i've been wondering about this for a while. considering i have a stock 12a, and i add a better flowing carb, and open up the exhaust, would the gas mileage actually get worse even if i don't drive the car hard? or will there be a difference no matter how its driven.

also, what about porting your engine, it would seem to me that a ported motor would eat quite a bit more gas, even if you weren't pushing it. i know of course that both these things make your engine capable of having horrible gas mileage, but like i said with the fitst question, since you give the "poissibility" to the motor to have more air, gas, and better flow, but drive it easy and not give it a reason to use any more gas, will it anyways? understand guys?

oh, by the way, im finally bringing the car home tomorrow. ahaha i have around 500 posts, and no rx7 till now...although i have owned 3 of them years ago. an 81, an 85, and a 87 TII

nick

 

YAY!! just got the car home finally. ahh, feels good to finally own another rx-7, and...

BUMP! anyone have an answer to my question?

nick

 

It's a good question Nick, I use my 7 to commute to work every day, 110 mile round trip. I'm planing to rebuild a back up motor and I was thinking about porting and maybe upgrading the Niki, but I don't want to loose gas mileage, which is now aroung 24 cruising at 80. Anybody know the answer to Nick's question?

Ray

 

to supply enough fuel to a ported motor im pretty sure your going to lose gas mileage, EFI on the other hand may be a bit better in that respect.

isaac

 

generally speaking for a well tuned engine:
street port in the city=mileage down
street port highway=mileage slightly up

 

why is it i hear rotary engines using up to 10 mpg when they're all modded? what causes this? hard driving, or all around everyday use?

when i free up the exhaust on my 12a, get a sterling carb, and a bigger fuel pump, but NOT port the engine, am i going to lose gas mileage even when im taking it easy?

 

You should get better gas mileage as long as you keeep your foot out of it.
Carb'd 12a's non ported generally get decent mileage on the highway. When i ran my 83 12a with rb header, lightened steel flywheel and a mikuni 44phh side draft
carb. I got about 23-25 mpg on the highway about still made 142hp. Like any 4bbl
stock nikki or sterling carb once you put your foot into it the gas mileage will suffer.
rx7doctor

 

anyone else? how can i rephrase the question? hmm... how about...

what mods can i do to the 12a that won't affect the gas mileage?

 

Weight reduction, A/C removal, e-fan.....yea, that is all I can think of.

 

The #1 mod you can do that will increase hp and fuel economy is the rb exhaust
system, However the point still stands, your gas mileage will go down unless you drive normally. Which means if you keep your foot out of it stock or not your mileage will be ok. The less the engine has to work to make hp the better the mileage will be. electric fans reduce drag on the motor, remove the air pump.
Install a lightened steel flywheel which greatly reduces rotational mass. Put in
a kn replacement airfilter or rb filter kit. Keep the vehicle tuned at all times. This means do not use any other plug besides NGK. Put a good set of ignition wires like
Ngk or accels 300+ thundersports. Install a 2nd gen leading coil system and maybe
a msd ignition system. All of these things stated will increase your mpg. rx7doctor

 

Depending on how you port it :If a engine has a 50Deg intake streetport,the mileage will suffer.if you have a small streetport (Mild Port)You will need a richer mixture in all rev ranges,as a little more air is sucked in,nedding more fuel and the air and fuel isnt mixed as good as before (smoother runners,faster airspeed etc).Except for that ,there is allso the issue of overlap.The more overlap you have,(intake and exhaust port open at the same time)the more the intake gas is diluted by the exhaust gas.Your mixture will have to be richer to overcome the diluted intake gas,inturn making it less fuel efficient.

I would say the best bet is to fit a less restrictive exhaust (RB preferable),it will give you some extra torque,and if driven mildly,will improve your mileage a bit.

karis

 

On my se when i added the rb system i gained 3mpg on the freeway when i drove
between 65-70mph. when i did my 12a i got apporx 4mpg more at the same speeds. rx7doctor