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How to Open a 355 Bypass with Pix

Discussion in '348/355' started by FL 355, Sep 27, 2004.

  1. FL 355

    FL 355 Formula 3

    Nov 3, 2002
    1,665
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    Frank Lipinski
    #1 FL 355, Sep 27, 2004
    Last edited by a moderator: Sep 7, 2017
    Many have asked about the procedure on wire opening the bypass valve…so here it is. You will need some wire. Go to Home Depot and get stainless steel wire used to hang a picture rated between 50 -75 lb. If you’re going to do it by yourself you should also get some heavy duty zip ties to temporarily hold the valve open. All procedures are sanding from the rear of the car.
    (I'll have to make about 7 posts each with a picture)
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  3. FL 355

    FL 355 Formula 3

    Nov 3, 2002
    1,665
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    Frank Lipinski
    #2 FL 355, Sep 27, 2004
    Last edited by a moderator: Sep 7, 2017
  4. FL 355

    FL 355 Formula 3

    Nov 3, 2002
    1,665
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    Frank Lipinski
    #3 FL 355, Sep 27, 2004
    Last edited by a moderator: Sep 7, 2017
    Under the valve is a “rod”. This rod moves up and down. Up is open. Here I’m pointing to the rod with a pen…notice that to get to it my hand went forward of the heat shield and back underneath. Try pushing it up…it takes so much pressure to move it open, you’ll think it’s stuck.
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  5. FL 355

    FL 355 Formula 3

    Nov 3, 2002
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    Frank Lipinski
    #4 FL 355, Sep 27, 2004
    Last edited by a moderator: Sep 7, 2017
  6. FL 355

    FL 355 Formula 3

    Nov 3, 2002
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    Frank Lipinski
    #5 FL 355, Sep 27, 2004
    Last edited by a moderator: Sep 7, 2017
    Take a metal coat hanger and snip it open. Now bend it in a U or
    V shape. Stick it under the rod and lift upward. This will give you an idea on how much pressure it takes to open it….it is not a “gurley man” valve…
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  8. FL 355

    FL 355 Formula 3

    Nov 3, 2002
    1,665
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    Frank Lipinski
    #6 FL 355, Sep 27, 2004
    Last edited by a moderator: Sep 7, 2017
    Wrap the zip tie around the rod – just like the coat hanger. Now while pulling upward with the coat hanger in one hand snug the zip tie with the other hand. This will temporarily hold the valve open.
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  9. FL 355

    FL 355 Formula 3

    Nov 3, 2002
    1,665
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    Frank Lipinski
    #7 FL 355, Sep 27, 2004
    Last edited by a moderator: Sep 7, 2017
    Wrap the stainless wire around the rod…NOW THIS IS IMPORTANT. Where you secure the rod is important…the only place that I have found that is safe is an exhaust bolt. The bolt is under the heat shield to the left of the valve. The bolt runs forward and back, just like the bolt I have placed on top of the heat shield to illustrate where it is and which direction it runs. DO NOT secure the wire to the valve or the vacuum tube. I’m pointing to the bolt in the picture.
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  10. FL 355

    FL 355 Formula 3

    Nov 3, 2002
    1,665
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    Frank Lipinski
    #8 FL 355, Sep 27, 2004
    Last edited by a moderator: Sep 7, 2017
    Now, take the free ends of the wire, place them in a set of pliers and start making a nice wrap by spinning. Cut the ends and bend out of way. Cut the zip tie, remove and you’re done. Should look like this. When you put the air boxes back on, you will not see anything…100% stock.
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  11. LetsJet

    LetsJet F1 Veteran
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    May 24, 2004
    9,238
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    Mr.
    Nice post...........

    Thanks.
     
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  13. Juice It

    Juice It F1 Rookie

    Sep 22, 2002
    3,233
    Maryland (DC Suburb)
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    Jeff
    Good illustration, but what will it do for me?
     
  14. riverflyer

    riverflyer F1 Rookie

    Nov 26, 2003
    3,560
    Mendocino, Ca
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    John
    Frank, thanks for taking the time to illustrate and explain the procedure, John
     
  15. SrfCity

    SrfCity F1 Veteran

    Nov 1, 2003
    9,842
    Orange County, CA
    Yea, thanks for giving us the step-by-step.
     
  16. brendon0

    brendon0 Formula Junior
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    Dec 13, 2003
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    Brendon
    What exactly does the valve do, and what does forcing it open achieve?

     
  17. Juice It

    Juice It F1 Rookie

    Sep 22, 2002
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    Jeff
    Still curious as to what this change does. Anyone?
     
  18. ferrarifixer

    ferrarifixer F1 Veteran
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    Jul 22, 2003
    8,520
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    Opening the valve reduces backpressure as the main cats are bypassed.

