Mazda Design Breakthrough Pushes RX Development Schedule Up

[OrbitalEllipses]

Originally Posted by blur

I hope mazda comes out with a high mpg 240hp 2+2 coupe that looks like the rx7...

and nissan debuts the s16 naturally aspirated inline 4 producing 240hp as well...

both coming in at 2900 lbs ish wet

Keep dreaming.

[glorydays]

I just hope they solve the flooding issues...

[serialk11r]

Originally Posted by OrbitalEllipses

Keep dreaming.

Well it's not actually that hard to do, but the market is kinda iffy imo. If he meant rotary, then probably not, you'll probably see rotaries restricted to high power applications for the reason I just described.

As for Nissan, 240hp NA isn't that hard to hit but Nissan hasn't built a potent low displacement engine I think. If it's cheap, it won't be V6. Tuned VQ25 could probably hit 240hp, dunno.

[tranzformer]

Originally Posted by OrbitalEllipses

Keep dreaming.

Isn't that the whole point of this whole tread?

[merlin2111]

I like the sound of this.

[Dimman]

Originally Posted by serialk11r

mmm 1.6L is quite a bit of displacement (3.2L equivalent), if they can hit 20/27 EPA that would be pretty phenomenal IMO. If they can get BSFC to within 10% of traditional piston engines they could squeeze those numbers out.

With a 1.6L engine with significant combustion efficiency improvements you'd be (hopefully) looking at well over 300hp though, since those rotaries rev so high. 100hp/L happens at about 7500rpm redline or so (power peak somewhere in the low 7000s such as on the FA20), 9000rpm gives you over 120hp/L on a well designed street legal engine (such as the S2000, which hits max power in the mid 8000s). 9000rpm with a 1.6L rotary with comparable efficiency to a piston engine would be like 3.2*120=380hp at a bit over 8k rpm :O. The Renesis managed like 230 out of 2.6L effective displacement with a really high redline, so its BSFC at peak power was probably about 25% higher (assuming comparable volumetric efficiency to the F20C). A lot of the fuel consumption is attributed to poor combustion, and so if they can fix the fuel consumption they should be able to increase the power output.

One of their big hurdles is they can't mess with their intake and exhaust events, since they are fixed ports rather than phaseable cams. They have their work cut out for them...

[Zaku]

What is the world avg. Mpg standards for about 2014 to 2016 cause i highly doubt 27 avg would pass @@ i might be wrong though

[OrbitalEllipses]

Originally Posted by Zaku

What is the world avg. Mpg standards for about 2014 to 2016 cause i highly doubt 27 avg would pass @@ i might be wrong though

Don't know world average, don't think there is one. There's CAFE here and I'm not sure if Euro 5/6 regulations are emissions and mileage, or just emissions.

[serialk11r]

Originally Posted by Dimman

One of their big hurdles is they can't mess with their intake and exhaust events, since they are fixed ports rather than phaseable cams. They have their work cut out for them...

That's true, although I think that matters more for improving torque at different points in the rpm range than emissions and whatever. Set up the ports for very little overlap, set up intake for high rpm power, low rpm VE goes down and fuel economy goes up. Of course, this is given that they can figure out the rest of the problems first.

Now the little overlap is bad for power, but one of those electric turbo systems could nicely take care of the problem and give efficiency improvements, albeit at higher cost. But we're talking >400hp anyways :P

[Dimman]

Originally Posted by serialk11r

That's true, although I think that matters more for improving torque at different points in the rpm range than emissions and whatever. Set up the ports for very little overlap, set up intake for high rpm power, low rpm VE goes down and fuel economy goes up. Of course, this is given that they can figure out the rest of the problems first.

Now the little overlap is bad for power, but one of those electric turbo systems could nicely take care of the problem and give efficiency improvements, albeit at higher cost. But we're talking >400hp anyways :P

They've mentioned the rotary in the context of the generator engine in a Volt-type hybrid in the past as well. This may be more realistic.

They are un-nervingly smooth, and can probably be tuned to be very efficient at a narrow rpm, and just spin there until the battery's charged.

[serialk11r]

Originally Posted by Dimman

They've mentioned the rotary in the context of the generator engine in a Volt-type hybrid in the past as well. This may be more realistic.

They are un-nervingly smooth, and can probably be tuned to be very efficient at a narrow rpm, and just spin there until the battery's charged.

