BLUE TII

iTrader: (9)

Direct injection, the new lean burn cat and improved ve with the new p-port intake renisis might get a 3/4 rotor (depending on rotor displacement) to squeek under the gas guzzler tax.

The work Mazda has done creating their dynamic stability control (RX-8) and traction control (Mazdaspeed 3) means Mazda could trust the public with a sporty chassis with some power withou spoiling Mazda's reputation of great handling cars.

I am not hopefull, but it is possible.

I will be happy if they keep the new RX from being a bloated pig version of the new MX-5!

fmzambon

Just for the record, I'm a male Here in Italy "Andrea" is a male name, even though most names ending with "a" are feminine names. But I was kind of expecting this misunderstanding sooner or later, so don't worry.

Back to the rotary, assuming that, as I said before, a 2 tier lineup is in the works, then I think that an NA 2 and NA 3 rotor (based on the same chamber design and size) is more likely than an NA 2 rotor and a turbo 2 rotor.

I already said this before, but by building a 3 rotor using many of the parts already designed for the NA 2 rotor, Mazda can have two power levels with both powerplants being highly optimized and spending only slightly more than they'd spend to develop the NA 2 rotor alone. They can reuse the rotors, seals, gears, housings and irons of the NA 2 rotor for the 3 rotor, requiring only a few additional specifica parts (the e-shaft, the thick center plate and specific intake and exhausts, as far as the main components are concerned).

Given that it's not possible for them to develop two completely different engines, with an NA and turbo lineup one of the engines would most likely be a compromise: either Mazda develops and optimizes the turbo engine and then also releases a turbo-less version of the same engine (and such an engine would be seriously unoptimized, being designed as a turbo engine in the beginning) or they do the opposite, risking serious reliability problems for the turbo engine (we know how difficult it is to add a turbo to a high compression NA engine).
In any case they'd need to spend more in R&D to develop an NA and turbo 2 rotor lineup, and there would be less parts commonality, so higher industrial costs, especially for the turbo engine.

In addition to that, when everyone else is going turbo, having a high performance NA engine could also be a sales point.

Andrea.

j9fd3s

iTrader: (3)

i haven't heard that as part of the rumors, which have actually been consistent for a few years now. although, they are on an island quite far from here and speak japanese, so they can keep whatever they want secret.

i do agree with this, turbo 2 rotor sounds really unlikely, especially after what happened with the FD, and the Cx7's.... the Cx7 is nice to work on, the engine disassembles itself, so it saves a bunch of work, how they put the same thing into the MS3 and 6, and its completely reliable, i don't understand.

having owned a 3 rotor though, i can tell you this is also an unlikely event. more heat issues, less mileage, higher emissions...

Montego

iTrader: (1)

Just messing with you dude

fmzambon

That doesn't come from a rumor, it's straight logic reasoning from my part. Mazda is a small company, so they can't afford to release a product where they know they'll lose a lot of money for each unit sold. They have to keep their losses under control, and preferably avoid losses at all. And the way of doing this with a rotary powered car is to have a highish volume rotary car in their lineup. That means they need a lower power model, possibly around the 250hp mark, as there's not much competition from other Japanese manufacturers in that power range.

At the same time, all of the other major japanese manufacturers are scrambling to release new high power sports cars, and I don't think Mazda wants to be left behind. It wouldn't be good from a marketing perspective to be the only one of the manufacturers that partecipated in the '90s sports car craze that doesn't come out with a proper sports car in the late 2010s. So they also need a higher power version of the car to cover that niche.

In addition to that, in the rumors that floated around in january (if I'm not mistaken), there was a mention of a switch to 600cc rotors and it was also mentioned that Mazda was still undecided whether the engine was to be 2 or 3 rotors. Obviously there is a high chance of such a source being unreliable (or the news being straight out fake), but if there is something true about that, I take it to mean that they are deciding whether to build a 3 rotor IN ADDITION TO the 2 rotor, not just one of them. The smaller displacement per rotor could be a marketing choice to better position the car: 250hp for the smaller 2 rotor, and 350+ for the 3 rotor.

