I'd rather be a Wankel than a piston...
Discussion
While I'm waiting for engineers reports & insurance company tw*ts to get their acts together,howabout a lighthearted debate thread?
I dont know a lot about it,but I'm an interested fan of the Rotary engine.They've been around for some time & (as far as I'm aware) only large manuf' to develop it is is Mazda (kudos guys).
SO
Howabout...
I'd rather be a piston than a Wankel
OR
I'd rather be a Wankel than a piston
as a starting line..Over to you..
I dont know a lot about it,but I'm an interested fan of the Rotary engine.They've been around for some time & (as far as I'm aware) only large manuf' to develop it is is Mazda (kudos guys).
SO
Howabout...
I'd rather be a piston than a Wankel
OR
I'd rather be a Wankel than a piston
as a starting line..Over to you..
The Wankel Rotary's a very interesting engine, much lighter and more compact than any piston engine. It's hamstrung by:
1. The fact that only Mazda can make them (they hold all the patents)
2. The piston engine's been developed for over a century, so even though it's not that efficient a design, it's been honed and perfected for such a long time, whereas the rotary hasn't had a fraction of the development
3. Rotaries have high thermal loss (equals high fuel consumption), burn oil (for most people this is normally a sign of a knackered engine even though it's perfectly normal for a rotary), and the rotor tips tend to wear out before 100,000 miles (though not always)
4. They also suffer from old prejudices based on '70's NSU's and the likes, issues the Japs sorted decades ago but still persist due to ignorance.
Reading the above, it's obvious why rotaries aren't in family cars or shopping trollies, but they seem perfect for sports cars and motorsport use. I'm really suprised we don't see them apart from the odd Mazda really!
1. The fact that only Mazda can make them (they hold all the patents)
2. The piston engine's been developed for over a century, so even though it's not that efficient a design, it's been honed and perfected for such a long time, whereas the rotary hasn't had a fraction of the development
3. Rotaries have high thermal loss (equals high fuel consumption), burn oil (for most people this is normally a sign of a knackered engine even though it's perfectly normal for a rotary), and the rotor tips tend to wear out before 100,000 miles (though not always)
4. They also suffer from old prejudices based on '70's NSU's and the likes, issues the Japs sorted decades ago but still persist due to ignorance.
Reading the above, it's obvious why rotaries aren't in family cars or shopping trollies, but they seem perfect for sports cars and motorsport use. I'm really suprised we don't see them apart from the odd Mazda really!
A lot of manufacturers (merc ect) tried em in the 60/70's on development cars.
All but mazda eventualy gave up - and in the late 90's ealy 00's mazda were down to a handfull of people developing them.
They should be more efficient, but as said are way behind on manhour development, do benifit from advances in materials/ancilaries tho.
Currently my RX8 is equivelant to a 230bhp 3.9l v6 but with the weight of a middle ground I4. And smaller than either.
All its benifits are for performance, light and small, but not ecconomical, so you wont see them in anything other than performance cars for a while.
Fuel consumption is heavy but as it likes 95 instead of 97/98 is probably cheaper to run than the 305z or TT etc.
Oh and there so smoooth, hard to describe but they just float forwards (with noise tho).
As for oil usage, It was 1l per 2000 miles but this has changed since the latest software, now uses more at high rpm and less at low rpm, I expect 1l every 3k or so now. Less than some piston engines(m5 etc).
All but mazda eventualy gave up - and in the late 90's ealy 00's mazda were down to a handfull of people developing them.
They should be more efficient, but as said are way behind on manhour development, do benifit from advances in materials/ancilaries tho.
Currently my RX8 is equivelant to a 230bhp 3.9l v6 but with the weight of a middle ground I4. And smaller than either.
All its benifits are for performance, light and small, but not ecconomical, so you wont see them in anything other than performance cars for a while.
Fuel consumption is heavy but as it likes 95 instead of 97/98 is probably cheaper to run than the 305z or TT etc.
Oh and there so smoooth, hard to describe but they just float forwards (with noise tho).
As for oil usage, It was 1l per 2000 miles but this has changed since the latest software, now uses more at high rpm and less at low rpm, I expect 1l every 3k or so now. Less than some piston engines(m5 etc).
Rob's spot on - the rotary shoudl be a better engine but hasn't had the investment of billions of dollars or design and research that piston engine have.
