For all of the threads asking about using the 98 S70 T5 ECU in a 850, I have finally done my own test. First and foremost, It is said that if you use your A/C compressor with the other ECU you will fry it. I did not take chances with that, and turned my A/C from auto, to off. Everything else however works. The start up times have significantly decreased. I personally did not notice a "smoother idle" nor did I experience any power gains even with the 16T and white injectors.

I would not recommend this swap if you are paying full price for one. I only did this because I have a S70 T5 parts car. However, the S/V70 ECU is 4.4 motronics. If you plan on tuning your car, you might have noticed that you can upgrade your 850 ECU to 4.4, but it is very spendy. $180 upgrade through ARD. After speaking with lucky, You can actually put a 850 tune on the s/v70 ecu. making it compatible with your A/C, and having the 4.4 upgrade. So if you can find one cheap enough, you can actually save money on the 4.4 upgrade. But unless you plan on going that route, the swap is pointless.

I hope this cleared up any issues on past threads.

 

Sean, your leaving out very important information. The mapping characteristics of the M4.3 to the M4.4 is huge! That is one of the reasons your car starts so much better. There is much more control over all aspects of the tune. I have been running an M4.4 for over two years and was in the pilot era when this was happening. I have tested many tunes for Lucky and love the ability to manually load the tunes with a laptop and the ARDVARC. Lucky came up with a product called Launch Control that allowed almost two tunes in one. Good driving around town but when you step on it the map loaded a different subroutine that made the car become a monster. Very fun.

I currently have a ARD Blue M4.3 and a Blue M4.4. I can go back and forth and absolutely notice the difference between the two. No question.

I whole heartily recommend the M4.4

Oh, my A/C works too.

Additional information on the M4.4


1. M4.4 has less latency in the boost control strategy which translates
to quicker boost onset in the midrange. Just switching to 4.4 and
running the adaptation sequence allowed for boost to develop 350rpm
sooner according to the logger. Some of this is contributed to the
faster response of the later TCV vs. the earlier BCS. The fixed orifice
in the BCS as well as the generally tepid wastegate adjustment seems to
be the main reason for 4.3 sluggishness in boost development aside from
the RISC architecture that appears more prevalent in 4.4



2. Wider adaption range. The total compensation for variation in
measured variables, like air flow, Detonation ceiling, O2 response,
etc.. if not wider is certainly quicker and more refined. This means
timing strategy is the main componens as a quicker PID loop where the
ECU compares knock detection to advance curve multiplier and modifies
the total amount of ignition retard. When comparing boost onset and the
adaptation of timing overlaid from the logger data it's likely that the
timing has nearly as much contribution to the increased midrange as the
boost control strategy. However the base data without considerable
review seems to trend that neither is 100% responsible for the increase.



3. Options. M4.4 has numerous map options M4.3 just doesn't. Manual,
turbo, with OBDII for instance. Additionally some 4.4 hardware setups
(98 V70R for instance) were equipped stock with green injectors and
larger turbos like the 18T/19T. Coupled with reduced latency in boost
control this further explains why M4.4 is more suitable to larger turbos
and why 4.3 never saw anything larger than a 15G in stock form. Not to
say a larger turbo can't be installed but my belief is 4.4 will maximize
the gain better than 4.3 will.



4. OBDII logging. M4.3 has it in the 1996-1997 models but for the -95
models you can't really log EOBD like you can with M4.4. So this becomes
desirable for trouble shooting as well as tuning. Also for the early
850 with on board diagnostic box in the engine bay you can keep this
function for all the remaining modules as well, climate, trans, SRS
etc..

 

Awesome write up! I realize this thread is oldish but i thought to mention how this is helpful in my own plans. I was originally searching ways to make my 850 awd but realized it really isn't the route to take so instead I'm sourcing an awd s70 and dropping my engine in (blue tune, 19t, forged rods while she's out).