Switched from VCMuzzler to S-VCM - Page 4
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Thread: Switched from VCMuzzler to S-VCM

  1. #46
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    Since you're thinking of mods, how about choosing a diode (Zener or other) that would just replace the muzzling resistor? The resistor right now drops the voltage a little, making it look like the thermistor has higher resistance, therefore cooler. The challenge with that is that as the actual temp gets higher, the thermistor resistance drops to the point where the muzzling resistor is a more significant distorting factor. A diode in that spot would drop the effective supply voltage of the circuit in a constant way. So the nonlinearity as temp increases would not be so significant. I haven't done that analysis, since I'm happy with my resistor, but I bet if you were to use numbers for the muzzling resistor (mine is 77 Ohms, and is perfectly sized for my car) and a reasonably accurate temp-vs-resitance function for the thermistor, you'd see a less-distorted effective resistance.
    Indeed that would be even better and even simpler. Just replace the resistor with a zener of the appropriate voltage. That would get closer to applying just a constant temperature bias (still the bias would not be constant but still not purely logarithmic/exponential as it is with the resistor. Again, still not as good as the S-VCM but something in between resistor and S-VCM

    ...and if a severe issue like a huge coolant leak were to occur, the needle would surely move enough to be visible...
    Unfortunately that is likely not true. As the temperature rises towards overheat the needle increments shrink towards 0. I bet that if the engine temperature rose to 500F the sensor resistance would drop to virtually 0 leaving the 82 ohm resistor only which would STILL likely correspond to to a needle indication below the overheat range. You would need a magnifying glass and a micro scale taped on your temperature gauge to see needle movements in the overheat range with the resistor only VCMuzzler. Adding the Zener, or even better your idea of completely replacing the resistor with the zener would make the needle movement less logarithmic, and thus more detectable. The muzzling ability of the zener VCMuffler would not be impacted at all.

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  3. #47
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    Quote Originally Posted by se88GGnka View Post
    ...Unfortunately that is likely not true. As the temperature rises towards overheat the needle increments shrink towards 0. I bet that if the engine temperature rose to 500F the sensor resistance would drop to virtually 0 leaving the 82 ohm resistor only which would STILL likely correspond to to a needle indication below the overheat range. You would need a magnifying glass and a micro scale taped on your temperature gauge to see needle movements in the overheat range with the resistor only VCMuzzler....
    I don't know if the temp values on the s-vcm site are accurate. I recall seeing a number of inconsistencies and misleads while reading through it. But here's a figure he's got on there:


    So if these numbers are close to accurate, I think even with the 82 Ohm resistor, or my 77 Ohm one, things will become noticeable pretty easily if there ever were a true overheat condition. And I was kidding about reading the gauge through the smoke in the cabin, but I expect in an overheat situation there would a smell or visible vapor that would be an extra warning to pay attention to the gauge carefully. And on the very rare times that might happen, one feature that every single muzzler option includes is the ability to remove it completely - although preferably once the car has cooled down to avoid burning onesself or setting a code.

    BTW - so proud of myself that I was successful in getting a figure to upload and display.
    2011 Odyssey LX, 106k miles
    1999 Odyssey EX, 234k miles, original owner

  4. #48
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    Sorry oldskewel the photo did not come through.

    I’m under the impression that a “normal” ECT for Odyssey under normal driving conditions (some airflow through radiator) is around 175F. The Resistor-VCMuzzler maps that to around 167F. Then (according to the S-VCM website data, reliable?) the Resistor-VCM maps a 210F ECT to 185F. So, a 35F difference is shrunk to 18F, roughly a 2:1 real vs displayed temperature compression ratio. Arguably that should still be detectable to a sensitized user/driver. Now I’m under the impression that an ECT of 210F is not quite pathological but is nonetheless not normal for an Odyssey. So there is indeed the opportunity to be alerted about overheats in that compressed 18F range shown on the gauge, if you know the gauge behavior – or have marked it accordingly...

    Another issue that I have seen debated (though it’s impossible to exhaustively read all that has been written on this site on VCM, so sorry if has already been mentioned) is whether the PCM takes any corrective actions when it sees the temperature rise to say 210F, or whether it relies on the thermostat and radiator to eventually lower the temperature, or whether the PCM does not really care at all.

    Of course, with temperature rising above 210F the real vs displayed ECT compression ratio should increase, making temperature gauge needle movements even smaller. Hopefully, the educated driver is already concerned seeing 185F displayed = 210F real, but then again, who pays this much attention to the temperature gauge while driving? Especially one with a compressed scale? The S-VCM allegedly does that for you with the small extra complication of a power wire to the battery. I guess we will have to hear from those who experience overheat (either real or simulated) to see how S-VCM really behaves in an overheat.

