Maybe I should post this here.

I need a VSS signal for my '730 ecm on a car that has a cable driven speedo (with no vss out at the cluster).

Will this work ?

http://www.summitracing.com/parts/DAK-SEN-01-4160/

I know the '730 can take a 4 or 8k PPM signal.

-- Joe

 

I wasn't sure on the 8K input to the 730 but that is a good price for one.
I never tried setting the bin to 8000 to see what it would read (or is there a hardware setting?)

This is the one I use (4PAC) costs a bit more but can screw right onto the 700R4 so I went with it.
http://jagsthatrun.com/Pages/SpeedSe...eedometer.html

 

I think the '730 takes an 8K on one pin, and 4K on another pin.. ?

I'll have to re-read the schematic.

I could use any transmission combo eventually, so since the cable connection is the only thing that is fairly universal I need something generic.

-- Joe

 

I've read recently of a guy using a Jeep VSS that is 8ppm, he set the bin accordingly and says it works fine.

You could also modify the speedo for an optical VSS, setting the bon accordingly for that and go that route. That's what I did in my Datsun, using $59.

 

Check this place out. It even explains some of the different VSS.

http://www.jagsthatrun.com/Pages/Spe...eedometer.html

 

You mentioned using the '7730 ECM, but not the code mask. On $8D the optical (digital) input is 2K PPM. The magnetic input is 4K PPM. Only the magnetic input is programmable via the calibration for PPM rate.

You can patch the code to change the hard-coded optical constants for other PPM values. 8K PPM is do-able, but need to be within reason for the PPM pulse rates.

Also, the VSS pulse stream outputs are only available when using the magnetic input. This is true of all '7730 code masks as it is a hardware item.

The sensor you show appears to be Hall Effect, which is a digital output.

RBob.

 

Hrmm. I can't find any documentation on it, even on dakota's website. Just says GM....

Yeah I'm using $8D.

I need a VSS input.. somehow.

-- Joe

 

Also FYI, when I was building my bench I found that the Mag input is sine wave, optical is 5 V pulse.
For $35 and someone has made 8K work changing the bin I'd say go for it.
Jp

 

Now I don't know what works with what...

ugg..

-- Joe

 

That unit is an AC sine wave so you should be good.
http://www.dakotadigital.com/PDF/SEN-01-1.PDF

 

This is what jagsthatrun.com says you'll need. (I know it's kinda high $82.)
3.Part # 4PAC. Four-pulse sine wave.

 

So If the ppm is switched to 8k in the bin, is there like a limit? If it uses a 8 bit integer, I'm thinking 114.8 mph?

-- Joe

 

im pretty sure there is a ppm limit to what the 7730 with 8D can use from a magnetic speed sensor.
im running a 700 from a pickup and have the 40 tooth relucter.
i tried to input the VSS directly to the ECM. it can set it up in the bin just fine, but it doesn't work very good.
i forget the exact speed, IIRC up around 55~60 the speed reading from the ECM starts dropping. the faster i go, the lower the speed the ECM reports.
as long as im running below where it starts acting up the ECM speed reading is fine.
if someone would do the math to find out what pulse per mile im getting, 2.42 rear gear, tires ~ 26 inches tall X 40, that should give you an ideal how high you can go.

 

That would make sense DENN why they have hardware dividers for the PPM. I would think 128 MPH would be the max but never looked into it.
Might have to fire up the bench and play with it this weekend.

These are set by three bits in the bin to configure the input.
Divide by 1 (ie for a 4000 ppm VSS)
Divide by 9 (36000 ppm VSS)
Divide by 7 (28000 ppm VSS)
Divide by 11 (44000 ppm VSS)
Divide by 6 (24000 ppm VSS)
Divide by 10 (40000 ppm VSS)
Divide by 8 (32000 ppm VSS)
Then there is the PPM setting in the bin as well.

Overall the 4PAC may be your best bet, I've never had a problem with mine since 04.

 

Now I'm going to have to test this cuz its bugging me.
I could almost swear I've read higher MPH but can't find a log to prove it.
If that is true then that will be added to the list of code changes to work on next.

 

I have not looked at assembler in 10 years. My calculation was based on the theory that it took a 1 second sample rate, and stored it in an 8 bit integer. It might not even come close to working that way.

But then again, when you consider how the MAF works on the '165 ECM, maybe it's nearly identical code. It would make sense that 255 counts at 8,000 PPM = 114.8 mph.


Too bad nobody could convert $8D into commented C code, so I could play too.

-- Joe

 

The hardware divisor is only for the VSS output streams. It doesn't affect the internal to the ECM firmware MPH calculation.

The output streams are for the speedometer and cruise control.

RBob.

 

The TPI '165 and TBI apps use the 4-out box don't they. If I recall, the VSS is 4PPM and the output to the ecm is 2PPM. ??

What is the "optical" VSS? Is that the output of the cable-fed in dash cluster on the camaros? Strictly speaking thirdgen fbodyapplication, is ALL of the electronic transmission mounted VSS senders magnetic?

-- Joe

 

When using the transmission mounted VSS, yes. And yes to 4K PPM from the VSS, and then 2K PPM to the ECM.

Optical is 2K PPM, used in the cable driven speedometers. This was also used in many other cars & trucks. It picked up the reflection of a bar (2-pole) in the speedometer head that spins with the cable.

All of the 3rd gen f-body trans mounted VSS are 4K PPM (4 pole) and magnetic.

RBob.

 

Thanks.

You know, it's starting to get rough when I'm forgetting more than I'm learning.

With the number of magnetic speedo's I have I wonder if I couldn't make my own silly adapter.

-- Joe

 

im still using a DRAC from a chevy pickup to output the speed reading to the ECM, speedometer, and cruise control. im on my second DRAC, the first one quit after a couple of years. i think a short on the ground to power is what killed it.
JP, i've played around with the hardware dividers when i tried to use the truck VSS as the input to the ECM. i don't remember if changing them made any difference right now or not, my sometimers at work, LOL.


anesthes, im thinking out loud here, the 7730 can output a speed reading much higher than 128. before i got into chip tuning and still had the T350 trans with a speed cable, i cobbled together a speed sensor from a ford and put it inline on the speed cable. i used my snapon scanner and with the car up around 80 MPH the scanner was showing 160~170 MPH.
when i first put the 700 in i wired up the speed sensor and found that at around 15-20 MPH the ECM thought i was running 255 MPH. that lead to a locked TCC as soon as the trans went into second. thats one of the main reasons that i got into chip burning. turning off VATS in the chip was the other reason.
as for the ECM speed reading going lower than actual speed with the car above 55~60 and dropping even lower as speed increases when i had the truck magnetic speed sensor hooked to the ECM, i don't know. i always figured it either had to do with it over loading the speed buffer thats built into the 7730 or the signal strength too strong. i've mentioned it in a few posts here.
(light bulb moment) but now that you mention it, it makes sense that it has to do with the counts maxing out too soon for turning on the light switch
for several years i've wanted to cut all but 4 teeth off a 40 tooth relucter and try it on my car, i just haven't gotten around to it yet.