Why Do Rotaries Suck?

[mid life crisis]

i had a suzuski re5 rotory bike yrs ago i pushed it more than i rode but when it went it went like a rocket cost me a fortune in spark plugs tho

[brodie7]

the reason why rotaries suck is people like you who have no idea and think commodores are still in..

do any research and you will find that rotaries quite often dominate drag, circuit and are a sweet street car.

make your on choices but after all my experience from the track i would have to say in the last 3 years theirs hasnt been one rotary break down, only ohter issues such as gearbox's and diffs have left them down.. On the other hand you would be suprised if you didnt see a V8 blow or a 4 or 6 punch a hole in a piston..

[scathing]

the reason why rotaries suck is people like you who have no idea and think commodores are still in..

That sentence, on a Skyline forum, is 24 carat gold.

Edited September 15, 2009 by scathing

[ylwgtr2]

further more....i will continue to bore dirty great big holes in my housings and fill up the original ports and be motoring past you all in my small light powerfull circuit car for the cost of a hyundai

[ylwgtr2]

Heres some interesting reading....mazda's engine has become quite a durable engine over the years....the engine that was dubbed "the little engine that could" was named "the little engine that did"in the end and this one was called "the big engine that did"....and it sure did...In my view its certainly has been a credit to mazda's engineering and metallurgy R&D

On 23 June 1991 Mazda won the 24-hour Le Mans endurance race with a Category 2 (C2) 787B racer, #55, powered by a 4-rotor R26B--the first and likely last rotary win because of C2 rule changes prohibiting rotaries in 1992. Just to finish Le Mans is an accomplishment--let alone win. The 787B covered 4923.2 km (3059.1 mi) at an average speed of 205.3 kph (127.6 mph), exceeding 320 kph (200 mph) on the main straight. Yet it still had 30.0 liters (7.9 gallons) of fuel left of the maximum 2550 liters (673.6 gal) allotted, giving an impressive 4.6 mpg. Here's a look at this historic engine, emphasizing the DIFFERENCES between the R26B and the 13B whose geometry it's based on.

The R26B develops 700 net bhp (Japanese) at 9000 rpm, its redline, and 449 net lb-ft of torque at 6500 rpm. It's only 39" long and weighs just 396 lb. The R26B has a 3-piece eccentric shaft; the long main shaft has journals for rotors #2 and #3 and tapered extensions for 2 hollow shafts with journals for rotors #1 and #4. Counterweights are used at both ends. To stiffen the engine, aluminum honeycomb is used where needed, including the aluminum oil pan, which is mounted on top. The R26B uses a dry-sump oil system. Tension bolts are anchored throughout the intermediate housings, further increasing stiffness. Engine coolant and oil enter through the center housing.

Rotor and side housings are coated with hot-sprayed chrome-carbide cermet ceramic in a metallic array) for high-temperature wear resistance. The intake as well as exhaust ports are peripheral. Each rotor housing has 3 spark plugs: a third "far-trailing" plug was added for better fuel economy and power. Rotors were precision cast to a 10.0:1 compression ratio using the lost-wax method to reduce rotating mass. Two-piece silicon nitride ceramic apex seals have, in the words of one summary, "a 'sprinkle' of an ingredient that raises heat conductivity", and they use 2 springs. The R26B has a sophisticated electronic port fuel injection system and telescopically variable intake pipes whose length vary with engine speed to improve airflow.

After winning, this historic engine was taken apart in front of the press. Little performance deterioration had been noted during the grueling race, and the R26B looked nearly new after dismantling. Even Mazda's head office engineer said, "In the case of the rotary engine, damage to the apex seal is the best reference. And as you can see, it's nearly untouched." After measurement, wear on apex seals, rubbing surfaces, and bearings were found to be only 1/3 to 1/2 the upper limits--in Mazda's words, "indicating remarkable durability and reliability". As racer Paul Frere was to say of the win, "A pity Felix Wankel has not lived to see it."

Edited September 15, 2009 by ylwgtr2

[gotRICE?]

For a good few mins i was totally confused.

R26B.. had me so many times.

[jetblack]

i was seriously thinking of buying a series 8 rx7. they are hott!

but have heard too many horror stories.

is it possible to make a 13b reliable for daily use if kept pretty stock?

[ylwgtr2]

dude.....read my first post......I will also add change the oil regularly.....do NOT let them run low on water or oil....they die in a matter of minutes without water

[Yo-Yo]

That sentence, on a Skyline forum, is 24 carat gold.

heh commodores were IN at some point? I'm gonna go crawl back under my rock now

[2LV8ETR]

At the end of the day guys, there's still no denying their capability:

[Beer Baron]

Who here when they first found out exactly how a rotary worked did not think to themselves: f**k. That's clever.

