Ram Air
08-17-2008, 09:28 AM
#21
2nd Gear Member
Join Date: Aug 2007
Location: Unstable
Posts: 213
Ram Air systems on bikes are HIGHLY developed from thousands of hours of track testing and dyno testing until they develop an opening and plenum shape that provides the best pressure increase. You won't see something nearly as effective on a car. It requires special instrumentation to test for turbulence and pressure variations across different parts of the ram's plenum, instrumentation that no one but the manufacturers have in testing labs. It also requires extensive wind tunnel testing to find the right size, shape and placement of the ram's opening. That's why they're so effective on bikes, the designers take the time to do that.
When sticking a ram air in a car as an aftermarket setup, testing shows gains of only about 2% over 100mph, and around 4% by 150mph, with 1% or less gains at speeds under 100mph. I'm not knocking ram air, but on pretty much every car production or otherwise it hasn't truly been a "ram" air. That's just a name like "Hemi." It does allow cold air in, which is denser so more power is made.
A hood scoop(I have one myself, with a sealed air cleaner from the engine compartment) will make extra power from cooler air, but the ramming will have little effect on power under 100mph. I picked up an immediate 1.5mph at the strip just by putting on a scoop and sealing it off, instead of huffing hot engine compartment air. Reverse cowl hoods work the same way, but rather than "scooping" the air the draw in higher pressure air that's dammed up in front of the windshield. Either one works the same. I've seen several tests where CAI, ram air and reverse cowls were all tested vs a stock setup, and they all produced the same power and track times.
As far as a cowl or hood scoop, either works well and is relatively easy to seal off from the engine compartment for cheap.
When sticking a ram air in a car as an aftermarket setup, testing shows gains of only about 2% over 100mph, and around 4% by 150mph, with 1% or less gains at speeds under 100mph. I'm not knocking ram air, but on pretty much every car production or otherwise it hasn't truly been a "ram" air. That's just a name like "Hemi." It does allow cold air in, which is denser so more power is made.
A hood scoop(I have one myself, with a sealed air cleaner from the engine compartment) will make extra power from cooler air, but the ramming will have little effect on power under 100mph. I picked up an immediate 1.5mph at the strip just by putting on a scoop and sealing it off, instead of huffing hot engine compartment air. Reverse cowl hoods work the same way, but rather than "scooping" the air the draw in higher pressure air that's dammed up in front of the windshield. Either one works the same. I've seen several tests where CAI, ram air and reverse cowls were all tested vs a stock setup, and they all produced the same power and track times.
As far as a cowl or hood scoop, either works well and is relatively easy to seal off from the engine compartment for cheap.
it works when implemented properly. Obviously it will not provide
gains any way near the magnitude of those from forced induction
such as turbo or blower, but there are gains to be had none the less.
With the pickup at the front of the car there is much higher chance of
laminar flow than turbulent flow. As for determining effectiveness,
a pressure transducer and interpolation circuit with a few other
sensors wired to a data logger will get you about to about 80%
of where most manufactures are.
Jav
08-21-2008, 03:13 PM
#22
2nd Gear Member
Join Date: Oct 2007
Location:
Posts: 241
The '68 hood scoops are effective because they are placed at the leading edge of the hood while the '65-'66 aren't and they aren't tall enough to break the boundary layer either. These are more decorative than functional, at speed air is just going to flow over them.
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