I copied Mike Davis MAF to SD conversion making an adapter harness like his last winter and this spring, so I can in theory go back and forth between setups, for poops and giggles. Today I finally had it tuned by someone local who is very knowledgeable with TPI (among other things) and has two of his own vehicles built up using TPI setups. He previously did my MAF tune at his place in 2010 then last year I splurged to get it done on a local dyno by him.

The SD tuning went well, got the car to run probably about as good as it should but the speedo didn't read anything. I have my wiring as on the Mike Davis page, A10 on the 165 going to BC6 on the 730 ECM. I didn't have some info with me (my fault) that referenced some change(s) to make in the tuning to let my 2000 ppm VSS work with the SD setup. At least that is how I understand it, that its just a tuning change. The person doing the tune mentioned a previous tune he did of a MAF to SD conversion, the owner purchased a adapter or such from Howell to mount to the tranny or speedo and run directly to the ECM to solve the issue. Not what I was hoping for or thinking of by any means.

From what I have seen, per the notes on Mike Davis' page, there is a change that is made in the tuning "Mag. VSS at 0x18 b6 for $8D PROMS". Also this is copied from a post in this thread https://www.thirdgen.org/forums/tpi/...ensity-my.html by "Grim Reaper": "Airdeano, the switch is bit 6 of byte at location $8018 in the SD eprom. If bit 6 is set to "1" ($40 mask) the SD ECM will assume you are using the 4,000 Pulse/Mile Magnetic Sensor. If bit 6 is not set to "1", then the SD ECM will assume you are using the older 2,000 Pulse/Mile Sensor.

This switch is now defined in TunerCat's $8D TDF, so all you have to do is put an "X" in the Switch Table for the "Magnetic Speed Sensor Installed" if you have newer 4K one or leave it "blank" if you are using the older 2K one. Changing the BIN is like a 2 second change."

I guess my bottom line is how do I explain this to the person doing my tune? I've done research on some of this but not an expert (or anywhere close) at PROM tuning by any means even though I was watching the changes he made trying to understand some of it. I plan to give him a call within a few days while this is fresh in both of our heads and maybe send him (or drop off) a chip or have him burn me one that allows the VSS to read properly, if this is all it takes. Without the TCC functioning I don't want to drive it on the street.

Any help appreciated!

And I have done some searches on here, to find the above info and other bits and pieces. The car itself is a 87' Monte that has a 2000 ppm VSS setup, just like a 87' Trans Am lets say that the TPI setup came off of originally. At least I believe this to be the case for both vehicles.

 

Anyone? Just looking for confirmation all that's needed is in the ECM switches portion (or not) when tuning. Maybe this should of been posted in the TPI or DIY tuning portion.

 

I also have an '87 the wire to c6 and click off the mag sensor in the constant section of the prom.

Because the VSS is on the back of the speedo.

 

Thanks for the reply. I spoke with the person doing my tuning, sending him the chip to make the change.