i've had a 1994 c180 for 4 years now, its my first benz, i bought the c180 coz at the time it was what i can afford. during the first 3 years or so ive been quite satisfied with the car, infact its safe to say that i love the car. Its been reliable, loyally transporting me to where i need to be, with good economy, and also quite a nice high speed performance too. although the acceleration was not that much (my late dad used to had a c230k) but once its ther its there. i regulary cruise the motorway at 100+ MPH, albeit i achieve it by flooring my foot down and avoiding any sort of braking LOL>
but, lately, i've been caught by the performance bug (again), i used to be a streetracer in my younger days where i would drop bigger motors to econoboxes.
the first thing i did was buying a used header from one of my mate at the indonesian 202 club.
there's a story behind this particular header. a couple of years ago, some guys at the 202club, who were track day fans had a so called rally car builder to design a header for them. there were 3 sets made in total, all of them being identical. two of the cars where these headers ended up were c230s and one of them was a c180 with an automatic trans. ive witnessed for myself how these cars perform when they were brought on trackdays. so when one of them decided to sell theirs, i jumped and bought it 9bearing in my mind how the c180 equipped with one of these headers performed on track).

to make a long story short, i put the header on my stock c180 motor< at first i just put it in without altering the rest of the exhaust whatsoever. the results was quite impressive, sudden ly my small 180 feels lively. i have the confidence to put my foot down and surprise other cars on the motorway. but, as a former part time streetracer/performance modder, i realize that the stock exhaust must be corking the header, and there must be more power to be had by properly tuning the rest of the exhaust system.

the first thing i did was to take all the silencers/resonators out, keepinng only the stock muffler, and replaceing them with straight thru pipes. the car performed better, nitoceably better, but. power seems to taper off after around 5300 rpm. so i think to myself : there must still be a lot of power to be had by reducing the backpressure of my exhaust. so i had a welding shop fabricate me a 2" straight thru exhaust pipe, but, it STARTED where the first resonator used to be at and all the way to the back , ending at the stock muffler.
with this setup i got an alot louder engine noise under power (understatement) , and i felt that the engine was able to rev freely up til the redline. but, with this setup i had a very very bad fuel economy , about 4.2kms / litre or about 12MPGs, when i drove it like i stole it, running constantly at around 100-110 MPH for about 30 minutes.

now, with this, i came to a revelation that, my exhaust must be having an over scavenging phenomenon, as theres no way a small 1.8 litre engine can consume such large quantities of fuel.

i checked out Vizard's exhaust tuning article that i got from a hotrodder site (very informative indeed). from it i learned that my exhaust was like having a resonator/ wave cancellation box, about 10 inch downstream from the header collector. and according to mr. Vizard, this would be similar to having the collector connected directly to a 1.5 inch (the stock ex pipe diameter) pipe that ends after only about 10 inch. so i think, maybe this is the cause of my alleged over scavenging problem.

right now i have put the straight thru 1.5 inch tubing back, ending at the stock mufflers. fuel consumption is back to around 20 MPG which was normal for city driving in the car.

i plan on redoing my so called exhaust piping system. what i know i have to do is to extend the connector by linking it to an equal diameter pipe for an extra 10 inch or so downstream of the header. what i need to put after that, is a problem that i hope u gurus could help me with.

here is more detail about my header

configuration 4-2-1
collector diameter 2.5 in

can you guys help me with desiging an exhaust sytem for my 1.8 l motor , equipped with the 4-2-1 headers, that would allow the engine to pull strongly from 300 RPM all the way thru 6000 rpm?

any input would be greatly appreciated

ps: im sorry if i sound a bit confusing since its 3.30 am here and i havent had any sleep, i just feel that i need to put this on the forum as soon as possible coz this matter has been making me find ot difficult to concetrate on anything else (my GF will testify for that LOL, im sure).