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  6. #49
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    Quote Originally Posted by CroMath View Post
    This is my understanding as well; the ECO indicator appearing in the instrument panel doesn't necessarily or automatically mean that VCM must be active. I don't know if there has ever been a definitive statement of all the criteria used to light the ECO indicator. If there has been, I don't think I'm aware of it. But I believe that for gen 4 Odysseys, the converse of that first statement is true - VCM never activates without the ECO light coming on as well. So the absence of the ECO light can be interpreted as the absence of VCM activation. Having VCM activate from time to time for a little while really isn't a big deal. In that respect, the resistor-based Muzzlers are perfectly fine. We only saw the ECO light a handful of times per year, and only in the summer. I won't stand here and pretend that's not good enough. It absolutely is.

    For me, the major improvement S-VCM offers is a more realistic indication on the coolant temperature gauge while still suppressing VCM. That is what I am really after by making this switch. With a resistance-based Muzzler, there is no point in time at which the temperature gauge is showing a true reading (not that a coolant temperature gauge with no graduations or markings is especially accurate at the best of times, but still, the signal from ECT1 is always modified). When I first installed the VCMuzzler, I studied the temperature gauge and learned the "new normal" and feel very confident I could tell when the temperature was getting too high before anything bad happened. And truly, nothing bad ever did happen.

    Like I said before, my wife knew about the Muzzler on our van and understands its purpose, but I don't think she is as closely attenuated to the behaviour of the temperature gauge as I am. I am not positive she would know that trouble was coming before it actually happened. I am hoping that the S-VCM controller will remove that potential hazard and keep her and the kids safer when they travel in the van without me.
    Thanks for the excellent writeup and pics. I'm using the VCMuzzler II with no issues on my '06 EXL-RES. After reading through this thread and the reason above, I'm switching to the S-VCM.

  7. #50
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    If S-vcm is not powered does the signal from coolant temp sender go through unchanged?

    Has any one put s-vcm on a switch and watched the gauge as the switch it toggled on and off?

    Having an easy to reach switch might be a way to check actual coolant temp if cutting power to S-vcm sends the actual temp through to the ECU.




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  8. #51
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    Quote Originally Posted by rjmyklebust View Post
    If S-vcm is not powered does the signal from coolant temp sender go through unchanged?

    Has any one put s-vcm on a switch and watched the gauge as the switch it toggled on and off?

    Having an easy to reach switch might be a way to check actual coolant temp if cutting power to S-vcm sends the actual temp through to the ECU.
    The S-VCM website states that if the power lead is disconnected, the signal from ECT1 passes through the device unaltered. So wiring in a switch would allow you to quite easily turn off the S-VCM controller anytime you want and see where the temp gauge needle would rest in that moment.
    2015 EX - Shear Comfort seat covers, Husky Liners floor liners, OEM cargo liner, S-VCM, Street Guardian dashcam, Lubegard Red

    There is no contradiction in having a soft heart and a hard mind.

  9. #52
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    I did some testing in the driveway. I was doing brake locks with the AC off to try and force the car to over heat. I didn't spend a whole lot of time doing it as to not cook the tranny fluid.


    With the svcm installed but not powered the signal passes through unaltered. And the cooling fans kick on about 208 degrees or so.

    In have a fuse in my svcm harness so I can easily unplug and plug the fuse in to get power on and off to the svcm.

    With the svcm installed and powered the hottest reading I got was 164 degrees. One time it said 207 degrees so maybe they is the point where svcm drops out to inform driver of a hot enging

    Conclusion is.... My gauge seems to be an idiot light. Slowly climbs to mid then stops no matter the temp. And no matter if S-vcm is installed or not.

    Also I was able to get a scanguage reading of 207 degrees with the svcm installed. The temp jumps from 164 to 207 but the fans come on quickly at that temp and it jumped back to 164 degrees.

    First photo if coolant temp of 204 svcm not powered

    Second photo is svcm powered coolant about 204 but svcm showing 161 on the scanguage

    Third photo is svcm not powered temp of 175

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  10. #53
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    One last observation. After the initial warm up the gauge never moved all test. Makes me want to disconnect the fans and see what temp signals an over heat or moves the guage.

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  11. #54
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    Very cool rjmyklebust - thanks for sharing this!

    So it seems like the numbers on the S-VCM website are true, give or take a small margin of error. The S-VCM controller lets the actual coolant temperature through at 207F, and below that modifies the output signal to show the 164F (which is a few degrees below the VCM activation temperature of 167F).

    I'm not surprised to hear that the temp gauge isn't the most accurate thing in the world (that has been one of my basic assumptions right from the start). But I am surprised to hear you suggest it's little better than an idiot light. I thought it was a bit better than that. Nothing wrong with finding out I'm probably mistaken though - we're all here trying to learn, right?

    Is this all with the stock thermostat? Are you still thinking about changing it?
    Last edited by CroMath; 10-02-2018 at 10:32 PM.
    2015 EX - Shear Comfort seat covers, Husky Liners floor liners, OEM cargo liner, S-VCM, Street Guardian dashcam, Lubegard Red

    There is no contradiction in having a soft heart and a hard mind.

