pt76jon

I was just wondering if any of you guy's have ever hooked up a BS3 computer to a factory tach, and if so can you please let me know how to do it! Thanks a million!

Ira

I think it depends on the year, and the car. On a 97-98 F-body there is a tach wire going to the dash, but on 99-2002 F-body the tach information seems to be transmitted over the bus and there is no way to connect to it. If you wanted, I have a way to connect a tach signal to a 99-02 but it involves modifying the PCB on the back of the gauges.

Ira

kp

iTrader: (34)

Mightymouse had his working. You need to have the stock PCM in the car either way to make it work since the PCM decodes the crank signal and converts it to the tach signal for the cluster, 99+ may serial bus but you need the stock PCM in the car for the factory tach to work.

I didnt do it since I dont want to fool with anything from the cam/crank sensor to the BS3, but I do still have the stock PCM for the the gauges and speedo hooked up.

Ira

You don't need the stock PCM for 97 and 98, you just need a correct tach signal. If memory serves me correctly, it's 166.7hz or 10,000 pulses per minute for 5000 RPM.

Ira

kp

iTrader: (34)

But its still driven by the PCM, how are you get that signal out of a BS3 or the stock crank sensor unless you build some kind of interface..

pt76jon

The car is a 2000 firebird and I do have the stock computer in it I just pinned out all of the wires for the engine controls!
Thank You for your help!!

Ira

Well, I'd assume the BS3 has a tach out of some sort and there's a good chance it's the same as the 97-99 tach out signal, if so it should just work if you connect the right wires. On the 99-02 you either use the stock computer or replace the electronics in the dash so it can use the BS3 tach signal.

Ira