Wankel powered W113?

[Steve.k]

I just came across an article in Jalopnik discussing some Wankel parts from the C111 on eBay and learned that prior to the C111, Mercedes tested a three rotor Wankel in four prototype W113’s in 1968.   
I’ve read a fair bit about the Pagoda over the past few years and must’ve missed that part.   Apparently it produced 203 HP and had a top speed of 130 MPH. 
Anyway, I’d love to hear any further details of this interesting aspect in the Pagoda’s history.  If anyone has more to the story, please share.
Here’s the link to the Jalopnik story https://jalopnik.com/is-this-really-an-ultra-rare-mercedes-c111-wankel-rotor-1832871492
It’s an interesting read in any case. 

[stickandrudderman]

I’m more surprised that you fo7nd some C111 parts on eBay! The C111 was never put into production.

[Jack the Knife]

For anyone who finds this thread in the future on Google or wherever, I've compiled every bit of info I could find on the Wankel motor. Alternative engines and alternative lines of development for the Pagoda really interest me, especially since I find the production motor options to be unsatisfactory.

First, from Mercedes' own website: https://group-media.mercedes-benz.com/marsMediaSite/en/instance/ko/The-rotary-piston-engine-in-Mercedes-Benz-SL-W-113-and-R-107experimental-vehicles.xhtml?oid=9918213

Note the actual photo of the motor.

Here's the beef of that article, "An M 50 F model three-rotor engine has been installed in the experimental SL with the designation W 33-29. It has an overall 3.36 litre chamber volume, producing 203 bhp (149 kW) at 5600 rpm and, between 18 June and 23 October 1968, it notches up some 69,000 kilometres. With a top speed of 205 kph, the vehicle is almost 10 kph faster than the 280 SL production vehicle at that time."

Also of note is the fact that they installed even more powerful four-rotor motors in the 107s, generating 277bhp. Quite impressive numbers for the time! Their concern was both the poor fuel efficiency and high emissions. I had always heard that the engine had reliability issues. Indeed, I remember seeing a notation for that on the Wikipedia article for the Pagoda, but it looks like that has been deleted. Mercedes themselves says it was the emissions/efficiency, "[. . .]  and not the constantly repeated suggestions of mechanical problems." While none of the original Pagoda Wankel test mules exist, it looks like Felix Wankel kept a 107 with four-rotors. Back when BaT did very interesting editorials, they published an article on that very car, seen here: https://bringatrailer.com/2020/05/19/technically-interesting-dr-wankels-quad-rotor-mercedes-sl/ There are many more drawings of the actual engine in that article, if you're curious. It's a fascinating read. The article notes the engine is 60kg lighter, and I'm inferring they mean lighter than the cast iron M116 3.5 block that was originally in Wankel's car. The 3.5 block weighed 250kg I believe, so Wankel's motor was around 190kg. That's pretty substantial, since I believe the aluminum block weighs around 28kg less than the cast iron block.

I'm not able to find any solid emissions or mileage data. Perhaps that is worth an email to the Classic Center. Anyway, if I were very rich, for posterity's sake, I would consider one of Mazda's Wankel motors, perhaps the 13B-RE, which comes close to the performance in Wankel's own 107 -- and likewise weighs only 112kg. Though I will say that the transmission options for the 13B are more plentiful and considerably cheaper, so while the motor might be more expensive than other swaps (M116, M110 DOHC, M117), the transmission is certainly cheaper ($400 or so compared to $8k~ for a 6-speed S&SG unit that is compatible with the 110/116/117). But then that doesn't get into if that transmission fits in the tunnel fabricating engine mounts or any other number of things the Mazda unit would require. An interesting thought, though!

Edit: As Mercedes themselves experimented with the Wankel motor in the 113, I resent the implications of this thread being moved to R&D. By that logic, any discussion of the 6.3 car, rally car, Pininfarina and Frua derivatives, and Bracq's design alternatives should likewise be in here.

[Jonny B]

I don't think Steven found any parts, it was the article from Jalopnik. The article refers to parts on eBay but is dated 2019.I wonder if they ever found anything more about the Wankel - Mercedes C111 connection.

Quite an interesting story. For the record, I had not heard of the tests of a rotary in the 113 before. Always, always learning.

Some friends and I were in Europe in 2021 for the Dutch GP, and we had some time to go to Berlin and then stop at the VW park in Wolfsburg. We completely missed the museum in Stiftung that has the 107 with the Wankel engine, almost factually a stones throw from the VW complex.

[MikeSimon]

The "Achilles' Heel" of the Wankel rotary engine was the seal strip on the tip of the rotor following the epitrochoid shape of the chambers. Neither NSU on the Ro80 nor any other manufacturer except for Mazda could get a handle on the excessive wear in that area. Jim Downing campaigned a Mazda 13B Wankel 4-rotor engine in his Kudzu prototype WSC race cars quite successfully. The sound of these was exhilarating.

[Swissomatic]

Not sure if anyone else has seen the recent announcement that Mazda is re-introducing the Wankel engine as part of a new hybrid setup. Not sure how they resolved the emission and oil consumption issue. Sounds like a compact, energy efficient package.

[Mike Hughes]

Perhaps, the operation of a Wankel engine in an electrical generation setup at a constant speed under a constant load makes it possible to minimize those issues.  It certainly would be smooth!  Hummmmmmmmmmmmmmmmm . . .