Technical No idea how fast car goes!!!

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Technical No idea how fast car goes!!!

zaphodski

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I've just discovered a pretty major problem with the Barchetta. On my way home this evening a "40 mph" sign flashed up as I approached it. Looking at my speedometer it was registering just over 30 mph. So I drove past it again and same thing happened. Bemused, I switched on my Tom Tom sat nav and went for a little drive..... It would appear the speedo has no idea how fast the car goes. Any speed from about 5 mph - 30 mph registers as 33 mph on the speedo. At 45 mph the speedo registers 35 mph, at 40 mph the speedo registers 50 mph, at 70 mph it registers 65 mph and taking it briefly above 70 mph the speedo says its doing 60 mph. Then slowing down the speedo drops to 33 mph stays there until the car comes to a stop then suddenly drops to zero.

I know I reported in a previous post that someone had jammed a screw into the odometer to stop it registering the miles, it would seem the whole thing is now knackered.

I know its not a mechanical speedo so my guess is its a "sender". Is this something I should attempt to repair or is it a trip to a garage??? Help:cry:

I'm at a total loss what to do.
 
hm... could be that needle is shifted for 5mph when they were jamming speedometer ... the best way is to check by other car(s), ask him to drive some constant speed and then compare to yourself. not sure how navigation is correct... also you can ask local policeman to measure your speed... but nobody have correct speed it's 10% +-... if you do not have standard wheel could cause wrong speed.

didn't help but, i will do that first before driving to garage. it speedo needle is shifted then is easy to fix... just turn around needle until you feel pressure on your finger, and then push for 5mph more. it's better to show you drive faster then your real speed is. (and feeling is better :D )
 
The puzzling thing is that, according to your figures, the error is not consistent as you speed up & down, so recalibrating it to read +5 mph, like F4usT suggests, won't work.

5-30 = 33
40 = 50
45 = 35
70 = 65
70+ = 60

I suppose it could be the speedo cable sticking/jamming intermittently, rather than the speedo head itself, but that wouldn't explain the consistent error, nor the over-reading, as in my experience a sticking cable causes a speedo to under-read.

So unfortunately it sounds like it's b*ggered.
 
Hi Gar074, unfortunately I don't think its a sticking cable as the feed to the instrument binnacle is electronic from the "pulse generator" on the differential, so a "kink" in the cable is a non-starter. I've had a look at the pulse generator and it looks fine to my untrained mechanical eye, no corrosion, cracks or loose wires. I also followed the speedometer signal cable to connector "B" terminal "1" on the rear of the binnacle and its secure and making a good contact. The fact that the speed inaccuracy is not consistent throughout the speed range i.e. it reads faster at some speeds and slower at others means the needle hasn't slipped. The GPS speed on my sat nav is pretty accurate, as the model I use also doubles as a speed camera warning device. This is really puzzling, I fear I may need to purchase a whole new instrument panel.....it won't be cheap :mad:
 
Hi Pete, That's exactly what I'm about to start doing this afternoon. Removal of the binnacle and careful dissection of the speedo. (I have a small air compressor with a computer cleaning attachment) which I'll attempt to blow all dust etc out with. I guess I can't make the situation much worse since the speedo is totally screwed (just been for a trip up the A19 and it registered almost 130 MPH......I was really doing 68 MPH. I'll attempt to remove the pulse generator and give it a clean if my fiddling with the binnacle does not fix the problem. See if that'll cure the problems.:bang::mad:
 
Hooligan.....moi?

Just a thought, how fast do these little cars actually go (I mean really go, not how fast my speedo says I go). I'm off to Germany soon to give the Barchetta to my daughter, so may open her up on the autobahn..........
 


220 kmh is 136.7 mph! The tests of the B variously put its top speed at between 120-125 mph.

Mine would probably be on the hard shoulder in a cloud of smoke long before it reached its theoretical maximum!
 
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not sure how navigation is correct... also you can ask local policeman to measure your speed...

Standard GPS is accurate to approximately 0.1 mph providing adequate satellite coverage and no signal degradtion.

However to be on the safe safe side 0.5 mph would be a safer figure on which to base your measurements.

GPS logs are accepted by the courts as accurate and a number of speeding offenses overturned by the judge on presentation of the data.
 
Hooligan.....moi?

Just a thought, how fast do these little cars actually go (I mean really go, not how fast my speedo says I go). I'm off to Germany soon to give the Barchetta to my daughter, so may open her up on the autobahn..........

Bloody fast for a 1.8 petrol, But it is more about the acceleration and the steering with the B.

I have never had so much fun with a car that is £3000~

The steering is just monstrously good, Makes me feel a little over-confident in it sometimes!
 
This has got me curious now...

How fast does your Barchettas go at about 3000 Rpm in gear five? Not meaning to thread jack.

I might be going faster than I thought :D
 
Ha ha, so it would appear the majority of Barchetta owners are all hooligans at heart. The comments about the steering and handling are very true, its a great little car to drive, just wish I never had so many annoying little problems to sort out before she goes off to my daughter.....
 
This has got me curious now...

How fast does your Barchettas go at about 3000 Rpm in gear five? Not meaning to thread jack.

I might be going faster than I thought :D

I was gonna ask the same question :) I reckon about 70mph, based on a a dysfunctional speedo, and the need for moderate speed based on that relative to other road users when passing a speed camera. Sounds complicated, but it's not really! Can anyone tell me what 4000 rpm in fifth is when converted to mph.. ;)
 
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