Thanks Skid Mark! That will help me get things rolling along.

If anyone has a speedometer cluster, I will still need that also.

 

It'll ship tomorrow!

 

Wow this is a hot topic (pardon the pun !!!!) I was just out for one of my last cruises until the salt hits the road for another long winter. Just an idea. The outside temp sensor, not sure where it is but it would be interesting to see what the range is of this. I personally would rather know my coolant temp etc than the outside air temp. Its 5 deg c today by the way. If this sensor does not have the range it may be possible to get one that does and tape or clamp it to the rad hose or something like that. Then all you would have to do is press and hold the external temp button and voila temp displayed in the car. May be possible and may be impossible but may be worth investigating.

 

I'm sure a tech will correct me if i'm wrong, but I believe the OAT is picked up by the mass airflow sensor and it's reading goes into the ECM as part of it's calculations on mixture etc. Our display of OAT inside is just a little bonus of this fact, if you did change this signal it wouldthrow engine operation off.

 

The AOT sensor has nothing to do with the MAF - it's a completely separate item fixed right at the front of the car, installed on the light/horn loom.

I think it's a brilliant idea to use this sensor instead of attempting to re-calibrate the engine temp display. Lateral thinking at it's best from hdsg!

 

Is the Temp display on the climate control three digits? Can't recall and my car's in the shop.

 

Anybody have a hair dryer handy? My car is on a transporter, so can't get to it for a week or so. Interesting to see how high it reads. It may not be linear in the 200+ degree range, but at least the readout could be compared to the ECM output to find out how closely they agree.

 

I'm looking at another approach to the problem. I've got an XKR, but have got hold of the 3 Gauge cluster and center veneer panel (can't stand the GPS). But then, realizing how 'useful' the gauges were, I began to wonder if I could do better.

My current plan (plan to work on this over Xmas as I have three weeks vacation to use) is to use a PLX DM200 as one gauge, and Arduino(s) driving OLED displays (matching style) in the other two (I think all three gauges need to 'digital' OR 'old school analog' - a mix doesn't work

This gives touch screen (on the arduinos), and a 'Jaguar' themed set of clocks, as well as OBD readouts, DTC codes and even reset. It's really a basic Car PC with 3 round screens, rather than single rectangular one.

Parts are ordered, but (as we all know) only time will tell how successful this is...though none of it is rocket science; it's really just bringing together bits and pieces of other projects. Won't be starting in earnest on this for a few weeks, but I'll be sure to keep everyone updated if there's interest in this approach.

I have done the first (and easiest) part - my default gauge background....

Edit: Just came to me. If WhiteXKR has worked out the signals to drive the stepper motors, we could perhaps use an Arduino (small, inexpensive embedded computer) to read the OBD (which I was planning on doing to drive the digital gauges and display a clock) and then drive the stepper motor. I'm already looking a the ODBD->Arduino end, this is just a different kind of output (to the original gauges).

-Steve

 

Looks like a great approach...please keep us posted!

I definitely would be interested in talking if you implement Arduino code to read OBDII.

Unfortunately though, OBDII (or the vehicle itself) does not have access to oil pressure data, other than a low pressure switch, so that needs to be an added sensor and analog.

 

I'd thought of that - luckily the Arduino has analog inputs as well, though that does mean an extra pressure sensor to actually read the value.

I'll definitely keep you updated; I'm keeping my fingers crossed that nothing comes along to interrupt my 'play time' next month....

-Steve

 

Update on progress....I decided I couldn't wait until vacation time to start playing, and have had some success....

I have the Arduino up and running with a small LCD display, showing a very basic analog and digital clocks (this LCD is really too small for the final gauge, but is good as a test)

I've also (just) got the Arduino talking to the OBD system on my Ford Ranger (testing on that first, as it's a lot less $$$ if I blow something up). At the moment I'm just pumping the data over another serial port to the PC and showing it there as ascii, but the two tests combined mean I can grab data from OBD and display graphically....this could work...

-Steve

 

Gee, and I was going to run my Taylor oven thermometer probe through the firewall and clamp it on my radiator hose as a high tech solution. Guess now I'll wait to see what develops with all this data stuff.

 

The present guage is nothing more than an idiot light. It did save my bacon once when I overheated. If you change to an actual analog sending unit with a calibrated guage, the next problem is to realize that the location of the sending unit does not provide a representitive sample of the overall engine temperature. Where are you going to relocate the sending unit? Maybe you will acutally need two or three wired in parrallel. Or, maybe a little program could give readings from each sender at five second intervals...... Just accept the idiot light. It works.

 

We are proposing using the data from coolant temperature sensor that already feeds the ECM to control the engine...so I think that it should be quite optimally placed.

 

There's something here I don't quite understand. As the car is warming up the temperature gauge acts like, well, a gauge. It creeps up to mid-range as we would expect.

So is the idea that above mid-range it becomes an idiot-light ... that it won't move above mid-range until temperatures are way above normal?

I've never had an overheat on this car, so no first-hand experience.

 

Yes, there is a wide mid-range where the computer just holds the needle dead center.

 

Without re-reading every post I think it's be concluded that you'll see a fixed reading from 180ºF to 230ºF. I don't think anyone has determined what the needle does once the temp goes higher. I presume it then behaves like a normal gauge again....as it does from ambient to 180ºF.

IOW, at 231ºF I don't think the needle suddenly bounces all the way over to the hot end of the scale.

Cheers
DD

 

I remember when I bought a 10 year old X300 Soverign, Having Totaled one that was 2 years younger.

The Totaled one had the plasibo gauges, so I was used to them.

I picked up my older car, which being an early car had the gauges operating properly, drove 100 motorway miles, then as I pulled off and was stationarry at the lights noticed preasure in the red and an increasing temp.

My Jag specialist had to calm me down whilst explaining all was well and this is why Jaguar put doctored gauges in.

Regards

 

Right you are.

The answer to my question was in the first post in this thread ... in the form of a graph no less. RTFM.

But I wonder if maybe there's some justification for what they did here. In the range up to ~ 230 deg. F. the pressure in the system should be well within limits ... no more than 10 PSI or so. Much hotter than that and trouble could be coming.

So maybe for most drivers showing 180 - 230 deg. as "normal" is not such a bad idea. They probably had something like this in mind.

 

I believe the author of the first post mentioned that he had no data as to what happens beyond the midway point of the gauge and/or beyond 230ºF. I think that area of the graph is speculation but probably correct. That is, conventional operation on both ends of a wide dead zone.

Yes, there is a certain logic to the arrangement if it works at the "hot end" the way I'm thinking it works.


Cheers
DD