As far as emissions and economy, the previous rotaries were all constrained to use the original 13b geometries, which were in turn largely based on the 12a, in turn based on the 10a, which was developed in the mid 60s.
If you were forced to take a piston engine designed in the '60s and only change its cylinder head(s), before adding stuff around the engine, how good or bad do you thing it would fare compared to modern engines?
That was a major roadblock to previous rotaries, being forced to reuse older design choices to a large degree. Having the freedom to create something competely new is going to dramatically improve the rotary's weak points. Mazda already mentioned that the 16x prototype was slightly more efficient than the old non-SKY 2.0 piston engine (link). And that is 3.5 years old news now, there must have been significant further improvements in the meantime. I wouldn't be surprised to see a 30mpg real world combined 250hp 2 rotors rotary.
And if fuel consumtion improved that much, I don't think that emissions are much farther behind. When the 2 rotor is clean enough, making the 3 rotor pass emission testing is going to be as simple as using a catalyst with more precious metals, which would be easily covered by the higher price point of the car. Done.

Whoa, that was a long write

Andrea.

BLUE TII

iTrader: (9)

A top Mazda powertrain executive said today that the 1.6-liter rotary engine, called the 16X, is about 30 percent more fuel-efficient than the current rotary engine used in the RX-8 sporty car.

In fact, the 16X so far performs slightly better than Mazda's standard two-liter gasoline engine, said Mitsuo Hitomi, general manager of the Japanese carmaker's powertrain division.

Okay, I have a 2008 base Mazda 3 with the non skyactive 2.0l.

This is either an exaggeration, a lie or the 16X is bad *** and they were only working out side seal reliability issues on it and that's why it wasn't released yet.


I have 60k miles on my 2.0 and with a 7 mile commute and 1 mile drive to lunch every day it has never had a tank averaged under 30mpg.

On road trips I have gotten as high as 40mpg average.

A couple months of adding a 20 mile trip twice a week in addition to my usual short commute had it averaging 35mpg.

These aren't rotary mpg figures!

fmzambon

You can always replace the DI system on the new rotary with a carb and get back the rotary-esque mpg figures if you aren't satisfied

Seriously, Mazda has repeatedly hinted at a 50% fuel efficiency increase target for the new rotary (and I assume it is in reference to the Renesis), so 30mpg or more shouldn't be out of the question.

By the way, in that article it says "Maybe within two years we can tell you when we will introduce it to the market". Guess what happened almost exactly 2 years later? this!

Andrea.

j9fd3s

iTrader: (3)

key word being target... and keep in mind a fuel efficiency % is not mpg. for example Mazda claims a 24% increase in fuel efficiency between the 1980 and 1981 Rx7 models, but the EPA mileage was only better by 1 mpg, and in the real world the 79-80 is actually better.

with the Rx8 they don't give an efficiency number, lots of graphs, and again, real world testing shows that the Rx8 gets worse mileage than the 79-80 Rx7....

my 79 would consistently get 23-25mpg. the Rx8 only gets 19.9, although its more consistent than say the FD, which would do 23+ on the freeway, but step on the gas and its 16-18.

the 3 rotor was even worse, highway it got 19, which is fine, but mix in some city driving, and it was 15-16, and if you stepped on the gas you're looking at single digits.

j9fd3s

iTrader: (3)

i agree here, the 10A was even based on the NSU engines, so the geometry is early 60's and they had different priorities then...

the silver lining of course, is that the 13B hasn't benefited from the CAD, or material improvements that every other engine has in the last ~20 years. so there is a huge scope for improvements.

in fact the 2014 SAE paper is about the oil seals, which were studied last in the early 60's...

fmzambon

I agree that fuel efficiency and mpg are different, but that's due to the anvironment that the engine operates into. If you put a Renesis into a '79 Rx-7, you'd most likely see a massive mpg improvement. And that's even before mentioning that the Renesis has twice as much power as that 7, and is much cleaner too.

If the new 4th gen Rx-7 is smaller and lighter than the Rx-8 (which it will most likely be), then almost all of the fuel efficiency improvement should turn into real mpg improvement.

And finally, it's true that the 50% figure is a target, but if the 16x was already more efficent than the piston 2.0 non Sky back in 2010, then that 50% figure should be within reach for the small Sky-R.

