So basically, on NA cars, the length of tubing doesn’t matter because it’s purely there to carry air… and the Boosted cars must pressurize the tubing in order to obtain the desired psi, right?
Makes a lot more sense now, thanks!
I’m going to skip the fender, and work with the shortest tube possible.
As far as location, it’s the coldest spot I know.
I’ll post pics when it’s complete!
Umm, I dunno about the length not making a difference…
I hear short rams help low and mid range
while CAIs with longer tubing helps top end.
On the 1st gen MR2s with TVIS it had 2 sets of runners from the IM - shorter for low end to help with torque and and longer ones to help up top.
Main thing = cold air
no no and more no
length of the tube will have a HUGE effect on where the car makes its largest gains.
its ram tuning
and cold air is good, but if your intake tube is 9’ long then you choke in the higher rpm range.
heres an artical about ram tuning.
"This is a reprint from July 1999 Hot Rod, story by Steve Magnante from
Ramming the Rat
What is Ram Tuning?
Ram tuning surfaced in the racing community during the early 1950’s. The idea was both simple and quite complicated, depending on how deep you dig. On the surface, ram tuning simply takes advantage of the inertia contained within a moving column of air/fuel mixture (only air on FI) as it comes to a stop against the closed intake valve. Traveling at close to 100 mph through the intake runner, you can imagine there is plenty of energy waiting to be released. By adjusting the length ot the intake runners, this energy can be used to improve cylinder filling when the valve opens again. The more pent-up energy waiting to crash the gate, the more air to pack the chamber. But there’s much more to it than this.
It all begins at the piston. After expelling spent combustion gases through the open exhaust valve during the exhaust stroke, the piston reaches TDC. At approximately the time the piston begins its journey back down the cylinder during the intake stroke, the intake valve opens and suction draws in a fresh air/fuel charge through the intake tract. By the time the piston reaches BDC, the intake valve is closing, and it is here that we can began our examination of the occurences along the length of the intake tract. For these few milliseconds, we aren’t concerned about what is happening inside the cylinder or the combustion chamber. Our attention is focused on the column of air that exists between the the back of the closed intake valve and the opening of the ram tube or, on a carbureted engine, the entrance to the plenum directly below the carburetor.
The instant the intake valve closes, it initiates a chain of events within that column of air. A set of four of these events will always occur in a particular order. These four events constitute a harmonic cycle. Each event involves a change in the pressure and velocity of the air/fuel mixture in the tube. These changes always begin at one end of the tube (either the closed valve or the open end) and progress to the other end. This progression, or trasversal, occurs at the speed of sound; a harmonic cycle consists of four traversals.
The first traversal is the result of the fuel mixture adjacent to the valve coming to a sudden stop. As it does, it builds pressure which is equal to the product of the air density, the air velocity, and the sonic velocity. As the incoming molecules of air hit this pocket of air that is already stopped, they also stop, and the volume of stalled air grows in size, creating a division between the two zones; this “front” is like a weather front on the evening news. The front separates regions that are at different pressuers. This front moves away from the valve toward the open end ot the tube at sonic velocity. It is the front between the two regions that traverses the tube at the speed of sound, not a portion of the air/fuel mixture itself. Each wave actually moves through the air itself without being of it.
When the front reaches the open end of the tube, the molecules of air nearest the open end begin to flow away from the opening of the tube. This volume of zero pressure air extends toward the closed valve at the speed of sound, constituting the second traversal, where the air in the tube is at zero pressure and negative flow. Then, the air at the closed valve experiences a negative pressure equal in magnitude to the positve pressure initially developed when the valve first closed, thus initiating the third traversal which also travels away from the engine. Once the front reaches the end of the tube, the air inside is entirely stagnant, and at the negative pressure, air once again begins to flow onto the open end of the tube. This represents the beginnig of the fourth traversal, where all the air in the tube is at zero pressure and has positive velocity traveling toward the engine.
