1997 850 GLT Engine Swap (M4.3 M4.4 AC compatability issue)

[BrickyardCustoms]

Hello all,
Used the forums for advice from time to time but this is my first post. My 1997 850 GLT has a ruined block due to getting too hot after a heater core blew. As many of you know these came with a 2.4 LPT, and although they’re cheap and easy to find, I would like to put in a 2.3 (B5234T) or whatever variation. I was curious as to how much of a plug and play the swap will be. I assume it’ll bolt to the auto tranny just fine, and I’m under the impression that with simply a different tune (will be from ARD again) the car should be fully functional. Is this correct or has anyone done this? I’m going for more power and had always wanted a 2.3 swapped in down the line, but now seems as good a time as ever. Any advice and input is appreciated. Thanks!

[tardcart]

I dont have experience with this, but you would think any 96 or 97 and possibly 98 and 99 t5 would plug right in with a 96 or 97 computer from a t5. 95 engine would work but you would have to illuminate the EGR.

[bmdubya1198]

Yes, the B5234T is a direct swap for your 1997 GLT. You'll want to try to find one from the same model year, although a 1998 S70 or V70 T5 or HPT C70 should be the same. Being a 1997, I'm assuming this is a Motronic 4.4 car, so a 1998 shouldn't be any different from a 1997 2.3.

You could use a 1999+ RN engine too, but further modification is needed, including drilling the intake cam for the distributor and disabling the VVT, among other things. In your application, I would recommend sticking to the -1998 engine.

I don't think the turbo cars ever had EGR, but instead had secondary air injection. That's something that's related to the ECU, not as much the engine.

As for tuning, if you're happy with ARD I would use him again to tune for the 2.3. I'm assuming you'll be using the 16t/15g turbo and blue/white injectors with this engine, which require tuning to run properly.

[Chuck W]

So, we had to replace the engine in my wife's '97 GLT last year. We went with another LPT engine ('01 RN motor) with half the miles on it.
The N->RN swap wasn't that big of a deal. We stayed with the dist ignition (for now) and didn't mess with the VVT (yet), and just left it unplugged. We added a 16T in the process. Aside from a few minor issues, it was an easy swap, hardware-wise

The biggest issue was the ECU. More specifically the AC controls. Yes, the '97 GLT is an M4.4, but it due to it being an 850, with the different ECC, the "std" '98 M4.4 stuff doesn't play nice.

A stock '98 turbo ECU works to allow the car to run, but the AC doesn't work, at all. A "flashed" '98 ECU with the VS "AC-Mod" doesn't work, either. The AC would cycle once, then stop working. A '97 HPT turbo ECU is M4.3, and not compatible. From what I recall, you can actually ruin AC components(Compressor and ECC module) trying to run the AC in and M4.4 car with an M4.3 ECU.

Went through all of this with the wife's car. No one had any solutions other than "When it got hot and we wanted AC, we just swapped the old ECU in", or they just didn't run AC. I think IPD claims to have a "upgraded" ECU for the 97GLT...but that's not really cost-effective (at least for me)

I picked up another '97GLT ECU (-936) and removed the chip and sent it to someone who could read the bin and compile an XDF for TunerStudio. Someone else was then able to compare the AC routines between the '97GLT M4.4 and the '98 M4.4 and found that they were different. They then mashed them together (A -607 bin with 97GLT AC routines) and we had a working ECU with working AC. I just haven't fully remapped it for proper use with the LPT motor yet, so we haven't used it much for more than basic testing.

This is what we went through. If someone had any other solutions, they sure didn't share them when I was trying to sort this out last year.

Now that we have that sorted, I plan to work towards COP and VVT on this engine, as well as upping the boost a bit.


A fun anecdote. When we were originally trying to get things running, we had a '98 V70R ECU in the car. The AC wouldn't work, but it would roast the tires for half a block from a rolling start. Wasn't safe (for the engine) to run it that way though, as it was detonating pretty heavily.


Anyway, if you want to put an HPT engine in the car, you're going to have to sort out a way to properly handle the engine management IF you want to keep working AC.

[erikv11]

Great post from Chuck. Thanks!

I have nothing to add except that I may want to get ahold of your bin.

[Chuck W]

Another thing I discovered was that the -936 ECUs do not like having another (M4.4) bin flashed to them. As least not that I found.

Flashing that extracted -936 bin to another M4.4 ECU or even another -936 ECU resulted in a non-start situation. The guess was maybe there is an immobilizer or something else that didn't jive. There is some additional circuitry on the -936 circuit board.
I also wan't able to get a running car flashing the -607 bin to the -936 ECU.

I had originally hoped that MAYBE I could use the extracted -936 bin to build from, but no joy there. Thus is how we got to the hybrid -607/-936AC bin.

[BrickyardCustoms]

I recently sent ARD an email and am waiting reply as to if they can get me an ECU to work for a project like this. I do not plan on going with an RN block, and have found what is said to be a 97 2.3t. Considering it’s not an RN block, and I will be using a completely different ECU (not sure what exactly they would send me yet). Should I still have this AC issue? The car doesn’t have working air conditioning as of now, and it may even be deleted down the line.

[Chuck W]

The AC in the '97 GLT doesn't play nice with any other M4.4 ECUs. At least not that I discovered.

If you don't care about AC, and are planning on using an N HPT engine, then just throw a '98 HPT ECU in there.

[BrickyardCustoms]

My current ECU isn’t the original ECU, and the AC didn’t work in the first place so I can’t say as to whether or not that was affected. I’ll mention it to ARD to see if they are aware of it or have a fix, and go from there. I won’t be using an untuned ECU since I will be swapping it anyways. If it’s easier and can be had for cheaper to go with a 2.4 again I will, but probably HPT swap.

[Chuck W]

What ECU is in the car?