Obviously a 3 rotor would burn more, but being fuel efficient is not the point of that motor

Andrea.

moritsune

iTrader: (3)

Has anyone presented the argument of a centrifugal style supercharger instead of a turbo? Minimal parasitic loss, no spool lag and boost. Alot of rx8 guys have used these systems for decent gains, limitations mostly being the exhaust restriction from the ports in the irons. IF 2017 they really release i need to finish the fd and start saving lol

BLUE TII

iTrader: (9)

Well, on the 13B, 12A, 10A engines all based on the same "short stroke" K-factor EVERYONES gripe is low rpm power and a centrifugal supercharger won't do anything for that.

In addition to that the rotary suffers from its two main bearing design. When you add the stresses of driving a supercharger the front bearing takes a dump pretty fast.

The "stroked" 16x will have more low end power from the K factor.

If they use the peripheral intake/side exhaust like the generator it will have more low end (and top end power) than the renesis due to overlap/superior VE.

j9fd3s

iTrader: (3)

its more like a when... and you're 100% correct on the other two points as well.

back in the 90's we had a customer who had an Rx2 (apparently one of the first in the area), and he was wondering why there were so many FD's in the shop, and we sort of stumbled upon the metric that the FD had 3x the power, better fuel economy, but the same reliability as the Rx2....

when i did my 1st gen P port, my second option was a renesis. the Rx8 engine would have been about the same power, passed smog, and tolerated mufflers. however in 2005, it was also really expensive

t-von

iTrader: (8)

I feel the 3 rotor can do better than this if certain aspects of the set-up is engineered for efficiency. The biggest problem to start is that pretty much every 3 rotor swap is still using the same gearing from the original drivetrain. That means the larger more power engine is spinning at a higher than necessary rpm while cruising on the highway. When you have more torque, you don't need higher rpms to maintain speed. No large displacement engine is gonna sip fuel when it's spinning near 3k on highway no matter how lean you tune it.

j9fd3s

iTrader: (3)

i think so, plus the 20B has all that additional low RPM power...

my friend put a 20B with stock ecu into a B2600 pickup, and the truck trans had the engine spinning at like 3400rpm, which puts the thing out of closed loop = 9mpg freeway.... that truck is the funniest thing ever.

its such a big sleeper you can take it to sevenstock, and pop the hood, and nobody notices.

fmzambon

I tried to find the fuel consumption data for the 20b powered Cosmo and compare it to the 13b version.

According to Automobile-Catalog the complete Catalog of Cars, car specs database, the 20b model has a combined fuel consumption of 12.5mpg, while the 13b gets 16mpg (this is for the 1990 model year).

It seems like adding another rotor cut the fuel economy by 22%. If that is the cost of having 50% more power and torque*, I can live with that

* I know that the 20b REW, in stock form, isn't 50% more powerful or torquey than a 13b REW, what I'm referring to is the performance potential of the additional displacement. Mazda wasn't allowed back then to pass the 280hp limit, so they couldn't use all of that displacement. But that additional displacement was still there when it came to fuel consumption.

Andrea.

j9fd3s

iTrader: (3)

the 20B also has much more low RPM power, and its even smoother, so there are some advantages.

oh and it sounds better. the 20B swap was worth it just for the noise.

jacobcartmill

iTrader: (6)

this thread is still open?

Bwarrrrrp

You're having a lend, yeh?

Fritz Flynn

iTrader: (263)

This thread will be open as long as there is any hope of another RX7

t-von

iTrader: (8)

Don't follow you?

j9fd3s

iTrader: (3)

be nice if they could just put a cat in this and sell it.... you can see the fenders, looks easy to park

Mazderati

iTrader: (3)

The four rotor really does sound amazing.

RCCAZ 1

iTrader: (10)

Guys, it really comes down to simple math for Mazda...

2017-1967 = 50, as in 50th Anniversary of Mazda's Rotary Car Production program. The chance of Mazda letting that milestone pass without some kind of public offering is remote.

arutha

iTrader: (2)

A 4 rotor might make me get a divorce and move back in with my parents...