Defeating the torque limit request on the Volvo 850 Turbo

[henrysin44]

Hey all im new to this thread but ive been following it for abit. Today I finally got around to tearing into a M4.3 ecu I got at a parts yard and well the mod can work sort of. When activated the front wheels spin a lot with WOT from dead stop but nothing like that from light throttle, light throttle has more of a punch though. Actually the first run I did at WOT up a slight incline resulted in my hood flying up so this hack may result in a new hood lol.

Mod done on a 1994 Volvo 855 Turbo, ECU M4.3 -0261 203 072-.

Parts: ECU M4.3, 1K ohm resistor, 20 ohm resistor, NPN transistor capable of accepting 12-13V.

Ok so to do the hack you gotta open up the ecu and find ground, 12v, b2, b3, and b4.

Solder a 1K and 20ohm resistor (in series) from a 12v source on the board to a voltage regulator to make sure the voltage is under 12v but between 8v and 11v.
Then solder the resistor pair to the base of the regulator and the collector of the regulator gets soldered to pins b2, b3, and b4 on the board ( cut the pins out to wiring harness). One extra thing to do that I diddnt was wire a switch before the resistor pair as to be able to controll the mod as ive already spun tire when not intending to.

I will add photos and a schematic soon.

[henrysin44]

Hey all im new to this thread but ive been following it for abit. Today I finally got around to tearing into a M4.3 ecu I got at a parts yard and well the mod can work sort of. When activated the front wheels spin a lot with WOT from dead stop but nothing like that from light throttle, light throttle has more of a punch though. Actually the first run I did at WOT up a slight incline resulted in my hood flying up so this hack may result in a new hood lol.

Mod done on a 1994 Volvo 855 Turbo, ECU M4.3 -0261 203 072-.

Parts: ECU M4.3, 1K ohm resistor, 20 ohm resistor, NPN transistor capable of accepting 12-13V.

Ok so to do the hack you gotta open up the ecu and find ground, 12v, b2, b3, and b4.

Solder a 1K and 20ohm resistor (in series) from a 12v source on the board to a voltage regulator to make sure the voltage is under 12v but between 8v and 11v.
Then solder the resistor pair to the base of the regulator and the collector of the regulator gets soldered to pins b2, b3, and b4 on the board ( cut the pins out to wiring harness). One extra thing to do that I diddnt was wire a switch before the resistor pair as to be able to controll the mod as ive already spun tire when not intending to.

I will add photos and a schematic soon.

Screen Shot 2017-02-15 at 8.35.55 PM.png (729.96 KiB) Viewed 1692 times

[matthew1]

Outstanding, thanks Henry. This is a real "proof of concept".

[henrysin44]

Outstanding, thanks Henry. This is a real "proof of concept".

Thank you! With my 855T manual swapped i could spin tire accelerating in 1st without trying , thought it was because of the manual transmission but decided to swap ECUs with a un-modified M4.3 ECU I have laying around and couldn't get the tires to spin so I'm thinking this mod might actually do something, not much but something.

P.S: Having or not having a voltage regulator has no effect so I wouldn't bother adding it.