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Idea for dealing with the Roadster's "Hoovering"

Discussion in 'Roadster: Technical' started by gregd, May 18, 2016.

  1. gregd

    gregd Member

    Joined:
    Dec 31, 2014
    Messages:
    571
    Hi folks,

    I was talking to one of my peers at work about the Roadster's air flow design, and it's acute ability to vacuum up all the little bits of cruft along our roadways, and pack them into the PEM and motor. We've discussed here already methods to put screens and filters around the underside blower intakes... He had a different idea.

    Consider what modern refrigerators do with their defrost cycle, where they temporarily reverse things to melt any ice and blow the vapors out of the system. What if we inserted a little board with some relays and logic on it, between the PEM and the blowers, so that after the car shuts down we spin up the blowers in reverse for a few seconds to suck out all the junk from the internal air channels and blow it out of the car before it gets totally packed in there? We presume the blower motor will run in reverse on reverse polarity. I don't expect the blowers themselves will be very efficient in reverse, but will it be enough to make a difference?

    I don't really care for the added filters suggested by others, in that they inherently impeed some of the air flow to the system. With the hot summers around here, the car needs all the air it can get. Maybe this would be enough to keep things unblocked between service appointments, or be able to stretch them out a bit?
     
  2. hcsharp

    hcsharp Active Member

    Joined:
    Jun 7, 2011
    Messages:
    2,532
    Location:
    Vermont
    A squirrel cage fan will not blow backwards if you reverse the direction of rotation. It will blow in the same direction but with a lot less air flow. Roadster owner @Eberhard who used to be more active here had his fans clog and fail so many times that Tesla Service installed an air hose quick-connect to his PEM. He was able to connect his air compressor and blow backwards through his PEM and fans on a regular basis to keep it cleaned out. I was going to see if Tesla would install the same system on my car but he reported it only resulted in a minor improvement for him. Then Tesla came out with the snow dam and new fan design and I experienced fewer problems after that.

    I also installed the green mesh type of filter. The way I implemented it I have a large area of filtration. I have almost 5 square feet so it doesn't impede air flow measurably. The snow dam impedes air flow a lot more than my filter does, even when it's dirty.
     
  3. gregd

    gregd Member

    Joined:
    Dec 31, 2014
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    Bummer. I was wondering about the fans; thanks for confirming.

    Interesting story about Mr. Eberhard... Hadn't hard that before. Sounds like the principle of reversing the airflow has some merit, but in practice there may be better ways to keep the system clean.
     
  4. JohnGarziglia

    Joined:
    Oct 22, 2011
    Messages:
    119
    Location:
    Reston, Virginia
    Well over two years ago, I wrapped my blower motor and squirrel cage blower in "Gutter Guard". I would know stuff was being sucked up into the fans previously because wet leaves would get in there and cause an imbalance and shaking of the fans. So far with the "Gutter Guard" installed, I have not had a recurrence of that. See PEM / Motor cooling fan filter
     
  5. Nvbob

    Nvbob Roadster 1256

    Joined:
    May 6, 2009
    Messages:
    229
    Location:
    Just east of Lake Tahoe, Ca.
    This is not about the PEM or Blower but it relates to the ability of the Roadster to inhale road debris.

    Driving home from Costco, all of a sudden we noticed a very strong cigarette smell. We checked everywhere in the car. I even stopped and opened the hood to see if we had picked up someone’s discarded butt - found nothing. Once we arrived home I proceeded to check under the car, in the boot, in the car, everywhere but found nothing. We got out a flashlight to take a look inside the front grill. Here, we not only found where the cabin vents intake is but also found a discarded butt (along with other road debris). We were able to suck it out with the shopvac and voila, no more cigarette smell! Luckily, the cigarette didn’t ignite the other debris!

    IMG_1321.jpg
     
  6. JohnGarziglia

    Joined:
    Oct 22, 2011
    Messages:
    119
    Location:
    Reston, Virginia
    Using 1/2 inch PVC pipe, I had to fashion a three foot extension to my car vac nozzle to remove such debris. See: Cigarette Butt in Front Air Dam
     

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