Rotaries?

[Crash Test]

Here you go Sparky, my post for the day!! I know this topic has been here before, but i think it will be better second time round

Why is that rotary engines have never really taken off? Down here in club level sedans, if you don't have a rotary, you are probably not in the competition.

[desmo]

Fuel efficiency, apex seal wear/durability, emissions issues, take your pick.

[Maisie]

Because all the cars we know that have rotary engines seem to spend far too much time with the whole car in a state of unexpected rotation?

[Sharky]

They are extremely thirsty. I think that they are very "lazy" at low RPM's as well.

However....I heard somewhere that they seem to be ideal for engines that use hydrogen as fuel.

[Crash Test]

But that doesn't explain why they can regularly pick off 6 litre Chevs etc..

Fuel efficiency? We're talking race cars here, isn't that why people go racing, to burn up petrol!

[KC]

Rotary engines are hard to classify for rulesmakers. They are typically small in displacement but can be boosted to produce large amounts of power for such a small size (1300cc is typical). This is difficult for rulesmakers like the ACO who typically use displacement, aspiration and weight to equalize the rules.

By its nature, the rotary does not reciprocate the same way as piston driven engine. The mass and stroke of a piston, conrod, and crankshaft all help to produce torque. The triple lobed rotary does not have this mass to use and thus are typically lower in bottom end torque. they can make up for this by producing higher rpms than typical reciprocating engines because of this reduced mass. Also, piston surface area can seriously increase torque as seen in larger V8 powerplants. The rotary has a much smaller displacement and cannot exploit this as well.

The reason a rotary is so thristy is that it does not have an exhaust cycle in its rotation like a 4 cycle engine does. In fact the typical Mazda rotary fires a spark plug three times per revolution. This results in extremely high exhast temperatures and was the usual fault in rotaries until Mazda perfected ceramic seals for their road going motors.

[chunder]

Let us not forget that a rotary engined car has won Le Mans. The Mazda win in the late eighties was with a twin-turbo (I think) rotary.
And also in the Uk the Norton team used a rotary engine in bike racing in GP's and the then F1 class. To great effect aswell. The machine was still winning superbike races in 1994/5 in basically the same spec.
As mentioned elsewhere. rotaries are rather thirsty and little is known about them. Shame because with so few moving parts you would think that the motor would be very popular amongst tuners.
I know of a Mazda rotary in a Mk2 Escort rallycar that is very effective and because of their light weight/low C of G, they are quite useful in all sorts of singe seaters from autograss to hillclimbers.

[Sharky]

That's right chunder. Who can forget about the Mazda winning at le mans. I also think that it had a twin turbo (I know the last RX 7 did) but it had 4 rotors compared to 2 of the RX7.

Looking up some old car magazines I found an article about the 1993 Mazda RX7 and here are some specs:
Engine type: Double rotor rotary ****el.
Bore*stroke: N/A (you don't say )
Displacement: 2*654cc (1308cc nominal)
Compression ratio: 9,0:1
Intake system: Bosh electronic injection with 2 Hitachi HT12 turbos.
Power: 237HP@6500Rpm
Max torque: 30.14kgm@5000rpm
Max speed: 251Kmph
0-100Kmph: 6 seconds.
Fuel economy: 24,1 km per gallon.

It's a shame I don't have a scanner because they have a pic of the engine taken appart piece by piece and I can count 16 parts!!! Extremely simple. Of course, some of those 16 parts are made of other parts but still, the pic looks extremely simple.

[Crash Test]

KC: with regards to classification, here in Asutralia they simply have different multiplication factors for the different engines. For instance a 13B = 2600cc, 20B = 3527 etc, and historically these have been accurate and fair.

[Crash Test]

Can anyone identify this engine for me?

[KC]

The Aussie's have done a better job than they have here in the US. Most roatry powered cars are treated as much alrger powerplants and it makes them a little bit of a hard bet on tracks with many slow corners where torque is a premium. However, they always run extremely well in the rain.

The Mazda 787B used a 4 rotor engine in 1991 to win the 24 Hour classic endurance race.

"The R 26B engine that won was normally aspirated and had four rotors and three sequential spark plugs per rotor. The capacity is 2622 cc actual, rated by FIA formula at 4708 cc. It produced 700 bhp at 9000 rpm and 62 mkg torque at 6500 rpm (448 lb-ft). Fuel was electronically injected and consumption was 51.881 liters per 100 km at an average speed of 213.58 kph (excluding pit stops). The air intakes had continuously variable geometry controlled by the engine electronics. The transmission had 5 speeds (full synchromesh) from a Porsche design gearbox and a limited slip differential.

The Mazda 787B car weighed 830 kg (1831 lb). The chassis was designed by Nigel Stroud and the body was carbon fibre. Wheelbase was 2.66 m by 1.53/1.50 m and overall size 4.78 by 1.99 m. It had 18 in wheels, ventilated carbon fibre brakes. Tires were Dunlop 300-640x18 front and 355-710x18 rear."

Curiously, the Mazda used displacement over turbocharging and is listed by the ACO as one the most consistent finishers in the seasons competed. Also, the drives are a name or two we all know, Johnny Herbert, Bertrand Gachot, and Volker Weidler.

[Sparky]

Crash, it looks like a 13B with aftermarket manifolds.

I might be wrong, I usually am!

[Crash Test]

Actually I've had to go and get the specs from the Horses mouth- try 13B Turbo, with extended ports. Would that give a displacement near 4000cc??

[Sparky]

Ian Cowley's your man. He runs that red RX7 in the CSCC. He'll be able to tell you what's what.

Sorry. It's all ****el to me...

[Crash Test]

I hate to do this to you Sparky...but it's Bruce DeBoo's RX7 Sport Sedan from their National Championship here in OZ... I actually do their website, which is at wink http://www.life.com.au wink.

It's fantastic because you get all manner of engines running together. 6-ltr Chevs/Fords, Turbos, and Rotaries.

[Sparky]

Issa Bloomin' setup, I tells ya...

I was right about 13b and the manifolds though, weren't I?!

And Oi! Off to cool sites with ya!