rotaries vs pistons

[scope]

haha yeah, which one do you prefer and why? (how long to someone says that rotaries only blow up?)

[Silent Knight]

(how long to someone says that rotaries only blow up?)

They do...

I can't stand the sound that they make. Gives me a bleedn headache every time I hear it. Also to me they seem to be extremely unreliable. Lastly they look ugly as sin.

This does not however mean that I'm saying that the engine is all shit and all that which most people do just because they can basically...

I've seen EXTREMELY good figures come from rotaries and very fast 1/4 times. So if done properly they can be very powerfull. Problem is just that the more power you pump out of one the less reliable it becomes...

Go the Inline 6 Cylinder!!!

[bluemaumau]

unless your loaded whats the point in having one? i hate mazdas full stop stupid engines and drivelines!!!

[Jebus]

Sound like a bunch of people who havnt really experienced rotarys first hand, well more than thier flat mates brothers friend that shoved a die grinder up the exhaust port of his 12A.

The sound they make is awesome....but thats down to opinion.
The power they produce from such a compact engine is brilliant, they are very simple which makes them easier to work on. Alot of them do break down, mainly because backyard cowboys are getting into building motors, they need to be cared for more than other motors, that and theier owners like to overheat them at burnout comps

When built by someone reputable who's had experience they can make VERY good power and be very reliable. I can think of a certian local 13B thats pumping over 600HP, has done hundreds of drag passes and has been doing so for the last 3 years, all without a single rebuild, oh and it runs 8's.

As much as I wouldnt really like to own one at this stage, If i had the dosh to chuck fuel down one, and money to build another car id definately consider it.

[Ako]

I never used to be that great a fan of them...

But the signwritten S4 RX7 we've got here at work has swayed me a little bit.

Full boost by 4000rpm, 9000rpm redline, it sounds like a supra or something at full noise, its making well in excess of 800hp (crank) at the moment and is yet to break 20psi.... All from 2L of capacity

We're yet to have it break (after being built properly ), and its spent a LOT of time under full load on the dyno + at the track.

Then there's the customers' batty we bolted a T51R to, which is making 300kW @ the wheels without a proper power tune, making some boost by 3500rpm and anything you want by 4000rpm, and so far hasn't gone more than 12psi of boost to make that number - and is still on pump gas.... And thats a 1300cc!

Yeah, I like rotrees

A 2JZ may be able to do similar sorts of numbers, but not with the same degree of response + spool up. Hate to say it but someone prove me wrong...

I've seen far too many of them making massive power for a LONG time to pull the whole unreliability card out. A bridgeport may not last long - but then its essentially a race engine being street driven (albiet still seeing 12000rpm at times), I wouldn't expect a formula atlantic engine to last long either when built by some munter in his backyard

I'm with jebus - If I could afford to do it all properly, I'd own one in a flash. They may be very capable engines, but in the wrong hands are also quite fragile, which is where the bad name has come from. Just look to oz for the sheer number of street legal, and legitimately street DRIVEABLE 10 and 9 second rotaries around.

[RomanV]

Yeah I'm in two minds about this one.

Firstly, I agree that it's unfair to judge it, based on the backyard mechanics that call themselves rotary engine rebuilders.

A well built rotary engine can be an impressive piece of machinery.

I've been in one or two that have been great, and I'm sure they were awesome cars to drive.

One of which was a 12,000rpm screamer! Insane.

However on the other hand, they have their downsides:
The $&#$% that your car will attract if you own one;
Insane theft statistics; (Leaving a mint RX3 somewhere for 5 mins? Dont think so!)
More maintenance required (Not so much of an issue for an enthusiast though)
Shorter lifespan from the engine than a piston equivilent;
And in some cases, power that isnt so great for the amount of gas they consume.

One of my mates has an 808 with a rebuilt and ported 12a in it, which is absolutely immaculate.
However it goes through an OBSCENE amount of gas, and made something like 150hpATW @ 8000rpm, without much going on under the curve either.
I mean some of the honda boys are making more than that with NA 1.8 litre engines, with considerably less gas usage, and more power throughout the band.

