TPMS on i-MiEVs

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CometBoy
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TPMS on i-MiEVs

Post by CometBoy » Wed, 04 Dec 2013, 19:11

Anyone played with TPMS on this forum?

The U.S. i-MiEVs must have it as the U.S. Federal Regulations require that all new light vehicles sold in the U.S. since September 2007 be equipped with a Tire Pressure Monitoring System (TPMS).

Thought I would check to see what is missing to implement the system on OZ delivered vehicles. But most likely better to use a simple after market system (type with miniature sensor/xmiiter built into the valve caps).

I am not interested in a readout so much as an alarm or LED showing a preset low pressure condition in one of the tyres. There are also guys playing with these on the Arduino forum as well so lots of options....

Bruce

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TPMS on i-MiEVs

Post by CometBoy » Thu, 05 Dec 2013, 04:32

Just borrowed one of these Tyredogs to try and seem to do the job nicely. So have ordered one with some spare sensors.... Most likely the easiest way to have the alarm feature and will just modify the case to suit my mounting arrangement.

Bruce



Last edited by CometBoy on Wed, 04 Dec 2013, 17:33, edited 1 time in total.

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TPMS on i-MiEVs

Post by acmotor » Thu, 05 Dec 2013, 05:57

I can't see reference to TPMS in the UK/Oz worhshop manual or wiring diagrams. Have you enquired on the US forums ?
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TPMS on i-MiEVs

Post by CometBoy » Thu, 05 Dec 2013, 13:29

Thanks

Yes I had a look as well and no clues...

I emailed the Mitsi dealer in Florida that supplied the Fog/DRL kits (seems very helpful) and he says there is no retro fit kit so out of luck.

But as you suggested, I have just posted on the US Forum some questions about the TPMS operation and how it is connected. Maybe someone has looked at its setup?

I'm sure the simple little Tyredog system will do all I want just fine. The tyre pressure does seem to drop slightly on the i?

Bruce

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TPMS on i-MiEVs

Post by offgridQLD » Thu, 05 Dec 2013, 16:31

The one you purchased Looks good to me Bruce.

Keen to see how you get on with it. Perhaps test accuracy against a reliable gauge.It would be interesting to see cold/hot pressures after a drive. That little display unit would stow nice in the shelf under the steering wheel.

How big/heavy is the sensor unit on the valve. You might need to get your wheels balanced after installing them. If your a perfectionistImage hmmm more things to spend our money on ...hey I thought these Ev's were meant to save us money? Image

Speaking of storage nooks I was thinking of lining some of mine with a non slip matting just to stop things rattling/skidding around in them.

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TPMS on i-MiEVs

Post by acmotor » Thu, 05 Dec 2013, 17:39

I don't experience tyre pressure drop, well less than 1psi in 2 weeks at absolute worst.
They are only little tyres so checking the pressure actually drops the pressure one or more psi each time you lose a bit of air with the gauge. Need to put it back to pressure once you've made a reading. I use a commercial air handpiece with 400kPa (60psi) oil damped gauge not a 250psi gauge that is common on some equipment.

TPMS does sound a good idea though for those slow leaks. I can see why it will become standard equipment. After all, the technology is there.
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TPMS on i-MiEVs

Post by CometBoy » Sun, 08 Dec 2013, 19:07

Some interesting replies on the TPMS question I posted on the US forum....

See http://myimiev.com/forum/viewtopic.php?f=26&t=1881

I had not heard of iTPMS until reading that posting and the associated wiki talking about it.

See http://en.wikipedia.org/wiki/Tire-press ... ing_system

That ABS stuff is an interesting topic.

Bruce

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TPMS on i-MiEVs

Post by CometBoy » Tue, 17 Dec 2013, 23:08

Here is the Tyredog TPMS update...

Image

Image

Well-made and can verify the + and - .5 PSI resolution.

Image

Temperature checks OK

I have set the alarms for a Low Pressure of 34 PSI and the High Pressure of 44 PSI and a MAX temp of 70 degree C. Will see how that goes. All tyre alarm conditions can be set to independent values (if needed for each tyre).