    At low rpm/in traffic etc, the valve stays closed normally to give better torque and drivability and make it a little quieter, but it is marginal. At high rpm/throttle it opens anyway to give better power...hence the WAAAA noise they make.

    If you jam open the valve, you will lose a little low down drivability, gain nothing under full power......but impress/annoy the neighbours.....
     
  19. FL 355

    FL 355 Formula 3

    Nov 3, 2002
    1,665
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    As ferrarifixer stated, it creates that WAAA sound you hear at about 4K, but now you can hear it through all RMP ranges.

    I'm not here to start controversy...just my experience. Before doing it I checked all threads, including Old FChat...seems like many in Europe do it.

    I also contacted Shelton and they said..no problem.

    With the valve shut a low RPM the engine creates more back pressure and gives you a little more power, then at around 4K (depending on which gear your in) the valve opens and you now have unrestriced back pressure and full flow (less cats and muffler).

    Since I opened the valve I have not noticed any reduction in power in the low RPM range...and I know my car like the back of my hand. Any loss of power or torque could not be more than 2 or 3 hp. F Cars are not 1/4 mile drag cars..I never go full blast from a dead stop...makes no sense for the clutch and every thing else.

    Now, the car has less back pressure and seems to run cooler at idle and as though a load is off the motor (like switching off the a/c comp)...

    The sound is great on a 355. If you want to "experiment" to see how load it is...set up the coat hanger to be able to open it manually. Start the car at idle, then go back and pull the valve open....you hear it first hand.

    The drawback is if you have OBD2 you will get a check engine light because there is a temp prob inside the valve to tell the computer if the valve is open or closed. The computer is looking for the valve to be closed, but because it's open...sends a signal to the ECU.

    To rememdy you can pull the bulb - not the best thing to do - or have the dealer reset your computer to only ignore the bypass signal which is what I had done.

    Additionally, if you don't like it, just snip the wire and your back to stock.

    I posted this becaue I get 3-4 emails every month on how to do it and I can't post the pix on FChat PM, so it's here as a reference...
     
  20. 355flyer

    355flyer Formula Junior

    Nov 1, 2004
    338
    Gadsden, Alabama
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    Andy Entrekin
    Frank,

    Any way that the pictures can be reloaded???


    Thanks,

    Andy
     
  21. Steve R

    Steve R F1 Rookie
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    Sep 15, 2004
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    TorQ Master
    Just wanted to throw-out some thoughts here....

    As you can read, this modification should be understood to only open-up the bypass valve at all times. Normally the bypass valve remains closed until about 4,000 rpm's. This modification is just going to bring-on that loud noise a bit sooner. That's it. The same condition exist when the valve opens itself around 4,000 rpm.

    I myself and many others may have been under the impression that there are baffles that the stock muffler has that are present throughout all conditions (above 4,000+) and that the removal of these such baffles would alter the stock muffler in a manner to provide better flow, more power and a better sound. In other words: a cheap substitute for an after-market exhaust system. This is not the case. Sadly. ;(

    I like the bypass valve....it lets me slip out in the middle of the night without waking the kids & neighbors. If you keep the R's down & drive mellow...you keep the noise down, hear the stereo and can converse with passengers & make cell-phone calls. You won't taunt cops to turn their heads and you can pass for a mellow player. The nice thing is when you do get on it, it allows everyone to know your taking it to the next level and opening-up the beast: let the big dog eat!!!

    I like being on the freeway just cruising along...then, at will...you just dump down a gear or two and stand on it: the world comes alive and it's time to get jiggy with it.

    At the same time, to each their own...at least this mod cost nothing and can easily be put back to stock.

    Thanks for the post!!!!!!!

    I myself have come up with the ultimate solution: I'm going to get a tape recording of a real F1 car, couple the tape recorders motor to the tach of my car and buy a CB with a PA system and gets some huge amps & speakers...then at the flick of a switch I can generate that perfect sound!!!!! even while sitting parked! :) ;)
     
  22. FL 355

    FL 355 Formula 3

    Nov 3, 2002
    1,665
    Ft Laud
    Full Name:
    Frank Lipinski
    Andy

    When I bought the Diablo I deleted pix to clear up disk space. It shoudl pull up here. Look at announcements - it may be a result of restoring due to the outage we had... like old FChat search did not work an just got restored. Send Rob a PM on this thread and I think he can reload.

    Also - do a old FChat search... A guy in Germany or UK did a good write up with pix also.

    Re: sound = It is Not that Loud at idle... The best way to determine if you want to do it is bend a coat hanger around the bypass rod. Start the car, go to the back of the car and lift upward on the rod to open it. You will hear the sound at idle... A "deep throat" sound is the best way to put it. At car show about 2 months ago a guy in a 328 with top down was behind me and said car sounded great and wanted to know what kind of exhaust system I had... lol.

    Give it a shot. If you have a problem PM me...I check a few times a day here.
    Best
    FL
     

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