Air Flow at 23 LBS Boost
 

This little mod gives your SS much more air flow, and much less cleaning while keeping the cold air box. You must already have a K&N kit with K&N air box cover for clearance. This simple mod allows for a K&N RX-2820 X-Stream flow filter. This filter is one inch longer, larger diameter, with additional filter material on the end. Requires cutting out the stop in the bottom of the air-box, covering the hole with a piece of plastic held in place with JB Weld epoxy glue, and wrapping a piece of 3M double sided tape with only one side of the tape covering removed onto the inlet to take up the minor difference in the filter inlet size. It fits snug, perfect. If you are not running 20+ boost this is not a benefit. This baby flows!. Also the original K&N filter had an internal lip on it to further decrease the flow. Yea i slipped with the cutter Lol, and made a mess with the JB weld, but then who can see it.
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Nice! Do you have the RPD or some other way to see an increase in HP or torque?

I've moved this to 2.0 Performance Tech, seems a little more at home here.

It’s still gonna ingest as much CFM as the charge pipe will flow, but that might be more then the original or first K&N filter would allow.
Nice mod, but don’t cut hair or outer body work!

Ran it today for a bit, i also installed a Walbro 255 pump and i am very happy with the results. Smooth fast acceleration and fast boost to 20+lbs. Maybe the pump or the Filter but im thinking both. I don't have HP reading as of yet. I still don't know what the fuel pressure should be, people on here say 55, 57, 60, one says he has 70 before starting the car. I have no idea how to achieve that. As far as i know its based on the regulator and the program.

Well i guess the computer calibrated to the new mods, it now jumps to 26 lbs of boost instantly. what a crazy fun ugly car Lol. And its my work car/truck. All the fancy 60K plus imports hate me Lol. I guess i would too if i spent that kind of money and a car like this stayed next to me or passed. I will be trying half a tank of E85 to see where that goes. I wish i did not tie the program to the traction button , i think it would steer better without the posi on.

Could this be your HP gain ? Correct fuel pressure is more than a 5% airflow (?) from the filter.

The Walbro 255 flows 67 GPH (255LPH) at 100 PSI so that’s an improvement!
According to the description for the OEM Delphi fuel pump that flowed 65 GPH at just 65 PSI.
I’m just wondering how you got it into the SS OEM fuel pump in tank unit?

I guess i should have made a video. I thought this was common knowledge that the 255 fits perfect in place of the stock HHR pump. I had to add the foam sleeve that comes with it to take up the little extra slop, and i added some rubber piece to the bottom of the pump that came with another Green Summit pump i had for another application. Also had to cut off the factory flex hose to remove it so i ordered a replacement flex hose that was dirt cheap. Heated the hose with hot water from the sink to make forcing it on easer, then added clamps as a precaution. Tried to use submersible fuel hose to reinstall but the tight U bend made it kink. OH! Note: the Walbro 255s polarity is reversed even though the GM power connector fits the pump perfect. Forgot to check it beforehand so the pump ran backwards, no pressure, no start Lol. I was not about to drop the tank so i reversed the black and gray wires on the tank connector at the frame by removing the connector pins and swapping them, easy piezy. I pity the fool that tries to install a stock pump in the future, he will hate me Lol. I wanted to install the Green Summit pump that flows much more than the 255 but the outlet was larger like 10mm so i would have needed the flex hose that has 10mm on one end and 7mm on the other, same price but got busy and forgot to order it. I think most of the universal pumps would work except that at some point its a waste and you may need a relay to handle higher current from a super high output pump. I think im maxed out on power unless Cams would make a difference. 26 Lbs boost is as far as i would feel safe to go without new pistons, rods and crank. Although i am working on a new mod to allow me to regap back to .035 even with the high boost. Still need to know what the proper PSI should be, i have solid 50 PSI but i feel 60 is more in line with GM. My motto, Just do it! Go forth young man and prosper!! Good video on replacing in tank fuel pump on You-Tube

Hay, I like this, & I decided to give it a try...:twothumbs:

You don't have to mod the airbox at all...
It fits just fine...:twothumbs:
I just used a screwdriver to force the end of the filter in front of that 'bump' on the floor of the box...
The K&N lid has a little flex to it, & holds the filter in place very well...

Now to the testing...
IT WORKS VERY WELL
I can 'feel' smooth increases thru-out the full RPM range...:twothumbs:

The stock filter & the stock K&N filter that comes with the K&N air filter kit 'feel' pretty much the same, so I figured that there wasn't anything else to 'gain' here...
But I was wrong, there is more to be 'gained' here by using this larger K&N filter...

Thanks to 'drspock' for making this discovery....:twothumbs:
And 'drspock', you are too modest, as this is not a 'little-mod', it's a GREAT MOD

Wondering why the big jump from 20-26psi. The HHR computer changes boost to reach desired torque/hp. A boost jump like that to make the same numbers the computer was programmed to before the mods means you lost efficiency big time. The computer is adding 6 more PSI to make the same numbers as you did before. These are set numbers unless you changed them along with the mods.

Am I correct in understanding how the HHR computer works?