Engine Management

Motronic 4.3 ECU

One of the challenges in preparing to upgrade the earlier T5 engine is what to do about the Engine Control Unit. In particular, the concern around the earlier Motronic 4.3’s  inability to manage boost spikes as efficiently as the latter 4.4 ECU. A failure to manage this area could well be catastrophic.

Furthermore, with the intention of upgrading the fuel injectors to the highly venerated Bosch 450cc Green giants, then apparently the 4.4 ECU is a necessity; something to do with impedance.

The 1994 850 t5 came with Motronic 4.3.  I think the changeover to 4.4 came around 1997 with the switch to OBD-II diagnostics. Unfortunately it’s not a plug and play kind of scenario in which you can go to your local wrecker, find a 4.4 and plug it into a 4.3 vehicle.

Again there are several issues, not least of which is the fact that the 4.4 will cook your air conditioning control unit, apparently.

Fortunately there are now several aftermarket suppliers offering Motronic 4.4 ECUs which will plug and play into the earlier 4.3 engines.

One such supplier I found in Portugal, sells his wares on Ebay under the name of Northern_Fisher. I did find a couple of Volvo enthusiasts who had purchased his product with quite glowing appraisals. On that basis I launched out and bought what he refers to as an M4.4 racing performance chip remap ECU, suitable for the earlier Volvo 850s.

As well as the necessary changes to go from 4.3 to 4.4 this particular unit has a remapped engine management chip which allows for some significant performance gains given the appropriate mechanical upgrades.

I’m not real sure on the technicalities of this remapping except to say that it suits the nature and type of build I am attempting.  I’m really hoping to avoid taking the car to a DYNO engine management tuner, as long as the car performs well and doesn’t drink copious quantities of fuel, I’ll be happy; for now.

I figure that a wideband air/fuel ratio and boost pressure gauge will provide appropriate feedback to manage the performance adequately. There is also the option of installing a Gizzmo – Rev dependent Electronic Boost controller if I’m concerned.

At this point in time the updated ECU has been received in prompt time and good condition given it’s 18,000 klm delivery path. I’ve not yet been able to test the unit and this is still some weeks away. I  look forward to posting further on this product once installed.

Just for fun I’ve posted the dyno graph that is listed as being applied to the remapped ECU. I’m aware that these figures rely heavily on more than just and ECU update but I liked the 320hp and 460nm output achieved with the associated vehicle. I would be more than happy with this level of performance.