Razz1

20.5 to 26MPG would be good.

arghx7

have you read the 16X patent? That's the whole point of the new architecture: to reduce the quenching on the combustion chamber walls and give the leading and trailing flame fronts more time to burn the mixture before they collide into each other.

Mazda would rather design a production engine that meets their goals without any kind water or methanol injection. Why make a 'weird' engine when you don't have to? We don't have the luxury of redesigning the motor. Some people take pride in all the little rituals they do with their rotary--the premix, methanol, being careful not to flood it, etc. But 99% of people can't be bothered. Why should they? It's like the urea injection systems on some recent diesels. I predict that those will die. Nobody wants to deal with that bs, and at least those last 10-15k miles before requiring a fillup. And you know what happens when the urea tank is empty? The PCM won't let the engine run. Any kind of water or methanol injection will need to be filled up more frequently than the oil. That's just not acceptable on a production car.

The rotary's maintenance quirks must be completely eliminated if it is to survive--high maintainence is not what makes a rotary a rotary. It's an unfortunate flaw in the motor. They need to design an oiling system so that you can go 5000 miles, never check your oil, and never have any problems. Otherwise people will just buy a 370Z. You know the new 5.0 Mustang engines have 8 gallon oil pans? That's so people can go 15k without an oil change.

olddragger

iTrader: (3)

Argh--no i havent--would like too--where can i find it?

The rotary engine --at this point---will never be a buy and forget type of engine.
It's very design dictates maintainence
1- the ignition system will always require more attention than recip performance cars
2- the oil will need changing more frequently
3- temps will always be in a narrow range of tolerance
4- it will will not be as detonation resistant as a recip.
Direct injection could help with detonation but word is direction injection is causing problems with maintaining a good oil film?
Without some major tech/ material discoveries the rotary upkeep will be what it is.
If a rotary car continues--it will be some time before we get that,
Putting water in a tank every month should not be that hard to do,

T-von

The concept is simple. You lower the rpms, you save fuel. The thing that most people forget is that larger displacement engines don't need as much rpm for steedy state cruising. Under cruising conditions, Mazda is currently reving the 13b based Renesis fairly high by comparison to any other previous 13b rotary engine. At 70mph, the Renesis rpms are well over 3k. Mazda is doing this to make acceleration in 6th gear more responsive for the heavier NA 8. The side effect is the fuel economy drops. By comparison, my 91 convertible and 94 Fd rev below 3k at 70mph. I easily got 25+ mpg on the highway. Funny thing is my convertible weighs about the same as the Rx8 but gets bettery highway economy. LOL!

Anyways with the added bottom end torque of the 16X, fuel econmy will drop automatically drop if Mazda properly gears to take advantage of it.

Spin9k

Maybe, and I'm not saying you're wrong in general for IC engines, but my experience doesn't show those things work as you say in practice in the rotary. 1st, at 70mph the RENESIS is around 4k RPM, not 3K. Any engine has it's peak efficiency at a certain point, and I'm not sure what that is for the RENESIS but my informal testing on highways show that my car gets best mileage at around 80-85 steady cruise, somewhere in the low 20s. Going 55 doesn't make things better, even thou the RPMs are far lower. Go figure, but that's how it seems to work out. The 25+ in your earlier engines is likey due to their lower output, therefore less gas used to produce less power at all RPMs. As you say SS crusing doesn't need much to maintain.

perhaps the rotary's best RPM is higher, similar to how a variable speed transmission keeps a normal IC engine at a higher SS RPM.

b'Eight'

The fuel efficiency from going from tuned port injection to direct injection is not all that great. It's only 10%. Direct injection is not going to be the saving grace of the rotary.

xsnipersgox

i cruise at 77 mph, and i achieve about 23mpg @ 75k miles all highway.

rotarygod

My 160 hp n/a FC RX-7 is at about 3000 rpm at 75 mph. If I'm lucky I get 22 mpg.

olddragger

iTrader: (3)

ok i will say again as its seems relavent now
my pettit s.c renesis over 300 to the wheels get 25 mpg after i installed the 09 trans. before it was about 22
my rpms at 70 in 6th gear is approx 3200-3300 .
gearing works.
OD

Vlaze

iTrader: (14)

And yet does the math work for the cost & time to do such a conversion contrast to just paying a little more for 2-3 gallons less?

Just inquiring, since I had no idea the cost involved for one to do such a thing nor time.

T-von

In my post I said well over 3k.


Your right about the older engines making less torque and using less fuel however, tuning plays a roll as well. I forgot to mention that I actually modified my primary and secondary ports in my 91 vert to have a slightly later opening timing to reduce the factory overlap. I think I'm the 1st to ever do something like this. I'm still with the factory ecu so now my idle fluctuates a little. My hope with doing the mod was to increase the air velocity in the low range and improve torque. It did! Cruising on the highway, I could easily tell the difference in how much less throttle I have to push to get the vehicle to accelerate and hold a steady rpm. I did this back in 2006 and have since put 30k on that engine. B4 doing the mod I was experiencing highway mpg around 22-23. So from my experience, increasing my torque gave me better mileage. I'm also still with the factory exhaust system.

velociti

iTrader: (1)

if they can make a N/A 255-265hp motor with better gas mileage in a lighter car, i'll be ecstatic. the question is how much it will cost, and i'd bet that since it wouldn't compete with other cars in its category short of the ft-86, the car's price will be about the same going forward (they just wouldn't sell at or below invoice). i can dream, can't i?

paulmasoner

iTrader: (1)

all this talk about mpg... i just made similar comments in another thread....

thanks to my local, i spend nearly ALL of my hwy time cruising 6th gear @~6,000rpms. and i dog it pretty hard in non-hwy driving. i still manage 18-19mpg. cruising US hwy speeds i get mid 20's no problem...

sure i've been able to achieve the 13mpg craptasticness as well, but only in totally stock form and absolutely thrashing it through an entire tank.