Rotaries have a lot of street cred, and IMO some of them sound cool, and its an interesting concept, but..... They're not my cup of tea really.

I mean my NA MR2 will probably make more power ATW than a fair amount of NA rotaries out there, and I can use mine as a daily driver, rather than something I can only afford to drive once a fortnight.

[Ako]

Your mates car sounds like a perfect example of exactly what jebus and me both mentioned.

Just cause its ported, doesn't mean its a decent job of it. I think a good example of a N/A rotary everyone will be able to recognise is mad mikes RX7 - its a 20B, sure, but even if you take away 1/3 of the power it makes (to put it in perspective), its still scary for a non turbo engine.

Like putting mega lumpy cams in a small engine - it may let it rev to the moon, and make the right noises, but it doesn't mean its going to make good power if its not set up right.

I can give examples of 3SGE's which make heaps of noise and make f-all power, a rotary is just the same. Too many "builders" of these engines will just give exactly what the owner asks for - "give it a pulse and make it rev heaps au".

[wde_bdy]

One think I can't stand about rotaries is people who say "its only 1.3L". Absolute bullshit, you cannot compare capacity of a rotary to a piston engine as they are not measured on the same basis. I am yet to hear anyone say "my rotary uses the fuel of a 1.3L piston engine" while still claiming it makes massive power for a 1.3L.
Other than that, they are not my cup of tea but good on anyone else who wants to own one. Unfortunately they seem to attract a far larger proportion of dickheads than any other motor, although most are dreamers rather than owners.

Callum

[Jebus]

One think I can't stand about rotaries is people who say "its only 1.3L".

Thats very true, I agree. Hence why I use the term 'compact' they are very small motors which fit into pretty much any engine bay and make as much HP as you may want, good luck fitting a 2JZ, RB, SR into a KE20 or similar with as much ease.

Unfortunately they seem to attract a far larger proportion of dickheads than any other motor, although most are dreamers rather than owners.
Callum

One of the main reasons theyve got such a bad name, Nothing I hate more than reading/hearing someone say "Im gunna rotor it"

[RomanV]

Yeah I'm not saying that the 3S is an amazing engine, by any stretch of the imagination.
I wouldnt say that my mate has done a bodge job.
But at the end of the day, it's a 12a running carbs I suppose.
I'd take a renesis anyday, but even then, I'd rather have an F20C.

I agree with the '1.3 litre' comment, it's more marketing hype than anything IMO.
If they said it was a 2600cc engine, that made the power that it does, while still consuming the gas of a 2.6 litre engine, people would think it was a POS.
But instead it's an amazing technical marvel, because it makes so much power from 1300cc.
A piston engine uses the same space to inhale air, compress it, combust it, and push it back out again, but a rotary doesnt. So using the same formula to assess it's capacity doesnt really work.

It's great that a rotary engine is so compact though.

I think that the reason that the rotary is so popular with munters, is because of how easy it is, to fit into ANYTHING that's RWD.

And re: reliability.
Every time this comes up, someone says "yeah, well I know a guy who's done 250,000kms without a rebuild, so THERE!"

Well there have been plenty of piston engines doing a MILLION kms! Tell me about rotary reliability when someone gets to that.

[the fallen303]

both have aspects that i like, and don't really know enough about the rotors to say what i dislike. some sound awesome, some sound like some dick with a rattley cough and a megafone. same can be said to piston engines (but those are usually 20v or vtec engines with the wrong exhaust!) end of the day for me it comes down to personal choice.

[Adamal]

The rotor vs piston debate. Just as prevenlent as the Honda vs Toyota debate. Haha.

As for the 1.3l thing.... Its best to look at it on a single engine rotation basis.
In a single rotation, a "1.3" litre rotary will use twice that volume. 2.6 litres.

In a 2 litre 4 stroke piston engine, it will only use a volume of 1 litre.

[Dell'Orto]

Love em, will definately own more.

