Crossflow vs. Looper

[randlemanboater]

TRUE!!!

I think the max speed is reached right before your boat becomes an airplane.

[Hammerhead]

Along with the V-20 I hava 1969 16' bonito walk-thru. It had a 65hp 3 banger johnson and cable steering when I bought it for 150 bucks. I replaced the deck( foam filled under it) repowered with a 115 evindude/ 21" SS prop. The boat was dangerous. At WOT it would chine walk. I still have the boat but, powered down to a 90 yam.

What's the fastest V-20s out there? The ICW limit is 25 around here and the ocean is always too rough to run WOT anyway.

[bigshrimpin]

Originally Posted by Hammerhead

What's the fastest V-20s out there? The ICW limit is 25 around here and the ocean is always too rough to run WOT anyway.

There was someone with twin 140's on the board . . . but I'll believe some of the early Alim v20 race boats were pushing 70+mph. CIA v20's with twin 100's were high 40's in 1961.

[bassarama]

Well looking at my motor owner's manual it says it's a loop charge. Are we talking the same here?

Also I was told by a pro that these "loopers" are equiped with low compression headers, thus running at lower compression.

Can someone translate that please? ;D

Thanks

Joe

[76GMC1500]

Low compression heads... *Using a low compression head reduces the fuel octane requirements of the motor. It also reduces fuel economy and horsepower.

I believe the compression ratio for a 2-stroke is actually the dynamic compression ratio. *A static compression ratio is the volume of the cylinder at BDC over the volume of the cylinder at TDC. *A 2-stroke dynamic compression ratio takes the volume of the cylinder when the exhaust port closes and divides it by the volume of the cylinder with the piston at TDC.

Lowering the compression ratio, raising the exhaust port in the cylinder so it closes later, increases the top end performance of a 2-stroke motor. *Lowering the exhaust port increases the bottom end. *Since the loopers are high rpm motors, they run low dynamic compression ratios.

[Skools Out]

bass the compression on Loopers have 120 to 130 usually on a V4 that's the same as a crossflow V4 but the V6 motors are different the loopers are 90 to 100 usually and crossflow's are 125 to 135. the Loopers have a single carb per cylinder. they are much better on fuel than crossflow due to the fuel flow inside the motor. look at the first page of the pics they show the fuel flow. Loopers produce less heat as well. if you have a 2 stroke choice go Looper for better fuel mileage, lower temps, better all around HP range, they turn more RPM's, and easier and cheaper to fix usually.

[THEFERMANATOR]

Originally Posted by Skools Out

bass the compression on Loopers have 120 to 130 usually on a V4

Mine blows those numbers out of the water. I've got a 145 on one bank both cylinders, and 150 and 155 on the other side. Mine is a bare to start without dual batteries, or at least a good group 27.

[bassarama]

Those are very technical explanations, thanks. :)

Now, I really like my looper. ;D

[76GMC1500]

My 1cyl. looper makes 205 psi! Premium gas only for me.

[Skools Out]

is that on an outboard? that compression is too high for stock heads, crank, rods, and starter. i have a racing jet ski with all race mods stock was 90 PSI now 230 PSI. but once you get that high on a 2 stroke you have to weld the crank so the plates don't turn. You have to use better rods as well.