More MPG for blocking off the air intake to the air compressor?

Discussion in 'Trucks [ Eighteen Wheelers ]' started by andre, May 9, 2014.

  1. andre

    andre Medium Load Member

    Feb 10, 2008
    Jacksonville, FL
    Hi you guys,

    I heard something really weird today. Basically, if you block the air intake to the air compressor, and then put a breather on the compressor side (obviously so it can suck air in) you can get anywhere from .75 to 1 MPG boost in your miles per gallon.

    Does anyone know if this is true?

    The only reason it even came up was because I blew out the tiny little air hose that connected the air intake to the air compressor and I had the window down (of course) enjoying the ride (of course), and it sounded like I had wreaked major havoc with my truck. Scared the bejeesus out of me when it blew.

    Anyhoo, everyone's thoughts are appreciated. Thanks in advance.
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  3. Dakota1358

    Dakota1358 Medium Load Member

    Jun 15, 2009
    If you heard it from another truck driver it must be true.
    Raiderfanatic Thanks this.
  4. GrapeApe

    GrapeApe Road Train Member

    Jan 7, 2013
    Compared to running with a blown hose (huge boost leak), I say it possble to increase MPG. But if all is well, I doubt you'll see any measureable difference.

    If this is an Acert cat, they have an update to stop that blown hose. It's 2 fittings and a braided hose. We used to blow those hoses all the time, but have had no issue since we updated them.

    I've seen a lot of S60 Detroits blow that hose too. They get soft after years of use, they are behind the compressor and often overlooked on PM's. We check them and change them if they're getting soft. The Detroits make a loud pop when they blow. Cats make a poping noise similar to an exhaust gasket leak, but on the drivers side.
    Cetane+ and puncher Thank this.
  5. Richter

    Richter Road Train Member

    Feb 13, 2012
    Philadelphia Pa
    truth is, on some trucks, the compressor robs air from the intake. Less air getting to motor form intake means less power. maybe .2 mpg, not .75-1. If you give the compressor its own air feed you can keep it from robbing still needs to be filtered. You then block off where the compressor grabbed its air from before. The compressor cant be blocked off or u will run out of air.
  6. Toomanybikes

    Toomanybikes Road Train Member

    Apr 8, 2009
    100% crap. The air compressor is no way robbing air from the motor and will not increase efficiency in any way.

    It would only be an issue if the restriction that limits the motor is upstream of the juncture. That is never the case.

    A diesel is a fuel throttle motor anyway. The power output and efficiency is directly related to fuel consumption and airflow is a result of that not the other way around.
    SHO-TYME Thanks this.
  7. crazycanuck

    crazycanuck Bobtail Member

    Apr 26, 2014
    Sicamous B.C. Ca
    Your biggest savings would be from over the road repair costs. I know Penske lease paid $1100.00 for that eight inches of 5/8 hose when it blew a long way from nowhere with a new driver in the seat.
  8. special-k

    special-k Road Train Member

    Dec 27, 2008
    Southern Ontario Canada
    No measurable difference either way. I put a newer air compressor on my truck that picks up air from the air cleaner as opposed tribute intake manifold and didn't see any difference. The service rep said they went that way because of issues with egr and soot in the intake causing problems with the compressor valves. One thing for sure you know when the compressor is pumping air ;)
  9. maggard359

    maggard359 Medium Load Member

    Nov 20, 2013
    I cant see mileage gains period unless you are already loosing boost. Compressor will kick on boost will drop momentarily and will spool boost right back up. May want to consider also unless you run south of I-10 if you change over to an external filter you run possibility of added moisture and ice in winter to a very sensitive air system. Could be a 1/10th of a mile increase and frostbit driver trying to make a repair on the side of the road.
  10. Helowrenchturn2

    Helowrenchturn2 Medium Load Member

    Apr 23, 2013
    I don't believe it would make too much if a difference myself. But, you may want to read up on a little item that is called a turbo cut off valve that is built into air dryers. It is designed SPECIFICALLY to limit boost loss due to the action of the air compressor.
  11. Gunner75

    Gunner75 Road Train Member

    Mar 17, 2014
    Jackson Center Ohio
    I say to hell with it, record your findings for one week without a modification, then do the modification and record your findings for a week, report back here when you have done so. Make sure you have solid proof of your findings.

    Only way youll know for sure is if you actually try it for yourself.
    t800kwopper Thanks this.
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