With this fourth traversal, one harmonic cycle is completed, although it’s difficult to imagine all of this taking place in a short timespan between valve closure and valve opening. The beginning of the first cycle of the next harmonic occurs when this flow region reaches the closed valve, and, again the pressure rise is equal to the product of the density of the charge, the velocity of the charge, and the speed pf sound, which----at 60 degrees F---- is equal to 13,420 inches per second! Shope divulged that tests conducted at Chrysler in the mid-'50s concluded that the most effective time to open the valve was after the third harmonic----the intake valve is opened just as pressure rise begins to occur at the head after the 12th traversal. These experiments also showed that when tuning for the fourth harmonic, the intake runner had to be too short and couldn’t contain enough air/fuel mixture to completely charge the cylinder. And efforts to tune for the second harmonic resulted in extremely long runners and the acceleration of an excessive air/fuel mass, so the third harmonic was the most advantageous.
Chrysler testing resulted in a formula to calculate where the ram effect will come into play. To wit: N x L = 84,000, where N represents the desired engine rpm to tune for and L is the length in inches from the opening of the ram tube to the valve head. Shope explains: “Let’s say you’re running at Bonneville with an engine that develops peak horsepower at 8400 rpm and want to tune for maximum ram effect at that level. Then, L should equal 10 inches, as in 8400x10 inches=84,000.” To achieve ram tuning at 5500 rpm simply divide the constant, 84,000 by 5500 rpm. The result is 15.27 inches, the ideal distance for the intake tract as measured from the opening of the ram tube to the valve head.
The effects of ram tuning reveal themselves as blips in the horsepower and torque curves, which can either be tailored (by manipulating runner length) to coincide with, and enhance, the power peak or to bolster some other area of the power curve. In other words, just because a given engine may make maximum power at 7000 rpm doesn’t mean you have to utilize the benefit of ram tuning at that speed. In fact most cases, you wouldn’t. A drag-race engine, for instance, would have its intake system tuned for a speed a bit above the midpoint of the engine-speed range. Is ram tuning responsible for where peak torque and horsepower are made? Well, it can shift the peaks a few rpm, but the more dominant contributors are found elsewhere (camshaft, compression ratio, and so on). But there is no doubt ram tuning can be a useful tool for enhancing the power curves.
*NOTE
How this is exactly applied to our Honda 4 cylinders with the common plenum feeding 8 valves is what I’m trying to research. My 1.5L shows a big peak in the power bands at 4800 rpm with the AEM intake installed. There is also a peak at 2400 rpm, which is the result of the second harmonic.
Charles Tague, a.k.a. Mista Bone
10/8/1999
"
look at any dyno of an AEM CAI, and you will see that hump. that is caused by the length of the tube. make the tube the right length and you can move that up to a higher rpm. (where you will use it on the track)
^^^^ Absolutely. Chrysler’s max wedge in 1960 had the aluminum “cross-ram” intake for and top-end power. There was a mean short-ram intake available through the Mopar performance department, which IIRC some cars had from the factory, but they shipped it to the dealer with the intake in the trunk. (AKA install at your own risk.) That was a drag special. The 413 with the cross-ram was 375 bhp.
Like zo:
Fast forward to today, and a car near and dear to me has something which combined the best of both worlds in the intake:
If you look close, you can see the short runner on the ass-end of the long runner. At 4000rpm, the rear portion of the intake, the “surge tank” opens up the long tubes, doubling a.) the amount of air into the motor, b.) the length of the runner that the air speeds through, and c.) the amount of growl now that there is another resonace chamber opened. BMW now has an infinately (or “steplessly”) variable intake manifold for all rpms. The center section turns, opening it to a variety of sizes.
Now on to the relevant stuff. I am always skeptical about the benefits of a different or aftermarket inatke setup, but AEM makes the Short-Ram intake for the 2.4L that actually has some dyno runs behind it to back it up. Of course, dyno runs are good tuning tools and yardsticks, not always 100% dead-on and there’s tons of variables, relative humidity, heat-soak, etc. (which I’m sure the tuner guys can attest too/add something too) but there’s no doubt, you can get a nice gain from it. We put one into my buddy’s '01 Z/24 and it seems a little quicker, but definitely sounds nicer at WOT. AEM’s charts claim a +8bhp and +11lb/ft gain, your results may vary. A homemade setup will net some gains, but their setup is very efficent and is a 20-min. bolt-in affair with everything you will need, and it looks nice too. aempower.com (dyno charts are of course, on the website.) Hope this helps.
-T
in the maxima world short ram and CAI have know to reduce HP mess up the torque curve and decrease throttle response…stock maxima intake setup uses a helmholtz resonator design which is >*