From Gas to Diesel/RPM Gauge Compatibility Question

[ein bora]

I am in the process of collecting the parts to convert my newly acquired 2000 passat 1.8T 5-speed to a 1.9 idi. As TD diesel version don't seem to be available for the B5 generations, I'm looking at getting a gauge cluster out of a B5/3B tdi. Would anyone know if the rpm gauge will work, and if not what if anything can be done to make it work?
Worst case scenario I could always try to use the rpm gauge from my mk3 donor car.
Any help appreciated. Thanks.

[RabbitJockey]

i have no clue, but do you wanna sell me the 1.8t real cheap?

since everything goes through the computers on the later cars i don't know if even the dakota digital tach converter would work.

[erice1984]

Most of the newer cars, the signal goes through the engine computer.  Also I was told something about an immobilizer or security feature that wouldn't allow the newer clusters to work with older stuff.

Check out VDO or something.   Dakota Digital is pricey.

[ein bora]

So if I change the computer to a B5 tdi one, thus recognizing the diesel should that work? 
Reading the write up on the Dakota Digital - this maybe an option as well.

Thanks for the info.

[RabbitJockey]

i think the tdis got the rpm signal off a crank sensor, so even if you switch to tdi harness and ecu you're still in the same boat as before because the 1.9 idi uses no computer, you will probably be best off going with custom gauges or retrofitting a b3/b4 aaz cluster or even a mk3 and eliminating the computer, how ever due to the immobilizer you could be stuck needing the computer in order for all the other electronics in your car to work.  perhaps you should read up on what the a4/passat people do when running standalone engine management

[Vincent Waldon]

If I understand correctly you are dropping a 1.9 IDI engine into a chassis that used to have a 1.8T engine, and then adding a TDI-specific cluster.

If so, there is no computer associated with the IDI engine...it's RPM signal comes from the W-terminal of the alternator and won't be directly compatible with your cluster... which is expecting an engine RPM sensor from the ECU/crank sensor from your old 1.8 or TDI engine.

A Dakota Digital conversion box is probably your best option, since you'll need to divide the W signal by something between 6-8X (depending on pulley size etc).  If this converter works it will also drive the tach of your 1.8T cluster, although you'd have a 6000 RPM tach instead of 5000 etc.  And no native glow plug light.

Speaking of which, you also have some wiring ahead of you in terms of the glow plugs, oil pressure warning etc etc.. depending on the version of TDI cluster you track down it may or may not accept analog connections... later models were Can bus so entirely digital.

You could opt for a completely manual glow plug system... if you check the FAQ section there's a couple of threads on adding a relay and pushbutton.