I took a look under the hood of my mate's S1 RX7 the other day and realized for the first time just how small they are too! I knew they were small, but this thing took up less than half the engine bay. It was all intercooler (V mount) and body kit up front. Yet this thing still makes over 250rwkw with minor modifications and a conservative boost.

So, reliability and fuel efficiency aside, why aren't there more rotor engines?

I understand the yanks love their big engines, but I'm sure they'll jump on board with a BIG (6-8?) rotor NA engine. I don't know anything about the engines beyond the most basic explanation, but surely if they can make the little 1.3L tri-rotor fit in half the hood of a tiny RX7, surely a Mustang with an engine bay twice the size could house an engine 2-3x as long.

What about AWD. Why hasn't Mazda created a crazy lightweight AWD rotor to compete with the GTR, Evo and STi?

Is it just... a lack of popularity? Technology? What's holding the ol' Wankel engine from really competing?

1. So, reliability and fuel efficiency aside, why aren't there more rotor engines?

because only one manufacturer sells them in production cars. and even then generally in only one model. and since the end of the FD RX7 only in a RX8 which is a very average package. that's why there isn't more of them. there are still many of them though.

2. So, reliability and fuel efficiency aside, why aren't there more rotor engines?

well reliability and fuel efficiency are a big deal to most people. so does there really need to be any more reasons? for people not worried about those 2 things they are very popular.

3. What about AWD. Why hasn't Mazda created a crazy lightweight AWD rotor to compete with the GTR, Evo and STi?

well they haven't bothered with AWD but as far as a 'crazy lightweight rotor to compete with GTR, EVO aqnd STi?"... well it's called the FD RX7. late models (2000+) and in particular the spirit R and the RZ compete pretty well against the other big boys of the day (R34 GTR, 2000 model STI etc). They weigh as little as 1210 kg, come with carbon kevlar seats, alloy guards and bonnet, bilstein suspension, 280ps twin turbo engines (which have a great sequential turbo system that gives great low down torque and good top end). and they are a 2 seater from the factory. having owned both RZ RX7 and a R34 GTR, I'd say both cars with say just a cat back exhaust, the RX7 is the faster and more fun car. the R34 may run slightly better qtr or lap times due to higher grip, but a good driver could probably equal it in the RX7 and the RX7 is a much 'sportier' car to drive, much more fun than a stock GTR. and with the usual stage one mods (more boost, ECU, intercooler upgrade, full exhaust) they both put out around the same power, possibly even a little more with the rotor (around 250rwkw with those mods). and being a good 200kg lighter than the GTR they feel pretty lively to drive.

they do have a lot of flaws and negatives as well (most of which I'm sure are covered in this thread) and any engine is only as good as the car is bolted into.... (look at the RX8.....)

but as far as 'why do they suck'. well the answer is they don't suck. why would you think they do?

ps 13b is a twin rotor, not triple.

[mad082]

The rotary engine in early aircraft was a different animal altogether!

It was an early and inefficient type of cylinder-based aero-engine, from the WW1 era, which became obsolete because of a lack of torque.

http://en.wikipedia.org/wiki/Rotary_engine

I suspect you're thinking of the similar-looking RADIAL engines in piston-engined aircraft from the 1930s onwards. They WERE successful and reliable. But 'radial' = the arrangement of the cylinders, and had nothing to do with rotors.

in fact you will find that people have adapted wankel engines into ultralights, and that is what i was meaning by rotaries in aircraft. i am well aware of the radial engines being used in other aircraft.

[Sydneykid]

So much fun to be had by all, I don't have time to respond to each one individually, so a quick list will have to do;

1. Mazda were banned from LeMans because they lied about the engine capacity, as they always have. They broke the category engine capacity limit, the fact is a 26B is actually 7.8 litres. They were told by the FIA to either enter the car as a 7.8 litre or walk away. Obviously entering it as a 7.8 litre would have proven what we all know and brought to an end the 40 years of lying. So Mazda withdrew.

2. Of course rotaries are popular in some drag racing where the Mazda lies on their actually capacity is still believed by some. Compare the performance of a 13B with any other 3.9 litre engine and their true worth is revealed. A 20B looks pretty dismal when compared with its true competitors, 5.85 litre engines. In comparison to big block V8's in true drag racing, rotary numbers are infinitesimal anyway.

3. I bet Mazda have spent more on 40 years of rotary engine development than Honda did on the their F1 and Indy Car engines. That's why it was a very valid comparison. BTW a 3 litre F1 Honda V10 engine weighs less than a race ready13B and produces more than double the horsepower.

