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355 Exhaust Bypass Valve Solenoid Wiring

Discussion in '348/355' started by Copperhed51, May 6, 2023.

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  1. yelcab

    yelcab F1 World Champ
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    #26 yelcab, May 12, 2023
    This came from the WSM. It takes the angle at idle adding another 72 degrees as maximum wide open. The idling angle is normally 17 degrees (it's never zero) so your value of 75 degrees is not fully wide open. Is something blocking the movement of the throttle linkages in the middle of the V? I have seen it by the way.

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  2. Copperhed51

    Copperhed51 Karting

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    #27 Copperhed51, May 12, 2023
    Last edited: May 12, 2023
    Just to make sure we are on the same page, the graph is reporting TPS %, not degrees. So it’s saying it’s ~75% open unless the car is reporting ° and the scanner reads that as %. I don’t know if that’s possible, but just throwing it out there.

    I just checked the throttle cable and it is more loose than I initially thought. Here are a couple of pictures of how much I can move it side to side without moving the actual throttle at all. I’m really starting to think this is due to the throttle cable itself. I don’t think I’ve felt what this car is actually capable of yet. Thoughts?

    edit for clarity: that’s my finger on the right side of the pictures moving the throttle cable from side to side



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  3. Copperhed51

    Copperhed51 Karting

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    #28 Copperhed51, May 12, 2023
    Considering the ECU won’t command the valve open unless it sees 80% throttle, this would totally explain why it never opens…except for the one time it opened randomly when I must have managed to hit the 80% mark by chance. Maybe I pushed extra super hard or pushed fast enough that momentum took it past 80%? Hard to imagine it would do so for any length of time, but I was already in the upper rpm’s when I punched it, so it wouldn’t have lasted long anyway. I wonder if there’s enough adjustment available or if I’ll need a new cable. Either way, I hope I’m not getting excited for nothing. I should probably have my wife floor the car with the scanner connected and then move the throttle the rest of the way by hand to see if my theory holds water.
     
  4. Copperhed51

    Copperhed51 Karting

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    #29 Copperhed51, May 12, 2023
    I guess I’m talking through this to myself a bit here, but I had my wife floor the car and then I attempted to move the throttle by hand beyond where she could get it. It didn’t really move much, if at all. So I don’t think I can expect a 25% bump in throttle unless the linkage is set incorrectly. I doubt that, but never know. So this leads me to possibly needing a new TPS itself or maybe there’s some other adjustments I can do? That’s where we’re at.

    Here’s the graph of the wife flooring it and me moving it beyond that by hand:

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  5. Qavion

    Qavion F1 World Champ
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    #30 Qavion, May 12, 2023
    I've looked for information on how tight the cable should be and couldn't find anything. When I fitted a new cable to my car (as it was fraying near the firewall), I adjusted so that the pedal wasn't pulling on the spring at all times, but with little or no slack. I assumed that ambient temperature wouldn't affect the length of cable enough to bother the system.

    Here's a graphical representation of what Mitch was saying:

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    The system takes a snapshot of the values at ignition turn on (that's why it's important not to put your foot on the accelerator for start).

    The WSM has this table of values for resistance across the TPS with a large margin of error.



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    I assume these are the limits of the TPS when fitted to the car (i.e. the normal throttle range, not the limits of the Bosch TPS itself). Why don't you check the values?

    Without knowing what your graph represents, it's hard to say if your throttle is reaching its potential. Does the scanner assume a Bosch TPS has a certain maximum resistance range
    (off the car)? You wouldn't want the TPS itself to be the thing which stops the pedal at full travel. There has to be a large physical range to accomodate all throttle positions.
    What does the horizontal scale represent?
     
  6. Copperhed51

    Copperhed51 Karting

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    #31 Copperhed51, May 12, 2023
    The horizontal scale is time. I don’t know what the scanner assumes to get this absolute throttle position %. If anybody else with the same scanner could graph their throttle, that would help to show if mine is normal or not (assuming their bypass valve functions normally).
    It sounds like I do need to measure the values from the TPS itself to see what’s going on there. The scanner data could be based on faulty assumed values that are leading me on a wild goose chase. The resistance in the TPS won’t lie.
     
