Achieving 22-26mpg on an FC
 

So I have a 89 FC n/a. Wanted to know is there any way to achieve 22/26mpg city/highway on a rotary engine. I know these engines weren't made to be fuel efficient. But the reason I'm asking is because I'm going to be working a lot in the next couple of months.. where as I will be traveling 60+ miles from home to work. although I will be working 3-4 days a week depending on how many hours I can get. And my FC is my dd at the time. I know someone in here knows what kind of things need to be done to the engine, and all to tweak it, and get a high mpg. So any help would be more than welcome! Thanks! :):icon_tup:

Where did you get these numbers from? The factory rating is only 17/25 for an S5 NA. If you drive like a grandma, decent highway mileage is doable. But getting into the 20s around the city will be tough. Stop light to stop light driving chugs gas.

Yeah long highway cruising without unnecessary stops is about the only way to hit 20+, especially for turbo models (which I realize yours is not).

the throttle is you mpg maker, that and a good running motor and you will get in the upper range

Working O2 sensor. Regular tuneups. Run 10w-30 (Just swapped over in hopes of slightly better mpg). Tires balanced and aligned.

Not much else you can do, beyond your driving habits. Biggest change in mpg you can make that I've observed, honestly, is in your driving habits.

I'd say your best bet is to check out ecomodder.com or some site like that. There are a lot of different modifications I've seen done, but don't think I've seen an rx7 yet, make sure to post back if it's anything special! Anyways, there are, grill blocks, smooth underbody panels, rear wheel well coverings, wheel well vents, of course lightening the vehicle is gonna help, getting skinnier harder tires or taller tires to change the gear ratio, building a warm air intake, standalone ecu, etc. Well i'm going kinda overboard but I used to have a lean burn engine in my old civic and I was close to 50 mpg.

For the 7 it would be nice to see an mpg improvement, but I imagine most would enjoy a performance improvement too. So some mods will help with both and definitely maintenance will help with both. Change your air filter, your spark plugs, set tire pressure, maybe set the ignition timing, switch to synthetic transmission and rear differential fluid. I bet it would help to switch to premix and use synthetic oil in the engine (but only if you block of the OMP).

But yea the biggest change always comes from driving habits.

I stopped giving a shit about gas mileage when i decided to pick up a gt35r........

Soo much fuel..... Oh well.


Shopping around for a geo 3 cyl as i type this. :D

That was the original rating before the EPA changed their system to more accurately reflect the fuel mileage that can be expected.

The new rating for the N/A is 15-23 with an all around average of 17.
Both the '88 TII and '89 TII, I purchased new, would see around 20, and this is with a lot of highway travel. With the G-Force ECU installed maybe 7-8 years ago, the mileage is around 19. Just an FYI for the TII-EPA old 16/24 avg 19, new 15/22 avg 17.

Difficult getting the higher mileage with the rotary.

For a properly running FC, highway mileage (if you drive sanely) in the mid to high 20s should not be an issue. In the city, mileage will fall to 15-18 MPG due to starts and stops.

+1

I knew a guy who used to get upper 20s pretty consistently in his S5 NA.

I've gotten 22 mpg highway in my 270whp Turbo and could probably get more out of it.

just don't drive like you have lead shoes and you'll be fine.

this isn't for most people... but you can up the gas mileage quite a bit if you get a standalone and tune the fuel :)

My stock 90 FC which I drive about 100 miles per day sits at about 21-22 mpg. I did experiment with different oil weights going all the way down to 5W20. What I found is that mileage didn't change at all between the 5W20 and 20W50 but the engine feels smoother with the 20W50. No reason not to use it. When I drove around with the auxiliary ports wired open, my mileage fell a little bit. Keep in mind most of my commute is freeway. I hae a couple of things to do that will increase mileage based off of past experience but until I do it and replicate past results, I'm not going to say what they are. An rtek or other ecu and some good tuning will definitely be able to raise it a bit.

I believe that the gas savings found in lighter weight oil lies only in the reciprocating motor world. We don't have crank counter weights slapping oil. Now I am sure higher weight oil puts a bit more drag on the oil pump, but that increase in drag would be negligible.

Your best highway mileage will occur in closed loop mode. I used a narrowband O2 sensor gage to see when closed loop activates. The trick is, once you cross about 60mph, the stock ECU makes it tough to maintain closed loop. Keep it under 60mph and youl'll get the best mileage possible.

