j9fd3s

iTrader: (3)

i've actually found that best mileage generally occurs at a higher rpm in a rotary. the nice side benefit of the 1000 mile sevenstock round trip is that you have ~400 miles each way on the freeway.

the SA got noticeably better mileage between 3500-4000rpm than it did between 2500-3500rpm. around 25mpg vs about 23

the FD got best mileage, right before closed loop turned off, mine which was nearly stock did 24mpg, my friend, who had a ported full exhaust car did ~26mpg.

the Rx8 gets better mileage at 70-75mph than it does at 65mph, its about 4k in that one too. it'll do 24 mpg @75, but 22-23 at 65.

i think there are a few reasons for this.

1. its MILES per gallon, if we increase the miles, it helps. its why city driving is so bad, we don't go anywhere.
2. the Rx7 and Rx8's are fairly aerodynamic.
3. the engine takes about the same fuel to go 2000rpm as it does to go 4000rpm, friction is higher, but not by as much as it would be in a piston engine, which does the same work in twice the amount of time, because they are lazy.

peejay

That's not really how it works... when I did 32mpg, it was with 185/70-13s and 4.78s. Cruise RPM was something like 4500-5000rpm.

plentymoon

when I had my 2nd gen and I drove it on the highway at 80-90mph I got really good fuel milage and I mean I hardly dropped anything on an 80 mile trip to nevada and back so a total 160miles and would barely be hitting above half tank worst fuel mileage was when I had to go 65mph on a small 2 lane highway and then gas would kinda since but normal 4 lane highway I could drive 243 miles to Boise, Idaho and get the same results as in the the 160 mile round trip one way so long as I drove over the speed limit that is gotta love that 90mph drive on the highway.

Edit: I should also say that my Rpms stayed at a constant 4500 rpm to about 5000 rpm in 5th gear depending on if I had change gears to climb a quick hill but on a flat surface I averaged 4500 rpm at 80 cruising speed which got probably the best results in highway mileage to Boise.

I will hopefully be testing this gain soon!

TLC

Dammm
I get 10 miles to the gallon all day, a few years back I noticed sometimes i would get 20/gallon, odd.
I track every gallon I put in and how many miles it gives.

chuyler1

iTrader: (1)

Things that make people report better mileage than they actually are getting:

• Using different pumps that shut off at different fill levels skewing gallons used.
• Assuming each 1/4 a tank is equal
• Running wheel/tire/differential combos or very worn tires that don't allow the odometer to report accurate mileage

Things that help achieve more than 22 mpg

• Stripping the car of weight and features (no air pump, p/s, a/c, no interior, no spare tire, no fat friends riding shotgun, etc, etc)
• Running a mechanical secondary setup that doesn't open until very late in the throttle travel or mucking with the jets to run super lean
• Installing a free flowing exhaust but never actually hitting the throttle to hear it
• Using hypermiler techniques to improve the aero of your car
• Driving in such a manner as to never go up a hill, hit the brakes, idle for more than it takes to get out of the gas station, or exceed 55 mph.

A stock 1st gen, driven at the pace of traffic with mixed suburb and highway driving, should get between 20-22 mpg unless something is severely wrong or you have gone hog wild with tuning and porting. You can probably get 25-27 mpg point-to-point on flat ground interstates keeping your speeds and RPMs low. Anything higher is highly suspect and if it was a "i got XX mpg this one time" I'd be willing to bet it was just a case where the two pumps used had different shut off points and the tank wasn't topped off properly, overfilling with the first pump and underfilling with the second could yield a 5mpg difference. You won't get better mileage at higher speeds over 60, you won't get better mileage at higher RPMs.

j9fd3s

iTrader: (3)

but you do.. there are reasons for this

1. the rotary does not add friction and other losses with rpm as much as a piston engine does.
2. due to the way the air pump air is delivered, the engines are slightly rich at lower rpms

chuyler1

iTrader: (1)

Well yes, there is a point at which a taller gear is going to put you into lugging engine speeds where that is the case, and we can't or shouldn't compare ideal rotary RPMs to ideal piston RPMs. The rotary is very inefficient at idle speeds and you certainly don't want to be highway cruising at 1,500RPM, but expecting better results at 5,000RPM instead of 3,500RPM when all other variables are equal is simply wrong.

