You would be surprised how reliable they actually are when compared to there equal displacement rivals. It's really never gonna be an apples to apple's comparison because mainly what Mazda put out in production only compares to 2.6l pistons. Piston engines have always had a displacement advantage and unfortunately, our little engines are always unfairly cross compared to something that's nearly double its displacement. He'll even our 4 rotor doesn't match the displacement of the LS you have in your fd (as it breaths like a 5.2l).

Now with that said! That 330rwhp 13b fd I mentioned a while ago is making around 380hp at the crank and has done so for over 100k on a rebuilt engine with 100% factory internal parts. Since a 13b breaths like a 2.6L, that's 146hp per liter. I would really love to see another piston application somewhere out there equalling that hp per liter output and lasting that long on factory internals.

The rotary is still an experiment. The right combination of parts makes that engine far more reliable than you can imagine.

Realistically, 1.5x is a much more accurate equivalency factor than 2x for piston engine equivalent. The RX-8 13B's equivalent piston engine is Honda's F20C. 1.3 liter rotary x 1.5 = 1.95 liter piston engine, close enough. Both revved to 9000, both made ~230hp give or take (F20C typically makes 195rwhp, RX-8 185rwhp).

The F20C in my S2000 has 160k miles on the clock. Properly maintained F-series engines (periodic valve adjustments required) don't just fail. That said they are not forgiving of mechanical overrevs to 10,000rpm, which a lot of S2000 owners managed to do somehow.
Even counting those operator-error induced failures, I would bet that F20C mortality rate at any given mileage is a lot less than for the RX-8's engine.

Also worth noting that S2000s on fuelly.com get 22-25mpg, whereas RX-8 gets 16-18 going by averages for each year model. DAMN...
(The S2000 does have a ~7% weight advantage, but the RX-8 has a 13% aero advantage.)

Hopefully any new rotary will be more reliable, longer-lived, and more efficient!

another major headwind against a rotary re-intro is... dealer service.

the amount of work to re-train, almost from scratch, service personnel could be alone a deal-breaker.

The S2k is a great car and it's too bad Mazda didn't beat them to the punch it's the perfect example of what the next RX7 could of been. The BRZ is cool car it's just a shame mazda didn't beat them to the punch because I believe they could of made a much better light weight sport coupe.

Mazda has been dancing around the RX7 ring for far to long and I seriously doubt they will stay in the rotary ring much longer it's embarrassing and so is this thread which keeps going on and on even thought the leader of the company has pretty much all but said the RX7/rotary is dead.

I'm fine with it because as Dan keeps reminding us piston engines are OK to :)

How do you come up with the 1.5 equivalent?


Engine displacement is calculated by a SINGLE fuel/air combustion event per cylinder or chamber "as in rotary chamber" and not by multiple events. All engines displacement is measured at bottom dead center on the intake stroke. On a piston engine that's 1 cylinder times however many cylinders with a firing spark plug. Lets just use a 2.6l cylinder as an example. 4 stoke piston engines need 2 crank revolutions to fire its full displacement. So only half the displacement is fired for every 1 rotation of the crank shaft. This means that only 1.3l of AIR was ingested and ignited to make power in 2 cylinders. We still have 2 more cylinders left that still have to ingest AIR an be ignited to make power. This will happen on the second rotation of the crank. Now after 2 full rotations of the crank, we now have had 4 power strokes and a total of 2.6l of AIR ingested to make power. Keep in mind that we have ONLY had 1 combustion event per cylinder.

Now measuring the rotary is exactly the same way. Bottom dead center on the intake stroke is what's measured in 1 chamber. You times that by however many chambers there are with firing spark plugs. Two 13b rotor chambers has a combined fill capacity at top dead center at 1.3l. So on a 13b when both chambers fill with AIR and you have a single combustion event in each chamber, you have ignited 1.3l of AIR in only 1 revolution of the eshaft. In two rotations, you would have ignited and move 2.6l total. This is exactly the same amount of air used in that 4 cylinder piston engine example I used.

