Page 1 of 2 12 LastLast
Results 1 to 10 of 19
  1. #1
    Bronze Member
    Join Date
    Jun 2003
    Posts
    65
    Location
    North Cen. Mo.
    Tractor
    JD2305 JD5205

    Default Ok, 1 more theoretical ?

    and then I'll quit. Maybe. It is hard on a gasoline engine to run it without a muffler. Why?

  2. #2
    Elite Member
    Join Date
    Mar 2002
    Posts
    3,491

    Default Re: Ok, 1 more theoretical ?

    OK....Why? The most powerful gasoline engines I know of , (top-fuel dragsters, 5,000+ hp), run without mufflers.

  3. #3
    Bronze Member
    Join Date
    Jun 2003
    Posts
    65
    Location
    North Cen. Mo.
    Tractor
    JD2305 JD5205

    Default Re: Ok, 1 more theoretical ?

    A muffler causes backpressure. Backpressure is needed to keep the piston pushing down on the connecting rod bearing. If it didn't the piston will have a minute amount of overtravel due to bearing clearance. It is called "slap" I think. The engines you are refering to are extremely short lived. They measure "worn outness" in seconds not hundreds of hours.

  4. #4

    Join Date
    Jun 2003
    Posts
    74
    Location
    New York
    Tractor
    Kioti LB1914home use. JD 310SG Pilot controls, Cat 325BL long stick, Sterling Actera

    Default Re: Ok, 1 more theoretical ?

    Yes, you'll loose exhaust valves.
    What do I win?
    Danny

  5. #5

    Join Date
    Jul 2001
    Posts
    1,806
    Location
    Houston, TX.
    Tractor
    2001 TN65, 1951 8N Ford

    Default Re: Ok, 1 more theoretical ?

    I haven't heard or read that one and I've been a mechanic for durn near 30 years. Even with back pressure you would get that slap effect when the piston and rod changed direction. If you had enough back pressure to push the piston down it would barely run if it ran at all. You also have a pressurized oil film for a cushion. Why would it affect a gasoline engine and not an unmuffled non- turbocharged diesel engine? I think someone blew some smoke up your hiney. [img]/forums/images/graemlins/blush.gif[/img] I've always heard that you didn't want to run an engine without pipes from the manifolds. It had nothing to do with back pressure, supposedly when you shut it off cold air could run up the manifolds and warp the exhaust valves. I have ran the pee out of a few engines without exhaust pipes on cold days and shut them off and never had a valve problem due to cold air intrusion.

  6. #6
    Bronze Member
    Join Date
    Jun 2003
    Posts
    65
    Location
    North Cen. Mo.
    Tractor
    JD2305 JD5205

    Default Re: Ok, 1 more theoretical ?

    That's what I was taught at Allis-Chalmers Engine school 30 some years ago. I did a google search for engine backpressure. Seems everyother result argued the need for or against backpressure. I'd say that is a subject that will be argued for eons.

  7. #7
    Epic Contributor MossRoad's Avatar
    Join Date
    Aug 2001
    Posts
    23,478
    Location
    South Bend, Indiana (near)
    Tractor
    Power Trac PT425 2001 Model Year

    Default Re: Ok, 1 more theoretical ?

    <font color="blue"> It is hard on a gasoline engine to run it without a muffler </font>

    Without a muffler or without an exhaust manifold?

  8. #8
    Elite Member
    Join Date
    Jul 2003
    Posts
    3,373
    Location
    Goffs Corner, KY
    Tractor
    IH 2444

    Default Re: Ok, 1 more theoretical ?

    Not really sure about the engine, but I do know it is hard on my ears. I like good mufflers and good hearing [img]/forums/images/graemlins/smile.gif[/img]

  9. #9
    Platinum Member
    Join Date
    Jul 2003
    Posts
    545

    Default Re: Ok, 1 more theoretical ?

    What if you replaced the stock exhaust with a less restrictive (louder) exhaust system (Cat back)? Would that cause engine damage?

  10. #10
    Bronze Member
    Join Date
    Jun 2002
    Posts
    58
    Location
    Roanoke, VA
    Tractor
    1999 Kubota L3710GST

    Default Re: Ok, 1 more theoretical ?

    I'm not an engineer, but for what it is worth. The amount of backpressure affects the performance of the engine, both overall horseposer and torque, and the amount of each at a given RPM. A term you may hear is a "tuned exhaust." It is done in lots of ways: pipe diameter, pipe length, mufflers, etc. On race cars (e.g., NASCAR) there are often multiple pieces of exhaust pipe of different lengths and diameters to get the desired torque and horsepower "curves." An important piece is having the same effective pipe length for each cylinder, hence the funny contorted bends you often see in aftermarket headers. I've seen a couple of books that explain all of the math needed to do the job right. Made my head hurt.

    Kevin

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
© 2014 TractorByNet.com. TractorByNet is a registered trademark of IMC Digital Universe, Inc. Other trademarks on this page are the property of their respective owners.