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  7. Qavion

    Qavion F1 World Champ
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    #32 Qavion, May 12, 2023
    Ah... so the wonkiness in the graph may be irrelevant. It would depend on how smoothly, progressively you pushed the pedal through the full range.
     
  8. Copperhed51

    Copperhed51 Karting

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    #33 Copperhed51, May 12, 2023
    To measure the resistance of the TPS, do I need the 5V input or will it change with no input at all? Again, I’m fairly electrically stupid. I understand the basic concepts, but that’s about it. If I do need the 5V input, what is a good, non-destructive way to measure the resistance?
     
  9. Copperhed51

    Copperhed51 Karting

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    #34 Copperhed51, May 12, 2023
    On the first graph, I tried to be pretty smooth from zero to full throttle, but there may be some latency in the data from the Bluetooth scanner that is causing erratic readings. I wouldn’t read too much into that part.
     
  10. Qavion

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    #35 Qavion, May 12, 2023
    No volts required. You just need to figure out a way to look at the resistance (ohms) values across the 3 pins of the TPS itself as you push the throttle (plug disconnected).

    The manual says the ECU only looks at the TPS at idle and max value (during normal operations) for engine management. Whether this applies to bypass valve operation, I don't know. The 2.7 part of the manual says that the bypass valve operation is dependent on engine rpms, but I think the 5.2 may be a combination things like throttle position, vehicle speed and engine load.

    You can also check the volts coming from the ECU itself (with the ignition on) across TPS harness pins 1 & 2. It should be about 5 volts.
     
  11. Qavion

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    #36 Qavion, May 12, 2023
    The resistance across pins 1 and 2 shouldn't change at any throttle position.
    Pins 2 and 3 should go from minimum resistance to maximum resistance (from idle to full throttle)
    Pins 1 and 3 should go from maximum resistance to minimum resistance (from idle to full throttle)
     
  12. Copperhed51

    Copperhed51 Karting

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    #37 Copperhed51, May 12, 2023
    Sounds like it isn’t specifically listed in the WSM, but it has been mentioned before on these forums that 80% throttle is required to open the valve. Not sure if this is only for 5.2 cars, but it has been vaguely confirmed in some threads. Mainly RPM, gear, and throttle position dependent.
     
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  13. Copperhed51

    Copperhed51 Karting

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    #38 Copperhed51, May 12, 2023
    Thanks. Hopefully I can get to this tomorrow, depending on the length of my honey-do list after my 8 days away on business.
     
  14. Qavion

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    #39 Qavion, May 12, 2023
    Never rely on memory...:p

    2.7:

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    What is the definition of "full power"? TPS reading?
     
  15. Qavion

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    #40 Qavion, May 12, 2023
  16. Copperhed51

    Copperhed51 Karting

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    #41 Copperhed51, May 12, 2023
    And what is “very high throttle valve opening (i.e. full load)”? Pretty vague, but I hope the reported 80% is accurate.
     
  17. Qavion

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    #42 Qavion, May 12, 2023
    Yeah, somewhat vague. Surely you would want the bypass valve to open without flooring the pedal every time.
     
  18. Copperhed51

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    #43 Copperhed51, May 12, 2023
    Are you able to read the absolute throttle position % from your car and share the values? We have the same scanner and mine seems to top our around 75%. If your bypass valve is functional and your throttle position % goes higher than mine, that would provide a pretty good clue as to what’s going on. Thanks.
     
  19. Copperhed51

    Copperhed51 Karting

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    #44 Copperhed51, May 12, 2023
    Last graph of the night. I tested pedal to the carpet until resistance is felt and then pushed very hard to try to get as much extra travel as I could. Still not sure about the scale and what it means specifically, but it shows that tightening the throttle cable a bit would indeed help to reach a significantly higher throttle reading when floored without having to push with unnecessarily high force. I will tighten the cable because it appears necessary. Whether the TPS is working correctly is another matter that I will also need to test. Here is the graph:

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    Edit to add the fact that pressed to the carpet is 67% of throttle compared to floored ridiculously hard. Don’t know if the scale is linear, but that may be something
     
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  20. Qavion

    Qavion F1 World Champ
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    #45 Qavion, May 12, 2023
    Sounds plausible.

