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Data on stock '05 N/A intake

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Old 14 Aug 2007, 08:31 am
Fresh Cruiser
Join Date: Aug 2007
Location: Olmsted Falls, OH
Posts: 9
Default Data on stock '05 N/A intake

Hi folks,
I’ve done some research recently on the stock PT Cruiser intake and wanted to share my information for the good of the order. My PT is an ’05 Limited, naturally aspirated with a 5-speed manual tranny.

First, I carefully measured the dimensions of the stock components. I found the following:
Throttle body:
tapers to 2.1” ID just in front of plate; 2.36” OD (60 mm), 2.52” w/ lip

Flexible Hose: 2.36” ID (60 mm) on both ends

Outlet on Lid: 2.075” ID, 2.350” OD
“Helmholtz” Air Horn: 1.820” ID inlet end, 2.075” ID exit end
Inlet Elbow (“black silencer”): Exit end (in air box) 2.30” OD, 2.11” ID
Inlet end of elbow: narrows to 1.98” OD, 1.82” ID
Hole in airbox: 2.54” OD

Second, I have the fortune of working for a company with a Superflow flow bench and I bench flowed the intake and its components. I removed everything forward of the throttle body. First I flowed the entire assembly, then each component, as described below. I also flowed a 2.5” OD straight tube (12” long) with a simple 45 degree flare on the end to get a baseline example. In previous testing I have found that adding a simple flare can add ~25% more cfm flow at the same resistance (inches of H2O). I am assuming that the maximum theoretical cfm used by the engine is 270 (2.4L @ 6ooo rpm with 1.05% volumetric efficiency), so I made all measurements at 270 cfm flow. I found the following:

12” 2.5” OD pipe with flare: 3.5” H2O
Full stock assembly w/ K&N Panel Filter: 23.3” H2O
Remove black elbow from box and put on mildly flared 2.5” OD 90 degree bend: 22.4” H2O
Same set-up with brand new Mopar paper filter: 22.5” H2O
Stock set-up with stainless elbow, no filter: 17.0” H2O
Stock set-up with bottom of box removed: 8.4” H2O
Same as last, with Helmholtz silencer removed: 14.7” H2O
Lid removed, flexible hose only: 7.2” H2O

My conclusions:
The black elbow on the outside of the box (entry snorkel) does indeed restrict maximum intake. The while air horn inside the lid, even though it narrows down to 1.82”, has such an efficient flare that it beats the “blunt” edge of the side of the air box lid hands down (even without polishing the evident parting line inside the horn). It should be noted that as I was testing, not only did removing the air horn increase the resistance to flow, it was also MUCH louder. Perhaps it is different on turbo cars, but I don’t see where removing this will actually help low or high speed air flow on any N/A car. Also, it seems that a clean K&N panel filter shows almost exactly the same resistance to flow as a clean paper Mopar filter.

My original plan was to modify the stock air box to allow for a higher volume of cooler outside air (per “diy,” Airaid, Volant, etc.). I’ve since decided to put everything ahead of the throttle body on the shelf and start over. I’ll post pictures and results after I’ve finished development.

I hope this is helpful!
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  #2 (permalink)  
Old 30 Sep 2007, 09:47 am
Fresh Cruiser
Join Date: Sep 2007
Posts: 2
Default Re: Data on stock '05 N/A intake

It is I think. I bought my wife an 05 vert 5 spd. It is a fine "cruiser" but thats about it. This same engine in my daughters 01 Stratus is much snappier so I don't know what's going on. I have been attempting to figure out if I should get the So-Cal intake as it starts large and tapers down at the throttle body. It seems a critical part to all of this is the inlet snorkel being enlarged, At any rate, I for one am interested in your findings. Hmm., I'm wondering if the brain in the Stratus will plug into the Cruiser ?
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Old 30 Sep 2007, 12:07 pm
Fresh Cruiser
Join Date: Aug 2007
Location: Olmsted Falls, OH
Posts: 9
Default Re: Data on stock '05 N/A intake

For one thing, I suspect that the PT is a good deal heavier than the Stratus, and the 0.411 Cd does not help at highways speeds.

Hey, we buy them for looks and utility, right?

It is a challenge to make them more fuel efficient, however.

I've finished the enclosure for the K&N cone filter, and the housing-to-throttle body routing. I'm working on the intake from the bumper to the housing. I'll try to flow bench test it before I get it all on.

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