Is compression slowing damaging in a 328? | FerrariChat
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Is compression slowing damaging in a 328?

Discussion in 'Technical Q&A' started by Jedi, Jul 19, 2009.

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  1. Jedi

    Jedi Moderator
    Moderator Lifetime Rossa Owner

    Mar 18, 2008
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    Seattle Area
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    Dave
    #1 Jedi, Jul 19, 2009
    Dumb question - but that's how I've learned so much from this group.

    I have a number of pretty big hills I go down in the city of Tacoma, WA - I'll
    often just keep my 328 GTS in second and slowly descend, at around 25 MPH,
    for a number of blocks rather than ride the brakes. 30th Street Hill in Old Town
    is the big offender for those who know this area...

    Does this compression slowing do damage?

    Jedi
     
  2. yelcab

    yelcab F1 World Champ
    Consultant

    Nov 29, 2001
    13,662
    San Carlos, CA
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    Mitchell Le
    #2 yelcab, Jul 19, 2009
    That is what you are supposed to do.
     
  3. Modeler

    Modeler F1 Veteran

    May 19, 2008
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    a.n.other
    #3 Modeler, Jul 19, 2009
    I've never heard it suggested.
    Common driving technique since the dawn of time. Trucks engage lower gear as the signs say.
     
  4. Jedi

    Jedi Moderator
    Moderator Lifetime Rossa Owner

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    Dave
    #4 Jedi, Jul 19, 2009
    I've done it since the dawn of time too :D But just wanted to make sure that I'm
    not doing some unknown damage in the only Ferrari I've owned.

    Thanks for the supporting replies :D

    Dumb but admit it,

    Jedi
     
  5. Ed_Long

    Ed_Long Formula Junior

    Nov 11, 2003
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    Salem, Oregon USA
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    Ed Long
    #5 Ed_Long, Jul 19, 2009
    I remember Click and Clack addressed this question some years ago on NPR. They concluded that there was nothing bad mechanically that would happen to the engine. But, they did advise that the extra use of the clutch would tend to wear it out quicker and be more expensive to replace than a set of brake pads.
     
  6. Aedo

    Aedo F1 Rookie

    Feb 22, 2006
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    Steve
    #6 Aedo, Jul 19, 2009
    Moderating speed through engine revs (including compression) as you describe is fine! :)

    Compression braking where you drop down through the gears (as trucks do) is not recommended on modern cars - the reasoning being increased wear on the clutch and synchros vs use of the brakes (four of them vs one clutch too) which are designed for the purpose. Also it is significantly cheaper to replace pad and rotors than clutches!
     
  7. gidge348

    gidge348 Formula Junior

    Dec 12, 2008
    343
    Perth West Australia
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    Ian Wood
    #7 gidge348, Jul 20, 2009
    Yes it is possible to damage an engine with compression slowing, but not very likely in a road car.

    Too much compression braking with high comp race engines WILL stretch the con rods the same as high revs. Ask any race engine builder, if they re-use rods will tell you they always res-size the rods.

    Having said that in a road car, the rods will probably stretch a little but not enough to cause any worry but should be checked during rebuilding.
     

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