I am not going to mount it so you can read the screen hence the brackets that come with it are useless to us. It will be located in that hidden compartment above the glove box storage hole. Apart from some early screen checking by me, I only want the audio alarm feature. It alarms for Low Pressure, High Pressure, High Temperature and Low Battery Condition.

Image

Only other thing I will do sometime is change the valve stems over to a shorter stem. The little lightweight sensors are almost flush with the outside wheel/tyre profile.

FYI the replacement sensors are about $50 OZ each. Batteries last a year or two for sensors and about a year for the display module (or it can be plugged with the adapter supplied). This seems to be verified on the 4 wheel drive forums.

Bruce

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TPMS on i-MiEVs

Post by CometBoy » Wed, 18 Dec 2013, 21:36

Some data on the tyre pressures...

On a 38 degree day today, tyre pressures increased from 37(Cold) to 40 PSI after city driving for a few hours. The temperatures went up evenly to a max of 45 degrees.

Amazing how little brake heat is involved with good regen braking. With an ICE I couldn't hold my hand on a wheel on a day like today.

Bruce

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TPMS on i-MiEVs

Post by CometBoy » Sun, 05 Jan 2014, 21:28

My wife noticed the tyre alarm on the way home last night and to my amazement one of the tyres had dropped to the low alarm limit I had set (34 psi) at the time I installed the TyreDog monitor. This now verifies what I saw happening prior to the addition of the monitor. Here are screen shots of the pressures at the time of installation Dec 17, 2013 and yesterday Jan 4, 2014.

Image
Dec 17, 2013

Image
Jan 4, 2014

So what is happening and have others seen similar pressure losses in relatively short time periods?

The TyreDog spec is + - .5psi and my tyre gauge is a good quality Michelin (with low dead volume).

I’m thinking maybe a valve stem issue given number 3 has dropped more them the others?

I have some new good quality Italian made short bodied stems that I will be switching over that suit the remote sensors better at some stage.

Image

Just hard to believe there is a problem with the current ones...

Bruce

edit: Should also add I’m pretty sure the tyre has not been hitting kerbs (given the location of number 3)

Last edited by CometBoy on Sun, 12 Jan 2014, 13:12, edited 1 time in total.

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TPMS on i-MiEVs

Post by offgridQLD » Sun, 05 Jan 2014, 22:18

This is just a stab in the dark. But are you seeing some kind of cold vs hot pressure change. With all the extreme hot weather we are having perhaps one side of the car or just one wheel is in the sun all day? The side in the sun will always show a few PSI more. So perhaps all 4 wheels have dropped pressure but only one was in the shade when you measured (its a long shot)

Perhaps take the valve out and reseat it again encase their is a slow leak. Take the wheel off the car and immerse it in water the bubbles will let you know where its cumming from.

I set all mine on the imiev at 40psi about 8 weeks ago so I will check again and see where they are at now. Has to be next weekend (gauge at the other house).

Out of interests, I set my 4wd & camper tyre pressure all at 40psi. before doing just over 5000km at times in 45 deg C heat on them over Xmas (some rough off road to) I checked the pressure again when I got home form holidays using the same gauge and all six wheels were all spot on 40psi. I was amazed at that though as I was expecting some change.SO Looks like the typical pressure loss is more of a time factor than a distance traveled and heat and shock / wall distortion.

One thing is checking the pressure with a gauge to often can effect the pressure as you loose a bit of air each time. This isn't a issue with the remote monitoring system. Did you confirm the low reading on that one wheel with a external gauge?

Kurt
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TPMS on i-MiEVs

Post by CometBoy » Sun, 05 Jan 2014, 23:07

Thanks for the ideas Kurt.

Have soap tested the valve stem on the worst tyre and can’t see anything obvious but such a slow leak could be hard to see (maybe?)

The TyreDog gives me temperature as well and I have taken that into account. Actually number 3 is the warmest wheel on those last photos, so worst then indicated (by comparison) and that is why it alarmed last night when it was cooler.

The calibration is as close as I can measure with what I have here. +-.5psi is about all I can do in that department....

Agree, our VW T4 camper holds tyre pressure for months on end (350 kpa).

