Is it worth changing gears for better MPG's???

[DA BIG ONE]

Good Day!

"I used a commercial VSS re-calibrator to modify vss signal only." Could you be more specific? Jim doesn't mind at all if we mention product names, as long as we're not hawking them.

Hacking the VSS signal looks like it would NOT be a resistor or pot situation - from a quick glance, that signal is a frequency that would have to be multiplied or divided to hack (clarification please).

Blessings!

(signature in previous post)

Ok, It is called and "electronic ratio adapter" (ERA) from ABBOTT ENTERPRISES, INC. Just use your divide ratio between changes match it the switch settings (micro-rockers) and your goos to go.

www.abbott-tach.com or www.atrol.com

[TurboDiverArt]

Ok, It is called and "electronic ratio adapter" (ERA) from ABBOTT ENTERPRISES, INC. Just use your divide ratio between changes match it the switch settings (micro-rockers) and your goos to go.

www.abbott-tach.com or www.atrol.com

I assume you put this in series? Meaning you cut the signal wire going from the VSS to the VSSB and put the ERA in the middle? That way the VSSB knows the actual speed as modified by the ERA but thinks the gearing is still stock?

Art.

[moondoggie]

Good Day!

Thanks!

Blessings!

(signature in previous post)

[DA BIG ONE]

I assume you put this in series? Meaning you cut the signal wire going from the VSS to the VSSB and put the ERA in the middle? That way the VSSB knows the actual speed as modified by the ERA but thinks the gearing is still stock?

Art.

Yes, that's it.

As for engine management on the 1999 6.5 w/NP246 the vss output signal @ pin C-11 from vssb does not connect to pin F-13 (speed signal) @ pcm.

[DA BIG ONE]

JET makes a re-calibrator SCU-2000 that hacks vss only, in a recent e-mail to them I asked if it will function w/NP246, they replied yes.

Their unit plugs into harness at t-case then requires modual to be installed into vehicle.

[TurboDiverArt]

Yes, that's it.

As for engine management on the 1999 6.5 w/NP246 the vss output signal @ pin C-11 from vssb does not connect to pin F-13 (speed signal) @ pcm.

Just for my own clarification. There are two computers at play, right? The PCM that controls the drive train and the ECU that controls the engine? If correct, any idea which each uses the speed signal for and why? What's the VSSB feeding then if not the PCM? Only the gauges?

Sorry for so many questions but I think it's an interesting topic and conversation.

Art.

[ronniejoe]

The PCM or Powertrain Control Module controls both the engine and the transmission (and senses engagement of the front differential). Therefore, it controls the entire powertrain of the vehicle. It's one box. There is no ECU or ECM separate from the PCM.

[TurboDiverArt]

The PCM or Powertrain Control Module controls both the engine and the transmission (and senses engagement of the front differential). Therefore, it controls the entire powertrain of the vehicle. It's one box. There is no ECU or ECM separate from the PCM.

I didn't know that, thanks!! For some reason I thought there were two computers in play. So, when you upgrade to a Heath or other computer, it's the PCM you are upgrading?

This begs the question, if the PCM is not getting speed from the VSSB as stated above, where does it get it from? I'd think it would care for management of the transmission, cruise, etc.

Art.

[ronniejoe]

Actually, it does get it from the VSSB. I'm not real sure I understand everything stated earlier in this thread.

[DA BIG ONE]

I didn't know that, thanks!! For some reason I thought there were two computers in play. So, when you upgrade to a Heath or other computer, it's the PCM you are upgrading?

This begs the question, if the PCM is not getting speed from the VSSB as stated above, where does it get it from? I'd think it would care for management of the transmission, cruise, etc.

Art.

@ vss 821 purple/white line "high resistance vss output" to pin C-12 vss input @vssb

@vss 822 lt green/blk line "vss output" to pin C-7 vss input @ vssb

C-8 @ vssb 451 blk/wht body ground

C-9 @ vssb 441 BRN 10 amp power ign on

C-10 @ vssb 690 wht to antilock ABS

C-11 @ vssb output blank but drawings have it going to F-13 of PCM

C-13 @vssb transmission output 437 bwn to F-12 @ PCM transmission output speed (NOTE: I don't know if this is an in or out signal at vssb) surely others may know.

C-14 @ vssb output 817 grn/wht to cruse control

C-15 @ vssb 389 dk grn to speedo

[john8662]

As discussed, the 45mph is the lockup point on the 4L80E with 4.10's and 245's.

I like that lockup point and want to maintain it during the swap to 3.42's and 265's (at the same time).

But, one thing I don't like is that once up to speed at say 65mph and above, I don't get a shift out of OD, so passing is done with boost and fuel.

So, my question...

If you use the vss modifier and I leave my VSSB at the stock 4.10 setting, will I still see a no-shift out of OD at 65+?

Hmm.

[john8662]

Art,

RJ's only had experience with the GM4 turbo which was used from 94-95. Being that you have a '99 you should have the GM8. I do personally believe there is a little better flow with the GM8, but the internals of the turbo are almost identical, the change is in the exhaust side. GM5 and GM8 are almost the same turbo too, except for a better wastegate bushing on the '8.