I always wondered how rotary engines worked - here is a brilliant model

Enjoy!

Wankel

Rannoch

 

Thanks for that , was quite a good write up in spin (rx8 owner's mag) of how it works recently

 

Thats the RX7 wankel isn't it on that diag? the inlet and exhaust show why the rotor tips would wear by constantly catching on them which I believed they fixed on the RX8 by moving the inlets to the sides..... IIRC....?

 

Yep, that's right.

Rotary's a great idea in theory, but hard to put into practice. Dr Wankel himself disowned the type of fixed-housing rotary motor that all manufacturers have used.

Wankel's original design had both the rotor AND it's housing spinning co-axially, god only knows how that would work but his prototypes produced stunning power figures.

This type could not be put into mainstream production because each trochoid had three spark plugs and you needed to completely strip the engine to change them

Wankel called it his "racehorse" motor, but when manufacturers put the fixed-housing type into production, he dismissed them as "carthorse" motors (but still trousered the patent royalties, obv )

More stuff about it here: Craig's Rotary Page: NSU Wankel rotary engines and cars

 

The exhaust ports were moved to the side in the RX8 "renesis" engine. This was done primerely for emissions. The main reason why the rotor tips were failing in the FD3 3rd gen RX7 was the heat. The twin turbo set-up caused the engine to run too hot resulting in premature tip wear, hence why they usually needed a rebuild by 60,000 miles. The tips in the 2nd gen lasted very well (normally aspirated), I know of some that are still going strong with 150,000+ miles on the clock.
The current renesis engine is far more technically advanced than it predicessors (sp) but it is not without it's problems, hence why I got rid of my RX8, just had far too much trouble with it.

Chris.

 

I'd be interested in hearing your problems with the RX-8 as I'm considering replacing my Scoob with one ....

 

"How stuff works" had good animations on it too, i love the simplicity of the rotary engines. always loved the RX7's and if i had more money (for engine rebuilds) I'd have got one!!

Still the best looking car on the roads today!!!

Dave

 

A work colleague of mine had an RX7. He used to use a tank of petrol getting from Brighton to Enfield.

Rotary engines are fantasically uneconomical.

 

LOl yup, i think they are about 16mpg out of the box!! give it some beans and i'm sure they will be in single figures!!!

 

LOL - thankfully the RX8 isn't quite that bad!

Mine averages around 22 to 23 - about the same as my Scoobs. The one thing I have found with the RX8 is that it doesn't matter if you boot it or drive it sensibly, it doesn't seem to affect the MPG. I've done just over 30K in two years in my car. So far it's been as reliable as my Scoobs (probably the kiss of death )

 

Ravster - Problems I had with mine as follows, Gearbox made strange scraping noises in 2nd & fourth gear (didn't make any noises at first) which dealer told me "its normal sir". Engine made a horrible rattling sound above 5500 rpm but this only did this after a 10 min cruise on the motorway, again "it's normal sir". Oh and when it made the ratting noise it also lost power. The cat failed at 15000 miles which was replaced under warranty, Most owners have had their cat replaced some have had at least 2 replaced (these are £800 each). I had a new starter motor, new alloys and the cills re-painted after a design fault with the rear doors rubbed the paint off. All of these items were repaired under warranty but the car spent more time at the dealers than it did on the road.
The first uk models are now 3 years old and are starting to suffer with broken ARB drop links. Go over to the RX8 owners club site if you want to know all the common problems.
To be fair I think I had a friday afternoon car but they all suffer most of the common faults.
As for fuel consumption, I had the high power model and I got around 17-18 mpg no matter how I drove it apart from on track where I got around 7-8 mpg. Oil consumption is not as bad as people think mine used around half a litre per 1000 miles. The handling on them is spot on much better than my STI, the suspension is a little soft and they do suffer from body roll but they are superbly balanced. The main difference I note between the two is you can drive the RX8 really fast around the twisties and it always feels very sure footed and in control.

Hope this helps.

Chris.

 

That's a shame Chris - they really are lovely cars. I've heard of some of the problems (my cat went after 10K, but then I lost cats and exhaust sensors on the Scoob) - everything else has been OK so far.

 

I do fancy an RX8 - but as a second car to my boring sooty Octavia (when it comes).

Steve