasing the power by like 50% you don't need to run higher octane. might as well run 91, but going higher won't help

 

i'm from the Fuel injected age with ECU controlled timing haha , but wouldnt advancing the timing increase power , but require higher octane to combat detonation ?

I beleive 12 a's have distributors so I'm not sure if you can advance timing on them lol

 

on a stock 12A advancing the timing a couple degrees adds power, but advancing more you don't gain anything, and then more than that it'll loose power, but it probably wont detonate until you get really stupid with it.

so no, on a stock 12A you can tune it for max power on 87, and not encounter detonation at all.

 

IC diminishing returns is reached very quickly then

 

stock timing is like 20ish degrees, and optimal is like 22-25, so the timing isn't that far off optimal.

 

Actually I understand there's more to modern high octane fuel blends than just limiting detonation.