After swapping an LS2 into my 92 RS Camaro with stock 110 mph gauge cluster, my tach was reading roughly double what it should. I know it's a common issue that tuners can take care of very easily. However, I recently installed a 145 mph cluster that I got off of eBay. When I start the car, the tach just stays pegged the whole time, regardless of throttle position. Do TBI and TPI clusters require different signals or is the tach on the 145 cluster shot? I guess I could swap out just the tach, but I'd prefer to avoid that. Any ideas?

 

Sounds like a normal busted tach for 91-92 camaros. Read about it in the long thread on the electronics forum. To fix it you need to solder a resistor in there

 

Just swap out the tach driver board, solder in the resistor that Pocket mentioned and you will be set.

After that, its getting the correct signal to the tach. Did the tuner use the internal pull up circuit, or will you have to make your own......

 

Better yet, solder a potentiometer in there, and dial it back to the right RPM... then you won't need to worry about reprogramming the computer to work with a "V8" tach.

 

interesting approach. what value do you use for the pot?

 

Oh crap, I read all about the tach stuff a month or so ago, my bad. I guess I'll try the potentiometer fix.

 

Off the top of my head, I don't remember if the v6 cars had a higher resistance or a lower resistance than the V8 models, so I'm not sure whether the final value should be higher or lower than the ~200k that the V8 car uses. Either way, I'd probably use a 100k pot combined with one or 2 more resistors in line to get it into the ball-park. You can try a 1M pot, but my guess is that adjusting that accurately will be too hard.

 

To the solve the problem I put the 110mph cluster's circuit board in the 145mph cluster and then had the tuner set the tach output to 3 and it reads pretty darn close to the correct RPM. If it starts getting out of hand later, I'll use the resistor/potentiometer method to fix it, but right now it's good to go.