As Jaguar saw fit to recess the speedo and clutter it with tiny close together numbers (kilometre ones in particular) making it impossible to read with a little daylight coming in.
has any-one been down the road of "Heads Up Displays" that are now available at a reasonable price?
Be the perfect answer for my ageing eyes to see a clearer readout. Some are GPS based but still need 12v constant power but the hard wired look interesting,but wiring in more after market things can result in my car having a Hissy Fit in the electrics.
Any thoughts? Neil.

 

Yes, I use a TomTom 'cos I can't see the km figures and the cruise control is about 5% out.
You could power it off the cigar lighter if yours is ignition controlled.
A GPS based one is far and away the simplest solution. Where does the 'projector' go ?

 

use an old racer trick ... learn the needle angles at the interesting spots ... then depend on reading the angle of the needle rather than the number at the end of the needle.

 

Thanks Plums,I have been doing that but our tolerance for speed is so slim that two K's over can get you fined. Thats about 1/4 of the needle width. Research for the Head up Display looks interesting.Projected onto the windscreen in large numbers just below eye level.
Only trick is to find the wire that drives the speedo,other two are just power and earth.

 

Thanks Steve,
The gps ones are not used as a guidance system.There just calibrate your speed. Not after the wire hanging across the dashboard look. These units are dedicated speed display. They are available for $50 - $150.

 

Yes, I realise they just get speed from the satellites but IMHO a better bet than tapping into the speedo with the attendant worries/calibration issues.

 

Ok then ...

the vehicle speed is available by means of interrogating the ODB-II interface

you need nothing fancy, just one of the generic ELM327 interfaces to drive custom software that in turn drives a set of LED digits

the command set is very similar to the old AT Hayes modem command set

you can put in any calibration you want because you control the software

it can be table driven or algo driven

for the computer you can use a 32 bit arduino

or ...

bluetooth ELM327 interface, old android phone, torque and some duct tape

 

Now, here's a thing. The OBD standard sends vehicle speed as an 8 bit byte which means the maximum speed we can travel at is 255 km/h -158 mph.
Is that why the speed is limited to 150. How do vehicles with a higher limit measure speed?

 

Geez Plums,Thanks for that but you are on a higher plane than me, about all I understood of that informative reply was Duct Tape.From what I can find is that the speed control could be found at the Speedo Head (going in there for the temperature realgauge shortly) or from the ECU and/or gearbox. But to identify which wire to tap and from where? And the consequences of doing it. Although splicing in the RealGauge doesn't seem to offend the wiring. (fitting a power source in the rear seat area does though)!
The available units seem capable of the doing the rest. I was hoping some-one may have been here before me.All other models of jaguar I have owned had simple easy read speedometers but the X308 is a total fail from me.

 

Short answer ... I don't know

The standard may allow an extension *and* the feed to the instrument pack is not regulated by the ODB standard. Indeed, the feed can be completely independent as is the case with Jaguars.

 

Well, the old discarded android phone with elm327 bluetooth ODB-II dongle would work. What may have confused you is the reference to "torque". That is the name of a android ODB-II app available from the app store. Duct tape ... well that's your best friend

Messing with the instrument pack is not a real good idea(TM) unless you are sure of exactly what you are doing. It is a very costly replacement *and* requires dealer programming as part of the venture.

What you could consider doing is getting some very fine pinstriping tape and running it as a match needle mark at the exact limited speed that you are interested in. Just lay it on the plexiglass face. You could try it with masking tape first. You should be able to immediately determine whether you are over the mark by the relationship between the needle and match line. Another old racer trick.

BTW, the ODB-II data stream on the X308 updates quite a bit more slowly than more recent vehicles. If you are monitoring speed only, about the best you can reasonably expect is 7-8 updates per second. Fine for cruising, but not as smooth as a speedometer.

What you really need is a visible and audible alarm that kicks in at a programmed speed.

 

I think that's called 'a wife'.

 

Ahh .. but that's subject to override

 

Regarding the 155MPH limit, European car manufacturers mutually agreed to it about 10 years ago when a number of vehicles were able to exceed that speed.
It was designed to stop manufacturers stating "my car is faster than yours, and therefore better" I suspect that governments were going to get involved, so the manufacturers got in first. 70 MPH on a freeway seems ridiculous by comparison.

 

Yes ... but that is entirely separate from the fact that a 8 bit value is limited to the range 0-255. Therefore, if using a byte representation in OBD, the maximum single precision value that can be represented is 255. In the event the value is being sent as km/h then the equivalent maximum in mph is 158.

In any event, it has no bearing on the goal of the OP.

 

"What you really need is a visible and audible alarm that kicks in at a programmed speed."
Yes I do. That is exactly what I was hoping to do with a HUD which has all those functions.
Choices so far:
1/ Buy a Bride with a GPS
2/ Pinstripe the speedo
3/ (and I thought of this first) That magnifying plastic cut to fit over the speedo.
4/ Use another car (safest option)
Our common speed limits are (in kilometres) 50,60,70,80,90,100 all of which I encounter on a short trip of 30 kilometres.These limits are vigorously enforced to within 2 kilometres of the prevailing limit. (each breach attracts demerit points of which you have 12 that last 3 years) I have used my 12 points twice. Side effect being unable to insure a vehicle as I am considered a bad risk. We don't need performance cars!

 

Doesn't your GPS beep at you if you exceed the local speed limit - my old TomTom does.

 

option 5: quit trying to crowd the limit and leave a cushion

 

Option one is a bit extreme.
No Jaguar owner should need to marry to get a companionable speedo monitor.

 

Yes I try to do that but it is too easy to let your guard down and creep over the limits. Very rural here and often no traffic to "go with the flow" Maybe I will just buy one (HUD) and see where it goes from there. Nothing ventured......