Many of the tables have a great description under them when I pull them up, but many of them are cutoff. Is there a way to see the full description? Maybe a location other than under the table when it is pulled up? It would be really helpful to see the full description at times. Thanks.
Update to VCM Suite 3.0. The area is scrollable in the newer VCM Suite.
We got this guy Not Sure, ...
Awesome thanks, will do! I also just found them in the help section under GM parameters.
This is the one I was after: VSS Pulses/Mile: This value is used to calculate the speed value for the engine routines and gauge cluster. It is the number of pulses received from the VSS sensor per mile traveled. If you know your gear, tire and location of your VSS sensor you can calculate this value manually.
Can someone elaborate on the manual calulation?
I am not recieving a VSS signal (maybe a very small mph reading at a high road speed). We are trying to feed the 4kppm output from the dakota Digital gauge cluster into pin21/vss high (2001 8.1L/originally an Allison trans but changed to no elec auto, now TH400). We are using a Dakota Digital 16kppm sender to the gauges that can then output 2k or 4k ppm. We have also tried grabbing the 16kppm directly from the sender. No luck, at least at low speed. ECM thinks we are in park/neautral and is closing the ETC, and pulling fuel at around 3000rpms (we are going to try and work around it with p/n cutoff vs. rpm limits, p/n rpm limits fuel until we get a speed signal). We have also ordered a 128kppm sender to try and resolve the problem, but this has prompted a few questions that are bothering me.
Question 1: Is the GMT800 platform and the Allison option causing a problem here? Is the pcm looking for a VSS signal from elsewhere like a TCM or transfer mounted speed sensor? Seems that it would still end up at pin 21 and the values in the speedo section don't look different than a 4L80E file.
Question 2: Will the non-elec trans option fitted with p/n or none still look for a vss signal?
Question 3: Is it as simple as changing the general vvs pulses per mile to 4000? Do any of the other values have to be changed by the same ratio? Will the general vss rev-trans matter at that point? Maybe changed to 1 to base calculations off of the 4000ppm?
Question 4: I have found that most LSX setups are expecting to see 128kppm. Why does that number only show up under vss output pulses per mile- ABS? Why wouldn't it be in some input field so that it could just be changed it to 4000ppm? The fact that it isn't make me nervous about changing anything else. I am not sure how 128k is derived from the vss general pulses per mile and trans-rev.
Dakota Digital 128kppm vss sender did not register either.......? Any ideas?
Can you post your tune?
I would think the dakota digital output to the PCM should be set at 4000 ppm.
I have found that changing the "VSS Output pulses per mile" section doesn't change the readings properly on mine. I have to adjust the "General VSS pulses per"
When I change the 4K or the mile ABS sections I will get weird speedo readings on the truck and also different weird readings on the VCM scanner....
Also, Have you done a segment swap for a manual transmission? Because you are running a non electric tranny, you probably should.
I will post my tune when I get a chance, just on lunch right now. Segment swap was the next thing I was going to attempt if I can find a compatible file.
If the trans diagnostics are turned off will the segment swap still be beneficial? Does it possibly change the pins the ECM uses to look for the vss signal? All we are really looking to get is the vss speed signal from the trans. There are no electronic controls for the trans, or ABS, etc. on this rig. The gauges are not fed from the ECM so I am not too concerned about the ECM outputs, I just want the speed to show up in the scanner and match it to GPS. We can get the Gauges to calibrate directly from the vss, but we can't get the pcm to recognize a signal. We have been using pin 21 for the high feed (there was originally a wire in pin 21, but no evidence of one ever in pin 20 that is called out as the low vss).
We have been told that the Allison communicates through can bus? We have also found some evidence that because it was a 4x4 donor vehicle with the Allison it may have had a transfer case mounted vss that either feeds into pin 16 from the Transmission control module or the vss sensor directly. Anybody have experience with this?
Here is the file we are going to try next. The trans, trans diagnostics, and speedo sections have been segment swapped from a 2001 Suburban 4L80E. It was a 2001 Silverado and Allison. Both 8.1L. Trans diagnostics disabled. Some mods to the fuel cut and the ETC close vs. rpm tables to try and work around the PCM thinking it is sitting still. Is there anything more that would be limiting the throttle body from opening, pulling fuel or causing the vss to not register from pin 21. I am still thinking I am going to have to change the general vss pulses per mile to compensate for an incoming signal, but we are going to try the 128k sender first on this one. Any help greatly appreciated.
The most recent file that we are going to try is attached.
Still searching for answers on how to re-calibrate the "Speedo" section for different trans ppr and vss ppm values. Having difficulty finding a reliable explanation on how the values interact with each other when one is changed and the equations involved.
Can you post up all of the specs. (Tire size, rear end ratio, etc)
Your pulses per mile is considerably different than what I expected to find, but depending on your specs, they might be right.
Yes, the calculations for the speedo section other than the tire diameter and rear gear via the wizard are not done in the file previously posted, I wasn't sure how to do them. I will attach the file with that done to this post. I just figured out how to do the calculations including the speedo drive ratio I believe and have modified that file to reflect them.Can you post up all of the specs. (Tire size, rear end ratio, etc)
Your pulses per mile is considerably different than what I expected to find, but depending on your specs, they might be right.
