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07-19-2022 #1Registered User
- Join Date
- Dec 2020
- Posts
- 24
Getting Tach to work with LS RPM Feed
I’ve got an LS9 in my 1973 Trans Am. Shop that did the install wired up the original gauges to work with the senders and bulkhead outs for the Crate LS9. This is the info I found for making the stock tach work with the LS signal:
“A tachometer signal is included in the bulkhead connector (see below). This is a 2 pulse/rev output which may correspond to a 4-cylinder setup in some tachometers or transmission controllers. Note the signal is a low voltage square wave, some tachometers or transmission controllers may need a pull-up resistor in order to read the signal, similar to a 5000 ohm, 1⁄4 watt resistor– this detail is left to the user. The following circuit has worked for numerous devices – the resister value may need to be changed if your device does not read this output properly“
This was done correctly, as the tach does read the correct RPM. But here is my problem: If I roll on the throttle gradually to medium, the tach ready and climbs appropriately. But if I roll on the throttle quickly, the tach will bottom out to 0. It will come back to life when I let off the throttle and then it will read appropriately as long as I am applying gradual throttle. But it will bottom out to 0 again the next time I roll on the throttle too quickly.
Any ideas on where I might start to get the tach to follow what’s going on during more ‘enthusiastic’ throttle application?
Problem 2 - my fuel gauge works, but the tank is genuinely Empty when the gauge reads 1/2 (ask me how I know). At legit 1/2 tank, the gauge reads 3/4. So as long as you know this and fill up when the gauge gets between 3/4 and 1/2 you are fine. I’d like it to read correctly. Any ideas on how to get the fuel gauge to work through the full sweep?
Thank you.