M57 engine swap

Hi All, new member here, apologies if this is a bit long winded...
I have a 1998 p38 converted to M57 (2002 E53 x5 flavour) and would like to know if there is anyone else out there running one?
I finished it in 2017 and have done around 70k since then using it as my daily, but never managed to get the cruise to work, so if anyone has managed that and would be prepared to point me in the right direction regarding road speed input to the DDE that would be great!
I've been doing longer trips in Europe recently and it has me considering selling my collection of P38s and spares to go the L322 route, cant make my mind up! Anyway happy to answer questions from anyone seriously thinking (not just armchair dreaming ) about going M57 with their P38, I think its fair to say it's the engine P38s should have had from the factory

I think the cruise control is controlled by the BECM but I might be wrong. @Datatek might know.

Hi, thanks for the reply. On the diesels (not sure about the V8's as they have a more basic system using cables and vacuum actuators) the cruise is controlled directly by the engine ECU, this is the same for both the 2.5 and for the M57.
The problem is the ECU (DDE) needs a road speed input, this comes from the ABS system on both the P38 and the BMW X5 (and probably other similar vintage BMWs) but it must be a different signal type, because connecting the input that originally went to the 2.5 ECU to the correct pins M57 ECU doesn't work :-(
I guess I could make a bastardised system using the V8 cruise components working directly on the throttle pedal but the cruise controlled by the ECU is a really good system in terms of how it maintains the speed so I don't really want to go that route

you need some sort of translator to get them to work

Road speed on bmw m57 devices are a processed signal usually abs unit too ecu,

Most bmw systems 98-06 (that i know) use the rear left for visual speedometer but another sensor rear right or one of the fronts for the cruise control,

If you connect diagnostics up and get on live data in the engine ecu can it read a road speed,

I highly reckon the p38 system has the wrong processed signal for the ecu,

Grrrrrr said:

I think the cruise control is controlled by the BECM but I might be wrong. @Datatek might know.

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Cruise control on the M51 is done by the EDC, the BECM only controls the availability and the switches.

stustrong said:

Road speed on bmw m57 devices are a processed signal usually abs unit too ecu,

Most bmw systems 98-06 (that i know) use the rear left for visual speedometer but another sensor rear right or one of the fronts for the cruise control,

If you connect diagnostics up and get on live data in the engine ecu can it read a road speed,

I highly reckon the p38 system has the wrong processed signal for the ecu,

Click to expand...

I agree it could be a signal compatibility problem but it could also be as simple as getting the connections right.

I think your right, that's where I was hoping someone might have done the hard work before me haha.
To explain the full back ground of what I did originally in case it helps anyone else (this was quite a few years back so might have forgotten something), I took the little circuit board with the cruise buttons on it out the bmw steering wheel and connected it directly to the M57 ecu, from the diagnostics I could see it recognised the button inputs but was not getting a road speed input, after lots of double checking the pin outs I came to the conclusion the signal from the P38 cant be what the M57 is looking for, although I don't have the ability to monitor these signals and be 100% sure.
Anyway I cant be the only person with an M57 engined P38 so hopefully someone with more knowledge than me has made this work!

P38UK said:

Hi, thanks for the reply. On the diesels (not sure about the V8's as they have a more basic system using cables and vacuum actuators) the cruise is controlled directly by the engine ECU, this is the same for both the 2.5 and for the M57.
The problem is the ECU (DDE) needs a road speed input, this comes from the ABS system on both the P38 and the BMW X5 (and probably other similar vintage BMWs) but it must be a different signal type, because connecting the input that originally went to the 2.5 ECU to the correct pins M57 ECU doesn't work :-(
I guess I could make a bastardised system using the V8 cruise components working directly on the throttle pedal but the cruise controlled by the ECU is a really good system in terms of how it maintains the speed so I don't really want to go that route

Click to expand...

A guy in New Zealand has also done this conversion and suffered overheating problems when towing. Solved by fitting the GEMS V8 rad.

stustrong said:

Road speed on bmw m57 devices are a processed signal usually abs unit too ecu,

Most bmw systems 98-06 (that i know) use the rear left for visual speedometer but another sensor rear right or one of the fronts for the cruise control,

If you connect diagnostics up and get on live data in the engine ecu can it read a road speed,

I highly reckon the p38 system has the wrong processed signal for the ecu,

Click to expand...

