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Technical_   Interior_  318i/325i Tachometer Upgrade

318i/325i Tachometer Upgrade
Fred Kim

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Let's face it, that 5k eta tach isn't going to get you any dates. It's not going to get you any respect from anyone other than Mack truck drivers, either. So what you can do is swap out the tach in there now for a 7k tach used on the 318i/325i cars. But like all things in life, certain conditions apply:


1) If you have a Motometer cluster, then you must pull a tach from another Motometer cluster. Likewise, if you have a VDO cluster then you'll need a VDO tach. They aren't compatible, so don't try mixing and matching.

2) If your car was manufactured on or before 12/85, then you must use a cluster off an '84-'85 318i. After 12/85 BMW stopped using the tachometer coding plug and switched over to a chip, mounted on the lower front right of the cluster. The easy way to tell if a cluster has a chip or a plug without searching for a production date is to look at the back color of it: If it's white then it has a plug, if it's blue then it has a chip. If your car was made after 12/85, then use a tach from an '87+ 325i.

3) You will need to retain your original coding plug (or chip) for accuracy.

4) Even though a higher redline of 6500 is indicated, your car will not rev over 4800 or 5200 RPM (depending on if it's chipped). You will thus have a portion of the tach that is now unusable. This is good if you are planning to mod the engine later on like I am. If this doesn't sound good to you, then stop reading now.

If all this sounds okay, let's get started.

I actually replaced mine because my stock eta tach was erratic and erroneous. Several trips to Palo Alto Speedometer and a $185 bank account reduction resulted in a temporary fix, so instead of wasting more money I went to the junkyard and found a Motometer cluster with a broken speedometer from an '85 318i. I bought it for $45 and proceeded to remove the 9 screws that held the back end in place:

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If the back of the cluster is white, remove the black coding plug (Codier Stecker) behind the tachometer. Do not mix it up with the plug from the donor cluster! Now slowly seperate the motherboard from the housing. It may be a little tight after being in place for over 15 years. If the back of the cluster is blue, then there is a coding chip in the lower front right side of the cluster that you need to swap.

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On the back of the tachometer you will see three screws. Remove them, then slowly pull the tachometer straight up. It will probably be stuck in place initially, so you may want to gently wiggle it to get it moving. Don't worry, it'll come out, but don't use excessive force or else you may damage the instruments.

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Using the above steps, remove the tachometer from the donor cluster. Line up the holes and drop it straight into your cluster. You don't have to change the economy gauge (Energy Control) because it functions independently.

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Installation is opposite of removal. Be sure to keep your original coding plug; do not use the one from the donor. If you are of the dishonest type, now is also a good time to roll back your mileage as well (did I just say that out loud? Hmm, that must be a joke. Har har).

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Now you have to watch your redline, since the indicated 6500 is not applicable. There is a fuel cutoff at 4800 (5200 chipped) for upshifting, but downshifting won't prevent overrevving. Be sure to warn other people who drive your car about this!

There is an initial weirdness driving around with so many numbers on the tachometer, but after a few days you get very accusomed to it.


DISCLAIMER: I am not responsible for anything that may go wrong with this procedure. If the new tach doesn't work, if your (!) light suddenly appears, or if your motor mounts mysteriously fall off, I am in no way liable for any damage that may occur. Sorry, gotta watch my back.

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