What's the Opinion of the M272 Engine?

[whitenemesis]

Both the E30 and the E35.

Any reliability issues? What's the refinement like, any differences?

Only 500cc between them but what's the driveability like?

 

[Still Learning]

Ensure the M272 engine serial number is later than 2729..30 468993. Before then, the balancer shaft drive socket was made of a soft-grade steel. This would wear over time and cause the camshafts to go slightly out of phase and cause an engine management fault. It is expensive to rectify.

Later engines utilise a harder grade sprocket and do not exhibit the problem.

I find my M272 more gutsy at low-mid RPM than the later direct injection model on the newer cars.

 

[whitenemesis]

Any other owners care to share their experiences with these engines? Good or bad?

How about our independent specialists? You must have worked on them?

 

[Cole@MBS]

Got a load of photos of them stripped doing the said shaft Pete......

Its a good old plodder, dont light any fires for me,

 

[whitenemesis]

"Plodder"? I thought the 350 was quite potent.

 

[Still Learning]

I'll add a bit more from my thoughts...

The M272 utilises a 90-deg block in common with the V8 engines. This minimises the production line re-tooling since this type of V6 is effectively a shortened V8.

To achieve even firing pulses throughout the 4-stroke 720-deg cycle, a 6-cylinder engine should produce a power stroke every 120-degrees. Here, with a 90-degree block, we encounter a fundamental challenge, since a conventional crankshaft will cause power cycles of 90-150-90-150-90-150-degrees. This will give rise to uneven vibrations at low-mid RPM as well as unwanted stresses.

The M272 uses a 30-degree offset on its crank journals to achieve the 120-degree firing stroke spacings and a balancer shaft which rotates at crankshaft speed in the opposite direction to reduce 2nd & 3rd order vibration.

Other technical highlights include continuously variable intake & exhaust valve timing by up to 40-degrees, and a two-stage variable length intake tract. At low RPMs it is advantageous to have a long inlet tract to take advantage of the momentum of a long 'slug' of inlet charge. At higher RPMs, inlet tract friction becomes a larger factor so a shorter route is an advantage.

So how does it feel...?

It is revvy and smooth. Peak torque arrives at 5000-rpm with most of this available from 2500-rpm. Torque is held at sufficiently high RPM to allow peak power to occur at 6000-rpm.

There is not much induction & exhaust sound below 3000-rpm but once wound up it sounds lovely. For the SL with the 7G-tronic gearbox, access to good acceleration occurs post 3500-rpm, although if all you want to do is cruise with other traffic, it is hardly ever necessary to exceed 3k.

The 7G-tronic box is able to change down 2-ratios at a time, so almost instant acceleration is always possible. If needed, I prefer to manually step down so I'm at around 4k before opening the throttle as to my mind, this seems kinder to the gearbox clutches and brake bands.
When doing this, the M272 never sounds harsh, and will rev to beyond 6k building power all the time. I'm always surprised at the 'shove' given that in the SL, this is the lowliest powerplant.

It is an engine that has really grown on me, and has far more character than some supposedly charismatic units from Audi (360-bhp V8 in an S8) and even the 2.7 biturbo in an RS4 which to me was tiresome and sounded harsh.
I use Mobil 1 0w40 and none has escaped.
I've seen 35mpg on a gentle run but 25-30 is more usual with shorter journeys thrown in (the SL is heavy).

I like this engine a lot.

 

[television]

Thanks,, at what year did the faulty shaft get changed please or number

I see that you have given this info, thanks

 

[Still Learning]

I'm not sure of the year but mine is a '57 with engine no. 27296630611845. Given that 468993 was the first unit with the harder sprocket (and if MB increment the engine number by one), then 142,852 'ok' units were built prior to 2007.

 

[Steve@Avantgarde]

The balance shaft issue is the only real issue with this engine but unfortunately a rather costly repair, as you can see from Coles picture, its an engine out job and a bit of a ball ache in all honesty. Its not my favorite job in the world.

The last one I had in with this fault swarfed the engine so bad we had to put another one in.

I prefer the 112 engine that the 272 replaced.

 

[television]

I'm not sure of the year but mine is a '57 with engine no. 27296630611845. Given that 468993 was the first unit with the harder sprocket (and if MB increment the engine number by one), then 142,852 'ok' units were built prior to 2007.

Thanks, I will have to keep this info

 

[Still Learning]

113 that the 272 replaced

Wasn't the M113 a V8? The M112 was the 3.7 V6 in the SL350 before the M272 came along...?

 

[television]

Wasn't the M113 a V8? The M112 was the 3.7 V6 in the SL350 before the M272 came along...?

Yes my mistake I have removed the post

 

[television]

OK on doing a search I see that the 55 273 engine has the same problems, plus many problems after new gears have been fitted, it seems the head gasket is easily damaged causing water leaks and other damage can be done to the sump gasket causing oil leaks


Again the affected engines are all 2007 and serial number up to M273 Engine Up to Serial No. 2739..30 088611
Check Engine Light On / Fault Codes FC1200 / FC1208 Stored in ME-SFI Control Unit

 

[Alex Crow]

Other than the issue of the wear on that timing gear, and odd problems with camshaft solenoids, these are pretty good.
I have had to replace 1x airmass sensor, 1x thermostat (electronically controlled) and 1x each of ignition coil and ECU on this engine. Other than that, and a few with timing gear and/or cam solenoid faults, it is a great piece of engineering.
Note that we now have the M276 to replace it, so the 272 is old hat!

 

[whitenemesis]

Still Learning - Thanks for the in depth write-up. It's great when some one takes the time to be so informative. Especially the "owned and driven" experience.

It's good to get the "spanners" views also! So, avoid the earlier engines with the balancer shaft problem and the engine appears robust and reliable.

 

[television]

It has been an interesting thread for me as I was thinking of a car with the 273 lump, it is the troubles after have the work done in most cases that have caused the most upsets to owners