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Chevy HP/Torq

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by bryane, Feb 25, 2014.

  1. bryane

    bryane New Member

    This is just a curiosity question more than anything; but why is Chevy engines HP and Torq always at the upper end of the RPM range when ford HP/Torq at the lower end. Is this a philosophy that chevy has?
     
  2. Cowpie

    Cowpie Member 1 Year 100 Posts

    I have always wondered that myself. Considering torque is the "work" part of what is going on, and pulling heavy or hard requires some decent low end "grunt", it has boggled my mind why someone would need to put the RPM's on the ceiling to reach max torque. That is why I have generally liked inline motors. I would kill for a decent sized inline 6 instead of the V8 in my Silverado. An inline 6.0 would be a killer engine. Not something for beating everyone on the freeway, but would be one serious motor for working. Oh well, not going to happen anytime soon.
     
  3. j cat

    j cat Rockstar 4 Years 1000 Posts

    with the 5.3 and 6.2 L engines the torque band is rather flat when compared to other manufactures engines . with the 4.3L gm engine you have little low end torque .. at the higher rpms you get the max torque but only at the max rpm.. the torque chart is a gradual slope ..

    with the GM truck V8 engines you will find the max torque is just below the max rpm horsepower mark. the amount of power/torque is not much different at the peak when compared to the middle of the operating rpm range. this then makes these v8 engines a good choice when towing or hauling.
    the torque chart is a very flat line from 1500-5000rpm...
     
  4. Cowpie

    Cowpie Member 1 Year 100 Posts

    Well, flat line is a somewhat misleading description. From the range you mentioned, we are talking about 20% or more (at least 70 ft lb) difference in torque on the 5.3 LC9. And inline engines will usually meet their max torque rating substantially lower than the GM V8's we are talking about here. Many inline gas engines meet their peak torque 1500 rpm or more LOWER than the GM V8's.

    View attachment LC9 Horsepower Curve.pdf
     
    Last edited: Feb 26, 2014
  5. j cat

    j cat Rockstar 4 Years 1000 Posts

    your chart shows from 1500-5800 rpm a torque of 300ft lbs and is pretty flat.

    other years the V8 5.3L has basically the same torque range. V6 is not very flat. it is a gradual increase as the RPM/hp increases. max is not a factor since , max to the ave value of torque with the v8 is not all that different.
     
  6. Cowpie

    Cowpie Member 1 Year 100 Posts

    Actually I would take exception to the relatively flat. At 1500 RPM, torque is barely at 270lb. At 4200 it peaks at 340lb, and does a nose dive after that. 270lb is a full 21% lower than max torque. Now, that 70 lb of difference wouldn't make that much difference in my semi truck which hits a peak of 1850 lb at 1200 RPM and holds it solid thru 1550 RPM, but 340 lb max torque minus 70 lb is really substantial. One has to get to 2100 before crossing the 300lb threshold. But then it just rides along that until about 3200 RPM before it rises to the max at 4200 RPM.

    While the graph looks relatively flat, the numbers speak another story. Very few people are going to run at 4200 RPM around the country side to get the power they need. Many are not going to constantly run above 3200 RPM. So the 2000-3000 average than most would be operating at, the torque is 40 lb off its max, which is roughly a 12% loss of available torque. Pretty sad.
     
  7. j cat

    j cat Rockstar 4 Years 1000 Posts

    if you need 340 ft lbs of continuous torque you are not going to use a 1500 5.3L GM chevy engine.
     
  8. Cowpie

    Cowpie Member 1 Year 100 Posts

    That is a valid point, but it still remains, that the 5.3L does not have a relatively flat torque curve based on the numbers. It is a sad testament to GM engines that if one needs max torque of their existing engine, they should move up to the next one. I regularly use the max torque, daily, for a lot of my engines. Doesn't mean I need to move up in size. Wouldn't help anyway on my diesels. I get as much hp and torque from a 12.7L as I would get from a 15L. To utilize the max torque of an engine is not overdoing it and needing to move up in size. It is there, it was designed for it, so it should be able to be used on a regular basis. Just too bad that with GM's you have to put the RPM's on the roof to get what you need out of them.
     
  9. bryane

    bryane New Member

    I think this is the best point. "To utilize the max torque of an engine is not overdoing it. It is designed for it". So let it rev!!!!!
     
  10. phoebeisis

    phoebeisis Epic Member 5+ Years 1000 Posts

    Need more torque-?? GEARING TQ multiplication etc
    It is why god invented gearing-different rear ends.
    GEARING-and HP are what actually make you accelerate faster. TQ X RPMs X CONSTANT=HP
    HP and gearing make you accelerate faster-
    For a given load-say moving one of our trucks-at 65mph with a 6000 lb trailer with 2x the drag and the same RR as the truck

    Low RPMS are good because they mean lower friction losses-BETTER FE-

    GMs KNOWS how to make V-8s-just look at the current 5.3 FE numbers(they beat Fords Twin turbo 3.6)
    We-you- us-know ZERO-by comparison to GMs engineers
    looking at a perfectly fine Dyno chart and somehow assuming a Ford is better based on a dyno chart-slightly more TQ at lower RPMS?? or tiny differences in the slope?
    Childish
    If an engine get better mpg-with the same load-who cares if it requires 150 more RPMS?
    A reasonable assumption is we don't know JACK by comparison to GMs engine engineers
    Look at what it does -FE and tow performance-
     

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