[shadycuz]

The engine is the size of a push mower.

> XTS-210 is about the size of a basketball, weighs in at 19 kg (42 lb), and displaces 210 cc.

So you are talking about a 26HP lawn mower.

While the Camry might make more power at its normal size. It would not if you scaled it down to the size of a basketball. I'm guessing it would make 1-3HP at that size.

[93po]

A Traxxas 5407 TRX 3.3 engine used in RC cars makes 1.42 horsepower, weighs 305 grams, and fits in the palm of your hand.

This is 1hp per 0.46 pounds of engine weight, nearly three times better than the camry engine.

Granted an RC engine runs on a mixture of fuel and nitromethane, and doesn't have any reasonable durability compare to a Camry engine. But it also only costs $200.

[seabird]

You can't just make the Traxxas 18x bigger and get linear performance improvement. Trying to compare power/weight between engines with radically different weight constraints is silly.

[kortex]

> Granted an RC engine runs on a mixture of fuel and nitromethane

That's a huge difference. The main limiting factor in engine power is mass air flow, not fuel. Engines are as much air pumps as they are containers for extracting expansion from explosions. Nitromethane provides extra oxidizer in liquid form, putting nitro engines in some ways closer to rocket engines in terms of power-to-weight ratio.

[cjbgkagh]

I've read about a lot of people complaining about the difficulty of getting the mixture right, perhaps that might be a show stopper for a UAV that must reliably work unattended for a long time. Though the military should also be able to get such mixtures down to a science - so I don't know.

[m463]

I'm not familiar with that engine, but I remember having little glow-plug engines and they didn't even have piston rings. (and were not efficient)

[bluGill]

Every motorcycle mechanic I've seen has a sign in the shop: speed costs money, how fast do you want to go. That sign isn't referring to the costs to modify an engine to go faster so much as the cost to constantly rebuild the engine after they modify it to go fast. I've seen two identical engines, one rebuilt to stock and one rebuilt to max speed - the cost for both rebuild jobs was about the same (the parts for speed were more - but not much more compared to the labor which was the same), but the engine rebuilt to stock ran for thousands more hours, while the one rebuilt for speed has the mechanic bragging that it lasted a whole 80 hours!

[sliken]

My dad used to say the perfect race car would explode into a million pieces just after it crossed the finish line. Anything more robust is wasted weight.

[0cf8612b2e1e]

What is done to modify an engine for speed? What kind of improvement can be seen for speed (accelerates XX faster? YY higher top speed)?

[ww520]

The Camry engine has 4-6 cylinders for its size. A single cylinder is not much bigger than a basket ball.