My car has an earlier stage of development than in Robs RX-8. I'm happily depleting the worlds oil resources in a '92 rx-7 twin turbo.
One of the main benefits in the FD (3rd generation RX-7) is the positioning of the engine weight is well behind the front wheels and very low down giving the car similar properties to a MR car then FR. Going for a blat round silverstone soon so I'll see if all the talk of the excellent handling is true!
People complain that the rotary has low torque and needs thrashing to make it drivable but it's not the case - I tend to keep the revs between 1500 and 3000 round town.
I've got the rev limit set to 8200 on mine and the 8's it set at over 9k rpm... loadsa fun. Unlike many piston engines it's actually good for the rotary to be opened right up when you drive it - it helps clear out any carbon deposits and crap that build up.
Downside is you need to find a garage that knows what it's doing and rotary limits the choice. I'd never take my 7 to a Mazda dealership as the turbo setup makes it a bit complicated by I think they should improve now the 8 is doing well.
For the £s/bang I chose rotary but there's plenty of good boingers out there.
I'm thinking that a turbo'd rotary in a caterfield chassis would be fun - easy to get to ~350 Bhp in a ~500kg package... zoom zoom zoom
Iain
My car has an earlier stage of development than in Robs RX-8. I'm happily depleting the worlds oil resources in a '92 rx-7 twin turbo.
One of the main benefits in the FD (3rd generation RX-7) is the positioning of the engine weight is well behind the front wheels and very low down giving the car similar properties to a MR car then FR. Going for a blat round silverstone soon so I'll see if all the talk of the excellent handling is true!
People complain that the rotary has low torque and needs thrashing to make it drivable but it's not the case - I tend to keep the revs between 1500 and 3000 round town.
I've got the rev limit set to 8200 on mine and the 8's it set at over 9k rpm... loadsa fun. Unlike many piston engines it's actually good for the rotary to be opened right up when you drive it - it helps clear out any carbon deposits and crap that build up.
Downside is you need to find a garage that knows what it's doing and rotary limits the choice. I'd never take my 7 to a Mazda dealership as the turbo setup makes it a bit complicated by I think they should improve now the 8 is doing well.
For the £s/bang I chose rotary but there's plenty of good boingers out there.
I'm thinking that a turbo'd rotary in a caterfield chassis would be fun - easy to get to ~350 Bhp in a ~500kg package... zoom zoom zoom
Iain
FLAT_STEVE said:
The Wankel Rotary's a very interesting engine, much lighter and more compact than any piston engine. It's hamstrung by:
1. The fact that only Mazda can make them (they hold all the patents)
I wouldnt exactly say theyre that light. Its commonly assumed that they are as theyre small. Problem is theyre alot more solid than a Piston engine which has alot of air in it. Yes theyre still light but not as much as their size would suggest.
I heard alot of Mazda's patents were due to expire soon which could spur more development. Any truth to this?
[quote=dejoux
I heard alot of Mazda's patents were due to expire soon which could spur more development. Any truth to this?[/quote]
That could be interesting,as Mazda have been the only developers-some thinking outside of their phylosiphies could bring about some new 'wankel ideas' etc.If the same amount of time/money/effort had been spent in development,as with the piston engine the Wankel could be miles ahead by now.
I heard alot of Mazda's patents were due to expire soon which could spur more development. Any truth to this?[/quote]
That could be interesting,as Mazda have been the only developers-some thinking outside of their phylosiphies could bring about some new 'wankel ideas' etc.If the same amount of time/money/effort had been spent in development,as with the piston engine the Wankel could be miles ahead by now.
Thne renesis weighs about 160-170kg total, which is a bit more than the k 1.8 and less than the honda I4 2.0's, and way smaller than either.
A lot less than any v6 of which its comparable to. And the renesis is capable of 250bhp in a fairly low state of tune, but is knocked back to 230 for emmisions.
Ofcourse there are less garages and fewer skilled mechanics for rotaries. But the engines themselves need less work. Theres no valvs, cams etc so when something goes wrong its usualy internal seals etc so it needs a rebuild. This is easier and cheaper than the equivelant (and just as common) piston engine gasket/piston ring faliures. Its just most 7 owners going through a rebuild opt for expensive upgrades at the same time.
In the 80's a NA rotary (from 7 gen1 I think) came 2nd in a long term reliability test , only defeated by a large merc desil v12.
Yet there still eons behind in terms of development, in theory they should be more efficient and more powerfull, isnt working out in practice for now.
