On the ForFour.co.uk forum, a question was posted about reading the engine temperature and using one of these HUDs was suggested. I decided to give one a go. Going on eBay and searching for OBD HUD, 963 listings came up for such contraptions.
Whilst I don't have a history of using HUDs, I have occasionally used a OBD reader device for measuring MPG in the past which would also read a few other things including the engine coolant temperature. In my 454 ForFour, I also have the official clock and engine temperature pods as well so I can see how accurate the two devices are.
For £23 pounds, a HUD arrived...
...and this is how the instructions tell you to set it up (mind, I had the device 180 degrees the wrong way around in this shot).
My first issue is the reflective plastic. As the name implies, it is a shiny piece of plastic that sticks to the windscreen with static electricity to make the readout of the HUD reflect the right way. However, I love not being stopped by the police and it struck me when I looked at the outside of the car, the pad refracted light so from the outside, it looked opaque and in the UK, obstruction of the drivers view through the windscreen is illegal, Luckily, the HUD LEDs are so bright, I found the plastic to be redundant so it was binned.
To note, I spent a bit of time lining that piece of plastic up to where the HUD was reflecting off of the windscreen and the below is where it projected to. If the connecting wire was the other way around. the unit would sit closer to the bottom of the windscreen so the reflective plastic would not need to be so high up.
Other than this, the device was wildly simple to get started with. Just plug it into the OBD socket and watch it start up when the car starts. Certainly interesting to have a secondary speedometer reflected in the windscreen.
To answer the original question of "does it measure engine coolant temperature?", yes it does. Comparing it to the official pod, there was virtually no difference in the readings. However, I cannot recommend using a device like this for any extended period of time.
My principal problem is that devices like these show too much data so can be a distraction. This particular example could tell me how fast from 0-100km/h I was doing, what the battery charge was like and so forth. However, once you are moving, you cannot change this without a passenger. They also do too much. Honestly, this device can read a whole load of data from the OBD socket which is cool and all but the interface is not intuitive to use and configure. The estimated litres used over an hour was my personal favourite as that was really twitchy although damn useful if I was cruising along.
The instruction pamphlet is also not the clearest read in the world. The key stuff is there and clearly listed in a table but reading it in any detail reveals obvious flaws in the translation and seems to have had no quality control applied to it. One quote is this when advising on how to reset the HUD to factory settings (quoted verbatim):
When HUD connected cars, pls doonot to start the engine, wait for the off of HUD detection (or turn off the engine stopping the car,HUD is off)...
It also scored the slightly contentious prize of "most annoying device ever" when I found that it also comes with a beeper in it that sounds like the ForFour internal beeper (so when you pull the handbrake when moving for example- DO NOT TRY THIS!). The beeper in the HUD beeps when the car goes over a certain road speed and I found myself regularly exceeding this limit. This would not be so bad but the limit was based on the devices measurement of my speed which was about 5 km/h too fast. The device would also beep wildly if the car was accelerating too fast (the default is 75% of the maximum revs the device can read I believe) again, the rev counter in the HUD seemed to be about 100 RPM too fast (though I did not specifically check on this, this came from informally looking at the rev counter and then looking at the HUD).
You can configure the offsets of this device so it does read correctly but that requires you to stop and fiddle with it before setting off again. I did manage to get the speed reading accurate but that was through sheer luck more than anything else.
To finish, the anti-slip pad, whilst functional, smelled foul when it got warm in the car, which it did when a brief hot spell rolled over the Wirral. You might say that for £23 I should be expecting these kind of things but no, the smell is a travesty. Furthermore, with the connection to the OBD socket, the thought of "is this interfering with anything in the car now?" kept on flashing in my head. Did I know the Traction Control or the ABS was still working for example? The last OBD device I had would always switch off the Traction Control in my 450.
Whilst useful to have readouts like this in a Smart (the pods are part of the design language for the interior in my opinion), always get the official stuff. It will fit in with the look of the rest of the interior and will work without needing to be calibrated. If you cannot (or do not) want the official pods (!), there are after-market stuff that will also do the same thing but will need some work to make it show in the car. Importantly, these will show one piece of information and only one. They will also not interfere with the cars electronics that control slightly more important things, like the ABS or the Traction Control for example.
Universal devices like these (specifically with those that connect via OBD) are something to be avoided because they are distracting and simply show too much data. Crucially, I cannot trust this device is not stopping something else from working. It was awkward viewing it and with an instruction sheet on how to configure it not very clear, I simply cannot recommend this. They claim that they can do a whole host of things and I am sure that it can but it is built to a price, doesn't suit any Smart car I have ever seen and the wiring is just plain ugly.
Opinion: Avoid. As an occasional fun thing to use, it is acceptable but this is not something you would want to keep in the car. I liked the things that the car doesn't normally display (the 0-100 timer was a laugh as was the estimated litres per hour for example) but for things that the car already displays, I'd use them over these devices any day.
To expand, if it showed just one piece of information (like the temperature readout), I'd have a better opinion of it but then, you may as well wire in a dedicated pod if you wanted a permanent fixture.
If you want a OBD reader in the car, Ultra-Gauge seems to be OK though I have never used one. There is still too much information on the screen for my liking but as a secondary display/engine monitor, it looks OK.
Meirion has a UltraGauge fitted to his W453 which is situated on top of the dashboard. I believe this was imported from the USA for about $70 (plus any import duty).
The display is pretty clear despite the small size and isn't that intrusive (a wireless version is also available as well if you don't like wires trailing about the car).
The number of reading this can take is pretty wide but I didn't get a great deal of time with it. Certainly, it is clearer and neater than a HUD but as a personal preference, I still think a single readout would be easier and safer as you are not distracted as much as a multi readout like this. The value in this really comes with a second person in the car I think where they can concentrate on the device readouts (perhaps in a bit of on the fly tuning perhaps) and you concentrate on the driving.
Quite small but the font is relatively big...
Can I recommend this device? Sadly, no. I noted previously that these devices seem to interfere with the traction control and this was no exception as the traction control light came on and the car warned me that the ESP was also not functioning, no matter in what order I turned the car and the device on. A shame particuarly with this as it came with a number of relatively nice features like a braking distance test for example but yet, if I just wanted to focus on my instant MPG for example, I could and it be obvious as to what the value was.