Plastic Engines – We Have the Technology – Is Anyone Interested?

Plastic engine block

Plastic engine block

Losing weight isn't just a perennial goal of human beings, it's the holy grail of motorcycle design, at least in terms of performance. If you want a motorcycle to accelerate quicker, stop faster, get better mileage or perform better in almost any area, just reduce the weight. Plastics have long been used for many reasons in vehicle design and weight reduction is certainly among them, so think about it, after removing the rider, where is the majority of the remaining weight in a motorcycle? It's the engine.

An interesting article in the New York Times talks about plastic auto engines, and they visit with Matti Holtzberg, an engineer and president of Polimotor (short for polymer motor) Research, who designed, built and even raced, plastic engines in the 1980s. He transformed a stock engine from a Ford Pinto, 88 hp and 415 pounds into a 300 hp, 152 pound engine.

Popular Science September 1982

... [he] used plastic for the block, piston skirts, connecting rods, oil pan and most of the cylinder head. Bore surfaces, piston crowns and combustion-chamber liners were iron or aluminum. The crankshaft and camshaft were standard metal components.

He raced a Lola in the IMSA Camel Lights series and had only one failure, a connecting rod from an outside supplier. Even with the success, interest from automakers was low, standard production and manufacturing techniques were working fine, why change?

Fast forward to 2009 and some companies are showing interest. Although iron engines in those days were heavy to start, plastic engines could even reduce the weight of today's aluminum engines by 30 percent. Technology has definitely advanced in the last 25 years so it seems natural to at least give it a try. Think about that sort of weight reduction on a motorcycle. In a car, the engine is a much smaller part of overall weight, on a motorcycle, it's the single heaviest piece.

Though other Polimotor engines were designed, no motorcycle applications were tried, from what I could find.

Polimotor attracted a lot of interest back in the 1980s, with articles in many publications but faded from the limelight. Now that there is a glimmer of interest, it's unlikely a motorcycle company would be in the position to take a chance on the technology just for its own use, but it might be the perfect place to test the technology for durability before using it in large scale application in the auto world. If it happened to work out, wouldn't it be neat if we got the benefit of some really lightweight powerplants in the process?

Link: New York Times


  1. Wave says

    This is already happening, in more of an evolutionary way rather than a revolution. Plastics are now commonly used for rocker covers, intake manifolds and oil pans (sumps) in cars and trucks. Converting the whole engine block to plastic will be a big leap for the auto manufacturers, but I agree with you that the application to motorcycles makes perhaps more sense, as the weight savings are more noticeable. Perhaps this could first emerge in Moto GP or even dirt-bikes? I’m sure we will see even more composites and polymers replacing metal parts in previously unthinkable applications soon.

  2. JC says

    There was once a time when nobody wanted aluminum block engines in cars, partly because of the fear of something new and partly due to the poor track records of some of the early cars that used them.

    I would not want to be a buyer of production version 1.0, but 20-30% lighter certainly seems like worth trying for. Plastics and manufacturing have certainly improved since the 80’s

  3. Doug says

    Plastics are one of the main pollutants in the ocean, and landfills. Plastics contain elements that are now being linked to birth defects as well. The repair and recyclability of plastic is suspect. Most used plastics in north america are being stockpiled, not recycled. Too light of weight on a road going motorcycle can be a hair raising experience on an main highway with strong cross winds, and larger vehicles. I’m not that thrilled.

  4. Chris says

    Oh NOOOOES! pollutants! Living is toxic, get used to it. How about mining for Bauxite or Iron, is that TOXIC?!!!!

  5. Rashomon says

    In many cases, engine weight savings of 20 to 30 percent over most current designs can be achieved through detail design work and improved metals and manufacturing processes. There are a lot of die-cast parts in engines with strengths only slightly better than that of pot metal. There are manufacturing processes that can produce aluminum cases with a 500 percent improvement in strength compared to typical die-cast cases; Ducati recently shaved kilograms from their 1198 engine going to a high-end vacuum assisted die-casting process that produced cases that could be heat-treated. (You typically can’t heat treat die cast parts because of trapped gases expanding during the heat treat process damaging the part). In comparison to better metals, plastic reinforced parts are relatively problematic, with thermal issues holding up their usage. You’ll see them for parts like cam covers and side covers first, because everyone is busy designing out structural elements in these covers (bearings, etc.) to eliminate noise transmission paths. If all it has to do is retain oil, it’s possible for a plastic cover to work given current technology, as proved in automotive applications.

