Engine swap question: from automatic to manual

eightfifty2x0 · Post by **eightfifty2x0** » 11 Aug 2020, 08:20

I got an 850 wagon, 1996, with B5202S, manual. And i got a C70 coupe, 2000, with a B5234T3 automatic.
Because i cannot find a 850 wagon with the T5 2.3l engine, in a price category where i found it make sense for me to buy it, i thought swapping the engine from the C70 into the 850.
Now i got some questions:
1) Will the ECU from the automatic C70 work with a manual transmission?
2) If yes, is that manual gearbox from the 850 i got a good one for the T3 engine?
3) If no, which manual gearbox will handle the power of the T3?
4) Is the swap real? I mean how easy or difficult it would have been to swap the engine from the C70 into the 850? They share the same platform, so, in theory the engine must fit well, but am no expert, what is your opinion/knowledge on that?

Post by **Chuck W** » 11 Aug 2020, 18:37

There's a lot to unpack here.

Firstly, yes the engine will fit in the car. But that's the easy part. The hard part is integrating the wiring and engine management.

Secondly, I have no idea if the manual trans from your 2.0 will fit the 2.3. I would think it *should*, since they are from the same modular motor family.

Third. You have 2 vastly different engine management systems. Fenix 5.2 in the 850 and ME7 in the C70. You're most likely on your own to get that to integrate. If you had a '98 C70 engine, with the M4.4 ECU, you'd have an easier time.

How much time do you want to spend pouring over wiring diagrams and schematics?

yanga001 · Post by **yanga001** » 11 Aug 2020, 18:58

The automatic ECU will not work with the manual transmission properly. I have heard of people dealing with a 4000 rpm engine limiter, and it will throw check engine lights. The wiring from a 1998 v/s/c70 to a 2000 differs in multiple areas in the cabin, dash, and engine compartments. You would be hard pressed to do the swap from a 1998 to 2000, and i imagine even harder pressed to do it to an older 850.

There is good news, i believe according to the nuceng website that the transmission will fit the later engine model. There may be some funny business with slave cylinders or something but the base components should it. Additionally, you could do an RN swap and put the 2.3t engine into your 850. Check out volvospeed as it is heavily documented there, note you need to verify your wiring diagrams to see if the fenix system required different engine wiring.

You may lose things like vvt from the 2.3t but i have heard that it has minimal effect, and will stay locked if not engaged. This means it will not ruin your engine.

Timewise, i would say that i would not perform this swap on a daily unless you are ready for weeks of no running car. Regardless, read up on the volvospeed posts on it as they tend to deal with more performance swaps.

Post by **FLXC90** » 12 Aug 2020, 16:43

A course of action that may work is to find a 96/97 turbo manual (sedan or wagon) to pick engine management pieces from. I haven't done the research for you, but if the 96 turbo cars used Motronic 4.4, then you could use the ECU, engine wiring harness and sensors maybe. As mentioned, you would not have a hook up for the VVT, but it should default to base timing in that case, and some people block off the hydraulics to the VVT in cases like this. You may also need an additional intake manifold since the 2000 had an ETM, and your 10 valve intake may not match the 20 valve head. And swapping the flywheel etc over should allow use of the manual. I assume it is an M56 or M58? The engine won't know one way or the other. So physically, the engine trans combo is okay, it will be the supporting wiring, hoses, etc. Also, you could get the cluster from the turbo car to have the boost gauge!

Post by **Chuck W** » 12 Aug 2020, 18:53

FLXC90 wrote: ↑12 Aug 2020, 16:43 A course of action that may work is to find a 96/97 turbo manual (sedan or wagon) to pick engine management pieces from. I haven't done the research for you, but if the 96 turbo cars used Motronic 4.4, then you could use the ECU, engine wiring harness and sensors maybe.

97 turbo cars were M4.3, but easy enough to convert to M4.4

eightfifty2x0 · Post by **eightfifty2x0** » 13 Aug 2020, 11:27

yanga001 wrote: ↑11 Aug 2020, 18:58 Timewise, i would say that i would not perform this swap on a daily unless you are ready for weeks of no running car. Regardless, read up on the volvospeed posts on it as they tend to deal with more performance swaps.

Chuck W wrote: ↑11 Aug 2020, 18:37 There's a lot to unpack here.

Basically... leave it as it is. Because what you, guys, explain here, sounds more like reinventing the bicycle, which, is pointless

yanga001 · Post by **yanga001** » 13 Aug 2020, 12:18

The fitting should go in fine, and this has all be done before in all likelihood. Preparation is the most important step. I once took 10 hours trying to fit the upper motor mount in my v70. With the correct tools and knowhow, i repeated the process correctly in 30 minutes. Just be ready to do all this.

Post by **FLXC90** » 13 Aug 2020, 15:41

As you say, it may not be worth doing. It may be better for you to find another car to put your motor into. Or if the C70 is worth fixing, do the transmission swap, and get the ECU re-flashed to accept the automatic. And then do the wiring for the clutch switch and reverse lights.

eightfifty2x0 · Post by **eightfifty2x0** » 14 Aug 2020, 09:17

FLXC90 wrote: ↑13 Aug 2020, 15:41 Or if the C70 is worth fixing

It has this particular damage. The appraiser said it will cost 9k euros. The local workshops - 3-4k. I know somebody who can fix it for much, much less. I dont know how good it will look eventually, but i hope the inspection will approve it. I need to change the cooler, because it leaks coolant when am flooring it and some basic maintenance should be enough to not worry that i will ride it directly to the junkyard

Post by **FLXC90** » 14 Aug 2020, 21:13

Pull the transmission and related parts from the 850, and junk it, or sell it and use the money to fix the C70.