Speedometer/GPS (split from ForcedFed's drive thread)

[doma]

>reads approx 9mph high however

Does anyone know of a way to correct the elise's speedo? Can you 'rechip' your gague unit?? I am very annoyed knowing that this gague reads incorrectly (stupid stupid euro laws - argh!)

[darkSol]

Originally posted by doma
>reads approx 9mph high however

Does anyone know of a way to correct the elise's speedo? Can you 'rechip' your gague unit?? I am very annoyed knowing that this gague reads incorrectly (stupid stupid euro laws - argh!)

What about taking it to a speedometer shop to see if they can adjust it (which is highly unlikely)... OR just remove the front glass/plastic faceplate, pull off the needle, go for a drive on an EMPTY highway - and carefully press it back in EXACTLY at 80mph - at 80mph GPS indicated. YOU WILL NEED A PASSENGER WITH A STEADY HAND to hold the steering wheel and read off the GPS speed... while I'll admit is not the safest thing or smartest thing to do... but at least it'll be a lot more accurate at speed. I did this several times in another life when I printed my own gauge overlays for my delSol VTEC....


Disclaimer: Please don't attempt this unless you are completely insane.

[Ground Loop]

Just to add another "me too", I held a steady speedometer 80mph on a straight stretch of highway and the GPS held 75. I have had this GPS for a while, and have every reason to think it's accurate to better than 0.1mph in steady state.

That's about 7% error, which is more than I would like to see.

[doma]

My understanding, from all the discussions/observations on this board, is that the # of mph difference to reality is non-linear and depends on how fast you are going. So ... simply moving the needle won't help.

For example...
Real Speed: 5mph
Indicated Speed: 5mph

Real Speed: 50mph
Indicated Speed: 53mph

Real Speed: 75mph
Indicated Speed: 80mph

Real Speed: 100mph
Indicated Speed: 109mph

etc.

>when I printed my own gauge overlays for my delSol VTEC
Now that would solve it! But I doubt I have the skill to produce a new face overlay that looks origonal.

[_JD_]

To me, an indicated 90 mph feels like 75-78. I agree with ground loop that it's unacceptable.

[Greg]

Most cars are this way.

It is possible to pull the gear for the spedo in the transmission, and replace it with the correct (smaller) gear. ..

I've not done this, but I know of people installing V8's in miatas, changing the differential and final drive ratio, and swapping out speedo gears to compensate the gauge.

Pulling the needle is stupid. The gauge will be reading 10mph at a dead stop. Will that make you feel better?

[Greg]

Actually, I guess that will be a larger gear to make the speedo indicate a lower speed than it did otherwise...

You get the idea...

[Chococar]

Palo Alto Speedometer is the place to contact to correct speedos. They have lots of ways to do it. They installed a little gear set in between two halfs of the speedo cable on my Eleven to get it just right.

They do lots of mail order work, in case you aren't in the Bay Area.

imho, I don't think the Elise speedo is far enough off to warrant it, though.

[ChrisH]

Is the speedo method in the Fed Elise simply the old mechanical rotating cable from the transmission to the speedometer, or is it an electronic sensor in the transmission and an electronic speedometer?

Both of my current cars actually read a few miles/hour less than what you are actually going. For example, my wife's minivan reads about 3 MPH lower than true speed when going 70. My Honda reads about 2 MPH low at that speed. I have to keep that in mind when police are about.

[Ground Loop]

The spedo in our Elise is not mechanical.. no spinning cable goes to the dash.

It's entirely done by CANBus from the ECU.

It may be possible to fudge the data from the ECU to the Dash to manipulate the dial readings. So far I haven't had much success trying, but I've been able to set both needles to crazy positions and wiggle them around. That's a start.

Another approach might be to fool with whatever sensor the ECU uses to read the speed, assuming it's not too tightly involved in the engine management.

[milcher]

I used one of these to convert a motorcycle from KPH to MPH, it worked great.
http://www.blackrobotics.com/yb_home.htm

[darkSol]

Originally posted by milcher
I used one of these to convert a motorcycle from KPH to MPH, it worked great.
http://www.blackrobotics.com/yb_home.htm

BRILLIANT! There you go! The Elise is probably just about 7% off or so... This thingy is WELL worth the $120 or so bucks to get an accurate reading (bet $ it's got a PIC in it) - PLUS if you ever change tires sizes/circumference then you can adjust it!

Good find!

[doma]

I would not try to change the signal to the gauge unit. Beit a different gear or electronic fudging. Then the odo would be off!

Right now our Odo is accurate, at any speed, but our MPH gague is not. I want them both to be correct.

-doma

[ChrisH]

It states that it is compatible with Toyotas, so I would guess it would be okay with the Elise. Just have to work out the connector compatability stuff. Whoever tries it, please post what you had to do to install and get it to work.

It only does a straight percentage change - same percent for all speeds. Some folks have stated that the percentage error is changing with speed. I don't know how that could be, but if true (after repeated testing), then this box won't solve the problem completely.

[darkSol]

Originally posted by doma
Right now our Odo is accurate, at any speed, but our MPH gauge is not. I want them both to be correct.

How can that be? Surely there's only one VSS (Vehicle Speed Sensor) in the car. If you're travelling at 60mph, why would the speedo indicate say 55mph but the odometer clicks over exactly one mile-per-minute? That's insane - and I'm sure theres some kinda of Federal statute that says they both should match. I certainly hope our tach is reading accurately...

[Ruediger]

Crankshaft RPM signal is very important for the ECU and for some careful drivers.

Wheel RPM signal is important to avoid speeding fines only.

This may help to allocate/ find the respective sensors and the physical principle on which they are working, too.

[Ground Loop]

Originally posted by ChrisH
It states that it is compatible with Toyotas, so I would guess it would be okay with the Elise. Just have to work out the connector compatability stuff. Whoever tries it, please post what you had to do to install and get it to work.

Careful. All the parts involved in this are distictly non-Toyota -- the ECU, dash, and sensor wiring..

[Prolene]

I use The Yellow Box on my S2000. It works. I changed the final differential gearing, and since the S2000 senses vehicle speed via driveshaft rotation, the speed would read entremely high with stock sensor outputs.

The Blackrobotics Yellow Box device changes the driveshaft sensor output that goes to ecu, making the ecu think the car is going the exact speed that it is actually going. That is a good thing. Crankshaft rotation reading, engine rpms, etc., readings to the ecu remain unchanged.

I calibrated the Yellow Box via GPS.

[scottyb]

According to the wiring schematics the Speedometer and odometer are linked. Thus if the speedometer is off so is the odometer.

In my car when the speedometer says 100mph, my GPS says 90mph. My GPS is dead on accurate on my other 2 cars.

That means that our mileage on the car is not accurate & it could have some issues with the warrantee. You would think that this is an issue that Lotus needs to correct on our cars.

[andykeck]

Originally posted by darkSol
How can that be? Surely there's only one VSS (Vehicle Speed Sensor) in the car. If you're travelling at 60mph, why would the speedo indicate say 55mph but the odometer clicks over exactly one mile-per-minute? That's insane - and I'm sure theres some kinda of Federal statute that says they both should match. I certainly hope our tach is reading accurately...

It's possible. My last Honda VFR was that way as is my wife's current BMW. It's been discussed elsewhere here, but there are some legal situations that mandate that the speedo can never read low, even with aftermarket wheel and tire sizes. So then it's just a fudge in the gearing or the electronics in the speedo to make it read some small percentage higher than the actual value.

I'll do some test with my GPS units, but it sounds like in the Elise, both the speedo and odo read high, which is bad warranty-wise.