INPA experts

UK forum for general and technical discussion about the Z3 roadster

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Gazza
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  M roadster S54
Location: East London/Essex

INPA experts

Post by Gazza » Thu 05 Apr, 2018 20:51

My speedometer is over reading quite a lot, 40mph shows 60mph after a couple of EEP_1 outages of the cluster.
Can you tell me if it can be reset with INPA ?
Gazza

"Understeer is when you hit the wall with the front of the car, oversteer is when you hit the wall with the rear of the car. Horsepower is how fast you hit the wall and torque is how far you take the wall with you"

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Robert T
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  Z3 roadster 1.9
Location: Cheshire

Re: INPA experts

Post by Robert T » Thu 05 Apr, 2018 22:02

Not sure about INPA, as that sounds more like a coding problem than an error or a simple calibration value in the cluster. You can use INPA to simulate a speed in kph, so for example 80 kph should read 50 mph. That way you can see whether gauge has gone haywire.

The Speedo is driven by a vaned disc on the diff, though I am not sure whether it is on the input or one of the outputs. If it is on the input, then I would expect that you can code the diff ratio so the same cluster can be used in different models. If it is on the output, then it would only vary with wheel diameter and I don't think there is any allowance for this.

Cheers R.

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Arctic Silver '99 Z3 1.9 & Black '59 Frogeye 1275cc
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Z3crazy
Joined: Thu 04 May, 2017 14:37
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  Z3 roadster 1.9i

Re: INPA experts

Post by Z3crazy » Sat 07 Apr, 2018 15:09

40mph is approx 60kph so maybe it's showing kph on a mph speedo.

FYI......

10mph = 16kph
20mph = 32kph
30mph = 48kph
40mph = 64kph
50mph = 80kph
etc,etc.

Dave
If it ain't broke, don't fix it
Z3 1.9 2000, Cosmos Schwartz

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Robert T
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Re: INPA experts

Post by Robert T » Sat 07 Apr, 2018 19:05

Nice theory, Dave, but I suspect that will not be the case. The entire car already works in metric units - so the speed is measured in kph, fuel consumption in litres etc. The speedo actually receives a different dial on a Euro car, so the KPH scale has the larger numbers - but the positions will be the same as the smaller inner KPH scale we have on UK cars - if they weren't then the speedo would hit maximum deflection before you reached the top speed of the car! AFAIK the only change when you code the car for KM instead of Miles is to the odometer display, and that is simply a multiplier on the value stored for the display, not a change to the recording method.

Something else you can test to see if the car is recording the correct speed is to put the odometer into self-test mode and select the speed display function. This displays the raw speed in KMH, before it is send to the DAC for the analogue speedo gauge.

Something else that occurred to me, but I discounted, is that the car could now be coded to the wrong engine - specifically to a 4 cylinder instead of a 6 - but this would only make sense to the rev counter, not the speedo. Assuming that the revs are measured by counting the ingoing LV pulses to the coil packs, then revs on a 6 cylinder are 1/6 of the count per minute, and on a 4 cylinder, 1/4 the count. Set it up wrong and it will read 1.5 times what it should. But that would not affect the speedo, only the rev counter. I trust that the rev counter is reading correctly?

Cheers R.
Arctic Silver '99 Z3 1.9 & Black '59 Frogeye 1275cc
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pingu
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  M roadster S50

Re: INPA experts

Post by pingu » Sat 07 Apr, 2018 19:26

Q1. Which car are you talking about (Z1 or M Roadster)?
Q2. When did it start doing this?
Q3. Had you done anything recently that could have prompted it? New battery. New diff.
Pingu

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Gazza
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Re: INPA experts

Post by Gazza » Sat 07 Apr, 2018 21:18

pingu wrote:
Sat 07 Apr, 2018 19:26
Q1. Which car are you talking about (Z1 or M Roadster)?
Q2. When did it start doing this?
Q3. Had you done anything recently that could have prompted it? New battery. New diff.
M Roadster
I get the EEP_1 dash fault sometimes (the cluster dies), it started from then.
Nothing.
Gazza

"Understeer is when you hit the wall with the front of the car, oversteer is when you hit the wall with the rear of the car. Horsepower is how fast you hit the wall and torque is how far you take the wall with you"

S54 M roadster Image, BMW Z1, BMW M3 CSL, Mustang Fastback

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pingu
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  M roadster S50

Re: INPA experts

Post by pingu » Sat 07 Apr, 2018 22:57

I would take the instrument cluster off and look at the circuit board for damage and confirm that the coding plug is secure. Check the wires and plugs for any damage.
Pingu

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motco
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  Z3 roadster 2.2i

Re: INPA experts

Post by motco » Sun 08 Apr, 2018 08:07

My EEP_1 fault lay with the coding plug. It also caused speedo drift but it was reading marginally fast not hugely. The original cluster with a second hand coding plug sorted it. I had to have the recorded mileage corrected because it was 80k too high on the replacement plug and that means I live with a tamper dot now.

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pingu
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Re: INPA experts

Post by pingu » Sun 08 Apr, 2018 10:38

I had my mileage reset by a dodgy yoof for £50.

He had never been asked to INCREASE a mileage by 100,000 :shock: .

The thread is on here somewhere.
Pingu

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Gazza
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Re: INPA experts

Post by Gazza » Sun 08 Apr, 2018 12:52

The EEP fault only happens when it’s cold (inside the car or outside) after driving for a while and on restart the cluster works fine apart from the speedo error.
Gazza

"Understeer is when you hit the wall with the front of the car, oversteer is when you hit the wall with the rear of the car. Horsepower is how fast you hit the wall and torque is how far you take the wall with you"

S54 M roadster Image, BMW Z1, BMW M3 CSL, Mustang Fastback

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motco
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Re: INPA experts

Post by motco » Thu 19 Apr, 2018 20:26

Gazza wrote:
Sun 08 Apr, 2018 12:52
The EEP fault only happens when it’s cold (inside the car or outside) after driving for a while and on restart the cluster works fine apart from the speedo error.
Mine did that too, but eventually a blow torch wouldn't have revived it! :twisted:

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