zoom44

no it doesnt :p everytime mazda has "re-invented" the rotary they have done so by enlarging/widening the rotors- 10a to 12a to13b. moving to a new larger 15b or 16b seems more logical

Nemesis8

iTrader: (3)

I wish I was a fly on a wall sometimes...

Renesis 247 / 2 = 123.5
New Engine 270 / 2 = 135

That's only a 9% gain in HP, right? Why would the displacement need to be 1.5L? Just fixing the exhaust ports might work better. Maybe it will have a wider intermediate housing with separate ports rather than the siamesed port??

Back to work

Xyntax

^ One of the reasons why they keep pushing for a 2-rotor engine is "Pride." The most common bragging points from Mazda has been the number of moving parts in a rotary engine. They say the rotary (virtually) moves 3 parts only: 2 rotors and the eccentric shaft. I guess they think people would be more amazed at a high power engine with 3 moving parts versus 4 or 10 :D

ok, im going back to work...

RX-Hachi

The Wheels article never stated 270 hp. It said "more than 200 KW".

So that means greater than ~270 hp (assuming that others did the KW to HP conversion correctly). My guess would be at least in the 290-300 hp range to make it worthwhile.

rotarygod

Where are you going to find the increased port area to feed this larger engine? It's not there. If you want a lower redline with no more potential intake and exhaust breathing ability over the current engine then it could be fine.

Xyntax

^ RG, this might be off-topic but I'll ask you while the thought is still in my head. Can a 2-rotor engine idle at one rotor? Has anyone experimented on that before? Maybe idle at one rotor or cruise on highway speeds at one rotor?

Aoshi Shinomori

I think RG tried this a while back with his RX7. If I remember correctly, it ran very rough and he said it felt not so good over 50mph. I was researching last night to no avail about going to a one rotor setup as it came up in a different thread. Please enlighten us RG :D

tuj

I'm not RG, but a 13B can idle with zero compression on one rotor. Not very well mind you. A miata can also run about 100 miles on 2 cylinders before the coil-pack blows. Don't ask how I know either.....

I believe Susuki made a 1-rotor motorcycle, and there was some Euro saloon maker that made a 1-rotor car.

The way to save gas while crusing on the highway would be to make the ECU cut fuel and spark to one rotor every so many revolutions, and alternate rotors (and faces, that's important) that it cuts on.

RX-Hachi

I'm no engineer, but where there's a will there's a way.

I did read an article where Noboru Katabuchi, RX-8 Program head, stated he would favor a larger displacement NA 2 rotor Renesis (like a 1.5 or 1.6) over an FI solution for use in the next gen RX-7 (if its ever made). Mazda engineers must know something you don't, even if you are a GOD.

zoom44

exactly^:D and displacement on demand is not on the table at all. do a search for our past threads on it.

Xyntax

^ Maybe it's because the running rotor would be carrying a dead rotor. Perhaps a splittable e-shaft would help? An eshaft that lets go of the front rotor when it's not running to free up the load on the running rotor. Just my wild imagination here...

:D

rotary crazy

^^ best way^^

rotary crazy

keep in mind that the last time mazda made the rotors wider the power jump was 12 hp, so dont think that just by making the engine a 14l or even a 15l your going to get 50hp.

I think the renesis 13b has 30 more hp in future development but time will tell.

personally I like more rotors

tuj

It doesn't matter. If you can utilize the airflow that the Renesis flows at 9k at a lower rpm, you have increased torque substantially. A lower redline is not a bad thing in terms of performance, especially if the trade-off for a lower redline is more torque. Imagine taking out dyno graph and changing the scale to only go up to 7.6k. That'd bump torque up to about 164 ft.lbs.

rotarygod

Believe me I'll be a happy camper if a 1.5L 2 rotor ever does come out. I would much rather see a 1.5L 3 rotor as it will be smoother and airflow issues are so much of a, well issue. IT would just be so much nicer to say we had a 3 rotor! Flame front issues due to a larger combustion chamber size also concern me. Mazda has had a 15A and 21A prototype in the past. Output of the 15A was at around 180hp. Not bad for it's day. The exhaust port was noticably larger on that motor than the standard 13B. There was a bit more to it than just making the chamber size larger as the Renesis can obviously eclipse the 15A power. There are really too many differences to compare that which was tried in the past and that which works now. If Mazda ever gives us an upgrade, I'll gladly take it whatever it is. Here's a question though, why don't we have 5+ liter 4 cylinder engines running around in street cars? Why is it always more cylinders which complicate things and make things more expensive. Why not all 4 cylinder cars with larger or smaller displacement? How come the nicest 10-12 cylinder engines on the planet use multiple really small cylinders rather than fewer large ones? Why did we have a 20B when we could have just had a larger 2 liter 2 rotor instead? I don't think complexity is the issue.

