PClink vehicle speed reading drop out

[iceman]

Hi,

Project vehicle/ECU’s:

Link G4+ Storm ECU and standalone HGM Compushift 2 TCU. Ironing out wrinkles with a Nissan Z32 with warm GM L98 LS and 4l65e conversion.

Back ground:

I now have the Nissan OEM speedo (AC sine wave) now reading properly using a reproduced 4L65E VSS (reluctor) signal supplied by the CS2 TCU, using a Dakota Digital SGi5 unit. I had no success trying to convert the signal through the G4+ without the SGi5 unit, even when using a grooming circuit I and others have previously had success with on other projects.

Problem:

While the OEM speedo works at all vehicles speeds reached so far (circa 140km/h) using 1 of the 2 available TCU repro VSS signals, I have noticed that the LR speed reading in PCLink from the second VSS signal, consistently drops out to 0 when 80km/h is reached and starts incrementing up in speed again from there, eg: 100km/h reads as 20km/h.  This VSS signal is 40 pulses/revolution.

I have tried tapping into the same SGi5 output signal that the speedo is getting but it upsets the latter with no speedo/PCLink reading as a result. I have tried turning the pull up on and off and swapping the signal active edge without improvement. At 40ppr, do I need to scale the signal back with another SGi5 or similar for the G4+ to read LR speed over a more practical vehicle speed range?

Cheers.

 

LS conversion.pclr

[Adamw]

Based on the calibration number you have in that map I would say you are well beyond the frequency capability of the G4+ digital inputs.  They were quoted as 500Hz max but they would often work up to around 1500 depending how many other interrupts were working. 

4-10pulses per rev would be more typical.  

[iceman]

Yes, thanks Adam, as I suspected. Unfortunately the older 4 speed GM autos like the 4L60/65Es' all have 40ppr square wave VSS signals OEM as suspect the newer autos will be similar. If anyone else using one wants to tap the signal for a DI speed input, the output signal will need considerable scaling down for this ECU to use.

To result this, the Dakota Digital SGi5 (now superseded with a speed and tach correction function in the same unit) I was using to get the OEM speedo functioning on output 3 with minor onboard  calibration, has 4 other scaled outputs available. Output 4 in this case is a 4K ppm square wave output which I was able to use simultaneously with output 3 without any cross interference between the speedo and PCLink vehicle speed signals. Output 4 could be minor calibrated from there using the PCLink scaling function on the  DI I used.

Bottom line, both speedo and PCLink LR speed working (past 80km/h) now functioning as they should with one DD SGi5 device.

Cheers.