I was going over my dyno plots for the last couple of years, and wondering what was causing a hump at about 4,500 rpm. Than I looked at various dyno plots posted on H-T and found something interesting in SurferX's archived posts. Here is a dyno plot from my engine recently. The hump is highlighted:

Then I looked at SurferX's dyno plot and found the cause. He had a DC JDM 4-1 header, as I do, then he put on a Hytech header. Note the lack of a hump in the Hytech plot:

Next upgrade for my engine will be a Hytech or SMSP header.

 

Actually, the "hump" that you're referring to is a well-known characteristic of the AEM CAI.

EDIT: Although your plan for an SMSP header is a good one.


[Modified by Padawan, 1:13 PM 3/21/2003]

 

I did not know that the hump was characteristic of the AEM CAI. SurferX did not post that he had an AEM CAI in his original setup.
https://honda-tech.com/zerothread?id=308642
I still am going to upgrade my exhaust, whatever the cause of the dyno hump. I just thought that it was interesting.

 

Yes, it's related to the resonance of the AEM intake tubing. Either way, you can't go wrong with the exhaust upgrades you have planned.

 

The ONLY reason to get a CAI is the hump at ~4400.
Otherwise it will make less peak power than a short ram intake.
Cold air doesnt mean much unless you are sitting still.

SurferX was comparing two totally different setups.

 

Why is it that the short ram is better at higher RPM? Does it have something to do with more piping and bends causing restriction?

 

im not totally sure, though that makes sense. the other theory is that its having to move too much air. either way i have done tests on a few cars, and CAI always lose

 

Anybody want to by my CAI ? Anybody selling a short ram? Boy, it really is true, you learn something new everyday! Thanks for the info SGT.

 

Steve, out of curiosity, which intakes did you compare? The comparisons I've seen of AEM CAI's and Comptech Icebox's vs. J's Racing "short rams", show the cold-air setups usually making more power (albeit only ~2 whp). In addition, the cars in the dyno tests can't really be considered "not moving" (which would give the cold-air setups an advantage) because of the fans/open hoods.

 

AEM ITR vs DC DAC, stock hose, generic, and aem shortram

all outdid the aem by about 5hp after 7500rpm.
of course if you close the hood the short ram is not gonna win on the dyno
in realworld though, when moving the underhood temps arent that much higher

 

I have an Injen 3" CAI that fits my B16 with ITR manifold.. the intake has a CARB stick on it.. it is polished..
What kind of Intake do you have?
Maybe we can do a trade...

 

What about in the lower-mid range of the power band? Which made better power?
Also, which made more power, the DC shortram or the AEM shortram?

 

low-mod were pretty much identical except for the spike at 4400 from the aem.
no noticable difference between the dc and aem short intakes

 

I was kidding. I just cut my AEM CAI and made a short ram of it. If I want a CAI in the future, I can just get the by-pass valve and hook the two pieces together again.