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Registered 2001 SLK320
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24 Posts
Discussion Starter #1
Over the winter I plan on buying and rebuilding a 3.7l M112E37 engine from an SL350 and swapping the stock 3.2 M112E32 engine for it.

The 3.7 litre engine only differs in bore size and fuel injector size to the 3.2l every other aspect, bolt locations, wiring loom, ecu version, compression ratio is the same.

I want to either

A: have the engine hex file for the M112E37 flashed onto my current ecu. Both cars use Bosch ME2.8 and the same TCU etc so the hardware is compatible just need the correct engine map put on to my ecu because you can’t swap different ecus into different cars as they are coded to only work with the car they came with.

B have my 3.2 engine file re written to account for the different size fuel injectors and fuel trims.

Apparently you can run the 3.7l engine on the 3.2 engine map and they ecu will adjust the fuel trims using the lambda sensors.

So basically I’m asking how do I get the ecu to have the correct info on it to run the 3.7 l m112.


My plan is to have a 300hp NA V6 r170. I don’t want to do a v8 swap because of cost and complexity. The v6 3.7 swap is much easier apart from the ecu issue mentioned above.
Yeah I could buy an SLK350 but that’s just too easy 😂

Can anyone shed any knowledge on the subject?
 

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Premium Member 2004 SLK350
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4,422 Posts
If you want to read me2.8 you need to open the ECU and read it with K-tag
https://www.aliexpress.com/item/Promotion-DHL-Free-Shipping-Newest-Firmware-V4-036-V2-12-KESS-V2-Master-Version-KESS-V2/32356882368.html?spm=a2g0o.productlist.0.0.5a10243aqJovbw&ws_ab_test=searchweb0_0,searchweb201602_8,searchweb201603_52&algo_pvid=56a197e1-d441-4792-83fb-8cf5ab0b6327&btsid=ddb086d5-e0ab-40bc-8705-4da86b5d2356&algo_expid=56a197e1-d441-4792-83fb-8cf5ab0b6327-0

Then you can try to write on your ecu ( i have a hutch that you will not be able to do that due to hw error )

Or you can read you ecu and have someone do the tuning for the bigger injectors.

Or you can find someone who has an original file for your ecu, tune that and write via obd using kessv2 ( ktag is bench open ecu, kess v2 via obd ) This is a less risky option.
 

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Registered 2001 SLK320
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24 Posts
Discussion Starter #3
I think that the best option is to use the ecu for the 3.2 and have it remapped for the 3.7.

The only diffrence should be fuel injector size settings. As he compression ratio is equal, cams, intake valve size etc etc is all the same the only diffrence would be more air and fuel need to go in. One the ecu has been reprogrammed to work with the larger injectors in the E37 engine surely it would just use the lambda sensors and MAF sensors to calculate the new fuel trims so it runs at the correct AFR.

So I guess if I take it to a reputable merc tuner and have a wide band o2 sensor installed they could change he ecu to work with the larger injectors and use the wideband to check its running the correct AFR. you can see all the ignition timings trough OBD2 and just check it’s running normally. Possibly a dyno run to see if is making the 245 HP ish the 3.7 is suppose to make.

Can anyone else think if any other potential issues?
 

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Premium Member 1999 SLK 5.4 M113
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1,433 Posts
take your 3.2L ME2.8, remove the immobilizer chip and install it in the 3.7 ECU.. then just use the 3.7 ECU.

@Dave2302 might have some ideas too.

edit:... just thought about this.. you will have some problems because that 3.7 ECU is from an SL. therefore you might need to modify Your ECU.
 

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Registered 2002 R170 SLK V8 5.0
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2,049 Posts
Hi @Sir_Wizington ,

Simple one that, well, it is now I have spent much money and R&D time developing this .........................

Firstly SL ECU will not work on R170, the R170 has a unique Starter and Cruise / LIM Circuit, way too much hardware differences within the ECU ............. Buuuuut ............

As your OP confirms they are both ME 2.8 the 320 ECU will be easy to convert .............

Read and Save the Flash File from the 3.7, Write it to the 3.2 and then change just the one Version Coding using SDS to Motor "E37"

I can provide this service via post provided you have both ECU's, just done a much more involved but "Software similar" job to my R170 320 V6 ECU to run an M113 V8, that one entailed micro soldering in extra Hardware Components for the 2 extra Injectors and Coils, but was still much easier than doing it the other way around ;)
Yours of course will not require Hardware Mods, just Bench Programming

HTH, Cheers Dave
 
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