So since displacement is the measurement of the total air volume ingested on a single combustion event per cylinder or chamber, I'm not sure were your 1.5 equivalency is comming from?

Also my fd got 25mpg on the highway and so did my 91 vert. The problem with the Rx8 is weight and gearing. Mazda had to make the vehicle more responsive and to give the illusion of more torque with high gearing. That same gearing is also why they run over 4k rpm on the highway at 70mph. Previous and lighter 2nd and 3rd gens ran much lower rpms on the highway and got much better economy as a result. Your not gonna be fuel efficient at those rpms. +S2000 doesn't have that extra 300lbs to lug around either.

The S2 R3 Rx8 is even worse with its 4.77 rear end. Driving that thing on the highway is damn near like giving it track time when all your doing is cruising. Those guys are starting to go through engines at 60k already as they are just being revved to high on a consistent daily passes because the gearing is all f*cked up.

*condensed version*

uh no, the firing per rotation halved makes the 1.3L displacement equal to a 2.6L piston engine, any discrepancies in power output is due to the poor sealing properties of the rotary engine. comparing it versus a piston engine and then handicapping it is what already partly what gives the rotary engine a bad name. if someone asked the displacement i would give both examples, it is a measured 1.3L but in retrospect to the majority of engines out there (read as piston engines, 99.999% of the engines on the planet) it would be considered a 2.6L engine in piston engine terminology.

the difference is the strokes in the engine, because a rotary engine does all the work it needs to in a single rotation of the shaft per rotor face, making it basically equal to a 2 stroke(1 crank rotation is 2 strokes). lacking valves the rotary and 2 strokes lack torque, but they make up for it in free flowing high revving engines.

you can't directly correlate a piston engines power output to a rotary engine, just as you can't compare directly a 2 stroke power band versus a 4 stroke engine's. technology has actually come to the point that a 4 stroke engine can come near to the same as a 2 stroke engine in it's ability to breathe via cam timing adjustment while the engine is running, giving them good low end torque and good high end power making them quicker engines nearly all around.

Oops had to use actual tire size and gear ratio figures for the r3 rx8. At 70mph the rpms are at 3,400. That's still very high when you consider that today's even smaller eco friendly piston engines are running barely over 2k on the highway so they can achieve nearly 40mpg. The Rx8 has enough torque to run lower highway rpms, I just don't know why Mazda choose to have so much response in what's essentially a highway gear.

it probably has a lot to do with the rotary engine using low revs lacking response, it also builds up carbon much quicker at lower revs which causes side effects in the engines. the automatic cars for example used lower revs, but they also died much quicker due to carbon buildup.

"Mazda has been dancing around the RX7 ring for far to long and I seriously doubt they will stay in the rotary ring much longer it's embarrassing and so is this thread which keeps going on and on even thought the leader of the company has pretty much all but said the RX7/rotary is dead.

I'm fine with it because"..................

i've got mine.

howard

Pretty sure this debate happens around 2-stroke and 4-stroke motorcycle engines too, but it's always in an "equivalency for racing" context, not in a literal one. A 250cc 2-stroke is still a 250 relative to a 250 4-stroke, it just has more power cycles out of that 250.

You think it is a joke to finish the 24 hr le Mans, let alone win without engine reliability a major component. 3000 miles treated like a sprint race from start to finish, is more like 300,000 miles street driving (all without an oil change).

1997 Race Stats (first book I pulled off shelf, I attended every race from '97 through '02):

10 Prototypes entered 6 finished, 49 GT1/GT2 started, 11 finished .. we are talking 29% of starters were still able to run at end of 24 hrs and if you look into stats more, some of those were running at end by sitting out the middle of the race in the garage. As to car makes: 1 Mazda (rotary) entered 1 finished. 16 Porsche entered 6 finished (38% success), 5 McLaren entered 2 finished (40%), 2 Ferrari entered 1 finished ..

Or more important by engine: Mazda 100% of 1 entry, Chrysler 50% of 4, Ferrari 50% of 2, Porsche 43% of 23, BMW 40% of 5, Nissan 25% of 3; and the failures Ford 0 of 5, Chevy 0 of 2, Jaguar 0 of 2, Lotus 0 of 1.

