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"... One engineer, who wished to remain anonymous, confirmed what we've recently outlined: that Mazda is in the process of developing its next generation rotary-powered RX-7. The automaker reportedly has two rotary engine prototypes at present, a gasoline version and a diesel version. The diesel sounds rare, right? Curtiss-Wright built a direct-injection rotary diesel in the early 1970s, but it wasn't a true diesel as it used spark ignition and had a low compression ratio. Rolls-Royce also dabbled briefly with diesel rotary using two different sized rotors.
Mazda hopes to change all that and create a diesel rotary that generates strong low to mid-range torque, while improving on the current RX-8's fuel economy. But our source said not to expect the new sports car -- which will be significantly lighter than the previous RX-7 -- to appear in showrooms until 2013 at the earliest."
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Thanks, Robrecht!
"When all is said and done, it's possible that Mazda will find a few more ponies in there than they've been alluding to. I would imagine that after the faux-pas over horsepower with the 2001 NB8B Miata, Mazda is being conservative on power output announcements." - bwob, 2/2/02
Diesel engines can rev up to 6000 rpm now in piston engines. Due to the way a rotary works, I'd suspect you could go higher on one of them. It doesn't mean you are making more power there though. Since diesel fuel is a lubricant, and even ULSD has far more lubricating properties than gasoline, the engine may no longer need oil metering. Maybe. That would be a good thing. The added displacement and stroke of a 16X combined with lowered pumping losses due to no throttlebody would make low end power quite nice. I can't think of a diesel today that doesn't have a turbo on it which would only increase efficiency more.
If a 16X could get around 190-200 ft lbs of torque in gasoline mode. As a turbo diesel variant, 250-260 ft lbs or more could be easily possible. Power would probably top out around 200 -210 or so though but in the right car that wide powerband could be quite nice. If it didn't need oil metering and hence no maintenance other than oil changes, it could really become an everyday engine. True it wouldn't have the driving characteristics that we know of in a rotary but it could be what it needed to keep the engine alive and I'm all for that. Especially if it could get mid 30's to 40 mpg on the highway.
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"None of us on our own is as dumb as all of us combined."
"I do have a strong yearning to revive the RX-7 during my tenure," Maeda said. "But in order for that to happen, we need the U.S. economy to come back, first and foremost."
basically the car is barely finished IMHO (or at 80% of the work)....maybe they are really waiting for a US Market recovery.
BTW i still bet a pint there will be BOTH rx-7 AND a bigger rx-9.
a lot of rumors o hybrid rotary, hydrogen and now DIESEL.....
though i wonder how they will solve the primary problem with diesel fuel, the amount of hydrocarbon particles vs NOx, and the flame traveling speed in diesel fuel.
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"I do have a strong yearning to revive the RX-7 during my tenure," Maeda said. "But in order for that to happen, we need the U.S. economy to come back, first and foremost."
basically the car is barely finished IMHO (or at 80% of the work)....maybe they are really waiting for a US Market recovery.
BTW i still bet a pint there will be BOTH rx-7 AND a bigger rx-9.
a lot of rumors o hybrid rotary, hydrogen and now DIESEL.....
Fantastic article. It gives a clearer view of RX7 possibilities (Still a bit faint but hopeful). It also shows how sportscar oriented Mazda's top people are.
Paul.
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"When all is said and done, it's possible that Mazda will find a few more ponies in there than they've been alluding to. I would imagine that after the faux-pas over horsepower with the 2001 NB8B Miata, Mazda is being conservative on power output announcements." - bwob, 2/2/02
i was hoping one of those pics on the desk would be a suprise leak. I see Mark Rechtin contributed- ill have to ask him if there were any other pics or sketches...
One thing I'm not clear about is how the diesel variant achieves greater torque if the engine is not supposed to auto combust like normal diesel engines.
I thought the high torque comes from high compression and auto combustion via compression.
This thing is mentioned to be spark ignited... so I take it to mean significantly lower compression and thus less torque? Possibly still more than the gasoline variant I guess.
There are 3 things that make a diesel more efficient and how combustion is achieved isn't one of them. The 3 things are reduced pumping losses from a lack of throttle, higher compression ratio, and a higher btu content from the fuel. Diesel fuel has more inherent energy potential.
The fact that it had to be spark ignited is an effect rather than a cause. They couldn't get a high enough compression ratio to reach auto ignition. A rotary not only compresses air but also flows it internally. If you raise compression too high, you aren't flowing it well and are incurring high pumping losses as a result. This doesn't happen in a piston engine as all you do is compress it. Air stays in basically one place. The current known limit for a rotary is about 11:1. A redesigned chamber shape may or may not be able to improve that.
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"None of us on our own is as dumb as all of us combined."
Soon a bio-diesel 8 The environmental sports car. Hydrogen cant work here due to the lack of supply. Bio diesel is everywhere. (Especially in the North East)
The reality about btu content of fuel is that we waste so much of that potential energy that the biggest gains are to be had fro getting the most out of what we have rather than using the highest energy content fuel. Diesel fuel actually has a low octane number so it could detonate pretty easily and would if injected in the intake manifold. However because of it's relatively slow flame speed and ignition properties, it's pretty easy to control which makes other things easier. When you get into fuels like hydrogen that are more volitile than gasoline, have a faster flame speed, and have a lower btu content, then you run into all sorts of issues that make it impractical. It's just too hard to control the flame travel which is the main reason why hydrogen is such a bad fuel and the opposite reason why diesel is such a good one. If you could gain so much efficiency from your engine that you didn't need a coolant system through conservation of heat (energy), you would have far more power for the fuel used which means you could use a lower energy content fuel and get the same performance or you could use the same fuel and gain performance. This is what the hydrogen proponents are putting all their hopes on. Personally I'd bet against that logic anyday. The only chance Hydrogen has to become a main fuel is through politics. Diesel however is here today. There is alot to an engine and no one characteristic has a large effect. It is all a balancing act.
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"None of us on our own is as dumb as all of us combined."
If only it made power like the Audi R10 or R15,yes I realise there 5.5 litre,but IF...
Or maybe some bright spark produced a 3 or 4 litre gas rotary. Flame suit on!!
The environmental sports car. Hydrogen cant work here due to the lack of supply. Bio diesel is everywhere. (Especially in the North East)
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