29" tire, 3.08 rear gear, 4000ppm rated VSS sensor. I still need to verify the speedometer drive gear ratio that is driving the 4k ppm VSS sensor/Dakota Digital gauge output. Assuming it is a 45 tooth driven gear and a 15 tooth drive gear the values I came up with are in the attached file and the math is below. Please chime in if this seems completely incorrect.
I can calculate the values with the vehicle in front of me using the 16k ppm signal straight from the vss sender if need be (instead of the 4k output from the Dakota Digital gauges, not sure if it is calibrated through the calibrated gauges or a raw pass though signal that is affected by the speedo drive gear ratio and I am not sure what to do if it is calibrated. Maybe put 1 as the value for trans ppr?) and once I find out the actual speedo drive gear ratio if the math I used with these assumed values is correct.
63360/(29xpi)=695.454 tire revs/mi
695.454x3.08=2141.997 value trans revs/mi actual input to HPtuners
45/15=3 speedo cable drive ratio
4000/1000=4 value for vss p/rev-trans from Dakota Digital 4000ppm vss sensor output to be affected by speedo drive gear ratio
4/3=1.333 value for vss p/rev-trans actual input to HPTuners ( affected by the speedo drive gear ratio)
2141.997x1.333=2855.282 value for vss pulses per actual input to HP
3.08 value for final drive ratio
These numbers changed the gear/tire wizard change the tire diameter to 28.98 (close enough I assume)
These numbers are also difficult to enter into the speedo section, but after playing around it took them. Seems that I have to save them one at a time otherwise they mess with each other.
The checks I did:
1.33x2855.282=3806.09 ( close to the sensor 4000ppm) edit-this check means nothing it didn't pan out on a different ratio/ppm calcualtion
2141.997/3.08=695.454 (tire revs per mile and calcs backwards to a 29" tire.)
Anybody know how to calculate this backwards to the vss rated ppm of 4,000?
Seems logical, but the proof will really be when and if the scanner picks up a vss signal and the scanner matches a gps reading.
Last edited by Cheekm; 04-25-2016 at 01:48 AM.
Well,
We were able to lift the 3000rpm hold back in park and neutral, so at least now the motor can be ran up through its rpm range without a vss reading.
The segment swap from Allison to 4L80E with diagnostics disabled seems to have been a success. We have now seen some data although erratic from the vss sensor in the scanner.
The info was seen using a 128k Dakota Digital pulse generator powered by the Dakota Digital controller, but the signal wire bypassing the gauges completely and ran into pin 21 on the ECM. I used the values that I had figured for a 4K pulse and a 45/15 speedo drive gear ratio to try and make the 128K sensor ultra sensitive which it did. It picks up a reading although too high and erratic until the engine revs up a bit and the signal is gone. It peaks and moves around as we move the gearshift from one gear to the next. We found that the tach wire from the ECM to the DD control box is ran right next to the vss signal wire. Right now I am thinking it is wiping out the signal. The owner of the rig is going to reroute the wire and confirm vss signal on his handheld scanner so that we can calibrate the speedo though HP and data log with speed info. We may then back feed the 4k output pulse from the ECM to the gauges instead of the other way around. I am not sure whether the 4L80E segment swap allowed this or the ultra sensitive 4k ppm speedo numbers used with the 128K ppm pulse generator.
Attached is the scan with some vss action and the tune file with the speedo calibration data used to get it.
Can someone explain this parameter a little more clearly? My calculations give me about 2142 trans Revs/Mile. When this value is entered and saved the next time I open the speedo section it is displayed as 2.3860288. Why is this and if it is a ratio what is it in relation to? It obviously can't be 2.386 actual Trans Revs/.MileTrans Revs/Mile: The number of trans output shaft revolutions per mile. This value is used to calculate the speed that is used for shift and TCC calculations. (A tire sanity check value is provided alongside so you can check the trans tire size calibration against the speedo tire size calibration. This is also useful for troubleshooting accurate speedo but trans shifting strangely issues).
I don't know what is meant by "Tire sanity check value" and do not see one displayed alongside? What is meant by this?
I just finished swapping a th400 behind my turbo 5.3 in a Nissan 240sx. I read that the 16k sensor that attaches is in square wave and we need sine wave. Also supposedly the Dakota Digital is suppose to convert it but never seen anyone actually say it works. This is what I have and did and mine works. In 88-90 some Gm vehicles still used a th400. But they had a VSS sensor and 40 tooth reluctor. So i ordered a 40 tooth reluctor from PATC transmission ($60). I went and found a 1988 th400 from a junk yard and bought the sensor for $25. The only place I found the sensor new was on rockauto but its $108 plus shipping. Its showing out of stock now though. Google part # sc191 to see a picture. (do not buy what someone else posted to work on yellowbullet part# 2VSS26. It will not work. Trust me I made that mistake. You will have to obviously change the VSS Pulses Per Rev - Trans setting to 40.000 for the 40 tooth reluctor. When I bought the transmission mine had the Dakota digital vss to cable sensor, but I didn't want to fool with spending money on another Dakota Digital SG5. If you get it working make sure to post up what you did. Good luck.
Last edited by jmac636; 05-02-2016 at 09:32 AM.
Jmac636, what was wrong with the Dakota Digital SGI-5? I've used those in the past and had good luck with them when I needed to convert a square wave to a sine wave or whatever. Apparently the current version is the SGI-5E with a digital display and the last one I used was the SGI-5C without the display.
Reply With Quote