A lot less than any v6 of which its comparable to. And the renesis is capable of 250bhp in a fairly low state of tune, but is knocked back to 230 for emmisions.
Ofcourse there are less garages and fewer skilled mechanics for rotaries. But the engines themselves need less work. Theres no valvs, cams etc so when something goes wrong its usualy internal seals etc so it needs a rebuild. This is easier and cheaper than the equivelant (and just as common) piston engine gasket/piston ring faliures. Its just most 7 owners going through a rebuild opt for expensive upgrades at the same time.
In the 80's a NA rotary (from 7 gen1 I think) came 2nd in a long term reliability test , only defeated by a large merc desil v12.
Yet there still eons behind in terms of development, in theory they should be more efficient and more powerfull, isnt working out in practice for now.
me down in flames, if I have got this wrong.That's basically it keith.
Each rotor face has a 'capacity' of 654cc. Each face of the rotor fires each revolution of the crank. There are 2 rotors so 654 * 3 * 2 = 3870cc.
As opposed to a piston engine where (in a 4-piston engine) 2 pistons fire per revolution.
For insurance purposes it's treated as a 2.6 by DVLA and insurance companies will use anything from 1.3 to 2.6l (including 2.4!).
Iain
Each rotor face has a 'capacity' of 654cc. Each face of the rotor fires each revolution of the crank. There are 2 rotors so 654 * 3 * 2 = 3870cc.
As opposed to a piston engine where (in a 4-piston engine) 2 pistons fire per revolution.
For insurance purposes it's treated as a 2.6 by DVLA and insurance companies will use anything from 1.3 to 2.6l (including 2.4!).
Iain
ok - working out volumetrics it is effectivly a 3.9
v6 piston engine at 6000 rpm.
Each piston fires every 2 revs, so thats 3000 * 6 = 18000 bangs at 6000 rpm.
On the renesis at 9000 rpm the rotors move at 3000 rpm, theres 2 rotors and each side fires once per rev.
So thats 2 * 3000 * 3 = 18000 bangs per min.
Now each of those bangs in the rotary is 653 cc, so each bang in the piston engine has to be that size to be equivelant.
653 * 6 = 3.9litre.
Thats if you look at it as 9k rotary = 6k v6, if you look at it as 6k evens then its more like a 2.6L
v6 piston engine at 6000 rpm.
Each piston fires every 2 revs, so thats 3000 * 6 = 18000 bangs at 6000 rpm.
On the renesis at 9000 rpm the rotors move at 3000 rpm, theres 2 rotors and each side fires once per rev.
So thats 2 * 3000 * 3 = 18000 bangs per min.
Now each of those bangs in the rotary is 653 cc, so each bang in the piston engine has to be that size to be equivelant.
653 * 6 = 3.9litre.
Thats if you look at it as 9k rotary = 6k v6, if you look at it as 6k evens then its more like a 2.6L
Don't want to throw a spanner in the works but I thought the output shaft turns at 3 times the speed of the rotors.
But there are three faces on the rotor and each fire once per revoloution (of the rotor)
So there is only one firing per (output shaft) revoloution per rotor. So two firings per output shaft revoloution.
Which is the same as a 4 cyl engine.
now as each firing chamber is 650 cc for the four cylinder engine would be 2.6 litre and on the rotary would be the 1.3
So in terms of firings its the same as a 2.6 litre four cylinder engine.
The reason its so smooth is because the power stroke is extended over 270 degrees of the output shaft rotation rather than only 180 on a four stroke piston engine setup.
Feel free to flame me if I'm talking bollocks or I'm wrong
Andy
>> Edited by andytk on Tuesday 21st September 21:00
But there are three faces on the rotor and each fire once per revoloution (of the rotor)
So there is only one firing per (output shaft) revoloution per rotor. So two firings per output shaft revoloution.
Which is the same as a 4 cyl engine.
now as each firing chamber is 650 cc for the four cylinder engine would be 2.6 litre and on the rotary would be the 1.3
So in terms of firings its the same as a 2.6 litre four cylinder engine.
The reason its so smooth is because the power stroke is extended over 270 degrees of the output shaft rotation rather than only 180 on a four stroke piston engine setup.
Feel free to flame me if I'm talking bollocks or I'm wrong
Andy
>> Edited by andytk on Tuesday 21st September 21:00
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