AusMB87

Of course there are things we can do. My argument is that, without changing at least the pistons, and with little flexibility on the tune, we are only ever going to get incremental increases. Increasing efficiency by such things as port and polishing is a good tactic but it isn't going to do much.

You are right, sky is the limit if you have the money, but by the time we spend enough to realise significant gains, well, we could just trade in for a 300 or better.

Knightmare69

Very true in a points, none of which I'd argue. I think another member is waiting for Eurocharged to confirm they can flash our Siemens ecu, depending on how that goes I may alter my future goals with this car. For now I've managed to get my hands on a massive OEM fmic which I'm hoping will fit without too much hassle.

AusMB87

Hey,

So I just got word form one of my Benz contacts. The Pistons, Cams and compression ratio are different between the models, as well as the turbo.

He is going to get back to me about specifics, but they definitely run lower compression in the 250's with higher boost pressure.

So basically, short of a substantial rebuild, we are not going to get the same performance out of a 200.

I will get back to you when/if I get my hands on specific details

Knightmare69

Awesome, thanks for the update. Unfortunately our cars aren't as simple to mod as say Japanese cars so I'm not sure how feasible it'll be to run 250 cams in the 200 especially since we'd probably have to reprogram the ecu for it right?

Wait, how come Edmund's information says it's the same compression as c180/200?

http://www.edmunds.com/mercedes-benz/c-class/2012/road-test-specs1.html

EvolutionDrock

Yeah that member is me lol

EvolutionDrock

When doing research several websites listed compression ratio as 9:3:1 across all the platforms. But there was one that listed c180/c200 compression ratio as 9:8:1 and c250 as 9:3:1. Also from reading other mercedes benz forums some members said that the bottom end block was exactly the same across all platforms. The difference was in the head and the turbo.

AusMB87

I would say it is not feasible at all to swap out cams and pistons etc. Parts alone would be so expensive, you may as well put your C200 back to standard, trade it in on a used 250, pay the extra couple of grand and throw all your mods on the new one.

The C180 is 10.3 (with the 1.6 M271)

I seriously doubt the edmund's, or any other vehicle reviewer, have actually measured the compression ratio in each vehicle. They usually go off of dealer released info. As we all know, Benz is pretty tight lipped about that. Take those figures with a grain of salt...

I am one hundred percent sure that the part numbers differ. Given that the turbo and cam part numbers also differ, it makes sense that the ratio would be different. From a mechanic's perspective, the best way to get more power from an engine with identical bottom ends is to either lower compression and increase boost (cam change required to optimise) or bore it out. They have the same volume (1796cc) so it hasn't been bored.

We will just have to wait and see what comes back form my sources

AusMB87

I am pretty sure those 9.8 and 9.3 ratios will be on the money.

The bottom end is almost identical. conrods, block and crank are the same. Pistons aren't

Knightmare69

Sorry, I'm in a haze from multiple forums trying to find answers. So did they get back to you about this matter?

Toxicity

Just an update guys, just installed the Unichip and got it tuned by one of the local tuners here. Some cutting and splicing required. Pretty decent results overall. The good thing about the unichip is that it allows for adjustments based on the RPM of the engine. Bad thing is as Knightmare mentioned, this seems to be the limit of what we can do with the stock configuration.

Tuning was done on a dyno (dynojet).

Overall results were -
Before(With Rado IC and DP): 175PS, 278Nm
After (With Rado IC, DP, and Unichip): 195PS, 306Nm

Keep in mind these are taken at the wheel and not on the crank / flywheel. I can post the dyno sheet if anyone is interested. Looking forward to more updates from you guys as well!

AusMB87

I would love to see the dyno sheet! Not bad results - too bad we don't have stock figures at the wheels :S

IRIDIUMSILVER

Gentleman..
why not just install a Rado down-pipe and jb piggybank and be done with it?

AusMB87

Well, I'm not sure if the rado downpipe will fit my RHD car - the own from Armytrix doesn't.
As for the tune - there are many benefits to going with something from brabus, carlsson etc. Much more comprehensive units.

Above all, why do what's already been done? The figuring it out is more fun to me than bolting it on. The day I run out of mods is probably the day the car goes up for sale :-)

Toxicity

AusMB, my car is RHD as well and the downpipe just about fits. the main problem is the o2 sensor. it is tight but it goes in. Please note though that mine is a SLK but it should be the same.

AusMB87

Good to know. I'm waiting on word back from rado with a definitive. Mostly because the postage to Australia makes the part really expensive