  6. pabsyboots says

    huh ? what a great idea i imagine they are mostly glass filled nylon, the parts should be waaay cheaper too, i’m suprised the automakers themselves arent doind more in this area

  7. nortley says

    Wanna save a few percent more in weight? Mold the engine/transmission “block” in one piece with the frame to eliminate a lot of hardware,bracketry, and structural mass.

  8. says

    hey Chris – sure there is toxicity in a lot of things, but does that mean we don’t consider the impact before manufacturing? I sure as hell hope there are recyclable standards for battery content before the electric vehicles start getting produced in the hundreds of thousands.

  9. bblix says

    Our company molds plastic parts that are used in the cylinders of small engines for at least one major manufacturer. I was at first shocked, but apparently it’s been in used for years. The engines are small, cheap, and not all that high performance so I don’t know how long-term wear plays into the equation.

    It seems to me, a well thought out, ground up approach could probably make use plastics on a production engine. They are certainly in high use in non IC applications (hybrid motors and power packs likely make extensive use). I can see where major structural components will be replaced by engineered composites and resins.

    I guess the question is, is it too little too late?

  10. says

    The motorcycle application of plastic engines does make sense.
    Assuming some bike models adopt a good % of plastic in their engine, it will be interesting to see how that changes the frame construction. One benefit of rigid, metal engines is that you can centralize mass around it by using it as a stressed member, reducing frame material & consequently weight of the chassis. Engines would probably be another type of “composite” instead of entire blocks being made of plastic.

  11. Oldyeller8 says

    Takes me back to the early 80’s when I first started racing. A mechanic / race friend asked me to think about the following;
    Rubber cam lobes – Increased lift and duration with increased RPM. Back then it was a joke – maybe today it could be real!

  12. C.P.T.L. says

    “Life is toxic”? No, specious B.S. is toxic.

    The problem of plastics is huge. While some just shouldn’t be, others are beneficial, or, their use tends to outweigh their detriment. Doug is right, we’re way behind the curve on dealing with all of them after their useful life is over. And thus far we’ve created an extraordinary mess by putting the ‘other half of the equation’ out of our minds for 60-odd years. Where and how plastic things end needs to addressed.

    As for plastic engine blocks and parts, if it’s done with their end in mind, it would be fantastic.

  13. Mel Beaty says

    I’m old enough to remember the polimotor and thought it was a great idea. I also remember another effort at a lightweight motor by using essentially sheet metal parts, brazed together in a high temp oven. I think some NASA folks were involved with it. As I recall it was as light or lighter than the plastic number and quite easy to manufacture. I think I’ll Google it and see what I can find.

  14. Scotduke says

    Reducing the weight of reciprocating components would reduce the forces being exerted internally so a plastic engine could feature a lighter duty block, while with lower inertial forces would mean that toque effects and primary, secondary and tertiary vibrations would also be reduced.

    As regards aluminium blocks, bear in mind that the shortblock, aluminium V8 developed by GM in the early 60s was only in production for a couple of years in the US. Rover saw this abandoned engine design, bought the rights to it and started manufacaturing it in the UK. The engine was in production in the UK for around 30 years, was developed (and bored out) and was installed in a huge number of performance vehicles (like the V8 Range Rovers for example). Just because GM didn’t have the imagination to offer a V8 with anything other than an old-fashioned, iron block it didn’t mean that others couldn’t profit from it.

    Incidentally, when BSA/Triumph first tested the prototype of the single OHC 350 parallel twin in the late 60s, resonances (chatter) from the cam and followers meant that the valves stayed open longer, increasing the power output.

  15. James Bowman says

    I think plastic engines could offer enormous advantages, no matter what directon we go you will get some type of pollution? All of a sudden global warming is taking a back seat as facts that it was really pseudo science propaganda and media hype more than reality. This is the problem, credibility or lack of it which will probably cause more enviornmental detriment in the end because people now realize they were victims of misinformation. So when eco cooks attack and label people as denyers etc… they actually will not be heard if and when they have more than fantasy and could offer useful information they will already have been discounted.

    Look forward to more information on these plastic engines maybe they could use some of the plastic thats already availible from waste.

  16. Stacius says

    Mr. Bowman,

    Global warming is NOT taking a back seat to anything. It’s merely a well-funded campaign to create FUD around the issue so no one will have to do anything meaningful about it. (
    I don’t offer this as “proof” (, because most people just believe what they want to. I suppose the ocean would have to be lapping at some folks doors before they’d accept it anyway.
    Nonetheless, plastic engines would be an interesting way to go. I’d like to see what one could do at the salt flats.

  17. kneeslider says

    Let’s all get back to engines and leave the global warming or cooling for another time. Thanks.