4. The rotors, that produce the power, cycle at 3,000 rpm, which is the same as the pistons, that produce the power, cycle at 3,000 rpm. Hence why a rotary engine only does 3,000 rpm, multiplying by the eccentric shaft gear up ratio is irrelevant.

5. Mazda have been lying both ways, they can't claim both 1.3 litres and 9,000 rpm at the same time. If they multiply the rotor cycle rate by 3 to get rpm then they have to multiply the capacity by 3 to get the true capacity. Conversely if they count only one side (of a 3 sided rotor) to get the capacity then they should only count 1/3rd of the rpm. It's a double lie and well overdue for being revealed as such.

6. It's irrefutable that rotaries are 2 strokes. In one complete cycle of the rotor they inlet, compress, combust and exhaust. That's the perfect definition of a 2 stroke. Whereas a 4 stroke takes 2 cycles of the piston to inlet, compress, combust and exhaust. Further evidence of them being 2 strokes is the use of the rotor itself as inlet and exhaust valves and the need for oil in the petrol. If it combusts like a 2 stroke and it smells like a 2 stroke, then there is no doubt it's a 2 stroke

7. For a compact FWD application, rotaries are not such a good package, they are quite wide (in comparison to a slim inline 4) and the inlet and exhaust are on the same side. Add their requirement for a 3.9 litre engine sized radiator, oil cooler and fuel tank and this makes packaging quite difficult.

8. As for the B2200 delivery ute, a valid comparison would be a 3.9 litre 6 cylinder engine. Hell, even a common old 3.6 litre Commodore engine would piss all over a rotary with their 195 kW and 340 Nm. As for a diesel comparison, if you wanted load carrying the most popular diesel conversion, a 3.9 litre Cummins in line 4 at 481 Nm would make a far better proposition. Especially when it came time to fill up the tank.

9. Why is there only one car company that makes rotary engines? Perhaps the other car manufacturers are too smart. Let's face the facts, Mazda didn't invent the rotary engine, Felix Wankel did and his patent was owned by NSU, now part of Audi. Mazda still pays royalty on every rotary engine. Audi wouldn't have to, but they have never bothered with rotary engines. Perhaps they don't want to perpetuate the Mazdas lies. Woudln't it be great if Audi came out with the truth and told the world the true capacity and rpm of a rotary engine?

When you get past Mazda's 40 years of lying the real issues with rotaries become obvious. When you truly compare them with their equivalent engine competitors they are deficient in every area, horsepower, torque, rpm, fuel economy and packaging.

Cheers

Gary

[GTR-32U]

^ hmm now this is getting interesting

[ylwgtr2]

So much fun to be had by all, I don't have time to respond to each one individually, so a quick list will have to do;

1. Mazda were banned from LeMans because they lied about the engine capacity, as they always have. They broke the category engine capacity limit, the fact is a 26B is actually 7.8 litres. They were told by the FIA to either enter the car as a 7.8 litre or walk away. Obviously entering it as a 7.8 litre would have proven what we all know and brought to an end the 40 years of lying. So Mazda withdrew.

2. Of course rotaries are popular in some drag racing where the Mazda lies on their actually capacity is still believed by some. Compare the performance of a 13B with any other 3.9 litre engine and their true worth is revealed. A 20B looks pretty dismal when compared with its true competitors, 5.85 litre engines. In comparison to big block V8's in true drag racing, rotary numbers are infinitesimal anyway.

3. I bet Mazda have spent more on 40 years of rotary engine development than Honda did on the their F1 and Indy Car engines. That's why it was a very valid comparison. BTW a 3 litre F1 Honda V10 engine weighs less than a race ready13B and produces more than double the horsepower.

4. The rotors, that produce the power, cycle at 3,000 rpm, which is the same as the pistons, that produce the power, cycle at 3,000 rpm. Hence why a rotary engine only does 3,000 rpm, multiplying by the eccentric shaft gear up ratio is irrelevant.

5. Mazda have been lying both ways, they can't claim both 1.3 litres and 9,000 rpm at the same time. If they multiply the rotor cycle rate by 3 to get rpm then they have to multiply the capacity by 3 to get the true capacity. Conversely if they count only one side (of a 3 sided rotor) to get the capacity then they should only count 1/3rd of the rpm. It's a double lie and well overdue for being revealed as such.

6. It's irrefutable that rotaries are 2 strokes. In one complete cycle of the rotor they inlet, compress, combust and exhaust. That's the perfect definition of a 2 stroke. Whereas a 4 stroke takes 2 cycles of the piston to inlet, compress, combust and exhaust. Further evidence of them being 2 strokes is the use of the rotor itself as inlet and exhaust valves and the need for oil in the petrol. If it combusts like a 2 stroke and it smells like a 2 stroke, then there is no doubt it's a 2 stroke

7. For a compact FWD application, rotaries are not such a good package, they are quite wide (in comparison to a slim inline 4) and the inlet and exhaust are on the same side. Add their requirement for a 3.9 litre engine sized radiator, oil cooler and fuel tank and this makes packaging quite difficult.

