Ideal cruising RPM for MP8?

Discussion in 'Experienced Truckers' Advice' started by Bdog, Feb 4, 2021.

  1. Brettj3876

    Brettj3876 Road Train Member

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    If a company has progressive shift enabled like the food service company I was with i could see how a new driver might think oh ####, Lol did I hurt something when they really didn't. 1600-1700 is where they limited the rpms to. Most were 1700 and a few 1600.

    Really the only time i take it over 1800 is in low gear to be able to grab 1st. Wind it up to 2100 and slowly wait for it to drop in a 1200. Any type of hill and I have to jake it on the 1st stage or your not making the shift. Enough time to smoke a cig with how slow the Mack's drop off
     
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  3. KB3MMX

    KB3MMX Road Train Member

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    Hahaha true !!
     
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  4. KB3MMX

    KB3MMX Road Train Member

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    Oil psi does not equal engine life though. Modern diesels are more oil flow principal vs oil pressure resistance to flow.

    40 +/- Mack/Vo , Detroit DD13 and MX13 about the same for oil psi warmed up at cruise.

    The one engine that so far seems to be weakest is the X15 , mine didn't like being under 1300 rpm it was dead pulling below that.
     
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  5. racemaxx24

    racemaxx24 Heavy Load Member

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    ive heard of them suffering catastrophic failures in some cases in super downsped applications
     
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  6. Atlanta trucker

    Atlanta trucker Road Train Member

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    Normal .... 35 to 45 psi
    They are built to do that no problem.
    How many modern engines do you know of that slipped a bearing or burnt out there bottom end ? Not many. My 2020 KW paccar engine will not even be at 1400 rpm at 80 miles per hour. It must have about a 3.08 or 3.25 rear end.
     
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  7. KB3MMX

    KB3MMX Road Train Member

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    2.64 - 2.85 is becoming the norm but yes, the new engines of the last 5 years(minus Cummins) are pretty incredible. The Volvo D13 bottom end has always been very overbuilt and great for downspeed capability, just like the MX13 has become it's closest competitor now. Cummins really needs to get it's act together, they lost allot since the days of the N14+ motors... They haven't returned with a superior product yet. Cat really needs to get back in the game.
     
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