By on December 18, 2007

pic06.jpgAccording to the official website, the Coates Spherical Rotary Valve System creates "a quieter engine with higher specific power output and longer life than conventional poppet valve engines due to better 'breathing' capability and higher speed capability." In fact, it's "the single most significant development in engine technology in the past thirty years." Not being the most mechanically-minded pistonhead on the planet, I asked Sajeev Mehta to check it out: "Its a logical extension of innovations like roller rockers: reduced friction, more power, efficiency etc. The general feel I got from people who know more than me: sealing a spherical valve isn't gonna work for a production car. Today's engines have to last over 100k miles without any trouble, and engine "blow by" will be even worse here… and don't even think about pressurizing these valves with a turbo/supercharger/ Good night! As for their claim of their valves not needing oil. Strap on an A/C compressor: sit in traffic in 100 degree weather on a heat-soaked hunk of tarmac and those valves will be begging for extra lubrication. The big red flag for me: their they compared it to a regular engine without an EGR valve. That's like challenging Carl Lewis to a 100m race and making him do it barefoot on hot asphalt. Everyone uses EGR valves for a good reason; they reduce NOx (the third row on their chart) emissions by something like 70% or more. "On the exhaust stroke the poppet exhaust valve stems allow "back" pressure through the valve guides into the engine casing. This pressure is then redirected through the fuel induction system and in turn is reburned in the engine creating yet more hydrocarbons, carbon dioxide and carbon monoxide." Except that happens on high mileage motors with worn valve guides/springs (valves snap shut plenty fine when new). It took 150k miles for my 5.0 Ford to get weaker/slower/dirtier from valvetrain age. Newer engines are even better at valvetrain durability for many reasons. I seriously question if the Coates engine will fare much better after that type of punishment. I'm skeptical, but would change my tune with better info. EPA-style tests that carmakers do wouldn't hurt." 

Get the latest TTAC e-Newsletter!


19 Comments on “Coates Spherical Rotary Valve System – Let the Rivet Counting Begin!...”

  • avatar

    As much as I like innovation, this ain’t it. There’s NO WAY to maintain the clearances for leak-free operation, except on a condition-controlled prototype or two. That is, unless the metals and materials involved are some form of Tomasite-Unobtainium alloy.
    We’re stuck with a reciprocating valvetrain for our reciprocating engine.

  • avatar

    Who’s going to work on these valvetrains? Normal machine shops?

  • avatar

    Hot Rod Magazine (I think) did a story about Coates several years ago. Their website has at least been graphically designed since then. I’m not sure if the content has been updated. This “technology” seems to have been around for several years now, but no one seems to have pursued this for manufacturing or even racing. I remain highly skepitical.

  • avatar

    I too doubt that there’s much a future in such a design, but I’m surprised we haven’t heard of somebody already trying this. Intuitively it makes since by reducing the number of moving parts in the valve train and eliminating the camshaft. Simplification can produce impressive and practical results, as in the case of the Wankel rotary engine, however this isn’t always the case.

  • avatar

    Someone on the interweb mentioned that its been tried in race applications and failed. Hard to verify, but I had enough questions/doubts after reading Coates’ website to say what I did. (and thanks to RF for publishing my thoughts)

    But I’m okay with vaporware if it isn’t promoted like Tesla’s non-existent roadsters.

    Stifling PR is fine, but let’s not do that with creativity.

  • avatar

    Wow, they have also solved the intractable problem of out of adjustment front wheel bearings!

    What a joke. Reading that page you would think that worn and improperly adjusted front wheel bearings are an epidemic. I can’t remember that last time I had front wheel bearing adjustment problems on a modern car.

    One problem with the Coates valve system is that it doesn’t seem well suited to dynamically adjustable lift and duration like the best modern engines use. I’m doesn’t look like they even incorporated dynamic valve timing.

    Their one “customer” appears to be a start up company in Canada which plans to sell natural gas powered generators to the oil and gas industry.

    Rotary valve engine designs have been tried for a long, long time. A nice summary history is here:

    The big advantage of a poppet valve is that the engine’s compression and combustion forces act on the valve in a way which just closes it tighter. With a rotary valve those forces are trying to push the rotating assembly away from the sealing surface.

    If you want to burn some time, read the latest quarterly report Coates has filed with the SEC:

  • avatar

    “the single most significant development in engine technology in the past thirty years.”

    Heh, it only counts when people are actually using it. I think the next “big thing” in valve train technology will be the move to valves controlled by solenoids. Those will be infinitely variable, could act as small throttle plates (a la diesels), and will eliminate much of the mechanical complexity and drag of existing valve trains. Unfortunately, I haven’t heard anything about this tech in a while and it would hardly be the first valve train tech to die a silent death (see desmodromic valves).

  • avatar

    Ducati would differ on the contention that desmodromic valve actuation has died a silent death! As nice as it is that they stick with tradition, there is no functional reason whatsoever to stick with the technology, what with the quality of today’s valve springs.

    If they did away with it I’d buy a Ducati in a heartbeat. As it is, the spectre of expensive valve adjustments every few thousand miles is off-putting.

    But I do agree that the next big thing will be direct solenoid activated valves. There are still a number of hurdles to jump with the idea, though. At high rpms the switching speed for a valve needs to be incredibly high, and the technology just isn’t there yet. I have little doubt that it is being worked on, however.

