http://www.mercedesengines.net/

I had an opportunity to spend some time with Mike, the owner of Metric Motors today (link above) A few months ago I asked him to call me if he ever was simultaneously rebuilding the engines from the 320 and 32 so I could take a look at the engine blocks and the internals to compare them for future mod. projects and educate myself some more...

When I arrived today, he had the entire re-furbished engine blocks, heads, intakes and internals ready for assembly for both the 320 and the 32... The re-furbished parts were blocks, heads, intakes, cams, balancing shafts and many other odd-and-ends, including re-sleeved cylinders on both engines... All of these re-furbished parts looked like they just came off the factory floor...

Mike also had all new factory pistons, valves, springs, connecting rods and the works for each of the engines... Most of the parts were still boxed, but I briefly pulled them out to compare the appearance between each engine...

I wish I had my digital camera with me at the time, because it would have made for some interesting/educational photos... But, I didn't want to take too much of his time since this is a pretty small shop with few employees and a HUGE workload... So I kept my visit brief, but my enthusiasm over the top...


Here's what I can report to the forum...

Engine Blocks:
Each of the two engine blocks have a stamped serial / part numbers that are different, but both begin with 112... and are followed by a dozen other numbers +/- (I will explain this difference in a later post) The blocks are really quite small and very light (Surprisingly, maybe 45 lbs)... and the cylinder diameter is tiny compared to a 350 block that was sitting nearby...Everything else appears to be exactly the same spec sizes, bolt locations, cylinder bore, exhaust, valve guides, intake, etc... I paid special attention to the shape, design and bolt patterns of the location that bolts-up to the transmission bell housing, every aspect appears to be exact, which means the manual transmission could bolt directly to the AMG engine...The exhaust ports contain the typical casting roughness and would benefit from the port/polish process (not nearly as bad as some of the old chevy and ford engines i've seen)...

Pistons:
I had to pull the (new) pistons out of boxes to look at them...My first impression was "these things are tiny"... Noticed that rings were already installed... Asked Mike what his cost was on each piston ($230 for either 320 or 32)... Piston heads are dished on both, but appears the 32 pistons are dished a bit deeper than the 320 (to lower the compression ?)

Gotta finish this later... But it looks like we can do this engine swap from NA to SC, providing we have the electronics to match...

 

Very nice!!!

1. Is there an accessory oil cooler on the 32 motor?

2. You could make some custom High compression pistons for that price, if you’re interested? There is a very experienced shop here in LA that makes pistons for F1 cars, and they can help you out in the design process. Let me know if you want their number for a future forged piston kit.

 

Sweetness, I think I might forgo my motorcycle to get an AMG engine put into this bad-boy.

 

I wonder if Metric-motors' over bores the sleeves in their rebuild for more displacement?

 

Yeah, Mike and I talked about that yesterday... They do over overbore cylinders all the time, but on our engine there is one oversized piston and sleeve available from MB which is only a few mm larger than OEM... He said that it's such a small increase that it would not serve any purpose other than for a rebuild...

But when I get the time to finish this post, I have some REALLY good info...

 

For a point of reference, the SLK320 has a M112.947 engine and the SLK32 has a M112.960 engine.

 

looks like you have a fan club... http://www.slkworld.com/slk-r170-gen...-rebuilds.html

 

Good eyes. Hope HDDP gets some recognition for his research and hard work.

 

Actually this thread may get traffic from the AMG PL. Someone posted the question that this thread is addressing. I think this will be interesting so I also posted it at slkworld.

 

What's going on with this thread? Did you get any pictures HDDP?

 

One piece of good news is that the engines physically are pretty much swappable... now here's an idea to get around the electronics issue.

Take the N/A engine out of a Base/Limited and stick in a S/C engine... wire the clutch to a relay for the S/C and put it on a switch.

Then you have Super Charging when you need it... and let the old ECU run the engine with new fuel mappings.

I don't know what other 'sensors' there are on the S/C engines... I'm sure some have to do with intercooler temperature, etc. But I'm sure some of those could be put on relays to override the S/C switch.

Great opportunity HDDP... I envy you.

 

waiting for the good info, don't hold out on us derek!

 

With the wire issues, couldn't you get a harness out of a srt, and merge the harnesses together. That is what we did to my buddy's subaru wagon, took the stock harness and merged the wrx harness, so the wrx ECU would work like the stock one.

 

BLK Coupe,

The problem with that idea is that the SRT ECU is looking to control the transmission too I believe... specifically an Auto-Stick not a manual gearbox. Therein lies the problem. What does it do if it doesn't get the feedback from an Auto-Stick? Does it stop the engine? I honestly don't know.

What I theorize is that the base/limited ECU could run the SRT engine and just put the Super Charger activation on a manual switch or direct pulley drive. Then the only thing you would have to monitor would be the intercooler temperatures. You could maybe even put a temperature switch on that with a relay that would cut power to the engine in case the intercooler was overheated.

Again, just a theory.

 

Why is the S/C on a switch, on the srt? When does the ECU turn it off? Looking at the srt ECU's wire diagram, it looks like it does need a signal from the trans, but that is just voltage, so in theory it can be told that it is in drive.

 

According to various SRT owners the S/C clutch engages somewhere between 2,500 and 3,500 RPM. Not sure if it varies or not. The only way I'd be able to say for sure is to put a tap on the line and monitor it during driving to see when it was activated. So, by putting it on a switch, you could turn it on only when you needed it (not sure what the performance impact would be). Another option would be to find out where the ECU gets it's RPM signal from and make a circuit to turn on the S/C above a set RPM via a relay. (Wish woody was here, he could explain it better than me).

So, the ECU does not have any control over the Auto-Stick? I find that hard to believe. If there is a separate Transmission Control Unit (I haven't looked at the wiring diagrams on this), then it still has to communicate with the ECU to get engine data to determine up and down shift points and limits. All modern electronically controlled automatic transmissions work in this fashion. Either you have a single ECU/TCU or two separate boxes, but there IS a computer system controlling that automatic transmission.

 

What's going on with this old thread HDDP, are you going to over bore and sleeve your motor after you drop in the AMG32?

Do you have any pictures of the block, I remember you posted them but since the site moved there was a loss of photos.