By on May 3, 2011

One of the cool things about the SAE World Congress is that there’s always at least a couple of radical new engine designs. Scuderi was back with their split cycle compressed air hybrid, only this time with a turbo that lets them use a much smaller piston on the intake side, reducing friction. FEV showed an engine optimized for compressed natural gas, with turbocharging, long intake runners, and a piston designed to increase turbulence. Two exhibitors were at the SAE for the first time. Grail Engine Technologies was showing their atmospheric-valve-in-piston engine that routes the induction through the crankcase and up into the combustion chamber.

FEV is a large company. Scuderi is a spin off from a maker of compressors. Grail is a startup but they have some venture capital behind them and a staff that includes respected engineering professors. The Doyle Rotary is one man chasing the American dream. Lonny Doyle is a machinist. He started out working for race teams and now owns Doyle’s Fabrication, a machine shop serving the aerospace industry. Twenty-five years ago he started toying around with an idea for a new engine design, refining it to the point of getting a patent in 2001. Since then he’s been building prototypes as his funds permitted.

<p align=
Doyle Rotary Engine. Photo courtesy of Cars In Depth

The Doyle is a rotary engine. Not like the Wankel, but like the early rotaries, a variation of the radial engine. At rest they look alike, but a radial is a conventional engine in that the crankshaft spins. In a rotary, the crankshaft is fixed and the crankcase and cylinders spin around it. Rotaries were used for World War One era biplanes, the most prominent one being Gnome. There has been at least one automotive application of the rotary. Adams-Farwell built 52 rotary powered cars between 1905 and 1912.  Their original production car had three cylinders spinning away above the rear axle, driving it with a ring gear. Animated Engines has a animation that shows you how the rotary works better than I’d be able to describe it.

Doyle’s invention adds a couple of very novel twists to the  concept of the rotary. A conventional rotary has the piston facing outward, and the connecting rods are connected to the central crankshaft. Doyle flips the pistons around so they face the center of the engine. The connecting rods point outward and are anchored to the external case. The external case, the pistons, and the cylinder case all rotate around a central combustion chamber on an eccentric, causing the pistons to go up and down. If that wasn’t novel enough, Doyle made it a split cycle engine, with two banks of pistons, one for intake and compression, the other for power and exhaust. Doyle says that with the cylinder case made of aluminum, rotational mass will actually be less than in a conventional engine of similar power. The Doyle engine has no valves. There’s a port at the inward end of the cylinder that allows gas transfer into and out of the cylinders and the central combustion chamber. To keep everything in its place Doyle has used off-the-shelf Mazda Renesis Wankel apex and rotor seals. The latest prototype has a total of 12 cylinders with 4.2L of displacement and 6 combustion cycles per revolution. In a conventional 4-stroke engine each piston has a power stroke ever two revolutions. Doyle’s engine is effectively a 4-stroke with each [power] piston having a power stroke on each revolution, though he calls it a Doyle Cycle engine.

They’ve gotten as far as running to failure. When fired in December of 2009 the latest prototype ran for a little more than 30 seconds but the seals ended up galling the aluminum and the engine seized. The next prototype will have steel inserts.

Doyle is not disheartened, since running to failure is itself a sign of progress. Encouraged by that progress he went public with a web site, YouTube videos, and booth at this year’s SAE congress, hoping to drum up potential investors or customers.

I think what Doyle has accomplished is simply amazing, particularly in light of his limited resources. The other engines above are being developed by actual companies, in FEV’s case an established automotive vendor. Doyle is doing this on the side from his day job and he got the engine to run.

I’m not the only one who is impressed. All the other engine innovators at the SAE show had been to Doyle’s booth and were intrigued. More importantly, there was genuine interest from automakers. Doyle couldn’t identify which one it was, but he said that one of the domestic automakers was interested enough that one of their engineers spent a half hour on the phone in front of his booth trying to get someone from the legal department in their headquarters down there. They told him that they’d rather he just put a curtain over his booth so nobody else could see it.

