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if "bigger" is better..then why..

Discussion in 'Chevy Trucks' started by spongebob, Dec 15, 2005.

  1. spongebob

    spongebob Senior Member
    Messages: 102

    don't the truck manufactures put on bigger dia. exhaust and a bigger intake system right at the factory?

    and before you say COST..how much would it add to do it right the 1st time..above the cost of what there doing now??

    i dont get it..:cool:
  2. wfd44

    wfd44 Senior Member
    from Maine
    Messages: 369

    2 reasons bigger than cost - noise and emissions (especially noise). They need to keep the noise level down from a sales perspective. One of the traditional negatives that hurts diesel slaes is the perception that they are noisy compared to a gasser. A lower restriction intake tract will by nature generate more noise. I speak first hand on this one. I had a 1994 GMC half-ton 2wd that I bought new. I made 2 simple mods - freer exhaust and I replace the "silencer" with an intake tube for a 6.5 diesel equipped 3/4 ton. The intake tube caused a very noticable increase in intake noise at half throttle on up - almost as much as the exhaust.

    The other factor is the vast majority of buyers of all vehicles keep them stock and are very happy with them that way.

    Also with the Diesel HP wars raging anything they don't do now they can use for next year's increase.
    Last edited: Dec 15, 2005
  3. PremierLand

    PremierLand PlowSite.com Addict
    from detroit
    Messages: 1,572

    not only that, they would have to change all their part's over for inventory and such. They have to keep making some parts for 10 years, so they would have to keep manufacturing something they are not even using anymore for years to come. It wouldnt be economical at all.
  4. ratlover

    ratlover PlowSite.com Addict
    from IL
    Messages: 1,325

    Becasue you dont really see HP on a stock type set up from those 2 listed mods. Now on a diesel a better flowing muffler and ditching the cat(emmision reasons why they have that) would drop EGT's but not much in the way of HP. But most people dont want a loud exhaust. On gassers if you go with huge exhaust you can take away some bottom end to gain some top end. Not wanted in most cases by most people. Plus noise reasons.
  5. joe_padavano

    joe_padavano Member
    Messages: 68

    Bigger NOT always better

    While cost and noise are the primary drivers (hey, automakers are in business to make money, despite GM's best efforts to the contrary), the size of the intake and exhaust passages impacts engine performance. An exhaust system that's too large will drop the flow rate in the system, which can result in reduced torque. Both the intake and (to a lesser extent) the exhaust need to be tuned to match the airflow requirements of the engine. Usually this means that the sizing is a compromise for the range of engine RPMs and loads. Larger intake and exhaust will help top end power, but at the expense of low end torque. Which is more important in a truck? Note also that many of the higher-end cars now have variable-geometry intake systems (and in some cases, exhaust systems) that open up different passages at higher RPMs to better match engine flow requirements over a range of RPMs.

    Joe Padavano