From darren_at_inet.co.za Tue Jun 25 06:19:58 1996
Date: Tue, 25 Jun 1996 15:19:52 -0700
From: darren <darren_at_inet.co.za>
Reply-To: darren_at_inet.co.za
To: dale_at_unofficialbmw.com
Subject: 323iMEX speedo

Hi Dale, my name is Darren, my BMW is a 1985 model 323iMEX ( South African specs ). I have M-technic sports suspension, 16-inch TSW Stealth mags, white dials, a 325i motor with a stage 2 cam, a 325is front spoiler, and a Brospeed free-flow exhaust. It makes the shadowlines in my neighbourhood sound like 1300cc cars, the purr is unreal. I am hoping to put a chip in which was used to upgrade the 325is 141kw motor to 157kw. The problem that I have is that the dials which were put in by the previous owner are for the '86/7/8 ? M3.

I have been down the highway, and my speedo reads 150 KPH, when my dad's M3 ('94) is reading around 120 KPH. The rev counter, petrol gauge etc. are exactly the same ( except in white of course )Do you know who I could contact to get the right calibrations for my speedo rg. 120 KPH is at approx. 12 o'clock, and 160 is at 2 o'clock etc. I thing calibrations for a 325i would probably be the most accurate. Thanks.

From dale_at_unofficialbmw.com Wed Jun 26 09:22:29 1996
From: Dale Beuning <dale_at_unofficialbmw.com>
Subject: Re: 323iMEX speedo
To: darren_at_inet.co.za
Date: Wed, 26 Jun 1996 09:22:19 -0700 (PDT)
Cc: dale_at_unofficialbmw.com

Hi Darren,
I haven't had a problem with this before on a BMW. But I can tell you what I do know of how this works.

In the differential is a slotted circular piece of metal that is mounted in the same axis as the ring gear. This spins at the same rate as the ring gear and provides the pulses to the hall-effect sensor mounted on the rear diff cover. So your speedometer receives X number of pulses per revolution of the rear tire, regardless of what tire size you have mounted.

When you install a different height tire, let's assume taller, you travel further for that same X number of pulses sent to the speedo.

For a given speed:
if the tire is taller, you send fewer pulses, causing the speedo to read slow if the tire is shorter, you send more pulses, causing the speedo to read fast

So the M3 guages are expecting a taller tire than you currently have installed I believe the E30 M3 came with 205/55 VR 15 tires, you can either try to match that tire height or change the speedo back to the 323i unit.

I don't think there is any adjustment you can make to the speedo itself.

hope this helps,
Dale

> Hi Dale, my name is Darren, my BMW is a 1985 model 323iMEX ( South African
specs ). I

> problem that I have is that the dials which were put in by the previous
owner are for
> the '86/7/8 ? M3.

> I have been down the highway, and my speedo reads 150 KPH, when my dad's
M3 ('94) is

> reading around 120 KPH. The rev counter, petrol gauge etc. are exactly the
same ( except

> in white of course )Do you know who I could contact to get the right
calibrations for my

> speedo rg. 120 KPH is at approx. 12 o'clock, and 160 is at 2 o'clock etc.
I thing
> calibrations for a 325i would probably be the most accurate. Thanks.

--

                       |            Dale Beuning           |
                       |       email: dale_at_unofficialbmw.com     |
                       | web: http://www.unofficialbmw.com |
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