Modify / Fool Tachometer Speed - How to?
Thread Starter
Racer
Joined: Jan 2020
Posts: 467
Likes: 47
Modify / Fool Tachometer Speed - How to?
Gents,
I would like to install a switch in the car that allows me to change the engine speed signal to the tachometer. In other words, the engine revs, say 3500 rpm and when I flick the switch, it shall only show 2500 rpm on the tachometer. What is the signal that runs to the servo/needle in the dash? Is this somehow possible?
Thanks for your help
I would like to install a switch in the car that allows me to change the engine speed signal to the tachometer. In other words, the engine revs, say 3500 rpm and when I flick the switch, it shall only show 2500 rpm on the tachometer. What is the signal that runs to the servo/needle in the dash? Is this somehow possible?
Thanks for your help
Race Director
Joined: Dec 2013
Posts: 12,502
Likes: 3,631
Lost on why you would want a false reading on the Tach, but No, it's not going to happen short of hacking the ECM software.
On the other hand, easy to change the speedo ratio signal since it needed if you change tire OD sizes.
On the other hand, easy to change the speedo ratio signal since it needed if you change tire OD sizes.
Thread Starter
Racer
Joined: Jan 2020
Posts: 467
Likes: 47
Drifting
Joined: Sep 2014
Posts: 1,924
Likes: 392
From: Atlanta - - - - - Save the manuals
Race Director
Joined: Apr 2007
Posts: 11,152
Likes: 890
From: South Western Ontario
Engine speed to the cluster is a pulse signal from the ECM. I'm not sure of the format but probably so many pulses per engine rpm. You would have to splice in a module that counts the pulses and then outputs a modified pulse train to the cluster.
Thread Starter
Racer
Joined: Jan 2020
Posts: 467
Likes: 47
Does anyone know which wire? I can simply measure it with an oscilloscope, easy. Just haven't ever removed the dash and am unsure which wire to probe.
This all surprises me as there are aftermarket exhaust systems such as this Akraprovic that only connects to a single wire in the car to read RPM.
This all surprises me as there are aftermarket exhaust systems such as this Akraprovic that only connects to a single wire in the car to read RPM.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Racer
Joined: Jan 2020
Posts: 467
Likes: 47
Thanks man. I have checked out this video:
Man! What an effort to get to this wire. Can we trace this back to its origin and access it a little easier? Does anyone have a wiring diagram.
I have the rest sorted on my end - in the most difficult case, I will read the signal with an Arduino, modify it, and send it back out to the dash in the modified fashion.
Thanks for your help.
Man! What an effort to get to this wire. Can we trace this back to its origin and access it a little easier? Does anyone have a wiring diagram.
I have the rest sorted on my end - in the most difficult case, I will read the signal with an Arduino, modify it, and send it back out to the dash in the modified fashion.
Thanks for your help.