I want a simple device that I can't find anywhere. If you got any leads I'd appreciate it. I want to have a sequential shift light go off at a different RPM depending on the gear I'm in. I also want a low-rev light to go for a different RPM for each gear. Right now my solution is to use mechanical switches that knows what gear I'm in. Then the switches control relays that selectively activates different sequential shift lights based on what gear I'm in. For the low rev warning light, I use MSD RPM switches triggered by the gear position switches. This solution works but is quite clumsy. A standalone unit would be nice

Dang man, your getting a bit complicated here aren't you?

Why do you need a light to tell you when to up/down shift. I understand a shift light in a 1/4 mile car, but other than that, why would anyone need a shift light?

And what are you doing you need a shift light for every shift/function?

Just wondering? Autocross?

What you described is probably the simplest way to go about it. You will need some sort of sensor to know which gear youre in, along with an RPM feed. The gear detection is where you get into trouble.

I think if you can figure that part out ure ok. I dont have a solution, but sounds like you might? You mentioned mechanical switches.

I made something similar to what you describe for my car, I'm using mechanical switches. Its a gear indicator/ shift light. Everything is handled by one microcontroller.



I programmed the chip to activate the shift light at 5000 RPM in any gear (flashing the gear number). However, by reprogramming with a bit of new code it could have a unique RPM shift point for each gear since the chip already knows what gear the car is in anyways. I'm interested, why do you need different shift points for each gear?

Could you guys elaborate on the Mech. switches??/ Im unfamiliar with them. How do they work? Thats a very clean setup you have, please explain how you did it.

Thanks! In my setup, I mounted 4 micro switches on an aluminum plate that I mounted on my hurst shifter:





I don't have a pic of the circuit board I made, but the microcontroller has 4 inputs for each of the switches, so it can determine the position of the shifter. When in gear, the chip outputs the gear number to the seven segment display.

It also has one input for the tach signal from the distributer. Through coding, I have it set up to determine the engine RPM from that signal and then flash the display at a desired RPM. I just finished this project about a month ago, I'll get some driving video of it in action as soon as the car goes on the road.

You have some serious skills man.....

Thank you for the awesome response. I'm going to respond to the questions in the order presented.

I was using shifting as an example because I thought that it was universally known that the upchange and downchange points depend on the torque curve, gear ratio, rear end, and tyre size. If you want to discuss this topic in particular then create a new thread in the appropriate forum. Link me and I'll be glad to discuss in depth with you.


I was referring to more general applications. For example, each gear needs a different timing curve. Nitrous and other auxiliary functions also come on and off at different RPMs for different gears. Electric cooling fan should be turned off at higher speeds because the spinning fans actually create more resistance and should be freewheeling. Boost level needs to be lowered in low gears, and in higher gears you can go full boost and let the car eat.

So as you can see, it's not just shift light. There are a lot of different things that need to be controlled based on gear and wheel speed.


The best way to describe it is with this: http://www.msdignition.com/rpm_7.htm

With the window switch, you turn something on at a certain RPM, and turn it off at another RPM. The example they used was nitrous where you want nitrous on at a certain RPM and off before redline. Clearly you don't want nitrous in 1st gear so the switch needs to be bypassed in 1st gear. This adds another level of digital control over the off-the-shelf stuff.

Replace nitrous with boost controller, shift light, timing advance, or anything else you want.

That's the general answer.

I'm using this in conjunction with gear selection and possibly a GPS (this part I will definitely need help) to let me know what I need to do for a specific place on the track. Some corners you shift early and others you hold the gear for as long as possible.

Also for 1st and 2nd gear I want to retard timing a little bit to reduce wheelspin. On 4th and 5th gear I want to advance timing as much as possible so it can go to top speed.

On shorter tracks I'll bring 3-5 down a little bit to help rear wheel torque and back off timing a little bit to reduce wheelspin and engine stress. On longer tracks I need to bump gearing up as well as the rear end for top speed.

The gearchange point for each setup can vary as much as 800-1000RPM depending on the corner, the gearing, and if I want to change up or hold the gear for the next corner.

That's the specific answer It's just a hobby to keep me out of trouble. I'm not competing.

This is excellent, and exactly what I'm looking for. What's the hardware you're using and what interface are you using to program? Care to spread the wealth of knowledge?


I can get a digital gear indicator. That's not the problem. The problem comes in when I want to output a digital signal representing the gear so I can control something else.

Right now the best I can do is to use the gear position switches to control a multiplexer that routes tach signal to redundant controllers, and each controller is set to a specific RPM window.

This is really silly because I have 4 or 5 of the same controller. Perhaps a better way would be to generate an artificial tach signal based on the actual tach signal and gear position?