But more importantly talking street cars. the FB 12a and 13b engines were one of the worlds most reliable engines, able to get 200k miles while not being babied.

My friend's 1992 MX3 with a 1.6 B6 engine has 350k+ miles on it and runs great. He's on his 3rd transmission and the rest of the car is literally falling apart.
But the engine runs like a top.

I love my RX-7, but I'll always have a boinger to go to the parts store in. :)

in most cases 2 strokes are classed separate from 4 strokes for this reason. a 500cc 2 stroke would have an advantage over a 500cc 4 stroke so handicaps are implemented or they are simply classed in their own categories.

it also goes to show how far below they are in comparison if you take a 250cc dyno sheet and compare it against a 500cc 4 stroke engine. they are purely inefficient but the half strokes give it the real advantage since the engines are still equally sized, giving you the "all things equal" mindset.

You guys are missing it. I'm fully aware that the 1.3 rotary cycles the same air volume in 1 rev as a 2.6 liter 4stroke piston engine does. But for power equivalency, 1.5 is a better factor, as the rotary loses a lot more to heat. Similar situation with 2stroke v. 4stroke (FIM went with the volumetrically correct but realistically wrong 2x factor *specifically to get rid of 2strokes in top-tier motorcycle racing). Hence the 1.3 rotary makes similar power to a 2.0 liter piston engine spinning to the same revs. If someone were to build a 9000rpm 2.6 liter six, it would kill the 13B in power potential.

then instead of trying to compare it directly it should remain in its own category, i never really compare the rotary engine to a boinger because it simply can't cope and you have to create some unorthodox comparison requirements.

if someone is bothering me, i call it a 1.3L. if someone wants to know specifics i give the boinger the advantage and call it a 2.6L. neither is truly false but neither is each truly correct. calling it a 1.3L is just stroking your own ego though, because like the 2 stroke argument it would have an unfair advantage. calling it a 2.0L is probably more accurate, but just a randomized averaged figure.

See my post above ^^^

RX-8 weighs the same as the FC convertible, maybe less. I'm thinking it's 3000 for the RX-8, 3100 for the FC 'vert?

Congrats on getting that mileage! It is definitely outside the norm. I guarantee if you were driving an S2000 in exactly the same way, you'd be getting 32mpg.
At fuelly.com, average is ~15mpg for the FD, ~18 for the FC. Three FC convertibles reporting 22.1, 15.5, and 21.6. Personally I never saw better than 22mpg on an all-highway tankful in my FC 'vert, and averaged ~18-19 for city/highway usage. All-highway in the S2000 I get 30mpg average, and city/hwy mixed-usage I see 25-27.

S2000 revs 4100rpm at 75mph in 6th gear. The s2000's 200 lb. weight advantage is MORE than outweighed by the FC, FD, and RX-8 aero advantage on the highway.

The rotary simply loses more energy to heat, which is why the *real* power-equivalency factor is 1.5x and not 2x, and also why it gets worse mileage compared to similar piston engines.

in practice its not a problem. or more accurately, its not really a different problem.

Mazda, as with every car maker, is always coming out with new stuff, so there is ALWAYS some new service procedure to learn. so the new rotary would just be like the new skyaktiv stuff, its just another bulletin/service campaign.

if there is a service problem its more rooted in the people who are willing to be a mechanic for $12 an hour, which is about half the salary of a mechanic in 1992...

i live near laguna seca, so i get to go to the montery historics almost every year since the mid 90's, and i have seen EVERYTHING run at the track.

among its peer group the 787B is by far the most user friendly. the engine was rebuilt after the race in 1991, and then again in 2011, the TWENTY YEARS in between, it ran track days all over the world.

the 787B starts up just like any other rotary from the 90's, hot or cold. there is no remote starter, or jumper battery or pit crew even, its just like they turn the ignition key, same as your FD.

normal procedure is to just fire it up, and throw someone in it, for the parade laps.

in 2011, the 20th anniversary of the Lemans win, they rebuilt the engine in the #55 car, and actually went vintage racing with it.

the silk cut jags have both been completely restored, but the 787's are refreshingly original, its got all the rock chips and bumps and scrapes from 1991...

