Fronzizzle

I know that some of this has already been covered, but I’m trying to get multiple things done at once and I’m not sure how to proceed.

My car is a 1985 Camaro, I upgraded to the 1227730 ECM out of a 90 – 92. The transmission is the stock 700R4.

Right now, I have no vehicle speed sensor hooked up to the ECM. That is one issue I want to fix.

The second issue is, I’m also installing a new gauge cluster, an aftermarket set from Autometer. This set came with a new speedo sending unit. It might be this one (Autometer Speedo Sending Unit), but I don’t have it front of me to verify the part number. If this isn’t the exact one, it’s very similar.

Also, the wiring harness I installed has an electronic speedometer lead. Not sure if that's what I use or not...

I’m not sure how to hook everything up. I’m going to have the dash apart & the gauges out, it would be a great time to wire anything back there I need to – I just don’t know what that is. Do I need to wire any of this stuff together? Or are the two projects (hook up the VSS to the ECM & hook up the new speedo sending unit) totally separate? If someone can help me out or point me in the right direction, that would be much appreciated. Thanks.

Tuned Performance

iTrader: (92)

Since you have a 85 you should have a speedometer cable. You need to get a retrofit vss and run the signal to a Dakota digital sgi-5 . The signal can then be recalibrated for tire size or rear end gear ratio change. The output 1 will goto pin b10 of your 1227730 ecm. You can used the ecm buffered signals or the sgi signal but will have the choice of 2k ppm and 4k ppm.

You do not state witch speedometer you are going to be using. Aother choice if this does not obtain your desired signal to the speedometer hook the autometer Hall effect to the retrofit vss and wire the speedometer seperatly.


http://tpiparts.net/inc/sdetail/7587

Fronzizzle

The gauge I'm installing is an Autometer Cobalt.

Yes, my car is currently a cable speedo.

I've looked at that retrofit VSS, that's what confused me. It screws into the trans, then the speedo cable screws into it. But the sender that came with my gauge also screws into the trans & the cable is supposed to screw into it.

If I'm reading your post correctly, I can go with the retrofit & sgi-5 to get my VSS functional, then use that speedo wire that is part of the ECM wiring harness to run the speedometer - is that right?

Tuned Performance

iTrader: (92)

If I'm looking at the correct install for speedometer you can use the buffered output of the ecm. The directions don't say what signals the speedometer will accept , but the install page shows a Hall effect, ad magnetic pulse vss. You should call autometer or see if there is a calibration for the type of vss.

Your right about reading what I posted correctly. Look at the last picture in this install instructions. The sgi-5 is only needed if you need to correct the signal going to the ecm for tire size change and rear end gear change. I wasn't sure if you needed that or not.
http://www.autometer.com/productPDF/2650-1164-00rB.pdf

Fronzizzle

Thanks for the information.

Yes, I think I would need that - I have changed the rear end gears to a 3.73 (I believe the car came with 3.42), and I'm putting 275/40/17 tires on it.

Not sure what you mean by "what signals the speedometer will accept"? Is that 2k ppm or 4k ppm you mentioned in your first post? I just want to make sure I know what I'm asking before calling them.

Thanks again.

Tuned Performance

iTrader: (92)

The install sheet is vague You will have a magnetic pulse 4k ppm with the retrofit vss. once that goes to the ecm it is buffered to 2k ppm and 4k ppm optical signal. The instal sheet shows it being hook up the way I described but it also shows you can use there hall effect vss. I would hate for you to buy a unneeded sensor.

Fronzizzle

Okay, I think I've got it. I spoke to Auto Meter today, as well as another very helpful company (Speedometer Services in Wisconsin). This is what I found out:

* The speedo sending unit that came with the kit will not provide the right signal to ECM, nor will the output of the gauge provide the right signal.

* According to what I was told, I need a sender that is 4 pulse per revolution & square wave (not sine wave). I assume the one linked to above will work, it says it's 4 pulse per revolution though I'm not sure about the wave type.

So, with this information, I think this is what I need to do:

1) Purchase the correct sender/VSS, hopefully the one above.
2) Purchase the Dakota digital sgi-5.
3) Wire the output of the new sender/VSS to the Dakota unit, then wire the output of the Dakota sender to pin B10 of the ECM.
4) Run the Speedometer Output wire in my ECM harness to the speedometer.

I think this would give the ECM the correct vehicle speed signal, give me the correct speed on the speedometer and the ability to calibrate it for the different rear end gears & tire size.

Does this all sound correct? Does anyone know if the sender/VSS listed above is the correct square wave type?

robotic_junky

The Cobalt Speedo instructions says this:

" The speedometer is designed to operate with an electrical speed
sender. The speed senders signal pulse range must be between
500 and 400,000 pulses/mile. Any speed sender or electronic
module that meets the following two conditions can be used:
• Pulse range generated proportional to the vehicle spee
d
• Output within the voltage ranges listed below:
2.0 to 16V peak (Square Wave), 3 wire
2.0 to 120V peak to peak (Sine Wave), 2 wire"

You could buy the VSS 4k ppm, like Tuned said. Then wire it to the ECM. Then wire the Speedometer output (B11) from the ECM to the Cobalt Speedo. Then calibrate the speedo it self. If you have the right drive and driven speedo gears in your transmission. Then you won't need the SGI-5.

http://www.austinthirdgen.org/mkport...F_and_vin8.jpg

Fronzizzle

Thanks for the info.

Is the SGI-5 just to make sure the speedometer is correct, then? Is it not needed for the ECM to measure the speed correctly? Or does that not matter as much having the speedometer be correct?

robotic_junky

SGI-5 "could" make the speedometer or ECM read correctly, but I don't think it is necessary if you have the correct drive/driven gears in the transmission for your rear ratio & tire size.

I just noticed you said in the first post that you already have a vss that came with the aftermarket speedometer.

You could do what I said in my first post or you could use the vss that came with the aftermarket speedometer with the SGI-5 to break down the 16k pulse down to 4k for the ECM, but then you'll send 4k from the ECM to the speedometer or send 4k from the SGI-5 to the speedometer (since the SGI-5 has 4 outputs).

Which option is better? After thinking maybe the second option, since you probably don't want to mess with the drive/driven gears in the transmission every time you change tire size or rear axle gear ratio. The SGI-5 would help you adjust if you change things.

Fronzizzle

When I had my transmission & axle gears rebuilt, they changed out the speedo gears to get the speedometer close. It's not exact, probably off by a mph or two. Since then, I've changed tire size. Not sure how much of that can be fixed by just running the gauge calibration versus what the SGI-5 can fix.

I'm inclined to go with the VSS above, once I get this set I have no intention of ever changing the gears or tire size again.

Fronzizzle

I have another question regarding all of this. I hope I can explain this correctly...I'm going to leave out the SGI-5 for now to keep things simple.

My ECM wiring harness has two wires (yellow and purple) that I wired directly to the VSS - this works fine as I can get a vehicle speed when I data log.

My new speedo & gauge cluster came with a whole wiring kit. Part of this kit is a plug that has a long purple & yellow wire already on it so you can wire it directly to the VSS, which I don't need to do. The gauge side of the purple wire goes to the speedo, so I know I can hook my wire from my ECM to that. However, I'm not sure what to do with the yellow wire. As far as I can tell, the only yellow wire on the gauge side has a ring terminal on it so it can be hooked to a ground. I think that means I can not worry about hooking the other side of the yellow to anything, right?

Tuned Performance

iTrader: (92)

Is this the autometer gauge that the PDF instructions are for ? The speedometer would need a ground and as far as the vss signals from the vss the purple wire is ground and the yellow wire is the magnetic high signal.