just wondering if anyone on this forum is getting better than 10mpg with their n/a rx7. i drive a 87 gxl and am have tried everything to get better fuel efficiency - full tune up, higher octane gas, i just did all of the fuel lines (not leaking anymore!!), timing, but im still getting shitty mileage. is there anything else i should try or was this car bound to have terrible mileage??

 

10 mpg is really bad I get anywhere from 350-500km per tank depending city/highway driving and how low I let the tank run. I typically fill ~55L for ~400km with 70/30 city/highway. I don't know what's wrong with yours maybe leaky injectors or a weak spark, how does it drive smooth power delivery? don't put higher than 87 octane in though waste of money on a NA and probably won't burn as completely.

 

check your throttle position sensor and water thermal sensor (on the back of the filler neck). Then you have your basic full intake and exhaust mods. Check to see if your 5/6 ports are stuck open. Replaced your fuel filter and intank strainer? Spark plug wires and spark plugs? Higher octane is a waste of money.

 

10 mpg is almost half of what you should be getting

 

The Viper GTS gets 9mpg....7.4L (I think) 10 cylinder....

10mpg from 1.3L is pretty sucky


How to make the FC more fuel efficient? Swap in a VW 1.8T.......hehe

Seriously though, do you have fuel leak? when's the last time you did some regular maintenace on the car?

edit: Maybe sticky injectors? does it have good power?

 

yeah... i still have the window sticker to my car (that i sold) it says 21 (or 24, couldnt remember) to 14 mpg. just depending on how you drive it. if you grammaw the car around town then you should be getting decent mileage, but we all know how hard that is to do in an rx7

 

I get about 17 average. I am suprised at the difference it makes whether you stomp on the gas alot or not. It is a much alrger difference than any other car I have ever driven.

If I mash on the gas alot, I get about 12mpg in the city. But if I don't, its about 17mpg city, and 23 on the highway.

--Alex

 

I just got 3 straight weeks of 23+ mpg driving, thats with a lead foot on the interstate and redlining her 1st thru 3rd (Properly warmed up of course and yes I know thats too fast for onramp travel.) My only mods to date, that count, are a cone filter without heat shield, RB header and broken presilecer to factory catback. New presilencer is on the way. Ive yet to change my plugs or wires but im waiting on my new FD alt kit to arrive before I do that. This is in a 88 SE FTW, no ac and no ps either and full emissions removal except airpump(Alt kit will also see this deletion). So if you're getting 10mpg you need to go back through everything and make sure its all hooked up right and working properly, you my want to check tire air pressures as well for that lil 2mpg more maybe.

 

explain what you're "complete" tune-up is, then we can help pinpoint something

 

ok, so this tune up included plugs, wires, a/f, f/f, i had all the fuel lines replaced (they were rusted pretty bad and one was leaking) i adjusted the timing (it was a little off) and did the injectors last august. the power is normal through any rpm. the only thing left to do really is the o2 sensor. more ideas would be appreciated. the car isn't heavily modded, ive done a borla cat back exh. and a custum intake

 

If your not leaking gas, or blowing it out the tail pipe try changing your driving style. It is crazy how much a lighter right foot an change your gas milage. And if it is a stickshift try and keep the R's below 3k.

 

so yeah, do the o2 sensor.

define "did the injectors" are they new?

 

SIGH, that O2 sensor is muy importante for gas mileage

 

ya the injectors are brand new, and it doesn't seem to matter if i drive like a grandma or not. if i keep the revs under 3k i can get 220 per tank as opposed to 200-210 with a heavy foot. i do 95% of my driving in the city, but i think i should still be getting better mileage.

 

first remove the engine

second cut two holes in each floor board

third, get some really grippy shoes and a nice strong friend

now, the only gas you'll be burning is out of your ***



Now, for something helpful

New fluids tranny, diff, engine, coolent
New air filter, oil filter, gas filter
Check all electrical connections and vacuum lines
Be sure to check spark plugs, wires, o2 sensor
check your TPS
Tire pressure is a big one
check your tread wear, is it even? worn suspensions can dampen gas mileage

Take the 50lb lead weights off your shoes


Oh, and depending on the kind of city driving you do can determine gas mileage, like i live 2 minutes away from my work, i drive two miles to get there, though its a short distance, all those cold starts and i do have three hills to go over, end up me getting crappy gas mileage, but when i get on the freeway on the weekend(burnnin carbon) it gets 23-25, during my work days i get like 10-14. its something to consider

 

ok cool thanks tournapart. does replacing your fluids really help that much?? i know my susp. is fucked, but how much of a difference will it make for fuel economy???

 

Whoa, whoa, whoa!
Doesn't your 1987 model come with a 16.6 gallon tank?
How are you figuring out your gas mileage?

I have a 1987 TurboII, and whenever I can break 200 miles per tank, I smile!
I typically fill it around 13 to 14 gallons per tank.
Are you draining it beyond that???
Even at worst case, 200 miles divided by 14 is still above 14mpg!
Am I missing something here?

Are you running the bigger 19 gallon gas tank by any chance?


-Ted

 

you don't need higher octane then 87.

how do the spark plugs look when you took the old ones out?

what temp does your car run at?

what weight of oil are you using?

how does the car idle and at what idle speed

when you stand behidn the car and it is idlining do you fumes make you want to die?

have you checked for codes yet?

 

not really
mine has become disconnected a few times. takes a while to realize it with the mielage dropping about 1-2 mpg

 

I think you must drive much harder than some of us... I usually average between 15.5 and 17.5 in day to day mixed driving which is around 210-240 per S4 tank and around 20 MPG (270-280 per tank) for highway only with an average fill of 13.5 gallons.

 

if u found a 1-2 mpg drop disconnecting the O2, then u have other issues with your tuning

 

Check the IAT sensor and water temp thermo sensor. These can affect the inputs to your ecu causing bad mileage. Too often overlooked. Only reason I know is it happened to me before. Then of course check the TPS.

 

like what? I'm running the stock ECU which I understand can't be tuned unless you use a piggy back, with the stock timing, with the stock emissions. the car is all stock other then a RB header, and straight pipe going into the stock cat-back with rusted out mufflers and a K&N filter. so far my issues with the tuning is netting me 22-23 mpg avg on a car with 210-220k miles (not sure on exact being the speedo cable fell out for a while there). have managed to get 30mpg with the TPS disconnected doing 75mph for a decent road trip. so far it seems that might be a joke to with the TPS being thise huge thing unless your tps is just flat out messed up. but between running my TPS vs disconnecting it I don't see a lot of difference in mileage. most of it comes from drivability. the car is more prone to jerking when on or off the throttle as well as giving me these nice little backfires.


any ideas on whats wrong?


think it has already been established that the O2 doesn't make the biggest difference on these cars. or at least the S4 cars. for one thing it isn't very hard to go out of closed loop during freeway driving.

 

ted - i would be more than happy to get 200 MILES from 55litres. the thing is, im in canada eh?? no, im getting 200KM per 55l. thats roughly 8.5 mpg. shitty. but i did pick up the o2 sensor tonight, so that'll go in tomoro on my lunch/spare...

 

Erixhvn, IAT sensor? what dat??