Lets talk Wankels

[miniv8]

With the other discussions on rotor/hub pistonless mistery engines, I want to start a discussion on Wankel engines.

Given the oppertunity I'd try one in my dragster, for shits and giggles. But I havent handled one of these engines, ever.

I wonder why, with so high power to weight ratio these engines arent more common in the automotive industry. Is mazda still copyrighting it?

First video is of the current door car record holder 6,58@208mph, second video is an unrelated wankel on the dyno. Beware of weedwacker audio.

http://youtu.be/U3uiuCqbHyw

http://youtu.be/coXB3xd6VK8

[Unkl Ian]

Three possibilities, off the top of my head:

Some sanctioning bodies factor them by 1.5x or 2x their displacement.
Low speed torque is typically not very good.
They sound horrible.

[Schurkey]

Difficult to machine. It's not like you can drop a boring bar into them for clean-up.

I don't know who has the license rights--NSU or whoever bought them, I suppose.

I've wanted to buy a junk Mazda and "see what makes 'em tick"; but there just aren't that many old Mazdas around here.

[sbs]

I've owned 3 Mazda rotaries.

My understanding is that the main reasons for lack of wider adoption are emissions & mpg.

They are also somewhat fragile and even at stock power levels don't last remotely as long as your typical Japanese 4 or 6 cyl engine with similar power output. They are usually pretty tired by 100k. The most I got out of one was about 180k, but it was a very tired engine and had been blowing smoke for 50-60k miles at that point.

So they have serious deficiencies for a mainstream car. Which can be overlooked in a small light sports car where we accept compromises for power/weight. Which is why the RX7s made a lot of sense.

[kirkwoodken]

As I recall, the Wankel was only 25% efficient, compared to about 33% for an ICE. Curtiss-Wright had the patent rights last I heard, about the mid 70's.

[ProPower engines]

I remember when they were outlawed in the midget class cause they just plain made too much power. They would turn
12-15,000rpm and just blow the VW based engine into the weeds.Had a local guy that built them. Higher compression rotors that were tipped better and they things lasted pretty good.
When they came out in the early 70's they did have oil consumption issues. and at the 50k mile mark as part of regular maintainance they just replaced the engine with a new one. They did get the oil consumption figured out by the time the later models came out but they were a really stout power plant concidering whet they are.
There was intakes available back then as well. I remember one that was done up that used a 650 DP holley. That thing was fast and would take on any BBC chevelle or camaro and have it for lunch.

[Engguy]

As I recall, the Wankel was only 25% efficient, compared to about 33% for an ICE. Curtiss-Wright had the patent rights last I heard, about the mid 70's.

Unless they are all steam or something similar with pressure developed outside the engine, a Wankel is an ICE. Oh and that would make a piston engine a non ICE as well.
Less effciency likely due to the greater combustion chamber surface area of a Wankel.

[SchmidtMotorWorks]

Anyone remeber the rotary that used to run in some stock or superstock class in the late 70's. The sound was so terrible people covered their ears.

They ran very well in some GTU class tha I saw them in at Riverside CA about 86

[Ratu]

Yes indeed, two rotor Wankels don't possess the most attractive exhaust sound. Then again, most piston engines of low cylinder count tend to produce a bland sound as well. On the other hand three rotor 20B engines sound pretty good and the four rotor 26B is outstanding- music. The Mazda 787 Le Mans car with its four rotor engine remains the best sounding endurance racer ever. I was very glad when it emerged victorious at Le Mans (Mazda is the sole Japanese car company to have won Le Mans outright- they never repeated the feat as their rotary was banned from participating again- rumours of a five and also a six rotor engine emerged and the race organisers were frightened that all the regular engine manufacturer teams would be annoyed and not show up).

There was a US based fabricator who developed a single shaft in-line five rotor engine. More recently a US outfit developed a three shaft, six rotor engine for off-shore power boats. I have not heard one of those running yet but I would expect it to sound quite good.

It seems to me that rotaries are analogous to piston engines. The higher the piston or rotor count the more likely the engine is to sound good (ceteris paribus).

Now, returning to the dragster. How about a pair of 13B rotaries? Phase them right and you should end up with enough power and an exciting exotic engine sound as well.

Ratu

[dieselgeek]

I have tuned probably 15-20 13B turbo engines, up to 700whp on street driven cars - for some reason where I live they are very popular. A friend of mine rebuilt one on his kitchen table - they go together like a Ham and Cheese Sandwich - in about 45 minutes.

I know that in the past 5-10 years the aftermarket has really sorted out the Apex seals. Another surprise is how popular they have become in homebuilt aircraft. Lots of guys are flying N/A and turbo 13Bs now.

I just recently tuned my first 20B, a three-rotor engine with a large single turbo, capable of an easy 1200whp if the rest of the powertrain can handle it. Pretty impressive really.

Another strange thing I learned about them, some people get "motion sickness" when they are around these engines at WOT. I have no idea what the reason is, but I know a number of guys who just cannot be nearby when we are running them on the dyno - they get queasy. I know one guy who had to quit his job on a drag team because every time they ran the car - he got sick.

They are not really that fragile anymore, I heard one detonating like mad on a dyno pull, I was told "one hint of detonation and they're done" but I don't think that's always the case - this one was rattling like a tin can full of marbles, until we sorted out his ignition and fuel.

They are fun engines to tune, easy and rewarding when you lean on them with lots of boost.
-Scott

[Kenova]

Another strange thing I learned about them, some people get "motion sickness" when they are around these engines at WOT.
-Scott

Maybe it's the high frequency sound messing with their inner ear(s).

Here is a thread I've been watching for a while. A home built four rotor. It will certainly appeal to anyone interested in machine work.

http://www.rx7club.com/showthread.php?t=974831

Ken

[Unkl Ian]

This guy couple a pair together:
http://grannys.tripod.com/4rotor.html
http://grannys.tripod.com/4rotorcoupling.html

[Mr 408]

not automotive but cool nonetheless,

a pair of worked 535cc single rotors in a Johnson [OMC] ice oval sled.

http://irocu20.tripod.com/imagelib/site ... rget=_self

http://irocu20.tripod.com/imagelib/site ... rget=_self

[autogear]

I was at a car show when a mobile dyno showed up; your typical muscle car guys showed up and cracked off ~200rwhp in their camaros; 2 ricer kids showed up with Hondas and got laughed at...and 2 brothers or cousins from Buffalo showed up with a really well put together RX7 and a Supra...impressed a LOT of folks. Coolest car was small dodge pick up truck with an Eagle Talon motor swapped in.
Re: sickness, there is an odd high frequency vibration it seems.

I like wankels, but my friends NA RX7 got worse gas mileage than his dads late 70s BB vette.

[Rizzle]

I like wankels, but my friends NA RX7 got worse gas mileage than his dads late 70s BB vette.

Why do production rotaries get bad mileage? Some of the links above got me interested (the custom 4-rotor build is impressive) and the research pointed towards the 787b, which, in its prototype C2 racing class with fuel consumption limits, it had a lower fuel consumption then its competitors, anyone know why? Also, how high compression ratio can you get with the mazda rotaries?

Yeroon