As for reliability as well, my S4 gave me far less headaches than my MR2 ever did!!even though i did more burnouts in it than was really necessary

[RomanV]

It's better to compare it one rotor vs. a single cylinder piston engine.

a 500cc four stroke single cylinder piston engine will inhale 500cc of air every two revolutions.

a '500c' single rotor will inhale 500cc of air, three times per revolution.*

*Assuming that my limited knowledge of rotary engines is correct

*Note: long, perhaps technically inaccurate ramble ahead*

Also, perhaps the lack of torque produced is due to the way that the rotor acts on the eccentric shaft?
A piston focuses the energy in a single direction, which acts on the rod, which puts a force on the crank at a known distance from the centre line.

Whereas a rotary's combustion acts apon the side of the rotor, since torque = force x distance, you're appyling more torque to the outside edge of the rotor (which is where the least force can be applied, because it narrows down at this point) than the same combustion pressure acting on the part of the rotor closer (where most of the area is) to the fulcrum. Wherever that is, on a rotor spinning around an eccentric shaft.

However they obviously make decent power in most cases anyway, because they can combust a $&#$% load of air/fuel.

[Brevin]

Owned one and didn't like it for the whole week i had it.
All it did was gave me a mega headache and attracted dickheads.

Maybe if they wernt so thrashed by fob's with their parents cheque books paying out for mazda 323 wagons with 12a bridgeports. Or pr*cks who shout "get a rotor" when they fail to produce a drivers license, i might like them.

I appreciate the fact that from a compact motor they can pull some insane HP figures and run some unbelievable 1/4 mile times... but other than that, give me a 2JZ any day of the week.

[Lith]

I voted rotary, only just. This is probably because at the end of the day - I think I'd have more fun in a rotary powered car than a piston powered car, PROVIDED I could afford it.
However, at this point in time - in terms of sheer efficiency, I think piston engines currently have it over them by a bit of a margain.

I love the fact that they come in a small physical package, however I think that people claiming a 13B rotary does well for a "1.3l" is a bit ridiculous. Its a 1.3l engine that will rival a 5.7l V8 on fuel consumption, but without being understressed. I love the amount of exhaust energy they produce for the size, but again - the amount of exhaust gas generated for the amount of air they can breath in and actually make power for is a little bit poor. They just don't justify the amount of fuel they use with the amount of power they make, and this really matters to me with the direction fuel prices are heading.

I'd love a 20B powered beast, but quite frankly in real world terms - screw that for anything other than a race car. In current times, I'm quite happy blat around in my 2.5l turbo 6cyl thing that can generate the same kind of power and torque as an equivalent 13B-REW - use less fuel, and put up with it not driving a big turbo quite as well. Not to mention make a nicer noise out its bum haha

[blackie]

some interesting debates..
id have to go with piston at the moment.

got some respect for rotangs tho, and they sound beautiful if done right, i remember hearing a S5 sitting on its turbo timer with a nice exhaust, just gently pulsing sounded f*n bad...

[ollieboy]

If I could afford a rotor I would own one.

Those who say they use heaps of fuel. You don't buy a rotor for good fuel consumption.

And with that its not 1300cc thing, in motorsport you have to multiply the capacity of a rotor by 1.8 I believe so this would be closer to accurate if you were talking about rotaries in my opinion. So talking about a 13B you would actually be referring to a 2340cc engine.

And the RX8 improved fuel economy a bit, its about 28 mpg which is no Toyota Yaris fuel economy but its still better( what did this do to the performance though?)

Heres a tribute to my favourite rotary vehicles:
http://www.ashburtoncarclub.org.nz/images/photos/originals/12.jpg

http://www.moller.com/skycar/m400/

And I've been for a few rides in that first one, the mascort, its an amazing vehicle.

[Mr Revhead]

ok what i want to know is why do they have to be so goddamed annoyingly LOUD????

wtf is with that? i cannot think of a more annoying noise at 3am than some thinng sitting there going bbaaaarrrrp baaaaarrp baaarrrp

[RomanV]

No barp, no bitches.

I think it's because a restrictive exhaust REALLY kills off their performance, really quickly.

I suppose you can still have free flowing & reasonably quiet though.

So I'm going with option A.