Cooler air in cylinders equals more, P O W E R Options

[gregrobbins]

At the DE today at Firebird Raceway, there was one very quick 2.0L 914.

I met and talked with the owner John Seymour for awhile. One of the innovations he came up with really looks interesting. Instead of the stock air filter box. he looked for a way to get cooler air into the motor. Study the photo (I have more if you want me to post). He ran a PVC pipe from the TPS to hoses that go down to the J tubes. From there they are connected to the air ducts in the longs and finally, he is pulling air from the opening in front of the windshield. He claims it works like a charm. I don't doubt him, as he is running D-jet and was as quick or quicker than the 2.0L cars that had been converted to carbs.

[jsteele22]

QUOTE (scotty b @ Nov 14 2005, 05:28 PM)

flow rate could easily be increased with two of the aftermarket blowers made for vw heating systems. Put one on each side, towards the rear so it would pull from the front and give a little boost just before the intake. I've thought about it befor but I was thinking of running it through the firewall and then through the center tunnel. Pvc in the tunnel, flex pipe at the walls.

That's really just a supercharger, but powered indirectly (and inefficiently) via alternator/wires/motor instead of a belt. If the fan motor is wimpy (like a VW heater blower) you aren't really gaining anything noticeable in terms of power. If it's not, you are placing a huge load on the car's engine (and alternator). In general, a supercharger is less efficient than a turbo, b/c it takes "good" energy to drive it (from the crankshaft) as opposed to "bad" energy (from the exhaust stream). So says Corky Bell, anyways.


The problem with this kind of thing, is that to get any significant increase in power, you have to increase the number of O2 molecules significantly. Just wafting them along through a tube won't cram many more of them into the cylinder. To get a feel for it, imagine using a bicycle pump to pump a car tire from 0 psi (gauge) to 10 psi (gauge). It's no manliness contest, but it does take a little time and effort. Compare this to a decent turbo setup which runs at 10 psi of boost. Since atmospheric pressure (for you lowlanders) is about 15 psi, that means an increase of around (25/15 -1) or 65% in oxygen going into the engine. So, ignoring lots of details, you get around 65% more power. Now for a 2.0L engine at 3600 RPM you breathe (3600/2 /60 * 2.0L) or 60 liters of air per second. Thats about 16 gallons of air. I don't know the volume of a car tire, but it seems rather less than 16 gallons. And 3600 RPM is kind of timid. But just imagine having to pump that tire up to 10 psi once per second, and you get a feel for the kind of job a turbocharger (or supercharger) has to accomplish. If you try something that's wimpy compared to a turbo/super charger, you'll get a result that's wimpy as well.

Using cool air, though modest, does help. It's like letting nature take care of all the hard work ahead of time. Working in absolute (Kelvin) degrees, density is proportional to temperature, if pressure is held constant (like atmospheric, fer example). So going from 55 C down to 35 C (i.e., 131 F down to 95 F), which is a 20 degree diff at (273 + 35) K, gives an increase in O2 (hence HP) of 6% without expending any effort.