Help me fool my 348 ECUs | FerrariChat

Help me fool my 348 ECUs

Discussion in '348/355' started by ///Mike, Jun 17, 2018.

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  1. ///Mike

    ///Mike F1 Veteran

    Dec 11, 2003
    6,097
    Bugtussle
    I installed bypass pipes on the 348 and subsequently eliminated the secondary air injection system, as it is now basically redundant. Turns out the ECUs generate a CEL when the solenoid valves for the SAI system are disconnected. I could just leave them in place, but with the vacuum ports plugged. However, a more elegant solution would be preferable.

    The right hand valve is component 7a in this excerpt from Qavion's excellent enhancement of the 2.7 Motronics diagram. As you can see, it's fed by ECU terminals 30 & 45. I measured the resistance across one of the solenoids at ~42 ohms. Would placing 50 ohm resistors across the feeds to the solenoid valves be a safe way of eliminating the CELs without risk to the ECUs? If so, what wattage resistor would last in that application? And if not, what would be a safe way of fooling the ECUs into thinking that the solenoid valves are still connected?


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  2. Qavion

    Qavion F1 World Champ
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  3. QSA

    QSA Formula Junior
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    Not to hijack, but is there a diagram for the 2.5?
     
  4. Qavion

    Qavion F1 World Champ
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  5. m.stojanovic

    m.stojanovic F1 Rookie
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    The secondary air solenoid valves are 17a and 17b, see connections to the ECU-s on the Ian's diagram. 50 ohm resistors should do the trick. At this resistance value, the current flow through the resistors will be 0.28 Amp at 14V with power dissipation of some 4 Watts so 10W ceramic resistors should be fine. If the solenoid valves are normally closed, it will be quite easy on the resistors as they will be under power for just 2-3 min. after cold start. If the resistors work, you can find a place on the chassis to clamp the resistors to with some silicone paste underneath for heat transfer. You can also try with 100 Ohm resistors and, if they work too, better use them as they will generate less heat.
     
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  6. m.stojanovic

    m.stojanovic F1 Rookie
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    Yes, see attachments.
     

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  7. Qavion

    Qavion F1 World Champ
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    Also off topic... I notice that the F348 2.7 diagrams show which coil in each coil pack powers which spark plugs (e.g. on the right hand side, one coil feeds spark plugs 2 & 3, the other feeds 1 & 4). On the F355 2.7 diagrams, the numbering on the spark plugs (1~4) is less specific: i.e. 02500, 02501, 02503, 02504. One coil feeds 02500 & (adjacent) 02501, the other coil feeds 02502 & 02503. I assumed that 02500 was spark plug #1, 02501 was spark plug #2, etc. Do the coil pack coils feed different spark plugs on the F355? Knowing this could help with the diagnosis of faults.

    F355 diagram:

    F355 Left Bank Engine Control
     
  8. ///Mike

    ///Mike F1 Veteran

    Dec 11, 2003
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    Thanks, Miroljub. Very helpful info indeed and a great suggestion to try higher resistor values first. I'm a bit concerned about using the hot engine as a heat sink though. I was actually thinking about using some much higher wattage resistors since their form factor would make it possible to just solder male connectors directly to the resistors, making for a really tidy (if somewhat spendy) solution.

    Again, many thanks for the help. I'll have another one for you in a bit. :)
     
  9. Cauf61

    Cauf61 Formula Junior

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    Mike try first with the 100 ohm resistors to be safe. Measuring a coil with a DVM is not the exact value for a coil under load as it is an inductive resistance and not the same as a resistor resistance. Even under DC current load.
    With the resistor in place you can measure the current and calculate the power dissipation needed for the resistor.
    Use a resistor at least the double power value as calculated. ( 3 x is even better)

    You can always use power resistors like these.Easy to mount and make good wire connection.

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  10. ///Mike

    ///Mike F1 Veteran

    Dec 11, 2003
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    Thank you for the advice, Patrick.

    I chose that style of resistor because i found some that are sealed and which are rated to something like 250C. Unfortunately, I decided to simplify things by just ordering 50 ohm 25 watt units. I guess I’ll order some of the same style in 100 ohms.
     
  11. SoCal1

    SoCal1 F1 Veteran
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    Nice guys I like this stuff :)
     
  12. Qavion

    Qavion F1 World Champ
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    Are you guys overthinking this power stuff? The battery/alternator is providing the volts (up to 14v), the ECU is just providing an earth (probably through a transistor). The coil is not an issue as it's out of the circuit. The resistor is controlling the current. Simple P = V2/R
     
  13. ernie

    ernie Two Time F1 World Champ
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    Nov 19, 2001
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    That is exactly what I did.
    They are still plugged into the loom but with not vacuum tubes attached solenoids. You can actually find rubber caps to put on the nipples of the solenoids.

    Keep it simple. ;)
     
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