AngryBumblebee

Gas mileage doesn't bother me as much as having a small tank. A 20 gallon tank would have been nice, I thought the FD's came with a 20 gallon tank?... I accepted the gas mileage when I bought the car. I would just like to be able to drive 300 miles on a tank of gas highway driving. Most I have ever hit was 240ish. Does mileage get better with more miles on the car? I just hit 18k...

77mjd

I was willing to accept the gas mileage when I bought the car too...but then again, my first fill up in '04 was @ $1.54/gal. I'm finding it very hard to accept it nowadays.

Spin9k

Gee..angry about having to stop for gas ...what every 4 hrs or 5 hrs on a trip...when do you pee anyway lol? Such silly bitching about nothing. And 77mjd, please sell the car quick .. that's so old... do you realize just how many peps have come on this board over the years, having bought the wrong car...the RX-8 that is... strike that...don't hav eneough disposable cash to own the RX-8...and bitch about the mileage AFTER buying the car... so lame...just get the economy car you know you actually should have got in the first place.

end rant.

BTW, on a trip at highway speeds I routinely get 280-320 miles per tank, wonder what's the problem with your car angry...auto?..drive in 4th gear? ..need a tuneup???

RIWWP

iTrader: (2)

I consistently get 280+ on a tank all highway on a trip.

I am a firm believer that mileage is a great health meter of your car, assuming you aren't a terrible driver. Almost all of them are wasting power where it isn't needed, instead of putting it to the pavement, meaning you have to put your foot down farther for the same effective load.

If your mileage is dropping you have something wrong with AT LEAST one of these:
- Engine compression (wasted power)
- O2 sensor (wrong A/F being used, generally too rich when MPG is affected)
- MAF sensor (unstable A/F being used)
- Air filter (restricted airflow)
- Transmission Fluid (excess drivetrain loss)
- Rear Diff fluid (excess drivetrain loss)
- Plugs (misfires or weak fires, incomplete burn)
- Plug wires (misfires, incomplete burn)
- Coils (misfires, incomplete burn)
- e-shaft sensor (mis-timed ignitions, incomplete burn)
- Catalytic converter (restricted exhaust flow and choked combustion)

And often one issue will lead to another in the list...

Old Rotor

I have a stock 04' A/T (K&N) and these are the MPG I got at different speeds.
At 55-60mph I got 29.5mpg
60-65mph I got 27.5mpg
65-70mph I got 24.5mpg
These were all done with more then half a tank of gas. Its very hard to stay in the slow lane for 200+ miles with the big trucks at just over 2000rpm on your tach. It takes patience too do this twice to verify your results, but I was curious what this my seventh Rotary would do at best. At 3000 RPM my speedo says 73mph, but I believe its really approx 70mph. Normal driving city 16-18mpg hwy 20-23mpg, it all depends on my right foot. My first rotary RX-2(in 71) got 12-city 20-hwy with half the HP.

@!!narotordo

What oil weight will Mazda say to use now? oh and where can I read this 16x patent?

HiFlite999

iTrader: (2)

Nice article! It might be heresy to say here, but I'm most interested in the diesel Mazda2 development. At the very least, making that a success would take some pressure off the rest of the product line (RX) by increasing their CAFE mileage enough to allow a few supercars (RX7/8) with less-than-stellar fuel economy numbers.

CyberPitz

To follow with the MPG talk, I got around 28 MPG going 60 MPH in 6th gear when driving around the Nebraska roads *60 mph speed limit ftl...*

Great article and a good read. I can't wait to see some of these points come into fruition.

rotorbound

i cant help but worry that the 16x will have problems, possibly more than what we have now, its practically a NEW engine, without having the engine out for awhile for the customer base to test. o well, i guess you have to expect that with any new engine that came out.

rotarygod

From what I've in the 16X pictures, they've fixed many issues. The fact that it's new seems like a good thing to me. it means they are just doing what they've always done. They are going back and are addressing issues that haven't been addressed before and fixing issues that were problems. They are also doing this while making things better. That's a good thing. Each engine gets better than the last. However they still always seem to do at least one thing bad. The oil metering on the S1 RX-8 is a prime example.

The last n/a rotary, the one in my '90 RX-7, had much worse emissions, much lower power (160 hp), and much worse fuel economy (22 mpg hwy with a 300 lb lighter car running at lower rpms). The Renesis was definitely progress and a huge improvement. The 16X will be too. The low power 4 port Renesis is easily a strong rival to my engine in terms of power and it is still cleaner and more fuel efficient.

redcopper06

i'm betting that some of the new lightweight components are made from this...

http://www.reade.com/Products/Alloys...loy_al_be.html

stronger than aluminum and better heat transfer properties as well

HiFlite999

iTrader: (2)

The 13b in my 1978 RX-4 was pulling all of 110 hp, but it did get ~25 mpg. Mazda made a big mistake in not going to a catalytic converter right away and stuck with a big air pump and EGR. The Renny is a fabulous engine by comparison, but in pulling 230 hp, it's really pushing limits of what one can expect from a street engine where longevity and reliability are important. I'd much rather see the 16x pull 250 hp and get a solid 28 mpg, than get 300 hp with the mileage and other issues we see now.