dragula53

this only helps it burn more fuel and behave similarly to an engine with a higher displacement.

you get more combustion cycles per eccentric shaft rotation than in a 4 stroke piston engine. Twice as many, actually.

This is why the rotary seemingly generates an obscene amount of horsepower for 1.3 liters.

IcemanVKO

1 rotor is like two pistons, yet its really one piston...

zoom44

Mazda has previously shown hybrid gas/electric rotaries. they have also in the last year shown a hydrogen burning rotary(which just was given street leagality for road testing in Japan) with an electrically driven supercharger (less power loss than a belt driven one). so they already have the capability and the know how to produce a hybrid gas/electric or hybrid hydrogen/electric rotary with an electrically driven supercharger. nice hunh

beachdog

Rotarygod answered this very definitively last November. Check out his treatise. It's post #7 in this thread:
https://www.rx8club.com/showthread.p...ght=efficiency

brillo

not to get off topic, but in a previous post I got ~26mpg hwy without my a/c on, and just recently I got 17.5 in city without the a/c still with some spirited driving. I think the a/c is a big factor, as I'm in houston and it can get pretty hot here. I'm going to get a air filter and see how it helps. Houston is the perfect mileage torture test, bad stop and go traffic, and hot and humid so a/c for 8/12 of the year. If I can get the EPA or better without a/c (and remember the epa doesn't use the a/c in their testing) then most people should be in good shape.

G-ReX

Thanks for the link, I hadn't seen the post before. Awesome!

brillo

That thread needs a sticky

Boricua

Yea definitely

sandia8

year m.p.g. m.p.g.

1978 17/26(12a)
1981 21/30(12a)
1984 21/30(12a) 16/23(13b)
1986 17/24(13b)
1993-1995 17/25
2004-2005 18/24



When developing the RENESIS, Mazda's engineers aimed to retain power output on a par with the turbocharged 13B-REW, the rotary engine that powers the Mazda RX-7, while offering improved fuel economy and reduced emissions.
What this design means to the consumer is better fuel efficiency and increased performance. Mazda estimates the RX-8 will get 20 percent better mileage in the city than the RX-7 did.

duh!!! 18/24 is not 20% better than 17/25

dragula53

Not to be a thorn in mazda's side, but those were all overrated too.

the fd twin-turbo rx-7 saw abysmal mileage (like... 10-20), as did all of the previous rotaries.

RX-3's saw in the neighborhood of 15 miles per gallon.. etc.

rx8wannahave

Oh I know, I’m not comparing the Vette to the RX8 (while they are both GREAT cars) what I always marvel at is the GREAT fuel economy of a 6L 400HP V8. If the EPA got higher avg’s with the Vette…even if it’s wrong, it’s still better than the RX8.

I heard/read a story (don’t remember) that they got 22mpg with the vette doing some city and some highway…so, I conclude that the Vette’s V8 is more fuel efficient than the rotary. But, again…they are both great cars…PERIOD!


Ohhh mama….I can’t wait to see more of that. They will need to watch weight gain but if they could add an electric motor assist (not hydrogen powered since you lose like 60% of the HP in the rotary) and an electric supercharger…

…and MAZDA MADE THE PERFECT CAR!

Heck, even a normal SC/Turbo with an electric motor assit would be GREAT! 100 more HP and 5 more mpg...I can dream can’t I…but it’s not completely impossible!

sandia8

no true dragula, naw, my 81 rx-7 was real close to the numbers
I got 27 m.p.g. highway at 75 m.p.h. every time, 30 if I drove 55 m.p.h
intown was 17-18

that 12a was the 'lean burn' rotary
why did mazda not redo the 12a , add side ports, and get extra HP
and fuel versus trying to milk 280 hp out of a renesis,
which ended up 238 or really 218 dyno?? now that a real question
we could be driving a new rx-7 version 12a with 170-180 hp and 24/34 epa mpg

ScottishRX

I had an 83 RX-7 for many years ( owned the same car twice cos I loved it so much) and averaged around 25 mpg. And those are UK gallons, which are bigger than US gallons, which I find most ironic since I'm now living in Texas and apparently everything is bigger here!!!

SDB

I also owned a 1981 RX-7 and put 140,000 miles on it and I seem to remember that the above is true. Granted the power was much lower than the RX-8, but the mileage was never a problem.

mazdabob

I think it has more to with revs. Most piston engines have peak power at 5000 or less, while the rotary has peak power at higher rpm. My C5 Corvette is turning 2000 rpm at 85 mph, while the RX-8 is turning more revs. My RX-8 would get 11 mpg around town, while the C5 gets 16. On a trip, the best I got with the RX-8 was 21, while the C5 got 28. The RX-8 is always at higher rpm than piston cars, because thats where the power is.

dragula53

ah, I stand corrected.

though somebody around one of these boards was talking about their rx-3 and it's 15 mpg on the highway.

But I am sure the fd rx-7 got poopy mileage

Nordic RX-8

I also think the revs are too high at cruising speed - If you run at 70 mph, the tach is at 3400 rpm. I average less the 21 mpg on the highway using the cruise control on flat road. I can get 17 in town with prudent shifting and getting into 5 gear above 40 mph. I would have prefered a 5 speed manual with a taller top end or a true overdrive for road cruising. I have had cars with much higher HP that could get better gas mpg if you were light on the gas. (They also got much worse if you lit it up, sometimes less than 10 mpg)

Maolin34

OK....let's be realistic.

RPM's are certainly more engine specific. It is understood that the Renesis needs revs to generate HP and Torque, but how much do you need to move a sub 3000lb car, and keep it moving. Cruising at 70 miles an hour at 3400rpm your not making 238hp and certainly not making 159lb-ft. So, if your shifting at 3000rpm and never at WOT, then why aren't we getting better mileage? At 3400rpm, the Renesis is loafing, any lower and you would probably lug the engine in any gear but first. The bottom line is that there are RX8 owners that are getting better than 19mpg. The question shouldn't be why is my gas mileage so bad...(thermaldynamics,low compression ration, odd shaped combustion chamber) It should be, how/why are they getting such good mileage out of the same car, same engine design, same gas. And better yet, why is there such a variance?

bdt

Maybe I'm wrong, but I thought on the RX-7 you could change the thermostat from 170 to 190 and get somewhat better fuel economy (w/ a slight performance hit). Has anyone investigated this with their 8?