air flow to air filter

[Joe Rhea]

The supply hose  from the intake grill is collapsed in a couple of areas so they could get around obstructions. The question is, has any one disconnected the hose from the filter and pulled the air from the engine compartment? That would be the simplest way to to increase air flow. I just don't know if the extra heat would create a problem. I have done the fuel filter conversion and looking at anything else to can increase fuel mileage.

[Rodney Luker]

I had the same thing with mine.
I ran it with the hose off & that kept it from showing it needed a new air filter all the time.
Didn't help the mpg & the filter did get more dirt in it.
I ended up removing the hose & opened up the opening where the hose had been connected then I enclosed the area across the the back & above the access door making a duct between the rear body & the inside wall.
I then used a l bow out of that area to the air cleaner intake.
All this must have made better air flow as now the filter gauge doesn't show excess restriction anymore but it still hasn't changed the mpg

[Jim Edwards]

When I Purchased my coach the previous owner solved the problem with 7" stove pipe. Although it worked it was difficult to service the engine. I went to a local HVAC and had them make some galvanized duct work and fitted it up into the recess behind the rear body work. Cost I think was about $45. It required a bit of fiberglass cutting to get to go from a round to a square hole in the air intake and a bit of foam to seal the gaps, but it seems to work nicely. Going from round to square in this size reduces the factory restriction on the intake (increased area). In addition there is a 7" adjustable elbow that is not pictured. I have a high resolution picture of this which has rough dimensions. (saying that because no 2 beavers are the same!) The photo is too large to attach to the post. Let me know if you would like me to e mail it to you. I installed it with a little pitch towards the air intake and left a weep holes at the lowest points for rainy days. Best

[Dave Atherton]

Joe, may I suggest the downside of pulling air from the engine area and not outside air.
Yes air is being filtered to a point. Remember a Diesel engine pulls lots of air through the
air inlet, this will also include pulling heated air, exhaust, wet roads will pull moisture into
The air filter etc. the area of what going to happen your air filter will get plugged and replacement
will be required. Next exhaust is going to suck into air filter and air will Restricted (exhaust not flow
through paper as required ). Pulling warm or heated air into the intake, Caterpillar engines
Gets its power and fuel milage with cool dense air. Air leaving your turbo charger is 330 DEG F
enter through your charged air to air cooler and enters your engine at 110 DEG F. Note: this
pulling outside air, taking air from engine area you are changing The above and basic what
Is going to happen loss of power and fuel milage and last air filter element. Think I have posted
this before on Ask Dave.
Dave Atherton Retired Cat Mechanic

[Jim Nichols]

Jim, that is very similar to what we had to do. We had a sheet metal man build in a low point area for water. We also gave him the air cleaner to make its opening larger, not the 7" round. Best single thing we did after buying the coach used in 2006 from BCS. We now get 7.5 on cruise and almost 8mpg without; prior to the change was 6.8 mpg. Also had Allison  change the economy mode to be priority when ignition is on. If we want power mode then we push the mode switch. We have over 120,000 miles on the coach now. The second biggest change after the air was the fuel filter electric fuel pump from CAT and that was done in 2015.

[Joe Rhea]

I would like thank everyone for their input, this what makes the forum worth while.

Thanks again
Joe Rhea

[Joel Ashley]

Thanks, Dave, for affirming everything I was thinking regarding the notion of not picking up air where it was designed to come from. 

I'm no expert on engines, much less diesels, but raised on a farm my concept has been that any engine benefits from fresh, clean, cool air.  That's not what would be the case if one simply left the intake ductwork off the air cleaner.  My initial thought was such a change would leave the system subject to tire-churned road debris, dust, and moisture, as well as significantly warmer air.  But lacking pure confidence in this realm, I didn't comment.

I appreciate your confirmation of my first impression of Joe's question.

-Joel