Motorcycle Myth # 5 - You need big ports to make big horsepower

[cujet]

Always of interest.

It may be interesting to note that my lowly airplane (177RG) has a 200HP 4 cylinder Lycoming engine with 5.125 inch pistons. Yet the intake pipes are 1.5 inch steel tubes with an inside dia slightly smaller than that . Sure, it's no high RPM monster, with a 2700 (3300 in helicopter use) redline.

Put another way, it's a 37mm intake port on a 1475 CC cylinder. It achieves a volumetric efficiency better than 85% at full output and nears 100% VE at lower RPM's. Of note, the intake port tube diameter is not the major limiting factor. Instead, the throttle body is the restriction (by design) . It can only achieve 26 inches of mercury intake manifold pressure at full power, about 4 inches shy of the 29.92 of a standard day.

Sure, by modern engine standards, those are not great numbers. But it does show a viable use for comparatively small intake ports on an otherwise good design.

As you might expect, it takes just a few simple alterations to achieve a 12% increase in HP, bumping it up to 225HP.

Bigger is always better?

 

[The Redrider]

Always of interest.

It may be interesting to note that my lowly airplane (177RG) has a 200HP 4 cylinder Lycoming engine with 5.125 inch pistons. Yet the intake pipes are 1.5 inch steel tubes with an inside dia slightly smaller than that . Sure, it's no high RPM monster, with a 2700 (3300 in helicopter use) redline.

Put another way, it's a 37mm intake port on a 1475 CC cylinder. It achieves a volumetric efficiency better than 85% at full output and nears 100% VE at lower RPM's. Of note, the intake port tube diameter is not the major limiting factor. Instead, the throttle body is the restriction (by design) . It can only achieve 26 inches of mercury intake manifold pressure at full power, about 4 inches shy of the 29.92 of a standard day.

Sure, by modern engine standards, those are not great numbers. But it does show a viable use for comparatively small intake ports on an otherwise good design.

As you might expect, it takes just a few simple alterations to achieve a 12% increase in HP, bumping it up to 225HP.

Bigger is always better?

I learned on a C152 long ago, 48 dual, 7hrs solo. It had a much smaller displacement engine than your bird. You must remember these birds are extremely light, so the power to weight ratio is neglegable, Clyde Cessna knew what he was doing when he designed it. Now you can slap a KandN air filter, and fab up some larger diameter pipes, change the pitch of your prop for more bite, but other than that, just fly your bird and enjoy it....

 

[cujet]

Now you can slap a KandN air filter, and fab up some larger diameter pipes, change the pitch of your prop for more bite, but other than that, just fly your bird and enjoy it....

Hard to believe (sarc) but I did install the Challenger K+N filter and a Powerflow tuned exhaust and GAMI injectors. My plane has a constant speed prop, so it's always adjusting pitch for conditions. The mods helped a good bit. It's a 2800 pound airplane with 200 HP, so not exactly overpowered. But sure is fun!

 

[The Redrider]

Hard to believe (sarc) but I did install the Challenger K+N filter and a Powerflow tuned exhaust and GAMI injectors. My plane has a constant speed prop, so it's always adjusting pitch for conditions. The mods helped a good bit. It's a 2800 pound airplane with 200 HP, so not exactly overpowered. But sure is fun!

Then of course there is always one of these..

 

[The Redrider]

Haaaa! 177 cardinal, my pops owned one, dual ownership back in the day. I flew it with pops, it was pretty cool, Cessna was stupid to get rid of it...

This sum bitch had some serious balls if I recall correctly...

 

[The Redrider]

What kind of bike are we riding today?

 

[Rich Rohrich]

I was having a discussion at work about this very subject so I thought it might be worth bumping this up for anyone who might be interested.