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V8 6L vs V12 6l

  1. Nov 28, 2009 #1
    Hi guys
    What would be advantage of a V-8 6.0L over V-12 6.0L. Or any disadvantage!
    Will it be more speed, smoothness or what?
     
  2. jcsd
  3. Nov 28, 2009 #2
    You may recall the old Cadillac V-16 or the Lincoln Zephyr V-12 before the War (WW II). These were developed (I think) for smoothness at low RPM. Maybe also because of the lower inertia of individual pistons and rods. However, this arrangenment was less efficient (in terms of fuel burn) than a smaller number of larger pistons, because the lower fuel-volume-to-surface ratio of the combustion chamber conducted heat away from the ignited fuel and to the walls (at ~ 180 deg F) faster, thus reducing the thermodynamic efficiency (Otto cycle).
    Bob S
     
  4. Nov 28, 2009 #3

    Ranger Mike

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    Bob S is spot on..plus the V12 fires every 30 degrees of crankshaft rotation vs. firing every 45 degrees in the V8..so the V12 is SMOOOOOOTH..but consider
    V12 is heavy, compared to the V8 block, you have more parasitic drag of additional 4 pistons, rings, 4 more rod bearings, probably two more main bearings, heavier intake manifold with more intake runners, heavy longer crankshaft, cam shaft, a lot more drag to open 8 to 16 more valves.
    it mat be worth it if you can up the cubic inch displacement but consider the size of the block...it really takes up a big footprint in the engine room so you got one long hood...also the damn thing will be nose heavy and hooking up the rear drive tires will be tuff..
    consider a V8 with aluminum cylinder heads can put out 650 horsepower and weighs just over 300 pounds...and iaa very compact package...
     
  5. Nov 28, 2009 #4

    brewnog

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    Possible advantages of the V8: size, weight, cost, complexity, fuel economy

    Possible advantages of the V12: balancing, smoothness, sound (subjective)

    Basically, it depends on the application and duty cycle expectations.
     
  6. Nov 28, 2009 #5
    V8 would have the potential to produce more torque, but more reciprocating mass (bigger pistons) so less revs.
    V12 higher revs so potential for higher power, perfectly balanced, slightly less torque.
     
  7. Nov 28, 2009 #6

    Ranger Mike

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    I dispute the reciprocating weight issue. No way does a v12 have less rotating and reciprocating mass.
    Also RPM is relative. Yes F1 spins um to alm
    ost 20000 rpm
    but are we talking practical application like 2500 revs
     
  8. Nov 28, 2009 #7
    I mean for each piston, the inertia loads are less for a V12 at the same rpm. As it's a set displacement he V8 pistons will be much heaftier. This is of course assiming the V12 doesnt have a silly bore to stroke ratio.

    So overall static load, the V12 has more. Under operation the V12 has less dynamic load at a set rpm.
     
  9. Nov 28, 2009 #8

    Ranger Mike

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    Right on xxchrisxx
    now I understand and is good point
     
  10. Nov 28, 2009 #9
    I heard of a professor at my university who a an old V-16 caddy in which the ignition points failed. So he drove home on the other 8 cylinders. (It had two distributors).
    Bob S
     
  11. Nov 30, 2009 #10
    the crank should be heavier on the v12 which adds rotating mass, and finding someone to turn that thing (re-size) if it needed it may be tough. my machine shop guy had a hard time finding someone to turn a straight 8 packard crank cause it was so long, some machines couldn't jig it up correctly

    dr
     
  12. Dec 1, 2009 #11
    So , which one gives more power and torque?
     
  13. Dec 1, 2009 #12
    Well it's pointless us just telling you, with no explination. It's also very hard to be all sweeping and general about this becuase it's not true in all cases.

    However:

    V8 potential for more torque.
    V12 potentially more power.

    Do you know why this is?
     
  14. Dec 1, 2009 #13

    brewnog

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    Impossible to say, power and torque depend on far more than number of cylinders.
     
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