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Just cut the belt! Then, happiness!

Discussion in 'Boxers/TR/M' started by rpissm, Oct 11, 2020.

  1. rpissm

    rpissm Formula 3

    Aug 11, 2013
    1,562
    Salt Lake City, UT
    Full Name:
    Joe
    Hello everyone!

    For fellow USA Testarossa owners who don't have to worry about emissions any more (over 30 years old where I live), here's something I recommend...

    First off, when my TR would start up, it would be so cranky: clattering, clapping, sounding blah. When it warmed up, it sounded better. I thought it was just because maybe my oil was too thin and took a little while to lubricate the clattering pieces, etc.

    I was reading somewhere else in this forum about how, when the aux air pump is going bad, you'll hear a bunch of clattering while cold (when warmed up, the air pump switches off)

    I noticed the clattering would greatly decrease if I covered the air intake on the little black air filter on the driver's side, above the oil reservoir. This feeds air to the air pump. That air pump exists to push extra oxygen in to the exhaust to help burn any unburned fuel in the exhaust.

    Anyway, I made an executive decision, climbed under the car and cut the belt that drives the air pump... And WHOA!

    The engine sounds so much nicer on startup, and even in general! Smoother idle, even when warm (but that could be the power of suggestion) And I even think I have more power now, too!

    So, in closing, if you hear clattering on cold startup and it goes mostly away if you cover the little black air filter on the driver's side, and if you don't need to be tested for emissions anymore, cut that belt and you'll be sooo glad you did!
     
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  3. vincenzo

    vincenzo F1 Rookie

    Nov 2, 2003
    2,810
    Qavion and raysur like this.
  4. MOSS

    MOSS Formula 3
    Rossa Subscribed

    Apr 28, 2004
    1,423
  5. c4b4the04

    c4b4the04 Karting
    Silver Subscribed

    Jun 9, 2017
    207
    Northern Virginia
    Full Name:
    Cassidy
    If you disconnect the belt/system, I highly recommend replacing the check valves with brass caps. Home Depot has a set of brass caps that screw directly onto the threaded air injection tubes. Liberally apply anti-seize so you could take them off if you ever wanted to.

    I find removing the air check valves is easier if you cut them off with an air grinder at the threads, then make a quick groove down one of the 8 flat sides. Once you've got a deep groove, twist a flat blade screwdriver in there and they pop loose, instead of risking breaking off the old and fragile air tubes by twisting with a wrench. My first set were seized on and it took less than 20 minutes to replace both.


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  7. rpissm

    rpissm Formula 3

    Aug 11, 2013
    1,562
    Salt Lake City, UT
    Full Name:
    Joe
    You're talking on the pre-cats, right? My cats and precats were hollow when I got the car :) and I put brass plugs in those a few years ago.
     
  8. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    19,497
    Texas
    Full Name:
    Steve Magnusson
    +1. The thread size is 3/4" NPT IIRC.

    No, He's talking about the check valves, Items, B, in this jpeg:

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    The way the system works is:

    When cold (water thermoswitch M closed), power is supplied to the Air Pump EM Clutch, H, which drives the air pump, and power is supplied to the electrovalve, D, actuating it, which applies vacuum to the Cut-off Valves, A, and opens them. Positive pressure air from the air pump is then blown thru the Cut-off Valves and the Check Valves and into the exhaust port.

    When warm (water thermoswitch M open), power is removed from the Air Pump EM Clutch (disengaging the air pump) and removed from the electrovalve, un-actuating it, which removes vacuum from the Cut-off Valves and closes them -- so no exhaust gas is back-driven thru the Check Valves.

    The problem with just disabling the air pump (either by cutting the belt or unplugging the EM clutch) is that, when cold running, the Cut-off Valves will be open so the exhaust gas will try to backflow thru the Check Valves and the (open) Cut-off Valves. The Check Valves often get "leaky" with age (especially when they don't have cool air from the air pump to cool them) so the plastic Cut-off Valves (and hoses) can get melted/damaged.

    Bottom line is that if you cut the drive belt (or unplug the EM clutch) you also need to either: 1) unplug the electrovalve, D (so the Cut-off Valves always stay closed and prevent backflow of exhaust gas during cold-running), or 2) replace the Check Valves, B, with pipe caps as Cassidy indicated.

    PS The round thing in the figure, near electrovalve D, is the differential pressure switch -- don't unplug that! Electrovalve D is a small cube thingy with three hose ports -- it has a red wire and a purple-black wire.
     
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  9. rpissm

    rpissm Formula 3

    Aug 11, 2013
    1,562
    Salt Lake City, UT
    Full Name:
    Joe
    Thanks for your extremely valuable input as always, Steve! Something else I noticed was, before, my car would backfire upon deceleration when cold. With the pump disconnected, no backfire when cold! What are your thoughts on that?

    Sent from my Moto Z2 Play using Tapatalk
     
  10. rpissm

    rpissm Formula 3

    Aug 11, 2013
    1,562
    Salt Lake City, UT
    Full Name:
    Joe
    Thank you for your valuable input too, Cassidy!
     
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  12. c4b4the04

    c4b4the04 Karting
    Silver Subscribed

    Jun 9, 2017
    207
    Northern Virginia
    Full Name:
    Cassidy
    Lol, sure thing! He got back to you faster than I could. My system was hacked up by someone in the 80's to make a Euro car into a Federalized system. I've since cut it all out and welded back over, you'd never know where in the pipe my air valves were. Before I did that though, the caps were perfect.

    Good luck, hope it comes out great for you. My air pump lives happily in a tote under my workbench.
     
  13. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    19,497
    Texas
    Full Name:
    Steve Magnusson
    With an active air pump, the only time I had backfiring on cold deceleration was when I had a rust hole in one of the check valve bodies -- perhaps you should check the conditions of your check valves and the pipes they mount onto.
     
  14. curtisc63

    curtisc63 Formula 3
    Silver Subscribed Owner

    Dec 13, 2005
    2,257
    Maryland
    Full Name:
    Curtis Campbell
    Once again Steve, you amaze me with your knowlede and willingness to share it.

    Polite, extended golf clap...
     
  15. vincenzo

    vincenzo F1 Rookie

    Nov 2, 2003
    2,810
    Keep your car original.

    The air nozzle off the Testarossa must be mounted on the mercedes version.

    No excuse - they are now on sale:


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  16. rpissm

    rpissm Formula 3

    Aug 11, 2013
    1,562
    Salt Lake City, UT
    Full Name:
    Joe
    I am keeping it original, but optimized. :)

    Sent from my Moto Z2 Play using Tapatalk
     
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