When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
This is my take on the long vs short tube power differences. I strapped my car on the dyno and did the best possible conditions for the long tube and kept the short tube in the stock location. Here were my findings...
Short tube intake setup
HPS post maf tubes
2.5" ID maf housing with air straighteners
blox 3" velocity stacks with short 5" filters
Long tube
same as above but with an extra 18" extension attached between maf house and filter
The short ram measures approx 17" in length from throttle body to velocity stacks. The long tube measured approx 35" from throttle body to end.
This would be the most optimal setup as the long tube had no bends and was a straight shot to the throttle body aside from the normal bend right before the throttle body.
Short story was the short rams made more useable power over the entire rpm range. These runs we're back to back. The point where the long tube comes out ahead is approx 7000rpm to redline which was about 4whp max tapering to 3whp at 7500. Below 7000rpm the short tube actually makes about 9whp more from 6000-7000 and also makes slightly more power from 3000-4000. When I designed the short intake I tried to tune the harmonics for 6500rpm and it shows.
I will get pics of the maf housings and 17" intake setup tomorrow when it's light out. I also had to use an eBay 3" to 2.75" silicone reducer to connect the velocity stacks to the maf housing. The housing I ordered was the 2.75" one which is actually 2.5" internal.
What most people don't seem to realize is that there is a such thing as pulse tuning (harmonic tuning) and a balance between that as well as air velocity. Although expensive for a short ram setup, my setup is pretty closely tuned for optimal power in the majority of your rpm band.
The thing about pulse tuning is almost no one outside industry has any idea how to do it. You need specialized equipment to measure and acoustic engineers to develop the necessary formulae to use during design and construction. I have
and it is useless for practical purposes. What I know is from reading car mags starting in 1975; everyone acknowledges the phenomenon but no one can provide practical info. Only automakers, header manufacturers and specialist racing shops seem to have a handle on actual design. This applies to intake manifolds, too.
I seriously doubt any aftermarket intake has length tuning as a primary parameter, it's all about packaging and cost with the general knowledge that CAI is better than HAI and that longer usually equals more torque.
Last edited by slartibartfast; 02-07-2019 at 06:33 PM.
From my testing on the dyno, logging maf g/s flow and crunching numbers, it seems the optimal length falls near 19" which isn't really attainable in this engine bay. According to my calculations though, optimal intake tube diameter falls right around 2.65". A better size for the short ram would have been the 3" maf housing which should be 2.75" internal. These cost too much though for me to order a second set just for testing purposes.
I will share what I can. This took over a month of planning, reading many different papers on physics, flow of fluid, harmonic tuning etc. I literally have pages of calculations but I'll try to simplify it the best I can when I get a chance to go back over it and pull the pertinent info.
Short story:
The intake pipe diameter should be a small percentage larger than the throttle body to encourage air speed and flow.
The longer the intake piping the less "bounces" the harmonic wave needs to make therefore increasing it's strength at the time of valve opening.
Velocity stacks help smooth flow and increase efficiency at all rpms. Without a screen in front of your maf sensor the readings can be skewed for worse. Nissan used very small tubing which helps bring back accuracy. As you increase tubing size accuracy of the maf reading falls but can be recovered using a screen.
Most tune for 2nd 3rd 4th harmonic waves however from my understanding there are infinite waves but they're strength greatly reduces as you go up in numbers.
02-06-2019, 07:03 PM
