I know thr rx-7 is not known for getting good gas mileage, but is 14.3 mpg normal? I just used 3.5 gallons to drive 50 miles. I do mostly city driving, i occasionally drive hard, and i also let my car warm up and cool down before driving. I only let it warm up and cool down for about 1 minute each, would this impact my gas mileage like this? I doubt my mods are the problem, (only downpipe and intake). Is this normal? If not, what could be causing it? Thanks alot.


-Jeff

 

I got awesome mileage on the long haul between Dallas and Denver, about 470 miles to a tank. Now that all I do is city driving i get about 290 miles to a tank..I think the car just doesn't like stop and go driving.

 

no warming up anfd cooling it down isn't the problem! it's probably the way you drive or maybe there's a slight fuel leak somewhere! so use your nose and go sniffing your engine. or maybe you're air/fuel ratio's isn't that great and you're getting to much air so your car's trying to throw in to much gas! not sure, but there can be many reasons.

 

That sounds about right:

https://www.rx7club.com/forum/showth...hlight=mileage

 

cooling down after a hard run should be at least 5 mins dude. In anycase, that seem just about right, I get 8 (God i hate traffic!)-15mpg.

 

I've got a streetport and a turbo timer(which runs for a while after you power down) and I always start my car and let it warm up for a bit before I get back in and drive. My gas mileage is horrendous! Probably get between 8-12 mpg city, and haven't really tested the highway mileage as I'm afraid to get too far away from my tuner when I break down lol. This car is a lush for gas. It seems like the combustion process is more inefficient at lower rpms (city driving). Factor in some spirited boost useage and a rich a/f mixture and you'll find yourself at Mobil wondering how premium got so damed expensive.

 

I wish mine went 14.3 :/

 

The rotary motor is known to be more inefficient at lower rpm's. This happens because the rotor is spinning slower and exhaust fumes are not being fully expelled through the exhaust port. Exhaust fumes become trap'd as the rotor turns and this "exhaustive" mixture requires more fuel for combustion. If larger ports are made to the motor, the worse this condition becomes... On the otherhand, at higher rpm's, sometimes fuel gets trapped in the corners of the rotor turns along the housing. As the rotor continues to turns it expels this unused gas into the exhaust port, which in stock cars is burned off by the cats.

This inefficiency was addressed in the making of the Renesis motor.

 

i get about 14-15 mpg with my minimal amount of mods. i am also running the PFC with the base maps, so it may be running a little rich with my mods. i've just learned to accept it. but it's also not a daily driver, so that makes it easier on the wallet

 

That's a good post and there is another intrinsic quality of the rotary that causes it to use a lot of gas at low RPMs and to get the car rolling. The rotary has laughable torque, which no matter how much hp you have, torque is what does the work. It's inherent in the design of the motor itself, and it's even more of a problem in FI motors, obviously.

Other fairly common things off the top of my head that would hurt your gas mileage (although yours actually sounds good for city, Jeff) ...

dirty O2 sensor
dirty plugs
dirty filters
clogged cats
low comp
vacuum leak
boost leak
bad/seized turbos
leaky injector
bad timing
lead foot

 

Thanks for all the responses. I guess it must be normnal. I also check for any fuel leaks, just in case.

One more thing...
I usually drive around under no boost for about 3-5 minutes. Then I park the car and let it idle about a min, or more depending on how hard i ran it.

Thanks again,

-Jeff

 

damn... you are getting 14.3 city and better freeway and you are complaining??? i drive about 30% city 70% freeway, and i get anywhere from 11-12.5 miles per gallon. and may i point out, gentlemen, that that is with hardly any boost time, just regular driving! that puts a hurt on the wallet with gas prices around $2.45 around here, and that is for shitty cali 91 octane!

i wish i got 14.3 mpg! you should be proud of your car for working that hard for so little pay

 

Seems about right.
I get around 13 mpg average. The best I have seen with all highway driving is 17 mpg. Play with the car, mash the gas a few times and it drops way down.

On my Volvo it has a function that will display instantaneous readings of fuel mileage. If I just mash the gas and keep the turbos howling, the fuel mileage shows 1.9 - 2.2 mpg!

It takes lots of dead dinos flowing thru our engines to make that high hp to displacement ratio.

 

i have noticed that my gas milage is realy bad...i get around 200 miles to a tank w/ highway and city driving (with little spirited driving, when i have a little fun it is worse). my car is bone stock except for a stock japanese DP (came w/ the japanese engine). what kind of gas milage should i expect? does a stock car get worse gas milage than a modded one??

 

I just about have to fill up every three days with this car, though I have noticed that slowly accelerating and and then trying to keep the car in the higher rpms, like 3 -5 gets beter mileage than just keeping it between 1-3 as you would in a piston engine. Maybe I should just drop a Renesis engine into my Seven and keep the stock 7 twins.

 

I just applied for a AAA visa card that is supposed to give you back 5% of all purchases made at the pump

Try getting a dedicated gas card. That'll help things

 

is this true?? will the car run hotter if you cruse at thoes RPM's?

 

14mpg isn't bad in the city. I get about 19mpg 70% highway 30% city. My trick is to keep the car in closed loop mode as much as possible (I have an A/F gauge), which essentially entails going easy on the gas and staying between 2.5k and 4k rpm. No need to let the car cool down if you go easy on the car before stopping, in fact, letting the car sit while running just causes it to heatsoak. In terms of warmup, the best and most fuel efficient procedure is to let the car sit just long enough for the fluids to circulate (30-60sec), then drive very gently until it is up to operating temperature. Letting it sit during warmup only prolongs the warmup cycle and keeps you in rich, open loop mode longer, wasting more gas and shortening the life of your cats. And lastly, and most ironically, if you want to keep those plugs clean and firing right (which helps mileage), you gotta waste some gas by blasting to 8k rpm at WOT over and over and over up the local winding road. Yes, save gas by wasting gas, you must own an RX-7 .

 

14mpg isn't bad in the city. I get about 19mpg 70% highway 30% city. My trick is to keep the car in closed loop mode as much as possible (I have an A/F gauge), which essentially entails going easy on the gas and staying between 2.5k and 4k rpm. No need to let the car cool down if you go easy on the car before stopping, in fact, letting the car sit while running just causes it to heatsoak. In terms of warmup, the best and most fuel efficient procedure is to let the car sit just long enough for the fluids to circulate (30-60sec), then drive very gently until it is up to operating temperature. Letting it sit during warmup only prolongs the warmup cycle and keeps you in rich, open loop mode longer, wasting more gas and shortening the life of your cats. And lastly, and most ironically, if you want to keep those plugs clean and firing right (which helps mileage), you gotta waste some gas by blasting to 8k rpm at WOT over and over and over up the local winding road. Yes, save gas by wasting gas, you must own an RX-7 .