Quick info:
The Mercedes M112 Engine that is in our Crossfires came in various displacements ranging from 2.8 - 3.7 ...
The 3.7 was available form 2004 - 2006 in the Mercedes ML and S class models ...
The 3.7 produces 232-245 hp depending on the model ...
The 3.7 has the same bore as the AMG 5.4 ... 97mm instead of 89
Why might you ask wouldn't I just do the M113 V8 swap well there are a several reasons ... One being the weight of the 3.7 is nearly identical the the 3.2 ... Second for states with emissions and inspections the is V8 frowned upon ... Third it'll look factory and keep the ease of maintenance ... Fourth you don't need any special electronic wizardry

And here for the first time the XF 370 in progress :

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Looks like you're well on your way!

Are you going to just use the stock ECU and get someone to tune it? That'd save a lot v. the V8 ECU gymnastics.

How much power do the benz world people get out of these with bolt-ons? Looks like they "only" have ~20hp more than the 3.2l stock.

 

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Good show old Chap! I'll be keeping an eye on You from now on. Hey, Umm You know engine stands are really not expensive. I'm sure you can get one for less than $100 at harbor Freight. It makes working on engines much easier bro.


Anyways good luck!

 

Maybe premature, but could this match up with a 6 speed? Subbed and good luck.

 

fantastic, keep it up.

 

Thanks guys. To Answer a few...

YES, You can use the stock ECU and tune it just like you would the normal 3.2... the difference being you have more air and more fuel to play with. The 3.7 comes with the larger fuel injectors from the V8.

I actually have an engine stand... it's currently cradling a diesel engine...

This will bolt directly to a 6-speed with the only mod (for auto or stick) is you have to tap in two trans cooler line brackets ... takes about 20 sec. and swap over the entire engine wiring harness from your Crossfire.

Here's her second start up:

 

Thanks for the info, care to share how much you spent on the motor?

 

There's one on Ebay, $2000 Buy It Now with 59K for Automatic though. Not sure how that will work with a 6spd... Local Junk yard may be the place to find one if you're lucky.

 

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It's the same motor. The difference is flexplate/tq converter vs flywheel/clutch hanging off the crank.

 

I see pictures on the net of a MB 3.5 that has the plug in the center of a DOHC head.
Apparently there is more than one version of the 3.5 motor - be careful what you buy.

 

Hi,

well, that's a lo of work to gain 25 hp and 40 nm. I think that conversion is only interesting and useful if you tune the engine with sport camshafts, modify catalyic converters, exhaust, intake and do an ecu tune. Than you can reach around 290 to 300 hp. But without this mods these engines are no power packs. The M112 3.2 V6 mostly reach real 200 hp and 300 nm in an Crossfire on a race certified dyno. The M112 3.7 V6 is around 225 hp and 335 nm. So there is a big difference between what are the numbers on paper and what are in the numbers in the real world.

Regards
Markus

 

Agreed, I really want to know what this one dynos at. All that work for only 20hp seems a bit much, but I don't know how much "headroom" the 3.7L gets with less-restrictive intake and exhaust and a leaner mixture.

N/A power is hard to get, though, and this is definitely one way to do it!

Do all the M112 E32/3.2L accessories bolt up? It sounds like they might - if so a junked long block could be a nice option too. Junkers often sell Mercedes long blocks for cheap because as we know they don't fail often and aren't in huge demand.

Yeah - there's the E35 M272 and the E37 M112. The M112 is comparatively rare - I think it only came in the S and ML class for a year or two before being replaced by the M272 in 2006.

 

It's the same engine block. If the accessories will bolt up depend on what car the engine was used in. Engines accessories which were used im ML, or G class cars, or Sprinters often differ from normal passenger cars. For example oil pans and so on. So it's best to research that in MB EPC before you buy an engine. I also would recommend to use to use the original Crossfire ECU with a 3.7 tune, because that's easier than to setuo a 3.7 ECU to a Crossfire SKREEM and BCU.

Regards
Markus

 

Great info Markus, thanks!

This swap is only really interesting to me because it can mate to a 6-speed and avoids the ECU issues and just needs a tune. Otherwise I would be hunting for a V8.

 

You're always welcome.

One more thing to mention. Look for an engine that was buillt after 2001. There were some minor but important changes in materials and production processes. Best will be engines from 2004 onwards, because they fit the same emission standards.

We have a V8 MT over here in germany. But you won't be able to do that without MB internal knowledge. And the peole who built it don't like to share there knowledge.

If you want to do a classic tuning to the engine i would recommend to use other camshafts (for example from SCHRICK). Problem is, they are very expensive. But there is an option. You can regrind them (don't know if that is the right term in english) In german this process is called "Nockenwelle umschleifen". That means you grind the cam so you get a sharper engine timing. Because you take a little bit of material from the cam you'll need other valves and valve springs to compensate that. So if you rebuild and optimize a used engine, this maybe an option.




Regards
Markus

 

First off thank you bigblock427 for all you insight on the subject! You're dead on. Cams would really wake this engine up... The only upgrade I've done so far is the 74mm TB upgrade.

Yes, if anyone here is going to do any MB engine swap make sure it's '04 or up!! There were huge material upgrades starting in '01. The 04-05 ML 350 and 06 S 350 are the 3.7L M112 ENGINES NOT THE 3.5L M272 ENGINE.

All accessories swap over... I swapped everything that I could. No one would know that this car has a 3.7L in it unless they ran the engine code!

 

Very interesting, thanks for all the info!

 

First real drive yesterday... took it around the block.. let it idle for 10 mins... then took it for a real ride. Man this thing pulls!! It's strong from 1-3 and still pulls into triple digits. and with all the extra air and fuel it even sounds a bit more aggressive. Needless to say its quick ... quicker than all the engine mods done to my stock 3.2 (tune, larger fuel injectors, throttle body, maf housing, etc)... much, much quicker!

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I've been able to put about 200 test miles on it and I'm happy to say that it runs, drives and operates just like oem. The Lambda is nearly dead even at 1 ... couldn't be more thrilled with how this whole project came together.