View Single Post
Old 04-07-2009, 09:20 PM   #22 (permalink)
Moderate your Moderation.
Join Date: Nov 2008
Location: Troy, Pa.
Posts: 8,919

Pasta - '96 Volkswagen Passat TDi
90 day: 45.22 mpg (US)
Thanks: 1,369
Thanked 430 Times in 353 Posts
Originally Posted by rkcarguy View Post
My opinion, the WAI is a limiter that slows your acceleration and reduces your WOT power output by inducing a hotter and therefore less dense air/fuel charge to the engine. Measured side by side I'd bet the CAI equipped car would be near identical mpg as a WAI equipped one, but obviously will walk away under acceleration.
Just put a wedge under your gas pedal so it only goes to 75% WOT and enjoy the same gains instead...
And that's all it is. The science actually does back up the use of controlled temperature intake systems. If you read a few posts up, you'll see references that I haven't read thoroughly, which denote this very concept.

Common physics also makes it quite obvious that yes, you're losing power, but you're not making anything close to "power" in eco-ranges to begin with.

If your engine makes 310 HP at 4400 RPM, it's doing that at WOT, not at 10% throttle, where you're sitting.

The primary function of a WAI is NOT to reduce pumping losses by heating the intake air and making it less dense, it is to increase the speed at which the flame kernel turns into a front and increase the amount of the (more) homogenous mixture which has been burned by the combustion event.

As a result of pre-heated intake air, the engine stays warmer, which means that more power from each combustion event (relative to the available power from the combustion event at the given temp) will go into moving the piston, rather than be leached into the cylinder walls as heat.

IOW - the WAI just makes it easier for the engine to turn, not b/c of pumping losses, but because of more complete combustion causing more power relative to the fuel/air mix's concentration and capability.

Obviously, if there is less air due to warmer temps in the cylinder, it will reduce pumping losses and compression losses, since there is less density to compress and pull in/push out. That's just relative though. It's not a primary function.
"ʞɐǝɹɟ ɐ ǝɹ,noʎ uǝɥʍ 'ʇı ʇ,usı 'ʎlǝuol s,ʇı"

  Reply With Quote