Graz (R8 unit) and LS3 VSS

[Dan Carter]

I have read a lot of discussion about the GM ECM and the need for, or not, the VSS connection. Not sure what the final verdict seems to be despite the guidance from GM itself (not needed, really??).

So the question is: The Graz appears to have its own VSS connection so will the GM VSS connection work from the Graz sensor unit (assuming the number of wires are compatible of course)?

Anyone tried it? My car is hopefully on the delivery truck soon.

:huh:

 

[PeteB]

I've wondered myself if the sensor on the Graziano would work. I used a magnetic speed sensor on one of the driveshaft, but I'm still having stalling issues. If I don't blip the throttle when coming to a stop, it stalls.

 

[Mike]

The GM ECM VSS labeled plug in the wiring harness is expecting a 0-5 volt sine wave. If the Graz's sender unit does output this type of signal you may be okay.

I also tried the 4 magnet drive-shaft device but I'm afraid the resolution was too low. I have since gone to this : Dakota Digital Speedometer GPS Interface Modules GPS-50-1 - Free Shipping on Orders Over $99 at Summit Racing it was on sale but superseded by the "-2" version - more money (see attached user manual). It will do more than you'll ever need, but it worked. And is simple to hook up. No more off throttle, de-clutching, low speed idle stalls... among other low to mid throttle drive-ability issues .

My issue was the lack of a vss sender off a G96.50 trans (it doesn't exist on this Porsche model). The GMPP tune is set up for an auto trans- Quote: "The ECM is programmed and looking for 40 pulses per revolution typical for automatic transmissions". Let's read this again GM - regardless of what you later say in the same document.

The info from GM says you can run without a VSS. Yea maybe you can, but it'll run like crap for a street driven car. GM should be bitch slapped for this misleading information. GM's info sent me on a goose chase at first and then hours of investigation to the truth.

Basically -- my ECM was having time value issues related to VSS input... one of them was a timeout between pulses to declare zero speed --- excellent huh. This explaining why the 4 magnet drive-shaft system worked sometimes and most times not.

The lack of a VSS signal effects multiple tune parameters within the program - it's more than it appears on the surface.

Do I sound a little disappointed at GMPP.... understatement

Your results may vary -- my car now runs great.

 

[Dan Carter]

Mike/Pete

Actually the reading I was doing was your forum heads up on this issue....thanks for that heads up by the way. I have no idea what the Graz unit has for a signal.....but would be nice to find out.

I looked up the Dakota unit based on your discovery and ready to install if Graz will not support the GMPP need.

I have a contact at GM so it's time to ask them about their VSS statement.

In my case, It would help if I could find more spec Data on the Graz.

More fun I wasn't expecting.........

 

[Alex]

you shouldn't need it - i cut it out of my wiring harness with no ill effects.

it does make me wonder though if the gmpp crate enginge controllers are setup differently between version (i.e., different tune) because some people need it and other don't. just like some of their tunes came with rev limiters set and some didn't.

 

[Dan Carter]

GM said the VSS is not required and is optional (we did discuss the install issues many have had with stalling). GM said the TCM should respond to basically the right gas pedal to prevent the stall.............

That being said, does anyone have any spec data on signal output of the Graz unit speed sensor? Could we be lucky enough to have the same voltage, same curve and the same pulses as needed by the optional GM ECM speed input?

Of course Dakota Digital has a converter, which is not self learning so manual programming required, hence spec data for the Graz signal conversion.

 

[PeteB]

GM may claim VSS is optional, but I've got stalling issues. My gas pedal is the one provided by GM with their control package, so it's GM's fault if it isn't the correct one.

 

[Mike]

Ummmm... our cars do not use a TCM (trans control module). This quote is directly from the LS376 install flyer: ""The ECM is programmed and looking for 40 pulses per revolution typical for automatic transmissions".

Optional - optional for what. If it's optional why have it, AND what are the options (i.e what happens) if one uses it or not?? Gm's response to you is so technically lacking I don't know where to start.

Is the Graz a two wire sender, if so just hook it up and see if it works. The ECM just needs to know that the car is moving and not sitting still. If the ECM is seeing an incorrect speed - it's better than no speed. And if an incorrect ECM speed bothers you - it can be corrected later via tuner. This does not effect the speedometer readings - completely different circuit.

Will somebody with a Graz trans jump into this thread and provide an answer. There has to be somebody who knows this - If I had a graz I'd google it till I found it, but I don't have a dog in this hunt.

GM said the VSS is not required and is optional (we did discuss the install issues many have had with stalling). GM said the TCM should respond to basically the right gas pedal to prevent the stall............

 

[Dan Carter]

Sorry for the confusion on the TCM abbreviation ......I was referencing a Throttle Control Module...... GM would not respond to what if any algorithms in the ECM actually uses a speed input, hence why is it "optional". I sent a signal output question to Graz factory, and while responsive with some data, nothing about signal output parameters.

