DesertRat wrote on 05/06/16 at 11:58:29:


Yep, it just pulls right off!  

Round 3 of SRX600 intake tuning.

So this is what happens when you have a big single that can only turn 7,000.  This is my third attempt at intake tuning and each time it got longer it got stronger.  Original setup was pods on the bells and that was garbage.



I did create an airbox area by installing a cover over the open ind of the swingarm. The priimary filter is now serviceable via the side cover. Since this filter sees 80% of the air intake duty it needs to be cleaned more often than the secondary filter so this is great.



Also... The secondary filter now has way more breathing area around it because the primary filter is no longer right next to it. not only that, the new primary runner has opened up space for fresh air to more easily reach the secondary filter.



So far I can see only benefits and no negatives to this very simple modification.

So now that we have increased the intake runner length what does that do for the engine? Total primary runner length is now right about 20" which gives:



+ For 2nd harmonic, RPM range is from 5,874 to 7,128 with a pulse strength of 10 percent
+ For 3rd harmonic, RPM range is from 4,414 to 5,044 with a pulse strength of 7 percent
+ For 4th harmonic, RPM range is from 3,441 to 3,848 with a pulse strength of 4 percent



Blah, blah blah... So what does it mean? It means the primary intake runner is now tuned for three different harmonics that are ALL withing my engine's operating range! I just get a BIG boost from 5,874 to 7,128, a GOOD boost from 4,414 to 5,044 and a SMALL boost from 3,441 to 3,848.



So what else? The secondary runner is tuned for 4th harmonic, RPM range is from 5,984 to 6,692 with a pulse strength of 4 percent. So while the secondary runner is not optimal it WILL add a small boost from 5,984 to 6,692. That coupled with the primary 2nd harmonic should work great.



So what did it do?  A LOT.  Kind of hard to believe what a difference it made.  The exhaust note now has a very distinct CRACK from about 4,000 to 6,000.  I believe this is from the mild ram effect of the system.  Absolutely stupid amounts of torque from an internally stock engine.  I can't wait to get the Web (3)87 in there with a Wossner piston milled for 10:1.



I know, I know...  It's in the wrong forum but I figured you guys might enjoy it.

Kris01 wrote on 05/07/16 at 07:28:02:


The formula is for Helmholtz Resonance and "*" represents product (multiplication).  There are many formulas for intake tuning and this is one of them.  Intake valve closing/timing also plays into it but that is only if you must be tuned for an extremely specific RPM range.  If I was a sponsored racer I would likely be a heck of a lot more precise.

The bottom line is the intake originally had a length of only 8", which was really not even usable for the big single.  The second intake had a length of only 11.5", which was starting to be usable for the big single.  This last intake has a length of 20", which is very usable for the big single.

I was fortunate because the SRX has ample room under the tank and under the seat.  It is kick-start only and has a tiny 3.3AH SLA 3.3 battery.  I used all that area to fit all the new intake components.

The factory SRX600 uses the same tiny flat filter the SRX uses.  My SRX now has 60 sq in of air filter area (not including p;eats) which is pretty large.

I used this site to get me close:  http://www.bgsoflex.com/intakeln.html

I think intake tuning is important. .. Still.
But sucking air in is not driven by a piston, so, if you want peak performance, you need to look at this. I would like to see this studied on the savage.
Like jetting, it's just doing the best you can. There's no
Perfect. But, if someone is gonna spend the money and time to work on the exhaust and cam, or more, they otta check out what a tuned intake can do.
I wish I woulda had the formula and smarts to use it. All I could get done was increase the volume of the airbox a little..

I finally tuned the secondary side as well.

Correct in that engines don't "suck".  The piston creates a low pressure area that is filled by way of 14.7 PSIA of atmospheric pressure rushing into the low-pressure area.

Runner area controls velocity and runner length controls resonant frequencies.  I did the best I could given the volume I had available, which is about 600 cubic inches.  Total air cleaner surface area is 63 square inches, not including pleats.

Each time I decreased runner area and/or increased runner length the midrange got stronger and stronger.

very interesting discussion
JOG, I wonder if the box you reference is a resonator, to muffle intake noise, some Fords had one, but the only Jeeps I know anything about are old CJs
on the 95 - up crown vics, we often had to modify the airbox as they would develop an intake howl over time that was very annoying

In that case longer is better.


I'm just Sure I've heard that somewhere, but dadgum if I can remember EXACTLY who said it.