Thanks for the info, no road speed on diagnostics (INPA), so unless there is some way to convert the signal from the P38 (beyond me) its a none starter, no cruise hadn't really bothered me too much until I started doing longer trips abroad (Sister moved over to France) other than I'm a bit weird and like everything to work as its supposed to...and yes I know that's not compatible with owning LR products! Now its making me think I should sell it on and get into an L322, next question is whats and M57 engined P38 worth?!

Datatek said:

A guy in New Zealand has also done this conversion and suffered overheating problems when towing. Solved by fitting the GEMS V8 rad.

Click to expand...

Thanks Datatek, is the NZ guy on here?
Never had any overheating problems with mine when towing (recovery trailer with other P38's on) I'm running the standard viscous fan without a shroud as it broke, and the original 2.5 rad, and temp never moves, its been over to Italy a couple of times and going at a good 80mph+ with AC on etc its all good. The plumbing is different though between the two engines, and I ended up relocating the header tank over to the passenger side to get it right so that might be part of the other guys issue.

P38UK said:

Thanks Datatek, is the NZ guy on here?
Never had any overheating problems with mine when towing (recovery trailer with other P38's on) I'm running the standard viscous fan without a shroud as it broke, and the original 2.5 rad, and temp never moves, its been over to Italy a couple of times and going at a good 80mph+ with AC on etc its all good. The plumbing is different though between the two engines, and I ended up relocating the header tank over to the passenger side to get it right so that might be part of the other guys issue.

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The problem was solved with the radiator change. From memory, it was I think mainly at low speed with a boat on the hook that caused problems, ram air does the job at speed. The temperatures where he is are a good bit higher than the UK, but maybe not hotter than Italy. I have not seen him on here since the problem was solved.
IMO from experience with a friends L322, they are an electronic nightmare.

I'd stick with the '38. The l322 has a whole different bunch of issues including rust in all the best places

Datatek said:

The problem was solved with the radiator change. From memory, it was I think mainly at low speed with a boat on the hook that caused problems, ram air does the job at speed. The temperatures where he is are a good bit higher than the UK, but maybe not hotter than Italy. I have not seen him on here since the problem was solved.
IMO from experience with a friends L322, they are an electronic nightmare.

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The other thing I've seen is several cheapo replacement 2.5 rads that don't cool properly (no baffle inside?) but yep maybe he was just working it harder.
The relative unknown of the L322 for me compared to the P38 that I know inside out, and the fact I have loads of P38 spares on the shelf, does put me off a bit, that and the rust I've seen on front subframes and rear arches of a mates L322 collection, but they are a nice place to be, and the 4.4tdv8 seems to be ok if looked after. It will probably boil down to how big the gap is between what I can get for my two and all the bits vs what I need for an L322 in the end.

Mark Piercy said:

I'd stick with the '38. The l322 has a whole different bunch of issues including rust in all the best places

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I know what you mean, the P38 must have been a mistake, just about the only LR product that rarely is ever has rust issues

P38UK said:

The other thing I've seen is several cheapo replacement 2.5 rads that don't cool properly (no baffle inside?) but yep maybe he was just working it harder.
The relative unknown of the L322 for me compared to the P38 that I know inside out, and the fact I have loads of P38 spares on the shelf, does put me off a bit, that and the rust I've seen on front subframes and rear arches of a mates L322 collection, but they are a nice place to be, and the 4.4tdv8 seems to be ok if looked after. It will probably boil down to how big the gap is between what I can get for my two and all the bits vs what I need for an L322 in the end.

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Nice place to be is a matter of personal opinion. I find the seats uncomfortable and the screen is a real distraction as my mate would testify, as he was busy trying to navigate the screens he got flashed

P38UK said:

Thanks for the info, no road speed on diagnostics (INPA), so unless there is some way to convert the signal from the P38 (beyond me) its a none starter, no cruise hadn't really bothered me too much until I started doing longer trips abroad (Sister moved over to France) other than I'm a bit weird and like everything to work as its supposed to...and yes I know that's not compatible with owning LR products! Now its making me think I should sell it on and get into an L322, next question is whats and M57 engined P38 worth?!

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Road speed might come from the BECM which in turn gets it from the ABS ECU. I'm tryingbto recall whatbthe ABS ECU does: itvaverages the signal from all 4 sensors amd assimes 4000 blips per something. Revolution of yhe wheel. Per mil Too tired and too many beers.