We know what GM input needs are, so once I get to the point I am ready to wire and connect I will connect GM to Graz. I am taking a field trip to Audi parts counter once I get the Graz "VSS" part number to "research".

Failing all this, I will go trial and error and if required try the Dakota Digital signal converter until the GM ECM is happy.

Graz units seem to be a more popular purchase so this GM Graz combo will need to resolved for current and future builders. Is GM the only ECM with this problem.......or are we GM users just lucky?

 

[PeteB]

Will somebody with a Graz trans jump into this thread and provide an answer. There has to be somebody who knows this - If I had a graz I'd google it till I found it, but I don't have a dog in this hunt.

Unfortunately, there's not much info out there about the workings of the Graziano. People who own Audi R8s and Lambos aren't generally the type of people who wrench on them themselves.

 

[Dan Hanisch]

I have the Graziano in my GTM and have been contemplating the speedo signal as well. I was planning on using the GPS module, but this raises a good point as I have stalling issues as well. I have the gear that was used for my G50, but you can't use the axle protectors if that is in place. The other option was to use an ABS sensor, but beyond that, I don't know.

Edit: I put in a message to my tuner NicD, who hopefully can provide some insight as well.

 

[Dan Carter]

Good idea to engage with a tuner. I was planning to attend a tuner school in Florida soon as well. Maybe make a little cash on the side (got to pay for this expensive hobby somehow...ha).

I will be interested in what they say. Wonder how to read the ECM before it's even installed.

 

[Dan Hanisch]

Well, I heard back from Nic and he states:

"And yes, you will want to do something for the VSS signal, it's not as bad on the newer ECMs like yours compared to the Gen3 PCMs but it still helps to have something even if it's not totally accurate. I've used ABS sensors before wired into the VSS signal."

I got the Dakota Digital unit as well as will be looking into digging out the ABS wires and hooking up to that.

 

[Dan Carter]

Dan. That doesn't surprise me one bit. My Graz has not arrived yet. Do you by chance have the part number off a Graz speed sensor? I want to run some spec numbers with one........ I don't think they are that expensive. I think VW uses the same pickup.
:idea:

 

[Dan Hanisch]

The Graziano does not have a speed sensor, that's the problem. If I'm not mistaken, the Lamborghini uses a sensor on the front diff or wheel hub, but not what's a part that would go into either of our cars. The LS ECM can be programed for whatever the pulse per revolution, so you could adapt the same as someone would use with a G50 with the gear and pickup. My GTM came with that setup and I can go see if I can find the old sensor to see if there's a part number on it. Since the Dakota Digital unit outputs a waveform that is acceptable to the LS ECM, you could just use that too. I may try both. I have the ABS sensor already wired and I have the GPS unit in the box in the garage. I'll report back either way.

The speed sensor for the Lamborghini is: 4E0927804F

I'm not sure how you would adapt that though. It's marketed as an ABS sensor too, so that's what lead me to believe that the Lamborghini just uses the wheel sensor and has nothing that can be mounted on the transaxle itself.

 

[PeteB]

There is a shaft speed sensor on the Graziano.

 

[Dan Carter]

Interesting on shaft sensor. Any idea what it's sensing?

From the many experiences it Seems best to give the GM ECU a speed input if nothing else, so it knows the car is not moving.

While not on my configuration list, I presume if anyone installed cruise control you have to receive a 4000 per rev input to the ECM, hence a signal converter or the GPS signal to provide a correced pulse. This may be too complex for now.....so for now just getting a pulse will work........

Looks like we need a long term build solution for LS installs.

 

[Alex]

Looks like we need a long term build solution for LS installs.

It should work fine without it - I've got 3 GMPP LS3/525 engine controller kits and in all 3 I removed the VSS. I just fired up the 3rd one over the weekend in my 917 and have no issues with it.

Makes me wonder if those having issues with the VSS are using one with a different tune.

 

[Dan Carter]

This gets better by the day. I am a long way off from a start, so I truly wont know until I hit that button and try to drive it.

Alex, did you tune the ECU or take the GM program as is? Every hotrod tuning book or article I have read on this subject says the ECU needs that signal, that seems odd considering your experience.

But if it worked for you, I will cross my fingers and hope it works for me as well. GM says good to go (and we all trust GM, right?).....guess I will find out soon enough.

 

[Alex]

I did dyno tunes on all of them (or will do in the case of my 917). It's an average middle-of-the-road canned tuned. One of them had no rev limiter set and was pulling massive timing because knock sensitivity was way too high.

But they all started up and idled fine and didn't have any weird issues like random stalling with the as-provided tune.

A canned tune is a good starting point but I would definitely plan on getting a dyno tune to maximize the potential of your setup.