I was experimenting with running a large open cone element vs. what I currently have, which is a ducted intake tract to a TPI aircleaner, and I made a neat discovery: Having a ducted intake tract dramatically broadens the torque curve with a cam that has overlap and duration.

The cam I have now is an isky 270 hydrolic (221 @.05/.465"/108 LSA). The induction system is a victor-E with a 1000CFM 4bbl TB. With basically just an open element on the TB, the engine has only marginal torque below 4000 RPM, and is very, very lazy off idle. With a ducted intake (basically a pipe connecting the TB to the aircleaner), the torque curve is dramatically different. The engines torque curve now extends all the way down to idle! I can even do a rolling burn-out off idle just by mashing the gas down, and thats with 2.77's. Its literally night and day. The air fuel ratio at WOT was within 2% during the back-to-back tests, and the IAT was only 10 degrees F hotter with the open element, so the operating conditions where roughly the same. The only difference being the induction system.

My theory as to why it works is that the column of air within the duct has inertia, which in turn prevents much of the inevitable intake reversion at low RPMs. It really DOES work, and results in an almost constant torque output from idle-6000 RPM. Its like having a diesel.

Just something to consider when getting air into the engine. I always thought that the intake manifold itself was primarily responsible, and the way the air gets in doesn't have much of an impact. But, its really the system as a whole. Ducting the air inlet could be a cheap way to dramatically improve the torque curve below the cam's recommended operating range.

 

In back-to-back testing at the dragstrip, I picked up 1.23 mph from a 4inch intake tube with cone filter to a home-depot microwave vent inside the passenger's side fog light opening, then 4inch tubing from the fog-light opening up to the 4 inch intake tube with no cone filter on the end. Home-made ram-air intake.

What I have not tested is the cold-air from the fog light opening blowing onto the cone air filter vs blocking off the opening. I will try to test that this saturday at the track.

I am a believer in forcing cold-air into the intake track now.

 

This is really interesting. If the intake air has inertia and prevents reversion, then you should see a difference in air fuel ratio i would think. Does that seem logical?

 

Sounds like the open air element was having a turbulence with a low pressure area around opening of the throttle body or something to that affect.

I do have to say...I have noticed something similiar to that when I had the air cleaner mounted straight on the throttle body on my Victor Jr. as well. However, I needed some more clearance around the linkage so I got a 1" spacer between the throttle body and air cleaner and felt the same results as you...a more throttle responsive/torquer engine.

 

On a speed density setup, yes. It would actually be a good way to prove it, as the VE would (or should) change with a tube vs. open element. I currently have my setup running MAF only, so the MAF will automatically register the change in airflow.

 

Possibly, although it was a pretty large cone element air filter. Also, both setups still used the carb hat, so teh airflow around the TB should be the same.

The cone element does better out top. The air filters in the TPI box are too small for performance. Even with K&Ns, it still pulls close to 3" of vacuum at 6k. But, it gives back more than it takes.