So i was pretty annoyed after i bought my tach then searched around on here and relized i would need an adapter, then i searched some more and found that the orange and white wires on the computer were a tach signal.....well why not just connect those two to my tach....it will f*** the computer up right?? wrong....what you do is this....
whats going on here is you hack into the white and orange wires then put in the diodes, the diodes only allow electricity to go one way through it, which means the signal from the white wire wont go into the computer through the orange wire and vice versa. Make sure the line on the diodes is on the side going to the tach not the computer. You can get diodes at radio shack etc.
Not to ruin your day after you went to all that work (buy the way, nice thinking, on the zenpfher [one way] diodes) but theres a lot eisier way to do that. I had my tach wired to the computer basically the same way you do on the Sunbird I used to have. All you need to do is find the one signal wire coming off the computer, and use a vampire tap to hook the tach wire to it, one crimp and your done. (then wire to power, ground, and ilumination wires as you see fit) You really don't have to worry about signal problams or direction of flow that way because the tach doesn't output any signal, and your not breaking to connection to the computer. Just to let you know if you ever put a tach in another car. (you could always solder, but taps are just way easier)
there is no one signal wire on the 2.2 because there is two coils and no tach originally in the car
umm. sorry. but some 2.2's did have a manual trans and therefore a tach. i know in my 2.2 i have a OE tach for my automatic and it works fine. so that means theres a tach signal. but the above theory. have you actually tried it. cause i was under the impression the ONLY way was to buy an adapter.
did you try this and if so what size diodes did you use
a tach signal is just a fuel signal basically....thats why with remote starts you hook up the tach wire to any fuel injector on the non common side....Technically all you have to do is hook to any signal wire the just hook up ground , 12v, and ignition as usual...and illumination if you want.
i have this hooked up in my car now, and i just took the diodes out of an old deck i had layin around, i i have an auto so im pretty sure there is no tach signal from what ive read on here
im not sure about your motor but if there isnt a tach wire you should be able to hook it up to the uncommon side of an injector...i dont know if this will be easy on your engine....
If I recall correctly, the wiring diagram you have shown above is exactly what someone showed was inside an Autometer tach adapter...
To the original poster, that will definitely work.
I was happy when I heard my car ran 10s. Then I found out that was 0-60.
J H wrote:If I recall correctly, the wiring diagram you have shown above is exactly what someone showed was inside an Autometer tach adapter...
not really. the autometer and msd units hook up to the coil hot, which is the wire that feeds all the power to the coils. it senses the load pulsesand converts that information into a square wave signal.
car audio noob since 1984.
John Sheppard wrote:i have this hooked up in my car now, and i just took the diodes out of an old deck i had layin around, i i have an auto so im pretty sure there is no tach signal from what ive read on here
I have an auto also. and i put an OE Tach in my cary. all i did was put it in and plug it in. There IS a tach signal in all our j-bodys. just cause you dont have a tach in your car dont mean you dont have a wire for it. its there. trust me.
just like someone here said, it's the uncommon wire on the injector, and it's going to be measured in AC volts, not dc.
Wojo is right, there is a signal wire in all our cars, how do you think the ECU knows the coils are workin? You can't run a tach off of injector wiring. The ECU also needs the tach (or rpm) signal wire to control the stock shift light, and auto or not, the car needs to know what rpm the car is at. The only reason you would need a tach adapter, is if you don't know enough about wiring to do it yourself. The original poster obviousley knows enough about electronics, he just did it the hard way because he overthought things, which happens when you know a bit about something. BTW the tach signal wires in our cars use the same signals aftermarket tachs use. Its the same signal that you'd get from the ground wire on the coil of old distribture equipped carburated cars. (where you hook the tach to).
so you can run an auto meter tachometer off of the injectore becasue i did it and it seemed to work
Alright Weebel... so, could you explain how to do this without diodes and by doing it "the right way" ?
weebel your wrong cuz you can use an uncommon wire on an injector....i know a little something and thats the easiest way to get tach on ANY car! If the injector isnt reachable you can get it from the coil...just test it with AC like lanman said all you have to do is rev the engine if the A/C goes up you got your tach wire. TRUST me it works....
OK, if you got it to work off the injector wiring I stand corrected, kinda strange, but if it works, thats all that matters.
