Why are Mazda persisting with the Rotary Wankel engine?

Why are Mazda persisting with the Rotary Wankel engine?

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Oi_Oi_Savaloy

Original Poster:

2,313 posts

259 months

Monday 18th April 2011
quotequote all
Can someone tell me why are Mazda persisting with developing the rotary wankel engine?

When I look at the horror stories associated with these engines in the RX8, then poor fuel consumption combined with the high vehicle tax these also attract - can't understand it to be honest.

Please tell me- am genuinely intrigued!

PaulB81

883 posts

159 months

Monday 18th April 2011
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I would assume they have found a way to address these issues. I think they will have learned a lot from the RX8 with the issues it has.

Edited by PaulB81 on Monday 18th April 14:56

Crow555

1,037 posts

193 months

Monday 18th April 2011
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More to the point, will the EU bullcrap allow another car of its type to be sold here?

The Wookie

13,909 posts

227 months

Monday 18th April 2011
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Because it's extremely light and small for the amount of power it puts out, which is good for both handling and packaging.

Hence it being slightly illogical when someone says 'RX8's have great balance and handling along with superb packaging to get four proper seats in, but it would be even better if it didn't have that thirsty, unreliable Rotary engine'

If they could sort out its problems then it'd be the automotive holy grail, but seeing as that's probably not going to happen, it can still carve out it's own niche in terms of usefulness

Tsippy

15,077 posts

168 months

Monday 18th April 2011
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I had heard that the rotary engine is more suitable for alternative fuels (there's already a hydrogen version out there) and so perhaps that's what they're aiming for in the long run?

ludicrous speed

959 posts

193 months

Monday 18th April 2011
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It's a good idea, and it's nice that it is being kept alive but unless someone invents some magic material to make it out of, it will be massively inferior to a piston engine. Gotta love the persistance to use it and to be different though.

otolith

55,899 posts

203 months

Monday 18th April 2011
quotequote all
Extremely compact dimensions and low weight for the power output. Lets you do things with the packaging that you can't do with a much bigger and heavier engine - like building a front engine rear drive car that has the entire powertrain inside the wheelbase (like a good two seat sports car) but has room for two proper rear seats. Unfortunately, the benefits are a bit too subtle for a lot of people to grasp.

I think future rotary models will prove too thirsty for CO2 obsessed Europe, we're heading into a future of small capacity three and four cylinder forced induction units, although Audi are considering their use as range extenders for electric cars;

http://www.carsuk.net/audi-a1-e-tron-detail-its-a-...

300bhp/ton

41,030 posts

189 months

Monday 18th April 2011
quotequote all
Oi_Oi_Savaloy said:
Can someone tell me why are Mazda persisting with developing the rotary wankel engine?

When I look at the horror stories associated with these engines in the RX8, then poor fuel consumption combined with the high vehicle tax these also attract - can't understand it to be honest.

Please tell me- am genuinely intrigued!
1. Why not? It'd be a boring place if all cars were 100% the same
2. Mazda have already spent much time and money developing it. It'd be silly to give up know
3. Mazda have actually sold a lot of Rotary powered cars. So sales wise it hasn't been a flop but more of a success, ESP with the RX-8.

It's also worth noting that many cars are actually no better on fuel. So it's not as if it would be in isolation in terms of running costs.

The tax implications are more specific to the UK and some parts of the EU. But US and I suspect JDM markets may well have different rating systems.

Rotary motors have actually been very successful from being used as large gas pumps to aero engines and being the device that acually powers seat belt pre-tensioners.

I for one hope they aren't ready to give up on it just yet.

MarJay

2,173 posts

174 months

Monday 18th April 2011
quotequote all
ludicrous speed said:
It's a good idea, and it's nice that it is being kept alive but unless someone invents some magic material to make it out of, it will be massively inferior to a piston engine. Gotta love the persistance to use it and to be different though.
Negative.

It is massively superior to the piston engine. It is just that the piston engine has been developed by thousands of manufacturers and researchers over a period of 100+ years. The Rotary (like the two stroke piston engine) Hasn't had anywhere near as much development, and yet is light, compact and cheap to build.

The Four stroke piston engine has its advantages, but it has nearly reached the limit of its development. The Two stroke and the rotary would be ready to take over if it wasn't for this whole pesky 'peak oil' stuff and this pesky 'climate change' nonsense.

Superhoop

4,676 posts

192 months

Monday 18th April 2011
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What cars do Mazda currently have in production that use the rotary?

Aside from the cars that Auto Express have suggested they have seen 'leaked images' of, and have 'caught testing', what cars do Mazda have coming in the next few years that have a rotary engine?