I have had a 13B run on only 1 rotor. It can idle at 750. It doesn't need to be at 2000 rpm. It is very rough though. The car shakes really bad. Cruising around on one rotor is even more fun. You nearly have to floor it to hold a steady speed and after about 50 mph or so it just didn't go any faster. Admittedly there were other things that I could have tried that may or may not have worked but I got far enough to know that it was going to be difficult to make anything work decently and then actually find a benefit in it.

zoom44

flame front issues are taken care of by things like direct injection- as we see on current concepts.

rotarygod

They've been playing with direct injection in rotaries for 20 years now.

NomisR

and no result?

brillo

If they have worked out a DI system that is capable of meeting emissions requirements, then the rotary may very well approach pistons in terms of fuel efficency.

DI has historically had two main issues, first it cools the exhaust gases off and therefore the Cat doesn't work as well, and section, ultra lean burning engines emit alot of NOx, which the Cat can't scrub. I'm guessing they found away around this, which is great.

currently the FSI engines Audi uses are DI, but not lean burning like they are in Europe due to the NOx issue

Japan8

Are multiple injectors per rotor necessary with direct injection? Speaking of which, using direct injection couldn't the combustion efficiency be further improved (obviously, but I mean in terms of the rotary flame propagation issue)?

Well if Mazda is really going to push the hydrogen rotary engine (HRE) and HRE Hybrid... then more flexibility in production will be needed. No company just uses one or two engines across all of their line of cars.

Japan8

Why not a 3.5L I-4? How many 2.3L I-4 were there 10-20 years ago? Even still now the majority are 2.0L. I remember being amazed at the engine in the Porsche 968.. 2990cc! You don't see anyone else making one of those, eh?

Why not a V4 like in the Honda VFR/RVF line of motorbikes? You've got me. I love the sound of those V4 and V5 (racing) motors. I suppose the bean counters say it's not worth the money... any packaging improvements being offset by increased complexity and cost (more camshafts).

As far as Japanese automanufacturers go... in the JDM, going bigger than 2.0L has a major drawback... increased yearly car taxes and taxes paid at inspection time. It's divided by engine displacement and weight. And yep... 2.0L and below is one class... 39,400 yen a yen tax. 660cc and below is another... 4,000 yen a year. I would suspect that this has had a significant effect upon engine choices in the JDM... thus turbo I-4 > V8.

BaronVonBigmeat

A couple of questions:

When we're talking about flame front issues, it's basically a question of "how fast does the flame spread throughout the rotor or piston"...err, right? So engines with big pistons or rotors are at a disadvantage, because they get to bottom dead center, and the flame front has not reached all the fuel/air mixture, and you're spitting out unburned or poorly burned fuel. Which is bad for efficiency, and bad for emissions. Thus we don't see 6 liter 4-cylinders, and we see engines with elongated combustion chambers (rotaries) have poor efficiency. It's also why GM doesn't use big blocks in new vehicles anymore. Or did I miss something?

So an even bigger displacement 2-rotor engine seems unlikely, I would think. Maybe a 1.5L 3-rotor though?

Another thing--how does the flame front from hydrogen combustion, or natural gas combustion compare to gasoline? Faster or slower?

Japan8

Hydrogen and natural gas aren't picked for burning efficiency. It's emissions. Gasoline has a significantly higher content than H or CNG. High school chemistry... gasoline is more complex with more high energy bonds thus producing more energy.

Flame front. I really don't know. Depend on how volitile the fuel is I suppose...

tuj

This is not entirely true. There have been some very large displacement / cylinder engines made. The biggest is a turbo-diesel with a cylinder capacity of 1820 liters! This engine is over 50% thermally efficient, which is much more than most car engines. So there is nothing fundamentally wrong with the idea.

rotarygod

How fast does it spin and what car is it in?

The largest rotary ever made was around 6 feet tall. It was a 1 rotor that made about 700 hp at around 700 rpm. The point isn't that it can't be done. How large does each piston/rotor have to be before it isn't a good option in a car? Remember not only power but also gas mileage and emissions also come into play. Don't forget about engine response either.