Scuderi kinetic cutaway:

Start the video, pause, then click on the 3D icon in the menu bar to select your choice of 3D formats or 2D

Grail Engine animation:

Scuderi running:

Get the latest TTAC e-Newsletter!

16 Comments on “The Doyle Rotary Engine...”

  • avatar
    Kosher Polack

    Cool! Except, how does cooling work?

    Every few years you see a guy invent a totally new internal combustion engine and then you neeeever hear about it again, either because (a) it failed, (b) he took his check and is living on a tropical island or (c) more sinister reasons. Hopefully this guy can make a (d) gives me a running prototype before licensing to install in an RX-7 (it’s still a “rotary,” purists.)

  • avatar

    GM guy on the phone, maybe? Looking for a new onboard generator engine for the Volt 2.0?

  • avatar

    Love reading this kind of stuff–thanks Ronnie for covering it.

  • avatar

    +1 Great writeup

  • avatar


    Sooner or later, someone will have an idea which will turn the automotive world on it’s head…thankfully, I believe we will read about it first!

  • avatar

    So this is an experimental engine, one running at thousands of RPMs, made mostly of aluminum. I think a transmission scatter-shield would make me feel a little better. Regardless, I would not stand next to it!

    Very cool, regardless.

    • 0 avatar

      I was also surprised that he didn’t have any barriers or PPE either.

      One of the advantages of this design is that it uses a conventional piston/cylinder arrangement. I think that one of the big flaws in Wankel design is that the geometry precludes optimizing the “combustion chamber”.

  • avatar

    Love these articles. It gets the inner geek in me feeling all excited.

  • avatar

    I’m a very close friend of the webmaster for the Grail guys. It’s a pretty neat thing to see, from inception to where it is now. It’s showing alot of promise, from what I’m told.

  • avatar

    Every “alternative” ICE arrangement that ive seen always had greater friction and less ability to cool and/or lubricate than “conventional” layouts. The Wankel was the only marginally successful one, and it certainly didnt take over, did it?

    • 0 avatar

      It’s funny that you mention that – one of the design briefs of Ecomotors’ OPOC is lower friction. I asked about friction and Doyle told me that the swept area of the two main bearings is less than that of the main bearings in a conventional engine, so there’d be less friction. On the other hand, with 12 pistons there’d be more friction than with the 6 or 8 in a conventional motor. Doyle’s response was that low friction piston rings reduce piston friction to a manageable amount.

      Considering he’s a one man operation (his sons are engineering students who help out when they can), financing this out of his own pocket, I think it’s an accomplishment just getting the thing to fire and spin.

  • avatar
    Felis Concolor

    6 firing pulses every revolution? That’s some smooth power. Increase the count to 18 cylinders and 9 firing pulses and you’ve got a miniature, inverted double-wasp.

  • avatar

    A scatter shield would make me feel better too. Hopefully this next one will run long enough to need one.
    Ronnie was correct about water cooling.
    Coolant runs through the stationary crankshaft, into the cylinder block via a mechanical seal, around each cylinder and then back through the mechanical seal and then back out of the crank to the radiator.
    Ronnie we owe you one on this article you have written, it is great!
    We have never tried to get funding for the Doyle Rotary. I have always kept it a secret. We are now looking for funding and articles like this will surly help.

Read all comments

Back to TopLeave a Reply

You must be logged in to post a comment.

Recent Comments

  • SCE to AUX: Unlike 3G, that CB radio would still function today! Sadness = 140 HP from 5.9 liters. The rollback of a...
  • 28-Cars-Later: “We have the Northstar system, do we even use it?” That’s the real question.
  • tane94: Two-tone exteriors were quite a trend in the late 1970s. Black and silver were available from several...
  • FreedMike: Bingo. And that works great, as long as you can pay. The problem comes when you can’t…or if...
  • eng_alvarado90: If I recall correctly, up to the late 70s Cadillac did not share any powertrains with...

New Car Research

Get a Free Dealer Quote

Who We Are

  • Adam Tonge
  • Bozi Tatarevic
  • Corey Lewis
  • Jo Borras
  • Mark Baruth
  • Ronnie Schreiber