  12. #55
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    As I mentioned above, I'm really not concerned with the coolant temp in my Odysseys. Not true, however, for my BMW. And those things are notorious for having a dumbed down idiot-light-type temp gauge. BMW does it with the goal of providing an 3-state idiot light (cool, OK, too hot), while having their customers think they actually have a real gauge in there.

    So they map the actual temperature readings to the gauge using the mapping shown in the following figure:



    Temps there are in Celsius, and it shows that basically everything between 75*C and 115*C gets mapped to a straight up needle. Of course, those numbers are not printed on the gauge. The gauge is unmarked just like on almost every modern car. Way back in the olden days, drivers were smart enough to understand numbers and gauges would have them. And drivers could even read the gauges while shifting gears. Themselves! Really! Before too long, drivers will not even be trusted to drive, let alone read gauge numbers. Just kidding, but not really, at all.

    For the BMW, it is a well known thing, and the solution is to reprogram the mapping to be linear. All discussed in detail on this page:
    PA Soft 1.4 | Crowz Nest

    So I don't know what is going on here for the Odyssey, and like I mentioned, it's probably not a weak point that needs attention, but I would not be surprised if Honda is doing the same thing that BMW does. All 3 pics by rjmyklebust above seem to have the needle pointing in the same spot, while the ECU thinks the temp is ranging from 161 to 204F, at least.

    Also, I do recall noticing a slight difference in where the needle sits on my 2011 Odyssey LX with my 77 Ohm home-brewed resistor in there vs. not. So it could be that different years have this more advanced temp mapping and others just have a straight through one, or a less aggressive mapping.
    Attached Thumbnails Attached Thumbnails Switched from VCMuzzler to S-VCM-72690d1511056195-solved-soft-fail-thermostat-crowz-original.jpg  
    Last edited by oldskewel; 10-02-2018 at 11:34 PM.
    2011 Odyssey LX, 106k miles
    1999 Odyssey EX, 234k miles, original owner

  13. #56
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    CroMath

    The photos above were all with the stock thermostat. I was able to get the van coolant that warm by turning off the AC which stops the fans from pulling air over the condenser and radiator and putting a load on the engine while not driving. If there is any air moving over the radiator the van immediately cools back down to 176F. It was about 45F ambient last night when I was doing the testing so even a slight breeze seemed to start dropping the coolant temp.

    I have still not decided if changing to a warmer thermostat is necessary. I am going to try it like it is and see what happens. If I do change to a warmer thermostat I am confident that SVCM can still handle the job of keeping the VCM and ECO off.

  14. #57
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    oldskewel,

    The behavior on the Odyssey seems to be consistent with the BMW since 75C=167F which apparently is the magical temperature that Honda considers the low range of normal operating temperature (which activates VCM).

    So the fact that the resistor does have an effect on displayed temperature implies that the temperature gauge is proportional (not linear) until 167F and then between 167F and some overheat temperature (still to be discovered) the gauge turns digital at some fixed steady reading.

    I wonder if the gauge turns proportional once again in the overheat range.

    I wonder why Honda does that. They don't want drivers being distracted by temperature variations in the normal range?

    rjmyklebust,

    Thanks for the very valuable investigation.

    Also good to know that the 164 to 207 sudden jump does not cause a CEL.

  15. #58
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    I guess taking the temperature sensor out, or better yet connecting a spare one, and heating it with a blow dryer (typically 130C air) simply with the ignition on would reveal the temperature where the display gauge "reawakens" from its frozen normal operating temperature display.

  16. #59
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    Quote Originally Posted by se88GGnka View Post
    I wonder why Honda does that. They don't want drivers being distracted by temperature variations in the normal range?
    My guess is that dealers don't want to waste their time and burn up their reputations in front of ill-informed clients by refusing to fix non-existent problems with the temperature gauge that are really harmless fluctuations within the normal range. The downside, of course, is that people who actually have the knowledge and ability to interpret the information properly are by default not trusted to receive it.

    There is a tendency to believe that a car's temperature gauge functions linearly like the thermometer outside the kitchen window, and it's a little off-putting at first to realize just how untrue that is. It's one of the things that makes devices like Scangauges and other OBD monitors so useful.
    Last edited by CroMath; 10-04-2018 at 11:56 AM.
    2015 EX - Shear Comfort seat covers, Husky Liners floor liners, OEM cargo liner, S-VCM, Street Guardian dashcam, Lubegard Red

    There is no contradiction in having a soft heart and a hard mind.

  17. #60
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    So I guess, per rjmyklebust's measurements, forget everything I said about being able to derive a compressed scale for the temperature gauge with the resistor based VCM suppressors. With the ECM intentionally plateauing the temperature gauge between 167F and at least (about?) 206F there's apparently no way the resistor based VCM suppressors will ever show anything at the temperature gauge for *any* overheat temperature. With the resistor based VCM suppressors the coolant will most likely boil over with the temperature gauge in the normal range. A driver would have about one needle width of range to discern normal temperature from possible overheating. So, with the resistor based devices the best warning that cooling is not up to par might be if the driver noticed a lot of VCM activation.

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