The amount of airflow through the 4 inch inlet hose would be dependent on the amount of restriction from the filter. A 4 inch pipe can flow a lot of air if it has no restriction.

 

I think you have to much time on your hands to sit here and wonder about this stuff.

 

You're looking at it a touch wrong...It all adds up to a total pressure drop (or suction-how ever you want to look at it). The drop across the filter + the drop through the tube. I suspect the drop through the tube is pretty negligable when compared to the drop across the filter - even with a size huge filter. So...to answer your question (I think) you can't get a filter big enough to overflow the tube - I suppose if you had a filter that took up the size of the bed you might turn the numbers around to the point where the filter was negligable compared to the tube...But basically youre after the lowest restriction inlet you can get -which is the sum of the tube plus the filter....I sure hope that makes sense to someone else

 

Its not ONLY the size of the filter that is important. The filter material has a lot to do with the retriction factor. When K&N introduced its gauze design it revolutionized the way air filters where made.

 

OK OK I admit I also have to much time on my hands!!! :<br><br> This reminds me of a sale display I seen for K&amp;N airfilters. They had a vaccum set up with a ball. They proved to me that sucking through their filter they could suck this ball higher up the tube than with my purolator. Proving to me they could flow more air. I sucked in. I bought one....and a boost guage....34 psi. with both filters and builds pressure just as quick....it seems. $69. filter vs. $6.90 filter.<br><br> My theory: If you produce the same boost wheres the gain? Air temp./ Air density. ??<br><br>I apologize for jumping in but I think it's sort of the same question...you can only flow as much air as she'll take..right? Anything past that would be boost wouldn't it?<br><br>

 

I don't doubt that those big filters are as big as the bed - there is a lot of pleats in them for sure. What I'm saying is the fact that you have losses from going through the tube doesn't have anything to do with the losses through the filter - The lower you can get the restriction through the filter the better - as they are both additive at the point it gets to the turbo inlet<br><br>As to seeing no gains with a low restriction air filter...the stock filter was probably doing just fine with no other mods to the motor- if you were to add fuel (fuel plate or chip) then you would need more air to go with the extra fuel and then you probably see a difference. The stock filter may not be able to supply air at the increased demand - compared to the K &amp; N.

 

<br><br>Sounds like thats the way it is supposed to be but it doesnt work that way. Volume, velocity, flow, density, and temperature all play a role. Really you just need to allow the air to enter the motor the easiest and coolest way possible. Flow test benches have opened up new and improved designs in all kinds of engine mods. You should check out the Scotty II. This system uses the &quot;stock&quot; hole in the fender (in the hush mode) and still produces more boost and lower EGT's through the design of velocity and flow volume!

 

[quote author=Amish hauler link=board=7;threadid=13432;start=0#126708 date=1050025323]<br> My theory: If you produce the same boost wheres the gain? Air temp./ Air density. ??<br><br>I apologize for jumping in but I think it's sort of the same question...you can only flow as much air as she'll take..right? Anything past that would be boost wouldn't it?<br>[/quote]<br><br>You can only flow as much air as the truck wants, but the objective is to flow this air as easily as possible. So proper air system design is not just strictly related to air flow/air restriction of the filter on a bench. You want to allow the turbo to pull air as easily as possible (or ideally, push the air to it so it doesn't have to pull a doggoned thing) so you don't increase drive pressures, and pull the turbo out of its efficiency map. The harder the compressor has to work to get its air, the hotter that air will be after it leaves the turbo.<br><br>Rod

 

Well said push-rod..I couldn't seem to get that on paper as well as you.