I took of the airfilter box on my E350 Powerstroke today. I discovered an extra box connected to the air intake pipe. What is this?

 

After searching the internet, the closest explanation I`ve found, is that this is some kind of a resonator box, designet to eliminate that deep intake sound when giving it full power.

So in other words, the box can be taken off and the pipe plugged?

 

The workshop manual for my 97 E350 calls it an air intake resonator. There is no mention of its function when used with a 7.3, but the 4.6 and 5.4 gas engines use a "variable resonance induction system" which, according to the manual, "improves charging efficiency by using the pressure waves of the intake air". It sounds as though it is used to acoustically tune the intake to improve air flow. I probably wouldn't remove it.

 

Ive seen that extra compartment on my 5.4 intake... wondered what it was for..

 

Well you are correct !! And I agree about leaving it in because it help improve velocity of the intake at lower rpms and helps with the sound. I have removed them before on other vehicles and it did hurt the power curve at lower rpms. But I don't know if that holds true with the 7.3. Try it both ways and let us know if you see any differents at lower rpms. But if you have a lead foot you might not notice.

 

I'm a Van Man. It is an expansion box, basically good for nothing. I asked the dealer myself. Something on the order of if your engine backfires, it won't blow something up or a hose off or something like that. nothing that was a big deal to tell you the truth. Your not under warranty right? Next how to plug that bugger. I'll save you alot of thinking about this one. Take out the unit, pull out your intake pipe with a hole in it. Go to Walmart or Target and buy yourself a rigid plastic cup that the bottom fits into it. Cut the cup off about 3/4 inch from bottom. Clamp it in place. The angle of the cup will prevent it from ever being sucked in. I've had mine on for about a year and a half and I live in Frigid MN.
The exact cup I used came from Sams Club. Its in the "Bakers" section. Thats a Brand name. where they sell cookie sheets, knives, spatulas, etc. This is the section for the chef wannabe's like me. They sell hard plastic cups, exactly the ones restaurants use, very tough and durable cups. comes in packages of 12 I believe. You can get clear or red. I hope that was specific enough for you.

 

And how does your engine sound/pull after that modification??