Question for those who may care to chime in. I'm currently in the process of building a new intake horn for my 12v and am stuck in the pondering process. In a pressurized system, ( i.e. intake tract of dodge cummins) the flow limitations/capacity are limited to the most reduced or restricted portion of that system. I have not yet measured the surface area of the inlet or discharge of the stock horn but, a stock HX35 has a discharge diameter of 2.050" or 3.29 sq.in. I'll come back to this later.

Numerous people have built tubular horns out of 3" tubing and claim quicker spool-up and a slight increase in performance. While smooth bends/transitions enhance flow, I wonder if they are spooling faster due to a reduction in plenum volume within the horn. A simple example, get a toilet paper tube, place one hand over one end and put your muzzle against the other. Blow into the tube until the pressure escapes from aorund your mouth. Repeat this test with a paper towel roll. You should notice it takes longer to pressure up the paper towel roll, right? Now using the same engine, your lungs, repeat the test with a straw.

Using that methodology, wouldn't you realize quicker spool-up/pressurization and better performance by making a intake horn out of 2-1/4" i.d. tubing?? You still would have a greater flow area than the turbo discharge and the difference in volume per inch of horn length going from 3" to 2-1/4" is substancial. (3"=7.065 cu.in per in vs. 2.25"=3.97 cu.in per in) Using an arbitrary tubular intake horn track length of approximately 12.5" +/- ( 4" radius u-bend), a 3 inch tube has a volume of 89+/- cu.in and the same bend in 2.25" has a volume of 50+/- cu.in. Thats a significant difference in volume that would certainly have an effect on spool time, right??? Again my assumptions are based on the stock turbo discharge diameter being the smallest diameter or restriction/flow inhibitor in the system. Any thoughts or comments??

 

Too many #'s formulas for me, I slept through math class. but I do want to stay tuned to this.

 

I'm not smart enough to help answer this question either... but it isn't just a 12v question and should apply to everyone's engine.

I too would like to stay tuned.

 

god damn i didnt join this site to get a math lecture thats what i go to college for, interested to see what other people say, i have a 3" custom made one i did in my shop i notice no difference good or bad but it looks sweeter than hell

 

Ya I have a high ram and didn't notice any diff.

 

my brother has a twin ram and noticed a difference but it is equalling the air flow to all cylanders instead of 2-4

 

I was told that unless you have a hopped up truck it will not do anything. maybe like 1% on a stock truck. You will not notice anything. This is what I was told by the manufacture. I do understand what you are saying but the air movement is not enough with the stock truck so the stock horn is ok.

The only way you would know if it is doing any better would be do a air flow test.

Just my input so please don't flame.

 

interesting gonna have to stay tuned to this one

 

putting a intake horn on makes no sense on a stock veh. being stock turbo, intercooler, head-ports etc... just think if you cut a mid section piece of your 4" exhaust out and replaced it with a 6" piece is that going to give you more flow out of the 4" tail pipe???

 

no but my 5" stacks look sweeter than hell and my 3.5" bacbrake is a blast when towing