# 273-1P cap plug Mod

[sentipede]

Has anyone had success with this particular mod? I ordered the caps about a year ago, and they have been sitting in my glovebox, never figured out how to install them?

Any pictures...maybe a DIY?

Thanks in advance!

Posted by MKW on funcarsonline

Just get a # 273-1P cap plug from .....

A company called Niagara , in Erie , PA . Pull off the rubber side bridge hose from the air box, drop in the cap plug , reinstall the hose and you have accomplished two things : bypassed the noise police required intake noise suppression resonator to improve induction sound above 4500 rpm and possibly smooth air intake from the MAF path.

Ask them for a sample and they will send it to you free. Works on all 99-03 9x6 motor 996s . Lot cheaper than the Fabspeed , even if you add a BMC filter and pop out the plastic screen before the MAF sensor - just don't remove the wire screen . Also, I'd cover the holes in the lower right of the bottom of the air box that does nothing more than draw hot air from the right muffler area - defeats the purpose of the cold air snorkle that feeds from the engine lid, IMO Don't worry - there are separate water drain holes in the bottom of the box, away from heat. Niagara Plastics

Edited December 8, 2003 by sentipede

[Scouser]

Any chance you could post pics of the caps themselves.

Cheers

[sentipede]

We never got much of a response, but Ghost Rider on Rennlist gave it a try and wrote up the directions with pictures....

CLICK HERE

Loren, is this correct procedure?

T.I.A.

Edited December 15, 2003 by sentipede

[Loren]

Well, that blocks off the baffle -- but still does not remove it. A while ago I tried to remove the baffle then clamp the plug in place and the orange plugs are just not rigid enough. IMHO... to get the maximum effect you need to remove the baffle (to increase the air volume in the housing). In order to do this you need a better sealing rigid cap like the Fabspeed one. What you don't want is an air (and dirt) leak on the clean side of the air filter - which is where this mod goes.

[clord]

I did a mod something like this on my '99 C4 some years ago. I used some of Evo's "quick flow" plumbing from the air box to the throttle body. I totally removed the resonator box from the inside of the air filter box.....and looked around the garage to find something to "plug the hole" in the top of the air filter box. I found a couple old black plastic blank plugs that once filled unused auxilliary instrument holes in a "add-on" instrument pod. The standard hole size for VDO, etc instruments is, I think, 2 1/8 inches......and the blank plug fit perfectly with some epoxy glue.

[Guest]

"The Cap!

[Poursha]

I got these in the mail yesterday. I have PSE--will installing this cap make a noticeable increase in sound, or will the lovely music of PSE make this unnoticeable?

And could somebody explain what this mod does to improve sound? I see it blocks off the smaller air hose, and inside the airbox there's a "muffler" so this cap prevents some of the air (that used to go through the small hose) from being "silenced" by the muffler? Is that it?

[Costa]

I would say that the bypass tube and the so-called muffler in the airbox form a tuned pipe/chamber of sorts.

As you advance your throttle you have sound waves which travel along the intake side and these in effect get "absorbed" by the tuned cavity ('Muffler Box' + Bypass pipe).

The sound waves are caused by the rush of air and also by noise generated from within the motor travelling back out the intake side.

I used to own a restored 1971 Australian 'Bathurst' Chrysler Charger which came equipped with 3x45mm dual throat Weber carburretors attached to an inline 4.3L six cylinder motor. At WOT the noise from the six intakes on the carbies would drown out the loud exhaust when sitting in the car - Music to my ears.... :D

Don - Would it be possible for you to measure the outer lip diameter of those plugs - I may have to do some hunting in my shed for a suitable substitute here in Aus - Thanks

Edited December 23, 2003 by ZX7R

[Pat]

Loren,

I bought into the hype too and got the caps but I want to make sure I'm doing the right thing and not screwing-up the car. Give me some good fatherly advice.

Would you advise installing the orange cap or not? If so, would you put the plug into the "box" or the tube? I'm not sure which way the airflow is going. As a result I want to make sure to put the cap on where is won't move.

On another note, hanks for all your help. It's great to know that there is someone that you can trust to give you sound advice. Have a Merry Chirstmas and a Happy New Year, or other significant religious holiday. Just want to be PC.

Regards, Pat

[Poursha]

You can see the dimensions here (the 8th one from the bottom):

http://www.niagaraplastics.com/prodcentp.a...htm&tabletype=1

[Costa]

Thanks Poursha

Merry Christmas to all and have a safe New Year.... :jump:

Pat - 'Ghost Rider' over at the Rennlist forums has posted some pics of the orange cap install.

Try this link...http://www.smiley.net/orangecap.htm

I guess you have to ensure that the cap is very secure and it should not come loose.

There are better ways of achieving the same thing (ie. Using a straight thru' piece of tubing without the bypass and then just blocking the top of the airbox opening etc - but the plug idea is quick easy and cheap)

Edited December 26, 2003 by ZX7R

[SPR]

so do you guys remove the muffler and plug that hole as well as plugging the smaller hose that connects to it???

[Pete P]

Well, that blocks off the baffle -- but still does not remove it. A while ago I tried to remove the baffle then clamp the plug in place and the orange plugs are just not rigid enough. IMHO... to get the maximum effect you need to remove the baffle (to increase the air volume in the housing). In order to do this you need a better sealing rigid cap like the Fabspeed one. What you don't want is an air (and dirt) leak on the clean side of the air filter - which is where this mod goes.

Any recomendation on using a K&N Airbox mod? Which one better fabspeed or K&N? see attached

[Purplxd]

Looks like they don't have this part number anymore on their site.

Anyone have the exact dimensions for this so I can look for an equivalent?

Cheers

Aaron

[Purplxd]

See part CPT19 for dimensions. The old part number was 273-1P

A

[A2MVS]

I'm a bit confused about whether it's safe enough to remove the muffler box completely. i've got a Schnell kit fitted at the moment and they say that the muffler cap + cover they provide is to allow for the items to pop off in the event of a backfire.

Can someone please confirm whether it's safe to remove the muffler box and seal off the bypass hole completely?

Many thanks

[balefire]

See part CPT19 for dimensions. The old part number was 273-1P

A

Thank you. I got both CPT19 and CPT19x. They both appear to work.