Diesels have lower RPM?

Discussion in 'Diesel powered automobiles' started by Chuck, Jul 6, 2009.

  1. Chuck

    Chuck just the messenger

    At the risk of asking a dumb question - this is from a British article on driving greener:

  2. smart-za

    smart-za Well-Known Member

    Diesels have lower redlines than spark ignition engines - think 4,500rpm vs. 6,000rpm. Not sure if this translates into lower revs during normal operation.

    What was your question again?

  3. Chuck

    Chuck just the messenger

    The article I quoted suggested diesels need a slower rpm to upshift.
  4. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Chuck:

    ___I read that non-sense in the past but it is not about diesel or gasoline, it is about the RPM's being way to high for optimal FE.

    ___Diesel's use a far lower range RPM's for a given output of torque and HP with displacement being equal.

    ___Good Luck

  5. MaxxMPG

    MaxxMPG Hasta Lavista AAA-Vee Von't Be Bach

    Diesel fuel burns slower than gasoline, so the engines usually have a longer piston stroke and a lower torque peak. The rotating and reciprocating masses are also greater in a diesel engine because of the higher pressures, but that limits the redline rather than dictating upshift speed. The lower upshift rpm corresponds with the diesel's greater torque at lower engine speeds. Revving a diesel higher will give better acceleration, but not much more than what you get while it's loafing along just off idle.

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