City driving, fuggetaboutit.

I had good results with a full exhaust (Header, high-flow cat, RB catback), cone filter in the engine bay (Warm air helps atomization), modded/polished TB and ported/polished intake manifold. With those mods, my '86 GXL got 25-27MPG freeway at anything from 55-70MPH and anywhere from 12(hooligan) to 20 (grandpa) in town. Removing restriction from the motor both makes power and reduces pumping loss.
FWIW I also maintained the thing like an aircraft. Everything that had an adjustment was adjusted, all fluids were kept fresh, always had good plugs etc...

That city number, frankly, is unattainable. Luckily, the vast majority of your commute sounds to be on the freeway, where 26 is pretty reasonable. The best piece of advice I can give, beyond having a car set up like mine (as described below), is to use cruise control and sit right around 70mph, or lower. Also, keep the windows up - at most, open the sunroof and turn on the blower if you need more air (but not the AC)

I managed to get as high as about 28-29 mpg pure highway once or twice, normally around 26-27 in my S4 n/a, driving about 90 miles to and from school. I did this on a newly rebuilt engine by Rotary Connection with no catalytic converters and a Borla exhaust. I believe at the time I was using a stock air box with a hole cut in the top. Additionally, I had 215/45R17 tires in front and 235/45R17 tires in the rear, with particularly light Enkei wheels.


As always, Aaron Cake knows what he's talking about.

the *best* mileage I ever got in my 7 was 9.8l/100km (about 24mpg for you american's with no math capacity)

That is on a ported, large turbo car,with an EMS doing ultimate highway driving. As in, gas up, get on the highway, lock in cruise control @ 75mph and go until the tanks empty. Racked that kind of mileage up constantly on road trips. I would venture to say that you will never achieve any higher mileage then 24-25mpg. I was pegging my wideband @ 16AFR the entire time.

I doubt to be honest that any FC with a stock computer would even get 24-25mpg.

^cone crushr has your answer, driving at or under 60mph is prolly your best bet to get better mpg. i had to drive about half as many miles in my 2002 4runner, all highway, and it was killing me going 70-75 mph til i started goin 60 mph or less got like 2-4 mpg better in a quad cam v-6 SUV that weighs 5k lbs.

Fill it with Imperial gallons instead of US gallons ;)

I get ~22-24mpg city (18-20mpg US), 27-30mpg (22-25 US)highway, usually drive around 70-75mph (120-125kph), although my city driving doesn't usually involve a lot of stop-and-go commuting, nor do I run the AC a lot.

Good tune, properly inflated tires, not to heavy on the throttle the majority of the time (gotta run it WOT to redline at least once on any trip, mind you). Synthetic lube in the gearbox and diff. I did notice my city mileage in particular dropped by 1-2 mpg when I switched to 16x7 Enkei rims with 225/50-16 Pirelli P-Zero Neros. They're about 6-8 lbs heavier than stock size tires on the stock rims - a bit taller, too - about 2%, so speedometer/odo reading 2% low accounts partly for the difference, but mostly it just feels less powerful/responsive, similarly to how a lightened flywheel does the opposite. Which I'm sure just confirms the worth of keeping rim/tire packages as light as reasonably possible, as spinning drivetrain mass means less power to the wheels.

Keeping speed down makes a significant difference too - I once got 32mpg (27US) on a 500km trip mountain driving (more up than down, roughly 1000' net elevation gain), with AC most of the time, because the 90km (55mph) limit kept me to 105-110kmh (~65mph).

As many have already said, driving style and speed make a difference in your MPG.

With my S4 Turbo II, Rtek 1.7, 720 secondaries, stock downpipe, highflow Magnaflow 2.5" converter, Racing Beat NONTURBO catback, and driving 60mph I got 26 mpg on a highway trip, going 360 miles before I got worried and filled up.

If you are worried about getting good mileage, get a 2nd car! When it got to be too expensive to daily drive my 7 (gas >$3 gallon), I bought a cheap Ford Festiva. I drove it for a year and got an average of 44MPG. Then I sold that and got a 96 Passat TDI that has power everything, dual airbags, and AC for $1000. It gets 43MPG and saves me enough money to still play with the 7.

Vince