8. As for the B2200 delivery ute, a valid comparison would be a 3.9 litre 6 cylinder engine. Hell, even a common old 3.6 litre Commodore engine would piss all over a rotary with their 195 kW and 340 Nm. As for a diesel comparison, if you wanted load carrying the most popular diesel conversion, a 3.9 litre Cummins in line 4 at 481 Nm would make a far better proposition. Especially when it came time to fill up the tank.

9. Why is there only one car company that makes rotary engines? Perhaps the other car manufacturers are too smart. Let's face the facts, Mazda didn't invent the rotary engine, Felix Wankel did and his patent was owned by NSU, now part of Audi. Mazda still pays royalty on every rotary engine. Audi wouldn't have to, but they have never bothered with rotary engines. Perhaps they don't want to perpetuate the Mazdas lies. Woudln't it be great if Audi came out with the truth and told the world the true capacity and rpm of a rotary engine?

When you get past Mazda's 40 years of lying the real issues with rotaries become obvious. When you truly compare them with their equivalent engine competitors they are deficient in every area, horsepower, torque, rpm, fuel economy and packaging.

Cheers

Gary

I dont care about what capacity it is or isnt......its small....and its light....how big is your 3.9 litre piston engine?and how heavy?Do you suggest i fit one in my race car?Show me an engine i can walk down to any wreckers and buy and fit in the tiny hole i have that will retain the cars weight at 490kg.....and if we are talking about 3000rpm....well then they produce quite good power for a "slow" spinning engine dont they?

Edited September 16, 2009 by ylwgtr2

[FineLine]

I dont care about what capacity it is or isnt......its small....and its light....how big is your 3.9 litre piston engine?and how heavy?Do you suggest i fit one in my race car?Show me an engine i can walk down to any wreckers and buy and fit in the tiny hole i have that will retain the cars weight at 490kg.....and if we are talking about 3000rpm....well then they produce quite good power for a "slow" spinning engine dont they?

I think you'd fit one between your ears quite comfortably too.

No doubt you would also be accustomed to walking down to the wreckers to get a replacement.

[warps]

Ah, Gary's just upset that the rotaries are dominating IPRA

Better tell CAMS that their rotary multiplication factor or 1.8 is wrong.

You can buy Renesis engines for light aircraft, and from all accounts they work pretty well, too. They run them through a step down gearbox to get the prop speed into the correct range. Why don't they just make a few slight mods to the rotary and have the rotors direct coupled to the crank, the way they always should have been? Makes sense as it could remove two potential failure points. Highly important in an aircraft I would think

[warps]

I think you'd fit one between your ears quite comfortably too.

No doubt you would also be accustomed to walking down to the wreckers to get a replacement.

No need for personal attacks. This is all in good fun.

[FineLine]

No need for personal attacks. This is all in good fun.

just raggin mate. I have no love for eggbeaters but its no skin off my nose if others like them.

[Birds]

Gary, by your logic manufacturers of turbocharged vehicles are lying too. Advertising it as a 1.3 litre rotary is no different to marketing a turbocharged 2 litre engine as a 2 litre, which many manufacturers do. Do you want them to say it's really a 4 litre and include an explanation of how their engine works in all marketing literature to avoid any confusion? Of course the idea of it having 1.3 litres displacement was used to marketing advantage, but just like with turbocharged engines you're your own fool if you don't discover for yourself how these engines work. Displacement is somewhat irrelevant anyway, for only racing homologation cares about displacement. Everyone else just wants to know things like how much fuel it uses, how much power/torque it puts out, how big physically the engine is, how long it will last etc. Whatever lies that Mazda may or may not have told, they stop at these variables that people actually care about.

You're missing my point about your engine speed argument. Your definition of engine speed is based on parts moving inside the combustion chamber...this is very biased towards piston engines, particularly as engine RPM is always taken from a crank shaft in any type of engine. It's just by nature that a piston engine's combustion chamber components move at the same speed as its crankshaft. Again, I ask you, how do you want to measure rotor speed? Or were you planning on taking rotor speed from the eccentric (crank) shaft, where it should rightly be measured from, and dividing that by 3? The eccentric shaft gear ratio is a means by which the engine turns the shaft, the engine can't operate in its intended manner without this part and it is therefore a part of the engine. Whatever ratio or speed changes take place in between the moving combustion chamber parts and this output shaft are irrelevant.