Not going to remove the wheel and water test now, will be changing the stems in the next month or so anyway.

Just seem so strange? Maybe I should just set the minimum to say 32 psi??

Bruce

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TPMS on i-MiEVs

Post by CometBoy » Mon, 06 Jan 2014, 00:31

Interesting info on OS 2012 i-MiEV tyre pressure and monitoring here:

http://tagore.drivingforceauto.com/site ... 231001.pdf

“-Tire pressure should be checked and adjusted according to instructions in the owner’s manual. Slight air loss may occur over time under normal conditions. Expect a 1 PSI drop over a 1 month time period.
-Tire pressure is affected by ambient temperature. Colder ambient temperatures will decrease tire pressure. Expect a 1 psi drop for every 10 degree drop in temperature. Tire pressure should be adjusted to compensate for seasonable temperature changes.”

1 PSI per month seems higher then I would have thought?

So I guess given the temperature range here in Adelaide and the 1 PSI drop per month, I’m in spec and just need to rethink my setup points and adjust the tyre pressures on maybe a 20 deg C day?

Bruce

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TPMS on i-MiEVs

Post by adelaide-ev » Mon, 06 Jan 2014, 04:52

I'm also noticing tyre pressure loss in Adelaide. Noticable handling difference has led me to check twice in 3 weeks over a total of 500km distance.
First time (after few days of very hot weather 40+degrees) - checked at night time( possible 30 degrees ambient temp - pressures had dropped from 36 to 33. Put them up to 37 to experiment.
Second time -further 2 weeks of cool weather -check at night again using same gauge (no fancy TPMS yet, temp poss 20 degrees ) - had dropped from 37 to 33 fronts /34 rears.
Annoying - is it the small tyres? as well as the Adelaide temp extremes? even allowing for small loss with each gauge reading?
Can't say I've ever noticed such a quick change in my ice vehicles. At least it's obvious as I find the handling at 33 is awful. Have put the tyres up to 38 this time and will check the valves.
Sally
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Post by CometBoy » Wed, 08 Jan 2014, 16:37

Well problem solved.

Tyre 3 once again lost pressure in 24 hours? (@ the same temperature)

Image

The car was due for its 1500km post sales service yesterday (she had done closer to 3,000km). She had absolutely nothing she could fault on the car! But they logged the data from the CAN and that was that. But they recommended we have the local Bob Jane look at the tyre pressure issue. They happily did that and found the valve stem did have a slight manufacturing fault at the seal lip that could most certainly cause a slow leak. In the process, all tyres were marked as to position on the rims, removed and the new shorter stems I supplied for the TPMS sensors fitted. All wheels were rebalanced with the TPMS sensors installed.

Image

It was noted that original balancing was not great.... BTW the reason I went for the external sensors is that I will be using the TyreDog on other vehicles – otherwise the factory style internal ones are much better. The current i-MiEVs OS are not using the ABS speed difference method yet – only the internal rim units.

Talking to the guys at this Bob Jane outlet, they commented about the tyres they had fitted to an i-MiEV a few months ago! I was amazed they knew what an I-MiEV was.... Anyway they have done a couple of the higher mileage lease cars that are running around Adelaide. At one stage we had 11 here, but I only now know about the RAA, Bob Gel and Marion council machines. So they had done the RAA i-MiEV last and the recommended tyres that came out of that exercise are:

- Continental Premium Contact tyres (3 or 2?) for the rear
- Continental Eco Contact EP tyres for the front

Apparently both as per the original spec and considered fairly LRR – but all this could be sales crap? But would think the RAA might be clued in on it.... Their price seemed good as well.

EV-Adelaide, as many have pointed out on the forum here, trying to use a tyre pressure gauge at a servo is usually hopeless and every time you re-test you spill air that can cause most likely a drop in pressure of ½ to 1 PSI depending how square and fast you get the connection. This and temperature differences between wheels can show differences of a few PSI easily. Maybe a reasonable Digital Tyre Pressure gauge could be a good birthday present! Maybe one with an accuracy: +/- 0.5PSI? They aren’t that expensive. I use one of my good high pressure bike pumps and set the pressures first thing in the morning before the sun hits the car – with a logically coolish night temperature. In my case the pressure just kept dropping and only one wheel, getting worst everyday – I should have picked it earlier…. I can’t tell any difference in the handling but then again I don’t drive it much – not sure I would use the words handling and i-MiEV in the same sentence Image .

