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Changed my coil…question for 348 owners

Discussion in '348/355' started by Lars_vet, Apr 25, 2008.

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  1. Lars_vet

    Lars_vet Formula Junior

    Feb 25, 2007
    603
    On the open road
    Full Name:
    Lars
    #1 Lars_vet, Apr 25, 2008
    I have had a misfire under 3000 rpms for a while. When idling I pulled each cable at coil to see/hear the change (..and YES, I got a chock too…) When removing the cable on cyl. No. 2 there was no visible spark between the coil and cable, and it made no change to the idle…

    So got a new coil in on 1-4 bank and now it doesn’t miss as before under 3000 rpms, feels much better to drive!


    But here is the real question, if you put the throttle down hard at 2000 rpms in 5th gear in your 348, how does is act?

    Is it just pure even and smooth
    Or do you have the feeling that changing down to 4th is the best ting to do?
     
  2. BT

    BT F1 World Champ
    Lifetime Rossa

    Mar 21, 2005
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    Bill Tracy
    #2 BT, Apr 25, 2008
    Definitely downshift to 4th or even 3rd. I love 3rd gear from 40ish up to redline. This isn't a truck, you need the RPM's!!!
    BT
     
  3. ernie

    ernie Two Time F1 World Champ
    Lifetime Rossa Owner

    Nov 19, 2001
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    The Bad Guy
    #3 ernie, Apr 25, 2008
    LOL!

    The word you were looking for is shock. I know english isn't your first language, so I though I would let you know. You were only one letter off.
     
  4. Lars_vet

    Lars_vet Formula Junior

    Feb 25, 2007
    603
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    Lars
    #4 Lars_vet, Apr 25, 2008
    thank you... you could have wrote an answer on the thread instead....
     
  5. Miltonian

    Miltonian F1 Veteran

    Dec 11, 2002
    5,966
    Milton, Wash.
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    Jeff B.
    #5 Miltonian, Apr 25, 2008
    At 2000 rpm in 5th gear, your engine is producing about 75 BHP, and you are doing about 45 mph in a 3000 lb car. Of course it's not going to accelerate very quickly unless you downshift at least one gear (the power curve is very steep), but the engine should pull smoothly without bogging down. The torque peak is at about 4200 rpm.

    Congratulations on getting the problem fixed yourself!
     
  6. msa

    msa Rookie

    Jul 19, 2007
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    Marcus Ahlberg
    #6 msa, Apr 25, 2008
    Good for you.
    An good idea now is to make an oil change otherwise the unburnt fuel will contaminate the oil.
     
  7. Marco Bussadori

    Marco Bussadori Formula Junior

    Aug 6, 2007
    430
    London
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    Marco Bussadori
    #7 Marco Bussadori, May 23, 2008
    Lars,

    Jeg tror jeg forstaar... I have the same engine and gearbox in the Mondial t as is in the 348...

    If I floored the accelerator in 5th t 2000 rpm, I USED to get a bit of uneven judder/coughing until the RPMs hit about 2500. Below that it was not very smooth or pretty (so best to change to 4th - som du siger ;-)

    In fact if you manually pulled the throttle in the engine bay to 1200-1400 rpm it also did not feel very well balanced DESPITE the idle motors being closed and the bypass balanced in both manifolds.

    I paired up the cables fro cyls 8&5, 6&7, 1&4 and 2&3 to match the resistance (using a multimeter) as closely as possible between the pairs. I did the same for plug condition and gap. The F119D engines, have 2 coils for 4 plugs per bank, and both fire simultaneously, one igniting the power cycle, the other wasted in the exhaust cycle. If the resistance varies by a proportion inverse to a function of current over resistance, then the spark could easily only go to one of the plugs skipping the other altogether, thus "missing a beat" - so by pairing them, you minimize this happening. (Can offer the math behind this if you care).

    Now when I floor it in 5th at 1500, I get a "grovtraek" up the RPMs but it is very regular, and when it gets to about 2000 RPMs it is a VERY smooth ramp up to the redline. Hand pulling the throttle to 12-1300 RPMs is also very smooth now.

    Changing the coils may have given you a current that was strong enough to be over the threshold to then power the fourth cylinder plug despite the resistance, or fixed a severe problem in the low power side of the older coil. I'd check your HT leads are within a close range of resistance...

    Marco
     

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