300bhp/ton

41,030 posts

189 months

Monday 18th April 2011
quotequote all
The Wookie said:
Because it's extremely light and small for the amount of power it puts out, which is good for both handling and packaging.

Hence it being slightly illogical when someone says 'RX8's have great balance and handling along with superb packaging to get four proper seats in, but it would be even better if it didn't have that thirsty, unreliable Rotary engine'

If they could sort out its problems then it'd be the automotive holy grail, but seeing as that's probably not going to happen, it can still carve out it's own niche in terms of usefulness
While I don't disagree with the above. I do wonder how easy you could have an RX-8 type vehicle with either a Boxer 4 turbo or a compact V6 like the Rover KV6. Either setup could match the hp of the rotary and I'm not convinced they are actually that much bigger and heavier. But I admit I have no stats to hand. smile

motco

15,919 posts

245 months

Monday 18th April 2011
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Wasn't there a Norton motorcycle with a rotary (wankel) engine in the 1980s?

rhinochopig

17,932 posts

197 months

Monday 18th April 2011
quotequote all
Because unlike a piston engine, you don't waste energy accelerating and decelerating 1, 2, 3, 4, 5, 6, 8, etc. big lumps of metal. It's a very elegant solution to a problem - albeit one that needs some considerable development.

The Wookie

13,909 posts

227 months

Monday 18th April 2011
quotequote all
300bhp/ton said:
While I don't disagree with the above. I do wonder how easy you could have an RX-8 type vehicle with either a Boxer 4 turbo or a compact V6 like the Rover KV6. Either setup could match the hp of the rotary and I'm not convinced they are actually that much bigger and heavier. But I admit I have no stats to hand. smile
I can't quote exact dimensions, but to me the Renesis looks about half the size of a Toyota 3.5 V6, and it's reputed to weigh about the same fully dressed as a K-series

The Wookie

13,909 posts

227 months

Monday 18th April 2011
quotequote all
rhinochopig said:
Because unlike a piston engine, you don't waste energy accelerating and decelerating 1, 2, 3, 4, 5, 6, 8, etc. big lumps of metal. It's a very elegant solution to a problem - albeit one that needs some considerable development.
Haven't we been through this one recently?

otolith

55,899 posts

203 months

Monday 18th April 2011
quotequote all
A major part of the efficiency problem is that the combustion chamber has a much larger surface area than a piston engine - heat lost into the engine block is not being used to expand gases, drive the rotor round and power the car. Mazda have altered the geometry of their next rotary to reduce the problem, but it can't be entirely got around with current materials technology.

Oi_Oi_Savaloy

Original Poster:

2,313 posts

259 months

Monday 18th April 2011
quotequote all
I'm not having a go at Mazda for being alternative - just asking the question why persist with something that appears to be useless? Even if the packaging is awesome people are not going to be buying a car that does 20mpg.

Unless, as someone has said it's viable with different fuels. I love the fact that it's lightweight, small and powerful but to the man in the street he's going to see pretty poor fuel economy and high tax?



Alex

9,975 posts

283 months

Monday 18th April 2011
quotequote all
Most of the power and efficency improvements of 4-stroke piston engines over the years have come from improved engine management (fueling and ignition), and engineering tolerances. All of these improvements are also available to the rotary design.

I am not a mechanical engineer, but I am inclined to believe that there is a fundamental design limitation that means that the rotary engine will never be as efficient as a 4-stroke piston engine. The piston engine wastes energy accelerating and decelerating pistons, the rotary engine must waste energy elsewhere.

saaby93

32,038 posts

177 months

Monday 18th April 2011
quotequote all
motco said:
Wasn't there a Norton motorcycle with a rotary (wankel) engine in the 1980s?
Yes - what happened to that?

I forgot to add
Say yes to AV. If you dont get your first choice you might get your second smile
(MRLP excepted)

otolith

55,899 posts

203 months

Monday 18th April 2011
quotequote all
The Wookie said:
300bhp/ton said:
While I don't disagree with the above. I do wonder how easy you could have an RX-8 type vehicle with either a Boxer 4 turbo or a compact V6 like the Rover KV6. Either setup could match the hp of the rotary and I'm not convinced they are actually that much bigger and heavier. But I admit I have no stats to hand. smile
I can't quote exact dimensions, but to me the Renesis looks about half the size of a Toyota 3.5 V6, and it's reputed to weigh about the same fully dressed as a K-series
Here's one being disassembled;



Here is a comparison of the external dimensions with a Honda S2000's F20C



Here is Mazda's take on the packaging benefits:



The main issue with the four pot is that it's a bit longer but a lot taller. A flat four would be lower, but wider - in the RX-8, the back of the engine is between your feet and the passenger's, so you would lose cabin space.