Mercedes used the same air cleaner filter and dozens of slightly different air cleaner assemblies. They started out made of steel with a single air inlet (snorkel). The snorkel could be found on either side of the air cleaner and later higher power engines came with dual snorkels. The air cleaner later came in aluminum with plastic snorkels.

There have been many people saying their V8 engine ran horrible with after market cleaners, probably because the plate of the fuel injection was fluttering with uneven air flow.

Taking the dimensions from the K2N 2872 filter, the inside diameter was 292 mm and the height was 79 mm. That equates to a surface area or 83,596 sq. mm or 112.84 sq. inches.

But less than 50 percent of that area actually allows air flow!!!

The bottom inch is blocked off by the raised ledge of the air cleaner, and the entire rear section essentially flows nothing! That is almost 9 to 10 inches with no flow.

Then you have the hundreds of holes punched into the inner ring. You would think that would be very little restriction. But after I cut out many of the sections with holes, I measured a 24% restriction in the area that actually flows air.

Combining the rear area restriction with the bottom ledge and the ring of holes the total restriction is more than 50% of potential air flow.

Now I just spent over $70 for a new K&N 2872 filter so I won't be making further changes to my 1983 380 SEL aluminum air filter assembly.

But I think someone who really wants the most from the stock type of air cleaner should cut out the entire mesh/ holes and install an air filter with a 15 or 16 inch ID and 3.1 to 3.2 inch height. That would allow about one inch of space between the inside of the air filter and the air cleaner inlet formed metal. It would allow 100% of the air filter to flow air into the fuel injection system.

The restricted air flow of the stock air cleaner comes in at less than 60 sq. inches while an 15 inch air filter would flow almost 147 sq. inches

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