  • avatar

    Funny you mentioned it, C/D did a story on a person who made a solenoid-actuated valvetrain. IIRC, the motor was a 2.3L Ford and it actually ran as promised. Its ability to perform to OEM specs is unknown.

    I’m not holding my breath, but I wish these innovators the best of luck. Its hard to make something new in the car biz for a plethora of reasons.

  • avatar

    “I think the next “big thing” in valve train technology will be the move to valves controlled by solenoids.”

    Lots of work went into that idea and it was found that the energy required to electrically actuate a pure solenoid system is excessive. Valeo has a no cams electro-mechanical system they have been talking about for several years.

    Don’t hold your breath though, this technology has been any day now for decades.

  • avatar

    Spherical valves and solenoid-actuated valves have been around for ages. (I know that some steam locomotives from the 1800’s had spherical valves) In reality the (mechanically controlled) poppet valve is the best way to run the valve train in a mass production engine that has to perform over a large load and RPM range. This is one area of “research” that engineers have been thinking about since the dawn of the engine. I’m sure that just about every possible idea has been though of by more than one engineer. The only one that can withstand the abuse in an engine is what we currently have. Improvements are going to be very hard to come by and they’ll be incremental, not revolutionary.

    Even going to solenoid-actuated valves won’t work. The idea of infinitely variable timing is so seductive that engineers keep coming back to the idea, but the work required in switching the currents involved is incredible. First, lets get a time scale: an engine running at 3000 RPM means a valve needs to be actuated 1500 times per minute or once every 40ms. Even on a small solenoid like a fuel injector getting 40ms pulse widths is hard and thats only at a few amps of current. It is incredibly hard, if not impossible, to switch the kind of current needed to actuate a valve on those time scales. I know a researcher who needs to switch 2kV at 100A with a time resolution of 50ms and he uses the state of the art electronics that he designs himself and it takes up half of a room. He’s also fixing it every week as the arcs burn through everything.

  • avatar

    Thanks miked, this also reminds me of the old electronic supercharger debate. The energy required to get modest (at best) boost pressures make them irrelevant outside of eBay scammers and forum trolls.

  • avatar

    Formula One engines have been using pneumatic valve “springs” for decades.

    They operate at up to 21,000+ rpm, but my understanding is that they are not reliable enough for long-term use in production engines. I’d think Ferrari would have done this in production engines if they could make it work.

    As Shaker said, there’s NO WAY to retain seal integrity on rotary valves for the long haul.

    I thin we will eventually see solenoid-operated vvalves, as they would give a real boost to emissions and power with infinite variability.

  • avatar

    If you look at BMW’s Valvetronic system:

    It provides 90%+ of the benefits of infinitely variable valve timing while still using mechanical and electro-hydraulic systems.

    Also, it turns out that variable valve timing is a high bang-for-buck modification. Much of the benefits come just from being able to vary exhaust cam timing. Ford does this on some engines (Escort?) because the additional benefit of varying intake cam timing doesn’t justify the cost.

  • avatar

    At one point news reports speculated that BMW would be using an electro-mechanical valve mechanism, but what actually came out was the all mechanical valvetronic system. I don’t think we are going to see a solenoid or even a Valeo style system in production for the reasons miked already summarized very well.

    Another “innovation” which is often speculated about is an electronic coil style suspension system to replace the springs and shock absorbers. Bose in one of the recent largish companies which invested a small fortune in that idea. There was a bit of a news splash about their efforts in 2004:,1759,1640050,00.asp

    Infiniti even sold an active suspension option sometime in the 1990s, but it didn’t last in the marketplace.

    For some things mechanical/hydraulic systems remain a much better choice than electrical ones …. and I’m an Electrical Engineer.

  • avatar

    Maybe they’ll work better with a Fish carburetor?

  • avatar


    There’s a reason the industry doesn’t use sleeve valves anymore…

  • avatar

    Naw, the “next big thing” will be the return of the Willys-Knight sleeve valve engine!

  • avatar

    The latest “Coates HOT OF THE PRESS” China will require – if everything pans out – that all engines will be Coates engines. What next? This should happen in 2 weeks – ad infinitium.

Back to TopLeave a Reply

You must be logged in to post a comment.

Recent Comments

  • pwrwrench: EEEK! A Gremlin van. They could have done like Chrysler (Omni/Horizon) and bought engine/transaxle from...
  • Fred: I haven’t heard of much good come of Brexit. Then again I’ve got enough to worry about here in the...
  • thegamper: Every time I see the new Accord from any angle other than direct frontal, I see the Chevy Malibu. Not a...
  • krhodes1: There is zero need for either the 1.4T or 1.8T to be 6spds. They make so much torque across such a wide...
  • Pig_Iron: Dauntless V6 Turbo ;-)

New Car Research

Get a Free Dealer Quote


  • Contributors

  • Matthew Guy, Canada
  • Ronnie Schreiber, United States
  • Bozi Tatarevic, United States
  • Chris Tonn, United States
  • Corey Lewis, United States
  • Mark Baruth, United States
  • Moderators

  • Adam Tonge, United States
  • Corey Lewis, United States