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Help with muffler questions please...

Discussion in 'Technical Q&A' started by bpu699, Jul 16, 2007.

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  1. bpu699

    bpu699 F1 World Champ
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    #1 bpu699, Jul 16, 2007
    In the process of removing the muffler/cats on an 87 testarossa...

    I am starting to understand why dealers charge $1000 or so to change out the exhaust...

    Getting off the cars rear cover/underskirt took some significant gymnastic ability to get to some of these screws...

    Then, getting the cats off...eeeeeeek. Most of the bolts were frozen. I couldn't get to most of them with an impact wrench...and doing it by hand was not fun. Several stripped. Several broke in half...Some required a Sawzall...and some I haven't gotten to yet... Not as simple as I had hoped...

    Now...I still need to drop the muffler...and I am worried here... I have another car on the lift, and the testarossa is just on the ground. It looks like I have to remove the precats...to drop the muffler. I really don't want to fire the car up with 1/2 the exhaust off, as the neighbors will kill me :).

    Here are my questions, any help appreciated:

    1) Can the muffler be removed with the car NOT on the lift?

    2) Any way to leave the precats on? At least I believe they are precats - they are the tubing that connects to the cats, wrapped in asbestos (?) and some thin aluminum...

    3) How do I get the temp sensors out? These are the small probes attached via the braided wire, inserted into the precats? One came right out. One comes out half way after unscrewing...not any further...

    And now to the cosmetics...

    The exhaust system looks great. What I thought before was rust, was just a discoloration of the stainless steel. Seems to polish right out...

    1) Whats the best way to clean up/polish the exhaust canister??? I don't want to spend tons of time polishing it, only to have it discolor after a 100 miles. Any chemical way of doing this?

    2) The precats look like sh*t. They are wrapped in some kind of insulation (asbestos?), and a thin metal casing. The metal casing is rusted through in quite a few spots. Can I just take this off? And polish the tubing? Do I need the insualtion????

    Help please!!!
     
  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #2 Steve Magnusson, Jul 16, 2007
    Never tried removing the silencer without the coachwork raised and the precats off so can't comment on those issues, but this, unfortunately, could be an indication that the precat's ceramic matrix has fractured/broken and a loose piece has collided with, and bent over, the end of the thermocouple metal tube that protrudes out into the exhaust stream. Not sure that you can do anything other than get a little physical -- i.e., withdraw to the stopping point and then gently "bend" the end on the outside towards the "straight" position, which should allow you to withdraw it a bit more, bend again, withdraw, etc. until free. Have you separated the cat from the precat on this side yet? Any evidence of precat debris present at the cat inlet?

    Situation normal IME. If the precat is functional -- yes, you do need the insulation or something similar. If your precat matrix is already toast/broken, just break it (and the shock-mounting metal wool) out completely and then the insulation's presence/non-presence isn't an issue. PLEASE DON'T DESTROY AN INTACT PRECAT. I've got a set of one good and one "cleaned-out" -- glad to trade/$/deal either way if possible (to get you an intact set or a "cleaned-out" set) to preserve a piece of unobtanium -- let me know which side (if you do have a bad one).

    Typically, the stainless steels used in F exhaust systems are of the ~10% Chromium Martinsitic alloys (e.g., 409) that tend to form a tough dark surface oxide so, if polished, it doesn't last as long as the ~20% Cr Austenitic alloys (e.g., 304) -- i.e., polishing the stock TR precat tubes not worth the effort IMO on a car that will be driven. If you want polished, go with the Hyper-flow Precats or Hyper-flow Precat Bypass Pipes (which are 304 stainless).
     
  3. bpu699

    bpu699 F1 World Champ
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    #3 bpu699, Jul 16, 2007
    Hmmmm....

    If you gut the precat...but leave the cat...will you pass emissions???

    What the heck is a precat anyway??? Most domestic cars just have a cat...

    If the precats are no longer functional...whats the downside???
     
  4. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #4 Steve Magnusson, Jul 16, 2007
    Yes, if the test is done under warm-running conditions, and the limit is something reasonable like 1% CO max (a good running TR at ~1.2% CO coming out of the cylinders should be 0.5% CO or less at the tail pipes with a working cat).

    An "act of desperation" to pass US emissions ;). I believe it's essentially just another cat that helps with cold-running emissions (when the air pump is running and the injection system is intentionally running rich). It may have different catalytic coatings, but I've never looked into it that deeply.

    Virtually nothing -- the cold-running emissions won't be as low with only the main cat as when everything is present and working, but it's a very minimal sin IMO. If you've got a well-running US TR running with just cats, that's a heck of a lot better than a fully-stock US TR running poorly with the precat inards puked into, and blocking, the main cat -- BUT PLEASE DON'T DESTROY AN INTACT TR PRECAT.

    You didn't answer my question -- have you separated the precat with the difficult to remove thermocouple from the cat? If so, is there any precat ceramic matrix debris present in the cat inlet?
     
  5. bpu699

    bpu699 F1 World Champ
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    #5 bpu699, Jul 17, 2007
    Thanks for all of the help. I haven't fully seperated the cats/precats. Once I read your post, I decided to temporarily re-attach the system to get the car on my lift. The rest will have to wait until the weekend. But I will let you know.

    I hate the way the precats look. If they are intact, I was thinking of stripping off the thin metal coating, wrapping them with header wraps for insulation, then a thin layer of fiberglass/epoxy...painted red. Thought it might look cool and preserve their function. Not sure how well the fiberglass would hold up...

    My Testarossa has always passed emmisions with flying colors, but I will have to look up the details. I wouldn't mind trying to make a SS precat bypass...but it would be a bit of work...

    Any other thoughts???
     
  6. bpu699

    bpu699 F1 World Champ
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    #6 bpu699, Jul 17, 2007
    As a follow up question:

    Anyone used the ceramic/fiberglasss header wraps to replace the ugly prescat covering? Summit Racing even has one that come in a blanket with a reflective coating...could look somewhat stock.

    I was thinking about using the ceramic fiberglass wrap, with a thin coat of superficial epoxy to hold it together and then paint. Should look pretty slick...
     
  7. bpu699

    bpu699 F1 World Champ
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    #7 bpu699, Jul 31, 2007
    Update...right precat had some debris. About 10% of the matrix cracked off in one big piece. It was in the cat, but easily removed. The left one looked fine...

    I sandlasted the catalitic converters...they look fantastic, they shined up nicely, and look dramatically better.

    The muffler canister also sandblasted nicely, and will be polished.

    I took the insulation off the worn precat, and tried to sandblast this...what a bear. The discoloration really doesn't want to come off. Should I try a chemical stripper?

    Any idea's? Its almost like trying to sand off powdercoating...
     

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