Bruce

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TPMS on i-MiEVs

Post by Gabz » Wed, 08 Jan 2014, 16:49

interesting results I pumped mine up again this morning haven't done it for a month and half i was down at 31 psi. but they where all equally around this value.

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Post by adelaide-ev » Wed, 08 Jan 2014, 19:05

Bruce, Which Bob Jane was it? Might as well try someone with a clue about the cars. Maybe get my tyres balanced and the valves checked. How much were the new tyres esp. the fronts? I recall someone bought them and found they lessened the wind buffeting.
I have checked the tyres with a home gauge - they all drop evenly so it's not just the servo -although I have to go there to pump them up (use the same one each time though).
The TPMS is definitely on the birthday list though!
And you're right, handling and imiev don't really go in the same sentence!! It's just better with higher pressures.Image
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Post by adelaide-ev » Wed, 08 Jan 2014, 19:11

Quote: '"haven't done it for a month and half, I was down at 31 psi"
Gabz -what did you start at?? and is this a recurrent issue with your car too? Just trying to figure out what's normal for imiev.

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Post by Gabz » Wed, 08 Jan 2014, 19:22

I always pump my tyres to 36psi, but last time i pumped up before today was on the way home from work so the car had already done 20km so hoter tyres.

its a recurring issue it terms of i have a entry in my calendar to check my tyres once a month and they always need more air.

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Post by acmotor » Wed, 08 Jan 2014, 19:41

I really don't get the pressure drop problem. I check every 2 weeks in the morning and more than often, other than replacing the air used to make the reading, the pressures are right. I run 40psi all round. So yes, if you are getting pressure drop it may be some assembly detail.

If the factory balance was considered poor then that was either sales talk at BJ or something has happened to the tyre.Image edit: I did 45,000km on my fronts at speed and they spun true. Maybe some tyres have flat spots from sitting around. Mine don't get a chance to do that.

I'm glad to hear Bob Jane in Adelaide are on the same track as Perth re the continentals. I commented on how good the performance but wasn't certain anyone had picked up on it. Here
If there are iMiEVs in Adelaide fitted with the conti's then drive one yourself, you will be impressed.
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Post by CometBoy » Wed, 08 Jan 2014, 19:53

Thanks acmotor.

I’m sure this was a one off issue and you guys most likely don’t have a problem! Just I should have noticed the problem sooner and assumed incorrectly they all had a problem. Another 48 hrs will show no drop on tyre 3 I’m sure. Was getting so bad that 1 to 2 PSI in 24 hours could be shown. Kurt I think the soap and water trick around the valve stem was actually showing small bubbles as well in the end. I have a couple of photos taken on Sunday that sort of do show bubbles forming after a few hours.

Sally imho the TPMS is most definitely over the top and hard to justify (ie waste of money) especially because you keep an eye on things anyway.

Portside Mitsi put me on to Bob Jane @ Alberton (young guy called Nathan Heinrich) 8447 8888. I know nothing about tyres improving the i-MiEV road handling but acmotor has answered that... Maybe the guy at RAA that drives the i-MiEV would be the person to see for a test drive???

Ya you are probably correct - sales BS about the balance...

But they didn’t offer me nitrogen!

Bruce
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Post by acmotor » Wed, 08 Jan 2014, 20:09

TPMS will be mandatory in the future like ABS and ASC. Makes sense. Not OTT at all.

I doubt nitrogen will achieve a similar status. Too many leaks for starters.   Image
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Post by CometBoy » Wed, 08 Jan 2014, 20:27

Wow 6 or 7 years after the US laws! Lots of newer cars have TPMS already here. The comment was more about retro fitting especially the external ones like I use.

Many disadvantages.... expensive if you buy a good quality unit, ugly and largish sensors, can be stolen easily (even with the Allen key lock thingy that most don’t end up using).

Still works for us... and the portability is great.

Bruce

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