  18. Trey says

    Hmmm, just to throw an idea out there… Produce a 2 stroke engine with this “plastic” block. Fewer parts, less weight, and I know 2 strokes can be designed “clean”…


    A rotary engine (ala Wankel). Already has fewer parts, can get a lot of bhp, and torque, and even mileage… Oh, and maybe save some weight in the process?

  19. Rev says

    Anyways, I would see a plastic engine being very advantageous to an automaker slightly more so than motorcycle makers. Mainly because with all the hype to create high fuel mileage cars, while increasing safety standards (which increases vehicle weight, a double negative) a major weight savings would allow the cars to increase fuel mileage, and be lighter possibly improving safety.

    Plus I’m sure that once these engines reach the end of their service lives, they’d wind up like most old engines do, and that’s sitting in a junk yard somewhere lying on the ground leaking their fluids into the earth.

  20. Bob Nedoma says

    Hm again. High temp tolerant plastic contaminated with oil and metals. How recyclable is that? Now “clean two stroke”? = I am reminded of a Kawasaki mechanic/salesman telling me that two-strokes are [The Future] back in 1972.
    And those weren’t made of plastic (b.t.w: his business is no more).

  21. FREEMAN says

    @ thekneeslider: well said.

    I like the concept. I see huge potential here. I don’t know if it’s possible, but a plastic (or lightweight) jet engine would also be hugely beneficial to the airline industry. The sheet metal engines referenced above sound very interesting too. It’s all worth a further look.

  22. says

    We have been using reciprocating compressors with plastic internals to pressurize gas (mostly hydrogen, pretty much the most difficult gas to pressurize!) to 700~875 Bar for years. I’ve always wondered why plastics haven’t migrated into other applications when it makes so much sense. Hopefully we’ll see more cool stuff like this in the future :)

  23. Hawk says


    I wonder if Ilmor has some plastic bits in the Skunk Works that came up with the 5-stroker?

  24. Lohmann says

    @Bob Nedoma
    Yes, clean two strokes is a very real thing. Better fuel mileage and close to no blue smoke. Take a close look at Bombardier/Evinrude/Rotax’s E-TEC engines: or

    I would love to own a motorcycle with the 593 E-TEC snowmobile engine:
    2-stroke 2 cylinder 594 ccm
    85 kW / 115 HP
    Liquid cooled
    Reed valve controlled
    Direct fuel injection

  25. OMMAG says

    Plastics in engine components is a reality.

    It’s just a matter of time till you see major components like blocks from carbon fiber and metal reinforced policarbonate.
    I believe that some F1 engine developers have been working toward this and I’m sure that connecting rods can be fabbed from these materials.

  26. OMMAG says

    Oh … BTW … for those of you who think that plastic or petro waste needs to sit around contaminating the environment ….

    Do some reading on gasification.

    Gasifiers can turn ANY cabon waste into clean fuel and in the process remove and contain other materials from the landfills.

    I spent two years working on one that converted landfill … dirt and everything … into combustable Hydrocarbon gas … it cooked 5000lb a day and left nothing but innert ash behind.

  27. says

    It seems conceivable that we’ll have more electrics motors than ICE before we see the plastic engine get the spotlight.

    Lets go all the way forward with our thinking, plastic DC motors! Wait, probably been done a billion times over already:)

  28. says

    @OMMAG; Funny you mention gasification, I was just talking to a work colleague about that very thing! The context was the use of syngas produced from gasified waste (especially plastics) to produce dimethyl ether, which can then be used as a fossil fuel replacement in any internal combustion application. I’d love to talk to you about gasification and get some functional details, please contact me at my company email;

  29. Kenny says

    I seem to recall a article in National Geographic from the 80’s about ceramic diesels which I have just realised is in the linked popular mechanics article. A quick google search brought up this quite detailed page on ceramic rotary engines
    I’d be interested to see the details on the material used in these engines. I imagine its a pretty complex thermoset polymer. Anybody know if there are any stress-strain or fatigue failure graphs?

  30. Paulinator says

    Think FRP. I’ve used some glass reinforced plastics in injection molding applications. I actually purchased a quantity of pellets that contained a high ratio of carbon fibre as a back up in case I needed the extra strength. I didn’t. The cheap 33% glass reinforced nylon was amazing enough. I really don’t understand why lawn-care equipment mfgs aren’t utilizing these low-cost, high performance materials and processes.

    On bikes? Well, the stuff don’t shine.

