Weird that the K&N FIPK sounds bad with your exhaust, I swapped to the AEM CAI for more power but I sorely miss the FIPK sound, it was soooo mean sounding at vtec engagement

 

It isn't that it sounds bad with my exhaust. It's that it sounds bad with any exhaust when VTEC engages at low RPMs. Think about how annoying it would be to just be cruising along at 40 MPH in traffic at about 3500 RPMs, and every time you slightly increase throttle, VTEC engages and the intake noise tripples for just 1 second before you reduce throttle just a bit..

 

hi gernby,
read the whole thread.
as length of tubing changes resonation, how do you experiment with the design? do you vary tubing length and perform WOT pulls to find the highest MAP-RPM curve?

 

Your graphs show pretty much exactly the same gains I saw going from the stock intake to a long 4 inch intake (pretty much followed the same "route" as an aem intake) The longer the intake the more friction you have on the air coming in, which is why making sure the diameter is big enough means alot. Hell on my last motor going from 3 to 4 picked up over 15hp at 9800 rpms.

there will always be some design that makes one or two here or there, but a long intake of sufficient diameter will almost always work very well. Velocity stacks and those types of things mean less and less the longer the intake gets.

 

Don't know how I missed this thread for this long. Made something like this myself about a month ago. Modified an aem v2 cai. Used a vibrant 6" velocity stack as well as a 10" to 8" hvac duct reducer from Lowes lol. Had a plan to make a whole ram air with a pressure chamber around the filter but only ended up having the space after cutting about 1.5" off the end of the aem cai to use the velocity stack with the filter with the reducer around it. Then cut a hole in the bumper to allow it to be ram air fed into the reducer around the filter. I didn't take pictures of the vibrant velocity stack or the aem v2 that I cut. Heres pictures though of how I made the reducer fit tight around the filter and then the filter obviously went over top of the velocity stack.

Cut slits in reducer so it would tighten down around the filter with a large worm clamp.



K&N filter inside the hvac reducer



Good fit


Butchered bumper idgaf





Bay

 

The length of the intake definitely impacts performancce, since it changes the acoustics of the system. By acoustics, I'm not really talking about sound, but am talking about the way pressure waves are reflected and / or rarefracted every time an intake valve opens. However, the length is highly influenced by the design of the chassis, since routes and space are limitted.

What's at least as important as length is the shape of the intake, since every change in diameter (up or down) causes rarefraction or reflection. An intake like the AEM V1 is a constant diameter long tube intake that only creates rarefraction, but any intake with an air box will create rarefraction AND reflection. Having the air box close to the engine strengthens the magnitude of the rarefracted pressure waves (good), but the same occurs for the reflected pressure waves (bad).

I still haven't landed on a final design, but I really haven't had time to think about it lately either. Once I get this first batch of exhaust systems shipped, I'll spend more time on the intake.

 

Since breaking in my new lower comp/bigger displacement engine for some time now, Ive been running N/A (typically SC) but for sake of ease, just been running the factory intake tube without the box( which is basically a short ram) and stuck the KN drop in replacement on the end. The car runs strong and I wonder what dynamic effects you mentioned above are at play? Maybe its actually a pretty decent config to run, besides some of the heat soaking that can occur. Got to be better then ITB in that regard though right

 

I really like it

Evan

 

I tested the stock box with and without the lid, and found that there is a significant drop in pressure without the lid that resulted in an equally significant drop in power. I believe this is due to the pressure zones that occur when the car is moving, and I also believe this will hurt real world performance of any intake that draws air from behind the radiator.

 

On another note, I stumbled across a really good deal on a like-new Mugen replica intake, so I bought it. I've wanted to test a Mugen intake for a long time, but haven't known anyone that had one. While I'm totally against the idea of replicas, there was no way I was going to break the bank for an intake that would only be used a few hundred miles and would probably be heavily "modified".

From a visual perspective, the intake looks very high quality, and if I didn't already know it was a replica, I wouldn't have guessed it. However, it only took about 15 miles with a 3600 RPM VTEC point to put a hole in it! I knew something was going on right away, since it made the same BRAAAPPP noise in the midrange that the PWJDM does. It just can't take the intensity of the pressure waves.