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  F40 VSS Calibration For Speedometer or 730 ecm Using the SGI-5c by Dakota Digital

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F40 VSS Calibration For Speedometer or 730 ecm Using the SGI-5c by Dakota Digital by Joseph Upson
Started on: 01-19-2011 08:36 AM
Replies: 5
Last post by: Joseph Upson on 01-19-2011 03:33 PM
Joseph Upson
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Report this Post01-19-2011 08:36 AM Click Here to See the Profile for Joseph UpsonClick Here to Email Joseph UpsonSend a Private Message to Joseph UpsonDirect Link to This Post
In my circumstance using code59 with a 730 ecm as well as for general engine management, a speed signal is crucial or at least very helpful for many ecm functions; boost vs. mph, decel, fan control, shift light, lean cruise mode, etc.

I'll post the specifics in brief form.

Make sure you have magnetic sensor use selected in the bin.
If you are using code59, the ecm is to be wired as a 749, but the vss part should be wired according to 89-91Chevy Beretta specs across B9, 10 and 11. B11 being your 4000ppm output to the odometer. The 749 diagram only shows a vss input from the DRAC at C6 and it did not register a speed in the datalog when connected to the SGI unit when I tested it (Because it is intended for the optical speed sensor).

Although the instructions for the SGI-5 indicate you can adjust speed up or down by simply pressing the up or down buttons I observed no response during a datalog while attempting to do so.

A Dakota tech stated I would need a "pullup" for the signal into the ecm. He suggested a 1k-10k ohm resistor between 12v and the vss signal going into the ecm. I used the circuit by Darth since it was already in the car and a little more sophisticated. I confirmed that the pullup cirucuit is indeed required for the ecm to sense the vss signal from the SGI in this configuration.

The settings for the SGI-5 using stock size tires 215/60R15 are as follows:

Set switches #3 and #4 to the on position.
Preset the SGI unit per unit instruction sheet to calibration 9,3, representing a calibration of 2.024, via the up/down buttons.
Use "OUT4" as your signal source.

I checked the above against a GPS reading and my speedo read right on target plus 2 mph for human error in reinstalling the gauge needle after the raw F40 vss signal violently shook it off the dial. It reads on target in the ecm.

The above configuration requires TWO pullup cirucuits, one for the signal into the ecm and one for the signal out of the ecm to the odometer.

I mentioned this in a thread on the topic a long time ago, and will do so again here. If you put together your own wiring harness, make sure the wires from the vss sensor to the unit are twisted together in the same manner those from the CPS sensor to the ignition coil are.

My odometer needle swings smoothly, I have observed none of the bouncing/ jumping that some have complained about after using the SGI to calibrate their odometers.

If you're using the more common bin options (Beretta A1 for example or TGP 8F) you will need to set the IP divisor in the code to 0 or 1 for proper output to the odometer, then the road speed constant will need to be set somewhere in the 120,000 ppm range as 4000 ppm setting for whatever reason with the 4000 ppm input to the ecm from the SGI unit is not enough.

Next is the Digital Cruise control.

I used an AR coded module. Some have used modules from trucks but the one I retrieved from an 96 S10 did not work. I noticed it is larger than the AR module which my be a point to consider in choosing a module that does not have the AR code, in other words, avoid the larger size unit.

The signal for the cruise module can be fed directly from the SGI unit output 5, along with Darths wiring instructions.

[This message has been edited by Joseph Upson (edited 05-31-2012).]

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1fatcat
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Report this Post01-19-2011 12:15 PM Click Here to See the Profile for 1fatcatSend a Private Message to 1fatcatDirect Link to This Post
Oh man, I'm going to have to deal with this at some point and it looks like a real pain! What if I was to mount a 4T65 reluctor ring to the jack shaft on the pass side and incorperate a mount for the 4T65 speed sensor into the jack shaft-to-engine block mount? That way I could use the 4T65 speed sensor & wiring and send the signal directly to the pcm just like the factory set-up (factory in a GTP), only it would be relocated to the jack shaft instead? Any downfalls to this approach? I realize the accuracy would be less than perfect around turns due to the differential, but how much of a negative impact would it have?
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lou_dias
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Report this Post01-19-2011 12:34 PM Click Here to See the Profile for lou_diasClick Here to Email lou_diasSend a Private Message to lou_diasDirect Link to This Post
Ryan (DarthFiero) plugges in a divisor value into the ECM that make my speedo read at 1/2 speed with the F40 on a chip he made for me. No Dakota Digital unit necessary.
His second attempt reported a code 24 error (VSS) so the value was out of range. My speedo is now pegged at 130mph at all times. I'm not sure if it's broken but we've been looking into not needing the Dakota Digital. My unit came with my original conversion done by Archie and was calibrated with a gps for accuracy.

-Lou
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Joseph Upson
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Report this Post01-19-2011 12:42 PM Click Here to See the Profile for Joseph UpsonClick Here to Email Joseph UpsonSend a Private Message to Joseph UpsonDirect Link to This Post
The DRAC module is an alternative to the SGI unit but ultimately a lot of the course of action has to do with the code mask you use, for example, the SY/TY code does not have a vss signal out address because that's taken care of by the DRAC module. It does have three switches that can be set for a number of different vss ppm input rates, unfortunately all of which are less than what I needed. On the other hand, the Turbo Grand Prix code has a working devisor slide to help with fine tuning the vss signal input to a degree.

If it's in the code to allow room for it, you can get the output/input value you need. The DRAC is probably the best way to go if it can be switched for the correct ppm signal you need. I've had the SGI in my possession for years and didn't bother seeking out the alternative approach. So far it works flawlessly.

[This message has been edited by Joseph Upson (edited 01-19-2011).]

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lou_dias
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Report this Post01-19-2011 12:55 PM Click Here to See the Profile for lou_diasClick Here to Email lou_diasSend a Private Message to lou_diasDirect Link to This Post
 
quote
Originally posted by Joseph Upson:

The DRAC module is an alternative to the SGI unit but ultimately a lot of the course of action has to do with the code mask you use, for example, the SY/TY code does not have a vss signal out address because that's taken care of by the DRAC module. It does have three switches that can be set for a number of different vss ppm input rates, unfortunately all of which are less than what I needed. On the other hand, the Turbo Grand Prix code has a working devisor slide to help with fine tuning the vss signal input to a degree.

If it's in the code to allow room for it, you can get the output/input value you need. The DRAC is probably the best way to go if it can be switched for the correct ppm signal you need. I've had the SGI in my possession for years and didn't bother seeking out the alternative approach. So far it works flawlessly.



I should note he gave me a circuit schematic to convets the 4000ppm signal coming out of the ECM from square to sine wave so the Fiero Speedo could read it... Something to that effect. The parts cost me about $10.

[This message has been edited by lou_dias (edited 01-19-2011).]

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Joseph Upson
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Report this Post01-19-2011 03:33 PM Click Here to See the Profile for Joseph UpsonClick Here to Email Joseph UpsonSend a Private Message to Joseph UpsonDirect Link to This Post
 
quote
Originally posted by lou_dias:
I should note he gave me a circuit schematic to convets the 4000ppm signal coming out of the ECM from square to sine wave so the Fiero Speedo could read it... Something to that effect. The parts cost me about $10.


I've been refering to that as a pullup circuit, not sure if it's in error though because it works to magnify the signal from the SGI which is already a square wave output. Cost me about half that to make with duplicates leftover so I don't know that it's the same cirucuit.
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