So I figured when starting the performance modding of my -99 230, I would just start with the start - the cold air intake, air filter box etc pre supercharger. So to know where the bottlenecks are, I made up a DMDPG inspired from these articles Eliminating negative boost
. Here is my DMDPG. :
I made three points of measure. 1st just in front of the intake funnel, behind the grille:
The next point of logging data is in the air filter box, below the filter, hence the difference between no one and no two would give the pressure fall trough the intake snorkel.
The third point was the hole in which the oil catch return hose enters the air filter box AFTER the filter, hence difference between no 2 and no 3 would give the pressure fall trough the filter.
Ideally, I would have measured just at the supercharger intake, to see how much is lost from the box to the SS, but I was not able to make a convenient connection here, so that part of the system is still without data.
I made a connection point where I could swap the three hoses and lead them into the cabin:
Then the hose was lead under the hood, around the A-pillar and in trough the window:
Audun, my assistant, ready to note negative boosts:
Pressures was measured at WOT in 2nd gear (MT) in the same piece of road, slightly uphill, from 2000 - 6000 RPM, and peak value (typically at the high rev end) was noted as accurately as possible
Measure point one, behind grille:
4,5 inches of water negative pressure
(Interesting part is, at 100km/h, at cruising conditions, there were 2 inches of positive pressure here)
Measure point two, in air filter box, before air filter:
17 inches of water negative pressure
Measure point three, in air filter box, after air filter:
18 inches of water negative pressure
While the data shows that the SLK cold air intake and air filter system is probably no worse than that of the Audi S4 and Subaru Liberty RS, there is a lot of parasittic drag in the system, of which the filter comprises only 5,5%, the pre intake duct area 25% and the intake snorkel a massive 69,5%!
Needless to say, there is a new snorkel design on it's way. Also, with a better system for collecting air in to the snorkel, there is a potential of getting rid of another 5-6,5 inches of water of pressure fall, converting it in to a positive pressure exceeding the drop over the filter given a good design.
Comments are welcome