Educate me: what is a looper engine and it’s differences

[Oldnbold]

go.....

 

[racerone]

Crossflow has a deflector on the piston to direct the incoming charge.-----A looper has a nearly flat piston.----Incoming fuel charge is aimed by ports to " loop " around the cylinder to force out the spent charge

 

[thatone123]

Loopers are race derived engines first used in 2 cylinder hydroplanes as far a I know. They had a name like someones last name but I forget what that was.

 

[flyingscott]

Loopers are race derived engines first used in 2 cylinder hydroplanes as far a I know. They had a name like someones last name but I forget what that was.

No they are not.

 

[racerone]

Lawnboy power mowers built in the 1950's and later were all the looper style engine too.

 

[Chris1956]

"Looper" is a nickname for a Loop Charged 2 cycle motor. To loop charge a 2 cycle motor, a number of transfer ports in the cylinder sweep out the exhaust. This occurs when the piston is travelling down, causing the fresh fuel to sweep up and over the piston, in a loop. High performance motorcycles had 7 port loop charged cylinders. Outboards are probably 4 or 5 ports.

Crossflow motors generally have 1 transfer port and 1 exhaust port. A deflector on top of the piston is used to help push the exhaust out the port.

All carb 2 cycle motors use fresh fuel/air to push the exhaust out. Some of the fuel/air is unburned, by necessity. Loop charged motors tend to burn more of the fuel, leaving less unburned fuel out the exhaust, and running a bit more efficiently than crossflow motors..

 

[Oldnbold]

Thx for the explanation. Now I understand why my 73 evinrude piston looked so different from my 78 Yamaha dirt bike.

 

[Chris1956]

Your motorcycle probably had the carbs mounted on the neck of the cylinder, vs, the bottom of the crankcase like the Evinrude. Yamaha used the piston skirt, plus a reed valve to control the fuel intake timing and volume. Much more fuel efficient than outboards.