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Grandrock muffler for KW/ IH underbunk type

Discussion in 'Trucks [ Eighteen Wheelers ]' started by 13letter, Dec 10, 2008.

Page 1 of 6
  1. Dec 10, 2008 #1
    13letter

    13letter Light Load Member

    109
    16
    Oct 19, 2008
    Fulton, IL
    0
    Has anyone used this muffler from Grandrock? Their performance replacement for the KW and IH reverse flow underbunk style muffler. Wondering what was noticed in performance and/ or mpg changes. Put one on my 550 Cat powered Binder and noticing higher pyro temps and mpg seems to have gone down. Had installed the fuel temp harness prior to doing the muffler. Did not notice elevated pyro. Mpg and performance seemed to improve then. Anybody have experience with this muffler? Thanks
     
    13letter, Dec 10, 2008
    13letter, Dec 10, 2008
    #1
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  3. Dec 10, 2008 #2
    Rock hauler

    Rock hauler Light Load Member

    264
    54
    Nov 26, 2008
    Deridder La.
    0
    can't help, but am interested in what you find out. I'm going to replace mine on KW in the next few days. how loud is it, i don't mind some but cats get loud about 1500.
     
    Rock hauler, Dec 10, 2008
    Rock hauler, Dec 10, 2008
    #2
  4. Dec 10, 2008 #3
    benthere

    benthere Medium Load Member

    321
    228
    Feb 14, 2008
    The shomee
    0
    If you can catch Brickman on here sometime, I think he put one on his w9 he had, or you could go to the here we go finaly an o/0 thread he pretty much desribed the switch in the thread, but it is 3000 pages long now but I know its in there.:yes2557:
     
    benthere, Dec 10, 2008
    benthere, Dec 10, 2008
    #3
  5. Dec 10, 2008 #4
    Native Dancer

    Native Dancer Heavy Load Member

    978
    3,259
    Dec 28, 2007
    Portland, Or.
    0
    Haven't used this muffler but I have used Grand Rock and been happy with their products and service.
     
    Native Dancer, Dec 10, 2008
    Native Dancer, Dec 10, 2008
    #4
  7. Dec 10, 2008 #5
    13letter

    13letter Light Load Member

    109
    16
    Oct 19, 2008
    Fulton, IL
    0
    Appreciate the replies guys! I really like the sound of this muffler. Sounds good runnin up thru the gears ( ie. loud) and loud on the jakes. But at cruise speed it's really not bad. It being 2 ft. shorter than the stocker, and both muffler brkts toward the back, I made 2 24 in. ext pipes w/ id/od adaptors welded on one end of each. This allowd use of both brackets and slip fit to the inlet and outlet pipes under the truck. Fit fine.

    The fuel mileage part is hard to pin down as I always run different areas and different loads. The pyro going up higher than before is what concerns me the most right now. When I put the fuel wire on awhile back the pyro wasnt coming up like this. Only now after muffler. I need to figure out how to test backpressure on it.
     
    13letter, Dec 10, 2008
    13letter, Dec 10, 2008
    #5
  8. Dec 10, 2008 #6
    13letter

    13letter Light Load Member

    109
    16
    Oct 19, 2008
    Fulton, IL
    0
    Of coarse there's always the chance I'm just losing my mind. Or a little more of it anyway. Been a little while since ran in warmer weather like it is in GA and FL yesterday and today. As for the mpg on this run. From central Wisconsin to Northern Florida with about 29k on the stepdeck, avg was about 6.25. Was plenty breezy coming down too. Load was humvees so not real tall. Before muffler, with fuel temp wire, load from sthrn. WI to Houston w/ 35k and about same ht. avg was 6.5 ish. So I guess for the difference in terrain, more hills to the S.E. area, It's to be expected. Just want more I guess.
     
    13letter, Dec 10, 2008
    13letter, Dec 10, 2008
    #6
  9. Dec 11, 2008 #7
    wallbanger

    wallbanger "Enemy of showers everywhere"

    1,399
    88
    Sep 4, 2006
    In the bougy 'burbs of Detroit, MI
    0
    It's natural to want more MPG- let's face it, diesel ain't ever going to be cheap again (I think $1/gal diesel is cheap!) so you want to get your money's worth. But a difference of .25 mpg is most likely due to terrain and weather, not the mufflers. Unless it continues going down...
     
    wallbanger, Dec 11, 2008
    wallbanger, Dec 11, 2008
    #7
  10. Dec 12, 2008 #8
    Captain Canuck

    Captain Canuck "Captain of the Ship"

    854
    541
    Apr 7, 2007
    Woodstock, NB, Canada
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    Don't forget that winter fuel doesn't typically do as well mileage wise either.
     
    Captain Canuck, Dec 12, 2008
    Captain Canuck, Dec 12, 2008
    #8
  11. Dec 12, 2008 #9
    13letter

    13letter Light Load Member

    109
    16
    Oct 19, 2008
    Fulton, IL
    0
    I'm most concerned with the rise in pyro temp. Had not seen it go this high before muffler install. And, looking at comparisons over the last few weeks only in mpg. Before muffler, with fuel temp wire, and now with muffler. Seeing the pyro up after muffler. How can one test backpressure?
     
    13letter, Dec 12, 2008
    13letter, Dec 12, 2008
    #9
  12. Dec 12, 2008 #10
    droy

    droy Heavy Load Member

    828
    160
    Jun 11, 2008
    Iowa, LA
    0
    Just as soon save your money, and eliminate the muffler altogether. End results are about the same.

    Remove your fuel wire, and run your truck, you may find that the wire is your problem, not the muffler. I recently posted an update on my PITA episode and fairly sure the wire was one of my problems. Elevated egt, and fuel mileage sucked, not to mention tips of my pipes turning black with soot. Removed wire, had to also replace sensor, maybe my wire was "wired" wrong, but I think it caused alot of my problems. I trashed it, won't even try to sell trouble to someone else.
    I know that a fuel wire has helped many, that's what makes me think that mine was bad.
     
    droy, Dec 12, 2008
    droy, Dec 12, 2008
    #10
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