What is the temp. of the exterior of the exahust and CAT used on a 360 when hot? | FerrariChat
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What is the temp. of the exterior of the exahust and CAT used on a 360 when hot?

Discussion in 'Technical Q&A' started by sparetireless, Aug 29, 2004.

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  1. sparetireless

    sparetireless Formula 3

    Nov 2, 2003
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    #1 sparetireless, Aug 29, 2004
    I am trying to calculate the length that the pipes expand during heating.
     
  2. GTO84

    GTO84 Formula Junior

    Dec 13, 2003
    566
    #2 GTO84, Aug 29, 2004
    500 degrees and up if the car is at operating temp. Of course, it varies with throttle angle, load, etc
     
  3. sparetireless

    sparetireless Formula 3

    Nov 2, 2003
    1,596
    #3 sparetireless, Aug 29, 2004
    If 500 is true, then they appear to grow in length by about 1.2 inches?
     
  4. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #4 Steve Magnusson, Aug 30, 2004
    Are you all using deg F or deg C in the numbers (i.e., 1.2" in seems about 2~3X too high for a 500 deg F temp change of a 10' 400-series stainless steel pipe)? What length and TCE are you assuming?
     
  5. sparetireless

    sparetireless Formula 3

    Nov 2, 2003
    1,596
    #5 sparetireless, Aug 30, 2004
    Degrees F

    and I am using a coefficient of 11 to the negative 6th power for Stainless, with a 400 degree delta. Assuming 36" of pipe.

    My actual observations though only indicate about 5/8", maybe due to the affect of airflow accross the pipe?
     
  6. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #6 Steve Magnusson, Aug 30, 2004
    I believe the average TCE for 400-series stainless over that temp range is a bit lower -- are you sure you've got the TCE in units of "in/in/deg F" and not "in/in/deg C"? But in any case, I don't follow the math:

    (11e-6 in/in/deg F)(400 deg F)(36") = a predicted 0.158" length increase (and going to a lower TCE would only decrease this)

    yet you're actually measuring a physical change of 5/8" over 36" from RT to operating temp?
     
  7. sparetireless

    sparetireless Formula 3

    Nov 2, 2003
    1,596
    #7 sparetireless, Aug 30, 2004
    I think its your number now times 11?

    .00001(this is 10 to the -6) * 11 (coef.) * 36" * 400 Degrees= about 1.6" ish???

    This predicts a 1.6" growth in length??

    I got the formula from www.engineeringtoolbox.com/6_283.html

    (not my site)

    (it was on the internet so its got to be true!)
     
  8. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #8 Steve Magnusson, Aug 31, 2004
    I think you've got an extra "10" in there (i.e., "10 to the -6" is 0.000001, not 0.00001) so your result would be 0.16" (not 1.6").

    10 to the 1 = 10
    10 to the 0 = 1
    10 to the -1 = 0.1
    10 to the -2 = 0.01
    10 to the -3 = 0.001
    10 to the -4 = 0.0001
    10 to the -5 = 0.00001
    10 to the -6 = 0.000001
     
  9. sparetireless

    sparetireless Formula 3

    Nov 2, 2003
    1,596
    #9 sparetireless, Aug 31, 2004
    Okay, I'll buy that, but for it to move about 5/8" it must get up way over 400?

    Another observation: the stock muffler splits wider down the middle by about .300" or so,

    I am just trying to see how much clearance we need for a new system. How much do you think engine/trans rock accounts for between gear shifts?

    This whole thing is going to be tight but I don't want it to hit.
     
  10. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #10 Steve Magnusson, Aug 31, 2004
    Can't really help with guesstimating the maximum "rocking" motion that needs to be accommodated (but I think you've got the right idea that it's not zero and needs to be accounted for).

    If you work your calculation backward, the required temp for a .625" change over a 36" length of straight pipe is 1578 deg F which is similar to the "you better shut the engine down because your cat is glowing red hot" limit. So your average temp is probably higher, but I think you'd know it visually (and maybe nasal-ly ;)) if you were really approaching 1600 deg F.

    Are you strictly measuring over a solid 36" straight pipe length, or are you measuring the motion of a particular point in a 3-D pipe system where slight rotations or bending (from asymmetric heating) can result in greatly added deflections? (i.e., What's the project/background/measurement?)
     
  11. bill308

    bill308 Formula 3
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    #11 bill308, Aug 31, 2004
    My source says the CTE for 400 series stainless steel ranges from 5.2-6.8 E-6 in/in/F. Are you sure it's 400 series?
     

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