  31. Mel Beaty says

    Steve, yeah I found some stuff that noted the Crosley engine, even tho they did go to a cast iron block because of sealing problems. The guy involved was named Taylor and he eventually did what was called the Super Sport engine, a two liter that weighed about 150 lbs, ready to go. This was in the late fifties so it was earlier than I remembered. Interesting stuff.

  32. James Bowman says

    Mr Stacius I am very interested in motorcycle technology not science fiction, I know you mean well but not one city is underwater from global warming and its been unseasonable cool all summer long in Mid America which is some how over looked by the press, I am for any and all reasonable polution laws however the scare tactics and misrepresentation of facts and data actually serve to damage credabillity and you only get to cry wolf so many times, no ice age happened and global warming is looking sillier by the minute. I have not been able to enjoy my green Yamaha xt250 I so love ironically because of the unseasonably cool summer. Now I think that plastic engines are very intriuging and long for more information about them. What kind of bike do you own just curious?

  33. Paulinator says

    James, Stacius,

    I built my kids a weed-whacker powered go-cart. Global warming aside, that little thing STINKS!!! Do three donnuts and your eyes burn. I might have to build a clean little two-stroke for it. Maybe out of plastic/ceramic/sheet metal?

  34. steve w says

    I have seen many plastic “rapid prototype” engine parts made where I used to work. V twin crankcases and heads, cyls etc. Very light. I doubt real working parts would weigh much more. Some of these parts can be put into short service working parts so real molded parts shouldn’t be that hard.

  35. Donald says

    I see it as having a great potential for success.

    Combine a fully plastic engine with modern synthetic lubricants and I imagine the possibilities are endless.

    There are only a few concerns I have right now, and durability testing would sort out these issues:

    1.) Durability. Most drivers, and definitely a majority of riders, put some serious strain on their engines. That’s fine, modern engines are built to handle the strain of stop-and-go driving, quick blasts to accelerate up to highway speed, and so on. This is something that must be addressed on the design for the plastic engine, and I’m quite certain they will. Composite material is a must.

    2.) Aging. Plastics have a tendency to become brittle with age, and some aged plastics crack with even the slightest amount of strain placed on them. This is a critical issue that must be dealt with, as I am NOT a fan of having to replace my engine every 10-12 years because the block, connecting rods, crankshaft, and associated components have become brittle. Better yet, imagine taking off from a stoplight one Christmas Eve and listening to the beautiful sound of sleigh bells – only to discover it’s the bits and pieces of your engine jingling onto the ground!

    3.) Vibration. Yes, this has been addressed in the previous comments, but this goes right along with the other two issues, and primarily comes down to the durability of the engine.

    Overall, a great concept, and I believe it can be done successfully – but durability issues must be resolved.

  36. James Bowman says

    Paulinator sounds like you should let the kids just use the riding lawn mower and save the effort ;o]

  37. netjustin says


    Can you possibly see a mass produced plastic engine block creating more unmanaged waste than plastic water bottles? If so, then I’d like to hear exactly how that would happen. But you sound like a whiny malcontent when you knock an idea like this because of an issue that may or may not be out of mind, as you put it, but just so happens to relate to the material(s) used in this idea. Very out of place argument in my opinion, and a poor place to peddle an otherwise legitimate complaint.

    As far as the engine block and con rods, great idea, I’d love to hear more about it from the designer’s perspective. Yet another way to discover the possibilities in motorcycle engineering.

  38. netjustin says

    @cyclox, +1 to plastic 2T. I wonder whether trannies could have a steel-ended plastic output shaft. Less reciprocating mass = better gas mileage and more power potential!

  39. joe says

    Back in the seventies I read the same hype about Ceramic engines being the future.I think it was VW who put millions into the idea and built some prototypes.Lighter,run cooler,easy to manufacture etc.Don’t know what happend to that idea ,it just faded away and was never heard of again.

  40. Tim says

    A two stroke, plastic engine would be great! Aerospace applications (piston/prop), motorcycles, autos-lower weight means lower fuel consumption and higher power output/unit of weight. The two stroke, not limited by valve train speed, would gain also from a lower reciprocating mass. Fabulous idea!

  41. says

    “Plastic” covers a whole bunch of very different (and differently derived) materials, not just the stuff they make water bottles out of. I may be time for those who shelved their plastic and/or ceramic engine programs to dust them off and look at what the last twenty or thirty years has done to the state of materials science as far as weight, durability and cost goes.

    Though I suspect that there are back-burner projects simmering even now in skunk works even MCN doesn’t have pictures of. :)

  42. JB says

    A plastic engine on motorcycles seems senseless. Maybe for the touring models, not for racing such as superbikes or dirtbikes. There could be disastrious effects if using for racing models.