As far as doing it without diodes....all you need to do is tap the signal wire from the tach into the tach/ppm signal wire on the car, thats it. Knowing where the signal wire on your car is takes some research and most people don't know its there. For Example, on 2.4's im pretty sure it's the white wire with the blue stripe going to the ICM, but I'd have to double check to be sure. The signal is just pulsewidth, you can make the needel on a tach move by tapping the signal wired rapidley on the positive battery terminal, there's nothing digital or computerized about it.
I'm not trying to bash anyone, this is just something I researched the crap out of when I installed the tach on my old car and figured I'd try to help out and make things easier for anyone else doing the same thing.
I believe it's the orange wire on 2.2's. right? And what's a vampire tap?
Man, there has been sooooo much talk and debate over a tachometer in the 3rd gens. I've installed three different tachometers, and three different tach adapters, and here's what I've found:
1. Some tachometers will simply connect to one of the ignition coil wires with no adapter required. The tachometer must have a 2-cylinder setting and be very sensitive to voltage fluctuations in order to work. My Summit tachometer did
not work this way (not sensitive enough), but my Equuis did. The problem is that the 2.2L has two ignition coil packs, and two signal wires, just like John Sheppard says. Some tachometers will need a true 4-pulse signal to read the correct RPM. Autometer tachometers (not the Auto Gage models) can be calibrated at the factory to run off one ignition coil wire with no adapter required. I think it's a no-cost calibration, but you have to send it to them for service.
2. Retail tach adapters out there from Summit, RK Sport, and Sun are basically the two diodes John described pre-wired in a little plastic case. The problem with these (and with wiring in your own diodes) is that you're still working with a very weak signal from the ECU. Some cheaper tachometers, like my old Summit, could not read that weak signal very well. MSD's 8920 adapter, however, is a digital circuit that senses the ignition wire and completely recreates a new square-wave tach signal - it even tells the difference between single- and dual-pulse ignition packs. This adapter will drive just about any tachometer out there. IMO, it's worth the extra money since there's no guessing.
3. The factory tachometer signal wire isn't any better or easier to use than the no-factory-tachometer ignition pack wire(s). The factory tachometer takes the same weak dual-pulse signal and uses that to calculate the RPM. Tapping into this factory tach wire has the same challenges described above. Your tach might be able to use it, but some tachs won't.
You can either experiment around with your tach to see if it will work without an adapter, but be prepared for some troubleshooting, or you can make/purchase an adapter. However, the homemade diode trick and the cheaper retail adapters still might not work with your tach. The MSD adapter is the most sure-fire solution I've come across. It's the only adapter that could drive all three of my tachometers. Autometer tachs also work very well with no adapter required, but you have to send the tach to AAutometerto be calibrated at the factory first.
Another solution is to use a signal-sensing tachometer, one that features a trigger sensor that attaches to one of the spark plug wires. My Equuis came with a plug wire sensor, but I didn't use it since I already had the MSD adapter. In theory, a tach with a plug wire sensor should work on any engine that has a spark plug wire (won't work with coil-on-plug engines).
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Wow bro... just wow. Thank you for your input immensly!!! Sounds like you know what you're doing and it's saving me from making any mistake from screwing something up! You are the man!
i tried it John Sheppard's way and have a huge difference in RPM between the daah and Autometer Tach!
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Tapping a fuel injector is a bad idea.
1. Unless you can configure the tach to display properly for a single cylinder engine, you're not going to get a proper readout.
2. Your tach will display 0 any time you coast due to injector cutoff.
2002 Cavalier 2200 5spd
A vampire tap is used to hook into wires without cutting them. There commonly used by people that pull trailers with there pickups, because they need to hook the wires for the trailer light plug into the stock lighting system without cutting anything.
You basically slide one side over the wire you wan't to tap into, and the other wire in the other side. (wires are now parrelell), then you squeeze the thing together, wich causes a peice of metel inside the tap to penitrate the wires just enough to make a connection between the two, then you clip the protective cover closed and your done. You can buy them anywhere. I'm actually pretty sure they come with tach adapters when you buy them.
this may sound like a redundant question, but but which wire(s) do i need to tap a tach adapter into? both the coil wires or just the ref sig wire? or am i completely off track?
Project Resurrection is in full swing!
if you've got the msd or autometer tach driver, it should have instructins for a dis setup. if not, i'll try to find mine to get a pic up.
car audio noob since 1984.