    By the way, what Bosch part number do you have on your TPS? 0 280 122 001 or 004?

    The original part is 004. Some have used 001 with mixed results. The 004 is NLA, I believe, or very rare.

    I have a -004 on my car (presumably orginal). I bought a -001 (really cheap) a while back and I just now checked the resistance values:

    The TPS only moves through 90 degrees. Not fitted to the car, the resistance values are as follows:

    1 - 2 : 2013 ohms
    2 - 3 : 932 ~ 2737 ohms
    3 - 1 : 2744 ~940 ohms

    WSM values
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    Looks like the 001 is within tolerance.

    If the 001 is identical to 004 (with regards to resistance and range of movement), I really thought that the range would be greater off the car. This is quite baffling. The 001 values are suggesting that the TPS hits its endstops when fitted to the car.
     
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  21. Copperhed51

    Copperhed51 Karting

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    #46 Copperhed51, May 12, 2023
    I’ll take a look in the next day or two. I hate to admit it, but this is kind of fun so far. If I can’t find a solution, I’m sure my opinion will change.
     
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  22. Qavion

    Qavion F1 World Champ
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    #47 Qavion, May 12, 2023
    Looking at your last graph, the Motronic ECU does seem to be zeroing the scale properly at the no throttle (idle) position, so it's within tolerance (electronically) at the lower end. I'm not sure what's happening in your other graphs.

    Your problem may well be caused by cable slack. Be careful with that as the cable can fall off its guides. Because of the latency in your scanner, it's difficult to know how significant the cable slack is. You would have to observe the actual resistance of the TPS pins as you pushed the pedal to see how much slack you actually have. i.e. how far do you have to push the pedal before the resistance value starts to change. You would have to be doing the pushing and the meter observing. Or, you could get someone to move the pedal a tenth of an inch at a time with their hand to see when the resistance changes.
     
  23. m.stojanovic

    m.stojanovic F1 Rookie
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    #48 m.stojanovic, May 13, 2023
    The TPS (except the one for 355 F1) is used by many cars:
    FERRARI: 142434
    BOSCH: 0280122001, 0280122004, 0280122008
    ALFA ROMEO: 605493590
    FIAT: 60549359, 7637025
    CITROEN: 1628L1, 72408124, 96038938
    GM: 826924, 90323839
    HYUNDAI: 3517022001, 3517022010
    KIA: 0K01118911
    PEUGEOT: 1628L1, 72408124, 96038938
    PORSCHE: 94460611600, 94460616600
    RENAULT: 7701047921
    SAAB: 885719, 8857915
    SOLEX: 72408127
    VOLVO: 1336385, 3450030

    I bought spare TPS-s on Ebay some 10 years ago. I found them under description "Saab Volvo Engine Throttle Position Sensor, 0 280 122 001", $35 a piece. I receive the sensors in Pierburg boxes with Pierburg number 4.02003.50.0. What was inside was a Bosch 0 280 122 004 with a sticker on it carrying the mentioned Pirburg number. Go figure.

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  24. yelcab

    yelcab F1 World Champ
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    #49 yelcab, May 13, 2023
    The best way to inspect throttle linkages and cable is ... to visually look at them for obstruction while actuating the cable. This means you have to remove the coolant tank. In one case, the previous owner of the car had modified the air intake housing so much that he had to move a few coolant bleed hoses around from their original positions. One of the hoses was impeding the throttle linkage from opening the throttle all the way to 90 degrees and the present owner of the car was never able to get full power out of the car. The problem revealed itself only after the coolant tank was removed and the obstruction was noticed.
     
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  25. Copperhed51

    Copperhed51 Karting

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    #50 Copperhed51, May 13, 2023
    I’m going to do a full, deep dive into the whole throttle area as the next step in this process. Are there visible stops on the throttle bodies that I can see to judge whether they are opening fully?

    Thanks again, everybody, for all of the help.
     
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