Right, they class them differently for racing, but they don't call a 250cc 2-stroke a 500cc motor.

Both my cars were stock powered so all I did was set cruise control. They just rev lower than the 8 in all conditions. Now I did modify the opening timming of my primary ports and secondary ports on that rebuilt 91 with used worn housings. I did the mod to get closer to zero overlap so I could improve the bottom end torque and fuel economy. I guess the mod worked because that's when I started noticing improved mileage with my fc. The engine has always ran richer since the rebuild because more fuel I'd being burned than waisted. The torque improvement was noticeable as well.

I was getting 23 mpg on highway and about 16 city in my fd aslong as I didnt abuse it tomuch hell I still abused it a bit and got the 23 mpg LOL that was with my old JDCM tranny which cruised at 3500 rpm

my FC vert was 3000lbs right on the nose with a full tank of gas, the base Rx8 was 2960lbs (its 25" longer too).

my 79 GS was 2410lbs, the 83 limited edition was 2330lbs, the GSL-SE was 2540lbs, the T2, with no AC or PS was 2820, same car with 3 rotor was 2860lbs. the 91 coupe auto was 2880lbs, a cat back and AL hood dropped it to 2800lbs. the 87 GXL, with ABS is also 2800.

all cars are stock, full tank of gas, same scale, although over a period of years.

best mileage was the 79, best tank was 25mpg, it averaged 23. the GSL-SE was next, it would do 22, and more like 26 on the freeway. the FD did 23 freeway. the Rx8 gets 20right on the nose.

i did some testing the vert gets like 8 around town, and 26 on the freeway, combined its like 16?

3 rotor was like 20 on the freeway, 16 in mixed driving, and if you step on the throttle its single digit.

If a new RX-7 came out today, I'd want to see performance from the factory in line with the FD in a straight line with improved handling and braking. Mazda would do well to just offer two engine options, a 250-300hp NA engine and then offer a larger displacement, extra rotor or FI engine option for a higher output car that can outpace all other Japanese cars aside from the GT-r (Leave it to the aftermarket to handle beating the GT-R)

The FC had an NA and FI option and sold incredibly well. Just price the base engine RX-7 a bit above the BRZ/FR-S price range and then price the high output model in the Evo X MR range, $38-45k. Launch an advertising campaign point out the reliability of the rotary, much like there "I fall to pieces" FC commercials.

Then if the RX-7 does well we can see Mazda back at the top of the sports car world, hopefully doing a GT-R beating RX-9 and an AWD Mazdaspeed 3 to take on the WRX STi and Evos of the day. Please Mazda, take my money.

I don't think it's a joke at all, it is a tremendous accomplishment. Unfortunately same-era production cars were not exactly reliable....

Loved all the race stats! I was paying more attention to IMSA GTP at the time, where one of the most beautiful sports prototypes ever was the RX-792P:
https://www.ultimatecarpage.com/images/large/4249-4.jpg
Good God, if beauty won races, that car would have dominated. Unfortunately there were issues...

Aside: here's my car with the same number at the Texas Mile October 2012:
https://scontent-b-mia.xx.fbcdn.net/...79767549_n.jpg

The 13B in the later FC models was NOT "one of the world's most reliable engines" by any stretch of the imagination. For every 200k example, there are thousands of 500k+ piston engines.

Anybody know if the old FC3S forum is still alive? I can't find it. I'd like to look back at my posts from the 2001. As I recall, my engine failure at 103k was regarded as perfectly normal, and life expectancy was in the 85k to 150k range. 200k outliers? I'm sure there are a few. I'm also sure there were examples that didn't make it past 60k. We're talking a whole different longevity ballpark from reasonably decent piston engines...

That we already know. ;) Besides what examples of 500k pistons are you talking about? Diesels and econo boxes don't count. :) The rotary has always been in a sports car so compare the same breed of vehicle.

long story, but no it isn't. i wouldn't count on it returning either.