The kd4crs/Power Hungry/Gotts Mod (revisited - and with pictures)

[Jackpine]

This is in response to the excellent posts by Jim Allen and Grabber523. I was typing it but had to stop for lunch and three other posts snuck in on me!

Both Jim and Grabber make good points, and one's that worried me too, but for a different reason. First though, I have a degree in Aerospace Engineering and know that airflow theory is SUPER complicated. I've been concerned that these modifications would induce turbulence in the intake (due to a non-streamlined cross-section in the modified area) that would actually work against the increased intake area. Then too, the "squared off" end of the new intake may in fact promote turbulence too.

However, Bill brought up the point that the CAI design doesn't really come into play until you're at high RPM's, and, something he said in one of his posts convinced me that he thought the airflow was increased under those demands with the bigger opening. (I think this was reprised in one of the posts that beat me to this one).

Grabber, there IS the inverse relationship between velocity and pressure, but there's also conservation of mass. You're not going to get anything more downstream of the inlet than you had AT the inlet, and, since the flow is moving, the static pressure is always less than ambient (meaning the air is less dense than ambient). I think the restricted opening can ultimately cause a lower pressure condition to exist throughout the inlet tube and at the throttle body if RPMs are high enough. At that point, it's going to be difficult to increase power since the MAF sensor is going to say "not enough air".

Jim, I liked your "smoothing" analogy. It goes back to what I was saying about turbulence possibly restricting airflow. And, it may well be the case that you are right on this. I certainly would like to see some objective data and won't throw my trumpet snorkel away until I'm convinced it's worthless. I will say, though, that the trumpet/bellows assembly is not the most streamlined, laminar flow design I've ever looked at with the inside "bumps" just downstream of the inlet, the rings at the bellows end of the snorkel and finally, the accordion folds of the bellows itself. And, the trumpet end widens too rapidly to my eyes. It seems like it should cause turbulence of its own due to this. It doesn't look like a reasonable airfoil curve to me.

Finally, since the cross-sectional area of the tube increases with the square of the radius, we have an intake cross-section of 3.14 sq inches with the trumpet, but 7.07 sq inches with the mod. That's over twice as much intake area for a 0.5" radius increase! I feel this almost HAS to increase the flow potential!

And, AgentOrange's "RAM" air mod probably provides even more. It's possible that the increased pressure from the RAM tube sort of cancels the fender inlet contribution at high speeds, but I'm nearly certain the combined effect provides even more air mass than one of them acting alone.

Again, gentlemen, I'd love to see some objective data and I'm delighted you two were not afraid to bring this point up.

As I said in another post, maybe a month ago: That trumpet restriction is there for a reason! You can bet on it. I'm betting it's there to reduce power potential at the upper end, which might reduce engine damage and warranty claims from those who abuse their engines.

- Jack