If Mazda could have put a shorter drive gear in any of their rotary cars and gotten better performance AND fuel mileage by forcing drivers to spin at 4500rpm instead of 3500rpm on the highway, they would have absolutely done it. The engine is certainly smooth and quiet enough for that to go unnoticed. Instead, they had to go the opposite direction with progressively taller gearing as the years went by. They weren't hiding fuel efficiency from its customers by putting 3.90 in the back instead of 4.77.

Regardless of engine RPM, a rotary engine car cannot defeat the laws of aerodynamics and that is where the majority of the efficiency is lost, as much as 15% between 55mph and 65mph simply due to wind and tire resistance, not rotating assembly of the drivetrain.

t_g_farrell

iTrader: (1)

I get 24 mpg all the time at interstate speeds of 70-80 mph which puts me at 3500 - 4000 rpm and this is averaged across multiple fillups on multiple trips across varying terrains (some in the mountians of NC). This is with a stock block, modified nikki, RB exhaust and modified ignition. It also doesn't get better at lower speeds which has been seen when trapped in slow interstate traffic on some trips. I fill my tank the same way, on level ground and don't rely on the cutoff of the filler, I look for gas spitting out to indicate full. The type of gas used can make a huge difference. Here on the east coast we mostly have 10 maybe 15% ethanol worst case. Out west my understanding is its E85 which will get much worse fuel economy.

Oh, and I drive it like I stole it all the time. I love to hear the RB SP exhaust when the secondaries are kicking in.

chuyler1

iTrader: (1)

Well yes, I've seen 24 with my RB exhaust, never came close with the stock exhaust. I mentioned above that modifications can show improvements.
This is because of the constant changing of speed. It takes more fuel to accelerate back up to 70mph than you would save going 60mph for a stretch of road behind someone, so when you're constantly changing speeds in traffic your mileage will be worse than if you had just picked a speed and stuck with it.
This is definitely something people in the midwest should consider. I totally forgot that we are all dealing with different fuels.

diabolical1

iTrader: (3)

I never needed to do anything "special" to get decent mileage from mine. I used to get mid-20s (25-ish-26-ish, from what I remember) from my '84 with a Carter pump (wired to 12 volts), a Dell'Orto 48 on a tired, old, stock S3 13B with mostly stock exhaust [I eventually did get a full RB system though, but I can't remember doing any MPG testing after installing it]. I didn't feel the need to go full throttle all the time, all day, but I never went out of my way to keep RPM low either. In my everyday driving I tend to short shift a lot. I do keep up with traffic though - both city and highway. I had full interior, plus tools and other stuff.

j9fd3s

iTrader: (3)

in CA we get some unique formulation of E10. its how we get our gas to be $0.50 more a gallon. we've been doing variations of it for a couple decades too. so my mpg numbers are on E10.

to wit:

79 GS, 90k mile car, completely original, between 3000-3500rpm it would get 22mpg, 3500-4000 it would get 25.
82 S, P port, getting on and off the trailer, a sevenstock and two track days; 11mpg.
83 LE; 22mpg. great car, if you have the coin i urge you to pick one up
85 GSL-SE. FC engine block, RB exhaust; 22mpg in mixed driving, 26 on the freeway
87 FC GXL this would get 19-22.
88 Turbo. stock, RB exhaust, 16-18mpg.
88 FC with 3 Rotor. once the ecu was dialed it would do 16 in mixed driving, and the sevenstock trip was 19.9mpg.
91 FC-REW. i'm getting 12mpg, its fun
93 FD, stock, usually 20-22, the sevenstock trip (1000miles round trip) was 23
2004 Rx8. 19mpg, setting the cruise control at 85mph brought the mpg up to 23, not easy around here everyone drives very slowly.

hat.paradox

Makes me think about my trips between base and home.. about 7/8s tank lasts me one way (230mi)!

t_g_farrell

iTrader: (1)

Thats the mileage that I usually fill up on as well on highway drives.

miasmicmonky

iTrader: (1)

Back when my only major mod was RB short headers, I once made a cruise from Little rock to Oklahoma city and back. Across the whole trip, I average 32 mpg at around 75 to 80 mpg. I was like what in the world? I never averaged more than 24 before then. The next time I took it for a long drive, I did an old highway cruise and managed to average 28 even though I was keeping the car really high in the rev range. Now that I have removed the air pump and shutter valve, I pretty much get 18-22 mpg no matter what I do. Kinda sucks to have dropped the ability to get good mileage, but if I want good mileage, I just hop in the 2018 Mazda 3.

Taefc3s88

Sups folks,
Any local sources for aftermaket engine management?