Defeating the torque limit request on the Volvo 850 Turbo

hanzbe420 · Post by **hanzbe420** » 04 Nov 2012, 07:16

so would it be pin 42 if i had motronic 4.3? Thats for automatics right? From the diagram i think it would be the green and yellow wire? So do i cut that and wire it to a switch? And when i want the boost turn the switch off? And to put it back normal, leave switch in on position?

Bondo1 · Post by **Bondo1** » 06 Nov 2012, 00:57

I found this post really interesting and would like to see some pics of this set up. My yellow is a monster past 30mph but could use a little more off the line. I plan on doing this mod I just want to be really sure what I have to do. If this works it would be awesome..... Well maybe not for my tranny.

Post by **jimmy57** » 06 Nov 2012, 07:16

I no longer have a car with this setup.
You are looking for the green with yellow stripe wire that is a jumper between rear of ECM base and TCM base.
IT requires removing TCM and ECM and then pulling the box apart so you can get some access. None of this is hard. You take the bolt out behind the washer reservoir filler and look for the tabs down on box base and the box lifts straight up.
There a 4 or amybe 5 wires that go between the bases for the two control modules. All the other wiring leaves the box to the front engine and trans harnesses or to the rear for car body harness wires.

anglveyes · Post by **anglveyes** » 09 Nov 2012, 18:07

just saw this and this is probably the best upgrade possible for these cars...i hate that rediculous lag off the line. now i was wondering if it was possible to wire this to the eco/sport mode switch and if so if somebody could tell me which wire to put it to.

Post by **jimmy57** » 09 Nov 2012, 18:47

No, the trans mode selector switch is wired to 5V signal out from TCM on two pins. You're grounding one for S and one for E and depressing W grounds both when depressed. No spare circuit in that switch.

Post by **BEJinFbk** » 09 Nov 2012, 21:41

Might be kinda cool to rig a small relay that energizes with the TRACS OFF light...

RSM-GA · Post by **RSM-GA** » 10 Nov 2012, 08:32

Has anyone tried this yet? Sounds intriguing!

Bondo1 · Post by **Bondo1** » 21 Nov 2012, 22:58

I tried this little "mod" tonight. It didn't seem to do anything. I split the green wire with the yellow strip to interupt the signal. Wasn't that hard but a little disappointing when i mashed on it and it was just the same as before. Any advice?

Post by **northernlights** » 22 Nov 2012, 17:07

That's why I was hoping for someone to have a breakout box available to look for the specific signal. The wiring diagram calls out three signal wires for the torque limit request - the green/yellow you mentioned, a yellow/red, and a yellow/violet. One should be the 1st gear limit, one a reverse gear boost limit, and one a shift boost limit.

There is also a green/white for the gear position signal and green/black for the MIL (flashing arrow of doom?). I'd leave those alone...

Any success with smokey reverse burnouts, or more boost after the shift?

Post by **jimmy57** » 22 Nov 2012, 19:30

Nope.
Three wires are used for the shifting torque reduction and the acknowledgement that ECM has acted on the request.
The other torque reductions are actually just boost reduction by shutting down the TCV operation which limits engine power to the much lower amount that the base wastegate setting boost reaches.
That boost cap is done for a number of reasons.
The wire for each is listed in a post by me much earlier in this thread.

Defeating the torque limit request on the Volvo 850 Turbo

Re: Defeating the torque limit request on the Volvo 850 Turb