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TPMS Canister

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pufferfish

Supporting Vendor
1,094
66
Maryland
Well, my latest mission was to figure out how to trick the TPMS computer into not tripping a code when i use my track wheels (which have an aftermarket setup with a readout in the cockpit). i did some experimenting to find out how it works.

first the facts:
the TMPS sensors need to be trained to work with the puter.
given about a 2 hour drive, i know they will relearn a previously learned set.
unsure if a set that was never trained to the specific car will be able to relearn.
ford sells a doodad that looks like a keyfob that will train the sensors to the car in about 2 minutes.
training the sensors with the doodad does not require them to be under pressure.
getting the puter to relearn a previous set may or may not require them to be under pressure.

the solution:
a pressure vessel you put the sensors into. there are lots of folks across the internet that have created a "TPMS bomb" from PVC pipe. i tried this and it worked...until i found out there was a slow leak from the glued joint. once you glue that stuff, you need to start over if the glue didn't seal it completely. there is also an issue that explains why they call it a "bomb". there are reports of schedule 40 PVC exploding under pressure. this is hardly what i would consider confidence inspiring...although, im sure its a remote possibility. but schedule 40 is not pressure rated. schedule 80 is, but isn't readily available. in any case, it looks hokey. people paint them and sticker them up, but they just look stupid.

so, i set out to find a pressure rated canister. if you can find one, its either too large, too expensive or both. i just want 4 little sensors in a canister that will hold air indefinitely, oh, and it has to have an opening big enough to actually get the sensors into. so, after striking out in my search, i looked at custom. its really not easy or cheap to come up with a custom pressure vessel with a lid! i remembered that in my day job engineering machinery, we have aluminum extrusions for quick one-off frame components. you tie them all together with brackets and hardware to create a frame. its like an adult erector set. well, some times, we use these framing extrusions, which are hollow, to use as air manifolds. cap the ends and they hold air. they are rated for 150psi, so they are plenty capable. the extrusion is cheap and it can be cut to length. so i created some end caps out of aluminum, with the fixed end siliconed and the removable end having an adhesive backed neoprene rubber gasket. the extrusion has t-slots in it to allow for fastening with t-nuts and bolts, so its perfect to hard mount to the car, so it doesn't roll around. i put a schrader valve in the removable end for filling with air. after a while, i realized a built in gauge would be super handy so you can know how much pressure is in it. i found that when i checked it with a tire gauge, i would actually lose 5-10psi just by checking the pressure. there is so little volume in the vessel that a tiny bit of air escaping makes a dramatic impact on the pressure inside. so, i added a gauge to the fixed cap.

i haven't mounted it yet, but i was thinking the best thing would be to mount it to the side of my battery box in the spare tire well. keeps it out of the way and i don't need to do anything but drill 2 holes. anywho, i was thinking maybe others would be interested in one if i made more up. what do you think?

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DGRacing said:
Steve. Brilliant. Sign me up for one.

Rick. Where can i get an extra set of stock sensors? Mine are long gone.

This is where we got them but they are sold out. There are some others on the bottom of the page.
http://www.ebay.com/itm/180975575464?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
 

pufferfish

Supporting Vendor
1,094
66
Maryland
the guy on ebay is where i got my extra set from.

this is not an item i can put under the blowfish brand. there is no margin. unless i made a thousand of them, the costs for professional machining of the end caps and the cost of the gauge and schrader valve are killers. i bought enough material to make maybe 20 of them. they get cut and drilled in my garage, so its not pro quality, although, i think my low standards are higher than some people's high standards. so, i am just interested in creating more "garage quality" examples. i want to cover my costs and bring in a few bucks for my labor. i can do more of them for $60 shipped in the US. paypal is the payment of choice. If you want one, paypal me the cash ([email protected]) and i will make them up as i go. i already cut all my material to length and sanded, so i just need to drill, tap, assemble and pressure test. i can probably turn them around in a day...2 tops.

for the international folks, email me (the paypal account is my email) and i can get you a shipping quote.
 
384
0
Maui
NFSBOSS said:
That seller has more. Again plug and play.

http://www.ebay.com/itm/181101131820?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Does this mean that no tpms tool is required??
 
I might be able to "hack" the ebay sensors so you wouldn't need pressure and even set them up to run off AA's. I just have to get one and see. I imagine the sensor is pretty basic since all they care about is making sure the pressure is in an appropriate range.

BTW, how long does it actually take for the car to throw a light after you switch wheels? My light has not come on yet and I have at least 1 hour of driving on the new wheels without TPMS.
 

pufferfish

Supporting Vendor
1,094
66
Maryland
good luck hacking them. its all epoxied together. a controls engineer friend of mine suggested one could create a circuit to send out the signal the computer is looking for. the trick is finding out what that signal is. if its RF (most likely), a signal reader could tell you the frequencies used. based on the training sequence, i am under the impression that there are 4 channels (one for each wheel). there has to be 2 signals for each frequency. one for "sensor present/functioning". one to trip the low pressure warning. the signal switch might be normally open or normally closed (signal until low pressure seen or signal when low pressure seen). how to identify these operating parameters is the big problem with electronically fooling the computer.
 
It seems some of the sensors won't transmit until the wheel spins so it save's power. Pufferfish, you said you tried it already, right? I was wondering which one Ford uses. Something else I was wondering about is how the RF signal would make it out because you device is like a Faraday cage. Not saying it doesn't work, but I would think you might need some kind of passive antenna. Just a wire hanging out would work, unless the valve stem is passing the signal.

http://en.wikipedia.org/wiki/Tire-pressure_monitoring_system
 
That is why I would not bother trying to mimic the RF signals, just bypass the pressure sensor part of the unit itself. I am assuming that that component might be a simple pressure switch since they only care about pressure below some level. I can dig through epoxy, but it will slow me down:) If anyone has a bad sensor or one with a dead battery they can donate to the cause, let me know and I will pay shipping!
 

pufferfish

Supporting Vendor
1,094
66
Maryland
well, the set i am using in the canister were purchased from the ebay guy. so, i don't know when the last time they were used on a vehicle, but they have not been in a wheel on my car, so they have been sitting idle for a month and still transmit just fine.

i read somewhere that the ford TPMS has a 5 year battery life. i can't tell you about other brands. and of course, wikepedia is known for flawed information.
 
pufferfish said:
well, the set i am using in the canister were purchased from the ebay guy. so, i don't know when the last time they were used on a vehicle, but they have not been in a wheel on my car, so they have been sitting idle for a month and still transmit just fine.

i read somewhere that the ford TPMS has a 5 year battery life. i can't tell you about other brands. and of course, wikepedia is known for flawed information.

I was referring to the canister you built, do they work. They look like they would act as faraday cage and block the rf path. I'm starting to read up on this subject now and did find that they work on 315mhz for domestics and 434mhz for imports, but some import's use the 315mhz.
 
Ok I learned trying to hack these things isn't worth the effort. Fords TMPS is made by Schrader, part# 33000, they took measures to insure the security was good enough and it would be a waste of time.
 
ArizonaGT said:
Bosch rail...nice. To be honest this is far too much effort when I could just ignore the factory warning message lol

Maybe you're right. A piece of electrical tape would probably hide it enough. It would be nice to avoid having to switch wheels just to get a sticker every year (Massachusetts), though.
 

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