Hi all,

I want to buy a small pylon racer and fit a 25size two stroke.

There is a big difference in rpm between an aero engine and a car engine.
Aero engine 17000-18000 revs
Car engine 30000revs

Why do car engines rev so much faster?
Is it possible to use a car engine in a plane? (The car engine has a prop driver fitted)

Any info would be appreciated.

Ulrich

The car engine revs faster due to a flywheel (low rotating mass) being fitted. These engines do have more advanced timing. I have converted a Thunder Tiger .12 buggy engine to airplane use. I basically turned the heat sink head down on a lathe to reduce the height. It now has a head two fins high instead of eight fins high. This engine spins up to 18,000RPM with a 7X6 prop. This is low compared to using a flywheel spinning at 28,000 - 30,000 RPM.

I have an Irvine 15 , that came from JUST Engines It was shipped with an extended prop nut and the head was already "chopped' , milled off fins for aircraft use, rear exhaust, carb is the same/ It runs great but not in the 20K range. HAVE YET TO PUT IT IN A PLANE martin
It was offed in both configurations do not rembember the prop it got 16K, most likley a smaller one would increase revs iIt was converted to diesel
with a custom head also

Put an r/c car flywheel on your airplane engine and watch it spin up to 30000 rpm!

Car engines do not stay at full power all the time. They are revved up and down continuously. A car engine also wears out very quickly, due to the high rpm and other stresses. Trying to run even a car engine at peak rpm for an extended period of time, such as an airplane flight, would most likely wear it out or destroy it in short order.

As a side note, in the early days of r/c cars they were powered by airplane engines that had extra clamp-on cooling fins. They also revved much higher than when used with a propeller in airplanes.

Car engines have slightly higher timing than most plane engines to get max power at somewhat higher revs but not excessively higher, maybe around the 20-25K range. My son's car engine is timed very near the same as my ST S45 but I've measured his revs at 36,000 on a short straight so all those extra revs is just the engine doing what's basically a shaft run. As Kmot said, put a flywheel on a plane engine (or throw the blades off a prop ) and they'll rev just as much. Car engines though have a stronger rod than plane engines to handle those shaft run revs.

AMB, does this Irvine .15 you have got a blue head? I had one of their first versions they made for freeflight. This engine was clocked at 39,000 RPM with a 7 inch prop on FAI fuel. Although it did have a glow button for a combustion insert, which I later exchanged for a more convenient one that I manufactured, machined to accept a turbo style plug. The glow buttons became hard to get.

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