6 cyl engine swap - Tachometer fix
 

Hey, wanted to drop this here for future swappers...

I just completed swapping an M54B30 into my 96 ti. My ti has only 82k miles on it and is quite clean, so I wanted to retain the original instrument cluster (and the chassis miles on the odometer).

Common wisdom is that you have to change out the 4 cyl cluster for a 6 cyl cluster in order for the tach to read accurately. But there is another way...

There are several "tach signal adjusters/converters" on the market for engine swappers. These products take the engine speed signal and convert it to match your tach. For example 6 cyl engine in a car with a 4 cyl tach. I used one called "Tach-Adjust" (https://ashlocktech.com/) and recommend it based on my use (no affiliation).

This is a simple product, which needs power and ground, and is inserted in-line between the engine and the tachometer. You configure the product using dip-switches to match the swap configuration you are doing. This should work for LS swaps, JZ, BMW engine swaps (8 cyl/6 cyl), etc.

There are 3 places on the ti where you can insert this, any one of them is fine:
1) at the DME or engine where the tach signal is output (for my M54B30 this is the DME X60004 connector, pin 17)
2) at the E36 X20 connector in the engine bay (pin 20)
3) at the rear of the instrument cluster (I didn't take this route, not sure which pin)

Whichever location you pick, connect the Tach-Adjust to 12v + and -, the wire from the engine side to the input of the Tach-Adjust, and the wire to the tachometer to the output of the Tach-Adjust. Done.

This was really one of the easiest parts of the swap. Very happy to keep my original cluster and the tach reads accurately.

Caveats: I have a base model ti - no OBC, no ASC, no cruise control. So the only thing affected in my instrument cluster from the swap was the tach.

cheers
drew

This is super useful information. Thanks Drew!

That is great information!

I initially thought, wow I'd like to see a video of that. But then I realized, well the point is it would look the same.. so yeah I guess I don't need to! :biggrin:

You can also reconfigure the original cluster for four to 12 cylinders.

Thanks -

I really get so much great info from the forums. Not much from the social media groups at all. Would love to continue to see all good info retained in the forums - I have some other tidbits from my swap I'll write up too. And a plug here for Jim's swap guide too, that was super helpful.

Jim - what??? is there a write-up on reconfiguring an existing cluster for different engines? Is it swapping out the tach control board or something? Sure hope I didn't miss that section in the swap guide, LOL!

cheers
drew

Just one of MANY tips and tricks in my engine swap manual. Below, an excerpt. It is not complete, as you need to get to this location within the cluster, which is detailed in the manual. But, you don't even need a computer... (and it seems the 12-cylinder cars use a different coding plug)

Test 2: Engine Data - This display is an "engine factor" value that is stored in the coding plug. The instrument cluster processor uses this factor in addition to the "TD" signal from the DME control module to process and display tachometer RPM based on the engine installed. For EXAMPLE:
*ENGINE FACTOR 2 = 4 CYLINDER
*ENGINE FACTOR 3 = 6 CYLINDER
*ENGINE FACTOR 4 = 8 CYLINDER

Ah, I did see that in the manual - I thought it was only for displaying the values/data for each test, and I didn't see a way to change the values. Will have to explore that a bit further!

Regardless, the above method (using something like tach-adjust) is super simple/effective. You are welcome to add it to the swap manual!

Okay, I’ll look into that but I prefer to keep things factory as you know.

Hi, I'm doing the same on my ti that has a M52B28 swapped in. Wiring is not my strong suite so I'm struggling a bit with this one. Would you be able to go into more detail regarding how you installed the adapter and where/how you connected the wires? What is the simplest way to tap into the tach output wire without ripping the loom open? Is there a best place to connect it to keep the wires as short as possible? Wanting a tidy/invisible install if possible.

I haven't got access or skills to use a soldering iron so planning on using butt connectors and heat shrink for the time being.

Hi - this can be done without soldering. Easiest place to do it without it showing is at the DME since you have to conceal the DME and relays anyway. Not sure if RHD cars are the same as LHD, but, if so, the DME is normally in a cubby in engine compartment on the drivers side in RHD car. There is room there for the Tach Adjust component to fit.

Wiring is easier at the DME, because there is already power and ground wires there to tap into, and you just need to identify which wire coming out of the DME is the Tach signal.

Some notes:
1) Find a power wire that is Switched On with the ignition so the Tach Adjust is only on when the car is. Use the Electrical Troubleshooting Manual/wiring diagrams for your car to see which wire to use.
2) For power and ground, you want to "Tee" into the existing wires
3) For the tach signal, you want to "break" the wire so that Tach Adjust sits in-line with it. The DME side of the wire goes to Tach Adjust input, and Tach Adjust output goes to the side of the wire going into the harness (which will eventually go to the Tach).
4) I'm using "Tach Adjust" as the example, but any tach signal converter will need the same connections.
5) This can also be done behind the instrument cluster, because there is switched power and ground wires available there too, and you put the Tach Adjust in-line with the Tach signal going into the cluster.

I'm not sure if this helped... the ETM/ETK will be your best resource to find the right wires. Happy to answer any questions.
Cheers,
Drew

Very nice! I have an M54B30 that's going into my '95 and it looks like this will be very helpful information! Thanks!

I'm local to you - let me know if you need a hand!

Thank you for posting this. I’m wrapping up an m54b30 into a 95 Ti right now and the cluster is still giving me issue…

M54 will probably require the M54 cluster as well as wiring changes...

I just plugged in the z3 instrument cluster and things didn’t work well. Temp gauge and fuel moved. Tach and Speedo did nothing. Swapped back for now until I can figure out what all the car needs. Did get to drive it on track, and what a blast!

The z3 3.0 rear end is comically too wide. Trying to figure out how to resolve that since m roaster rear ends are nearly impossible to find…