Volvo 850 10v to 20v Conversion.

[Chuck W]

Okay, so the project took a big stall while I was sourcing parts and in the end, I ended up finding and buying a 98 s70 20v with a manual transmission. The car was 1 owner and was very well maintained. The engine runs much stronger than my 850 did so we've decided to just drop the Engin and transmission into the 850 instead of taking apart both engines.
While this thread won't actually answer the question of whether or not this swap can be done, well, I believe that it 100% is possible. More than likely, you'd need to convert the car from the Fenix ecu to 4.3m ecu. But that is just installing a new harness and the new ecu which isn't too hard.
Thanks to those who answered the question in the first place!

Yeah, that doesn't sound like too difficult of a swap.

The 20V NA motors were m4.4 in the (US) 850's in 96-97, so if you might be able to just swap the engine side harness to the ECU and leave the rest alone. Getting a 96-97 NA engine harness shouldn't be too difficult to find, though. Did your 10V have the OBDII port as well?

[2ndGenVolvos]

Okay, so the project took a big stall while I was sourcing parts and in the end, I ended up finding and buying a 98 s70 20v with a manual transmission. The car was 1 owner and was very well maintained. The engine runs much stronger than my 850 did so we've decided to just drop the Engin and transmission into the 850 instead of taking apart both engines.
While this thread won't actually answer the question of whether or not this swap can be done, well, I believe that it 100% is possible. More than likely, you'd need to convert the car from the Fenix ecu to 4.3m ecu. But that is just installing a new harness and the new ecu which isn't too hard.
Thanks to those who answered the question in the first place!

Yeah, that doesn't sound like too difficult of a swap.

The 20V NA motors were m4.4 in the (US) 850's in 96-97, so if you might be able to just swap the engine side harness to the ECU and leave the rest alone. Getting a 96-97 NA engine harness shouldn't be too difficult to find, though. Did your 10V have the OBDII port as well?

Yes my 850 has OBDII.

I assume I can just use the harness off the 98 S70 that I am taking the motor and transmission from. That way I take the motor, harness and ECUs for the swap.

[Chuck W]

Yes my 850 has OBDII.

I assume I can just use the harness off the 98 S70 that I am taking the motor and transmission from. That way I take the motor, harness and ECUs for the swap.

You MAY find differences in the '98 S70 harness vs the 850 ones. I haven't pulled apart a '98 myself to be able to verify. It may be close enough to use, however.

A 96-97 850 harness would be a drop-in, though.

[2ndGenVolvos]

Yes my 850 has OBDII.

I assume I can just use the harness off the 98 S70 that I am taking the motor and transmission from. That way I take the motor, harness and ECUs for the swap.

You MAY find differences in the '98 S70 harness vs the 850 ones. I haven't pulled apart a '98 myself to be able to verify. It may be close enough to use, however.

A 96-97 850 harness would be a drop-in, though.

From what I've read on the forums and seen in the wiring schematics, the 98 harness runs the same as the late 850 models. I don't know if the harness is actually different though, beyond the fact that one is for the Fenix 3.2 and the 98 is for m4.3

[misha]

All '98 B5254S (2.5 20v n/a)are M.4.4. NOT M.4.3.