Bigger Supercharger

[R2D2]

I have the possibility of changing the standard kompressor on my C180k for the C230K one. Both engines are the 1.8 M271 but in difference stages of tune. Given that my car has allegedly 143bhp and the C230k had with this engine 193bhp should I change. Miro has explored the differences in the M271 engine variants and has written elsewhere the following:

""C180K, C200K conversion to C230K with M271 series 240, 246, 248

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After many hours of sifting through the data and checking 6 VINS against each other I can suggest the following findings about the M271.

* If the engine is 2005 spec then it will be specially upgraded already with low noise parts that were recently introduced.

* In all M271 2005 the 5 speed transmission is identical

* In all M271 the crankcase and 5 speed auto slip ring are identical

* all results exclude CGI and SLK for now.

DOES NOT APPLY TO CGI
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[series 240, 246, 248 only]


C180K, C200K and C230K differ in the following ways
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- piston
- supercharger (only 2 models - one for 230K and one for others.
- ECU (engine control unit)
- Some differences in intercooler and hoses are possible with year of build.

= 140Kw in total without pulley mods

RESULT
--------
In some cases that means 20-40Kw improvement.

CAVEAT
--------
This mod uses only MB parts and should only be done with informed risk and has no implied warranty.
__________________
Modz ... enjoy the difference. www.benzmodz.com""

I wrote elsewhere that:
The M271 engine has a bore of 82mm and a stoke of 85mm
The C180 has a compression ratio of 10.2:1 and prodcues 105kw (143bhp)
The C200 has a compression ratio of 9.5:1 and produces 120kw
The C230k has a compression ratio of 8.7:1 and produces 141kw (193bhp)

So what I need to know is what chance is there of my engine exploding if I chuck lots more air at it with a bigger supercharger?? Will having the higher compression ratio cause a problem??

All comments welcome.

[bolide]

Flowing more air will do you no good unless you can burn more fuel. If the injection system will give you enough fuel to give a decent power increase then you'll need more air to burn it

Looking at the compression ratios and power outputs is confusing. Power goes up as CR comes down which is the opposite to an NA engine and is counter-intuitive

More power comes from burning more fuel so the higher-power versions must have a greater charge - ie more air and more fuel - and I think this must come from more boost pressure. I assume the greater boost pressure more than compensates for the drop in CR

So, in theory, delivering more air via more boost pressure will let you burn more fuel

Two unknowns: how will you map the engine to deliver more fuel and how will greater boost work with the high CR?

I guess this is exactly how AMG / Kleemann / Brabus / etc derive power increases. I wonder how long they spend mapping each model? You could easily spend tens or hundreds of hours mapping a setup and then have to do it again when you change just one part of the equation...

Nick Froome
www.************

[R2D2]

Thankyou. What would happen if I just put a bigger kompressor on and don't remap?

[bolide]

Originally Posted by R2D2

Thankyou. What would happen if I just put a bigger kompressor on and don't remap?

Absolutely nothing, I expect, unless the ECU knows to deliver more fuel. If it detects boost pressure it may increase fuelling automatically within the limits of the existing map and that would deliver more power

You only need a "bigger" kompressor if the existing one doesn't flow enough air. If you run the existing kompressor faster it'll deliver more boost across the rev range but it may run out of puff at high loads / high revs

Nick Froome
www.************

[R2D2]

So maybe some more bhp but not a ruined engine!?

[GRAV888]

If it aint broke, don't try and fix it Greg.

[R2D2]

Originally Posted by GRAV888

If it aint broke, don't try and fix it Greg.

...............or I could do the cams

[GRAV888]

Originally Posted by R2D2

...............or I could do the cams

Mine was broken though

[R2D2]

or cats

[andy_cyp]

Me thinks you need a C55 matey.

[R2D2]

I know but I'm being good (ish)

[280gee]

One very present danger with not getting the fuelling correct and also increasing the effective compression ratio is that the engine may lean out at some as yet undetermined r.p.m. and something will let go in a big way!

Often happens just when one thinks "this is going well!" :-)

[R2D2]

Originally Posted by 280gee

One very present danger with not getting the fuelling correct and also increasing the effective compression ratio is that the engine may lean out at some as yet undetermined r.p.m. and something will let go in a big way!

Often happens just when one thinks "this is going well!" :-)

Might the ECU not just correct the mixture? ( I don't know)

[280gee]

It might, but I'd personally want more reassurance than that. As a minimum i'd suggest looking at least at, fuel remapping, ignition timing, and any heat issues that would arise. Or OP could just blow it and see...

[Ultymate]

Without major surgery I don't think you can fit a bigger supercharger, the one on most modern day Mercs is the Eaton M45. There are several companies that make smaller pulleys to up the rpm of the blower and therefore the pressure, but I'm sure with this as suggested back up this thread you'd have to have the fuel system re-mapped accordingly.