Plastic Race Engine Returns as Polimotor 2 Project Underway


It looks as if the concept of a plastic racing engine will be tested again as a leading manufacturer of specialty polymer materials recently announced plans for the Polimotor 2.

Solvay, a Belgian-based chemical company with facilities in 52 countries, will team with the Polimotor’s original designer to revive the composite-based 4-cylinder and update the original with more plastic parts as well as a turbocharger. Plans then call for the engine to be tested in a Norma M-20 prototype next year with further goals to race in competition.

Crude concept drawing for the next generation Polimotor with participation from Solvay

“[Solvay] came to me and asked if I’d be interested in resurrecting that program,” confirms Matti Holtzberg, the engineer who developed a number of polymer-based cylinder blocks in the ‘80s and carried that work over into designing the original Polimotor. “Coincidentally I was in the middle of resurrecting it with plans to go racing again. Nothing is different in this new engine except some of the materials. From an architectural standpoint, nothing is different.”

The first Polimotor weighed 168 pounds and was a DOHC 4-cylinder configuration that pumped out 290 naturally aspirated horsepower at 8,500 rpm. The main composite material was Torlon, which at that time was produced by the Amoco chemical company. Solvay now has the rights to Torlon but will also use the project to showcase new ideas and materials.

“They will try to put as many polymers as possible into this engine,” adds Holtzberg.

Turbocharged version boasts 450 horsepower

The updated Polimotor will sport a turbocharger, improved fuel injection and a few other modern racing tricks to produce 420 to 450 horsepower at 8,000 rpm. It should also weigh about 138 pounds.

“The first Polimotor was glass reinforced while this is carbon fiber,” says Holtzbert.

Popular Science

Mounted in a Lola T616 aluminum chassis, Polimotor 1 raced two seasons in the IMSA Camel GT series (see video above), making the podium once with a third-place finish at Road America in 1985. Even after the IMSA cars were retired, the engine lived for a few years in midget and European hillclimbers. A turbo V6 prototype was constructed but never made it to the dyno.

The Polimotor drew considerable attention and headlines in the ‘80s, although many of the facts from the time have morphed into myths. For example, Popular Science put an illustration of Holtzberg’s first engine on the cover and declared, “Ford’s Impossible Plastic Engine.”

“Ford was not involved at all,” says Holtzberg.

That first SOHC engine was designed around a crankshaft from a 2.3-liter Pinto engine. The plan was to test the viability and capabilities of a composite cylinder block.

“There weren’t a lot of 4-cylinder engines in the US in those days,” explains Holtzberg. “I chose the Pinto crankshaft, that’s about it. Nothing else on that engine was in any way related to the Pinto.”

Unique block construction

Holtzberg refined the original design into a DOHC configuration for the first Polimotor. Although some observers feel the Polimotor shares design cues with Cosworth YB and BDA engines—especially since the YB is based on the Pinto crank—Holtzberg says there are no relations.

Early cutaway of first Polimtor. Eventually the connecting rods and pistons were replaced with metal units.

The first race Polimotor displaced 2.0-liters. The block design was quite unique with the crankcase and sump formed as a unit. Just above were the water jackets and cast-iron cylinder liners. Finally, the cylinder head and valvetrain were positioned on top.

The main and head bolts were same, holding those sections together. The race engine used a steel crank, steel rods and aluminum pistons, although prototypes were built with composite rods and combination plastic/aluminum pistons.

“The combustion chambers are individual pods attached to the cylinder liners,” says Holtzberg.

Additional engine parts made from composite materials included the stems on the intake valves, cam buckets and piston pins. The team also experimented with composite lobes on the camshafts.

A turbo V6 prototype was built but never dyno tested.

“The first Polimotor didn’t have a lot of moving parts made out of Torlon,” says Holtzberg. “This new project is designed to show the commercial feasibility of compression molding engine blocks.”

Holzberg has a number of blocks left over from the ‘80s so that preliminary dyno testing of the new internals can begin. However, block manufacturing and materials have improved over the years, so tensile strength should be better with the final units.

Comes in one color 

Compression molding isn’t as easy it may appear at first. While a resin-and-fiber mixture is poured into a mold, considerable detail work is required before the finished product. For example, each fastener gets its own cast-in insert.

US engineer Matti Holtzberg built a composite block for a 2.3-liter SOHC engine, then refined the design to a DOHC 2.0-liter dubbed as the Polimotor.

US engineer Matti Holtzberg built a composite block for a 2.3-liter SOHC engine, then refined the design to a DOHC 2.0-liter dubbed as the Polimotor.

Solvay says it will replace up to 10 traditional metal engine components with parts made from seven of the company’s high-performing thermoplastic materials. Targeted parts include the water pump, oil pump, coolant plumbing fixtures, throttle body, fuel rails, cam sprockets and more.

Here’s the original Polimotor mounted in the Lola T616

The Polimotor 1 started with a Hilborn mechanical fuel injection because a Lucas EFI system was unavailable. The team eventually moved to a Kugelfischer mechanical system but the new engine will have a modern EFI setup.

“It’s not a DI head but it’s port injection, and it’s quite contempory in its design,” says Holtzberg. “It makes all the horsepower we need, so why change anything.”

There is one downside to a composite cylinder block. The racecars have to have larger cooling systems since the plastic doesn’t dissipate heat as efficiently as metal. And for those who may fantasize of building a multi-colored plastic engine, the composite block will be available only in black.

Polimotor 2 will be raced in a Norma M-20 prototype.

Polimotor 2 will be raced in a Norma M-20 prototype.

About the author

Mike Magda

Mike Magda is a veteran automotive writer with credits in publications such as Racecar Engineering, Hot Rod, Engine Technology International, Motor Trend, Automobile, Automotive Testing Technology and Professional Motorsport World. He was the editor of four national automotive magazines, including Chevy High Performance, and has authored hundreds of automotive technical briefings. In covering nearly every type of motorsport, Mike has collaborated with many of racing's top engine builders and factory engineers.
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