As an electric power generation unit peak efficiency would be most important as you know. The challenge I see here is that the surface area to volume ratio on these things suck, so they reach peak efficiency at 5000rpm or something whereas piston engines of comparable displacement reach peak efficiency usually no higher than 3000rpm. I imagine 5000rpm is a bit noisy. If they can redesign the seals as described in the article, friction could be much less of a problem compared to piston engines though, and it would be promising.

Oh right, does anyone have any idea how the friction of a rotary compares to a piston engine? Rotaries have inherently less friction in the design, but I remember reading that because of sealing considerations they have more? friction.

[Dimman]

Originally Posted by serialk11r

As an electric power generation unit peak efficiency would be most important as you know. The challenge I see here is that the surface area to volume ratio on these things suck, so they reach peak efficiency at 5000rpm or something whereas piston engines of comparable displacement reach peak efficiency usually no higher than 3000rpm. I imagine 5000rpm is a bit noisy. If they can redesign the seals as described in the article, friction could be much less of a problem compared to piston engines though, and it would be promising.

Oh right, does anyone have any idea how the friction of a rotary compares to a piston engine? Rotaries have inherently less friction in the design, but I remember reading that because of sealing considerations they have more? friction.

You really need to be in one to get the experience. They are spooky quiet/smooth. They don't feel like normal cars (personally I don't like them at all).

5k with a good muffler would probably be fine.

[old greg]

Originally Posted by Dimman

5k with a good muffler would probably be fine.

Not to mention that if you're only going to run it at a single RPM, you can tune the engine mounts and muffler/resonator specifically for the frequencies produced at that particular rpm.

A rotary would package really well with a YASA-style generator mounted directly to the eccentric shaft and end plate. I want to do it myself, just to bask in the awesomeness.

[NastyNate]

Give me rx7 styling and go with piston ease of maintence and Im in. Othan a turbo'd e46 m3 an rx7 is one of the few cars I would ditch my miata for. And even then it would be a very tough call

[Dimman]

Picked up a book on 2-stroke tuning to see how much more advanced they were in their exhaust tuning. Then I realized they are practically at full overlap for their whole events. D'oh. Is interesting to see how much of a change pulse tuning can make on them, though.

Buuuuut... I found out that some use a power valve that basically alters the height or shape of their ports. Since a rotary is essentially a 2-stroke except with a fairy-pushed couple of triangles rather than natural and godly pistons, I figured why don't they use something like this, too?

If they used one on either side (or top/bottom, whatever...) of their ports they could effectively change their advance and retard like cam phasers, AND have control over duration. However this looks more likely to apply to a peripheral port setup, and the Renesis is side ported (? in the end-piece separating parts, not the barrels) for emissions, I believe?

But if it was an overlap thing for emissions, and if they can control it they can go back to the more flow-friendly peripheral porting maybe? But maybe peripheral porting is worse for apex sealing?

Any reason this isn't used? Or maybe it has been used in the past? Reliability and complexity are the first strikes against it, off the top of my head...

[old greg]

Originally Posted by Dimman

Reliability and complexity are the first strikes against it, off the top of my head...

As opposed to laser spark plugs?

Actually, I would think it would be harder to do properly with a peripheral port because of the curved surface and the water jacket. Interestingly though, I've heard that N/A rotaries respond quite well to headers with expansion chambers.

[Dimman]

Originally Posted by old greg

As opposed to laser spark plugs?

Actually, I would think it would be harder to do properly with a peripheral port because of the curved surface and the water jacket. Interestingly though, I've heard that N/A rotaries respond quite well to headers with expansion chambers.

The expansion chamber doesn't surprise me a bit. At the drag strip there was a ported to the nuts 12A car and it had the typical 2-stroke ping-ping exhaust sound.

One of my old co-workers was a rotary eccentric (see what I did there?). He would spout off all about how awesome they were all the time. Yet in the 3 years I worked with him he went through 5 FB's 12A and 13Bs and blew up an FD. I've handled more rotary guts helping him rebuild them than is probably healthy.

Him: "There's nothing wrong with them once you dowel pin the barrels, replace the apex seals, ditch the emissions equipment, add oil to your gas, and rebuild them every 60,000km because there is no indication from the apex seals about when they will die and seize your motor..."

Me: "Uh, right. What killed this one?"

Him: "I won't know until I take it apart."


I still envy their packaging, though...

[Tbomb 25]

Originally Posted by merlin2111

I like the sound of this.

Me 2....i grew up in a rotary...but i gotta say a lighter miata skyactive turbo has me drooling...