I purchased these, then saw all the negative posts here about them not fitting so got concerned.
Only way to get them on, is to unclip the hard plastic y-pipe off its seat on manifold, rear of engine, then place the spacers, and begin screwing everything back in a trial and error sequence.
It is a tight fit, but no leaks or codes.
I am happy, and as you can see, used two of the metal things for more height on front engine cover.
Price difference between my p30 and a p31 means the couple hundred dollars for more hp makes sense.

 

^ Fixed it for you.

 

Do they actually do anything?

 

For your car or your wallet?

 

They raise the included performance filters up into red spacer, creating unobstructed path for air to it.
OEM design has them 'hanging down' in the tunnel disrupting the flow, but also likely creating condition where only part of filter sees the action and therefore gets blocked up with debris first.
Members here are hostile toward them, for some reason, preferring the 'placebo' effect that obstructions do not matter.
I have no idea about actual gains, but long as no leaks or codes, they will very unlikely be slowing me down.
From memory and because I bought other stuff, UPD discounted its price to match similar product at VRP...
http://ultimatepd.com/2003-2007-merc...boost-kit.html

 

 

Why has nobody done a back to back before/after dyno of these to put this debate to rest?

 

1 - Because the manufacturer/ vendor doesnt want to be proved wrong about their claims
2 - Because the person that bought and installed them based on the manufacturer claims of 25whp gains doesn't want to spend more of their money to be proved wrong
3 - Because people that are on the fence don't want to waste their money on these plus a dyno in order to prove the claims


I would dyno test them if someone sent me a set but no way would I purchase them on my own because I don't believe you would see decent gains.

 

Why don't someone make a dynotest with a temporarily setup?
Duct tape and some material to space the boxes up would be the same, and good enough for a result.
Dirt cheap and those who want to prove the manufacturers wrong, can get their results so they can go full kill on this forum

If my dyno could take cars i would have done it already =)

 

Exactly. For the dyno pull, just take an old set of air filters and completely cut out the filtration medium (keep only the rubber surround), or for that matter remove the filters altogether and simply reinstall the air box tops upside down in open air (keeping the MAFs connected so the air will flow through them) with the hood open. No obstructions of any kind and no air flow restrictions, which would also shed some light on the perceived gains of the charcoal-delete Euro boxes vs. the ones we have in NA or for that matter "high-flow" air filters. I can't wait to see the claimed 20-25 hp gains.

 

Already did this. Picked up 3 hp going from stock filters to kn and charcoal delete
then to see how much rows could potentially add we did as you said and had no filters and open flipped lids. 2 hp more than kn setup

 

Despite the fact that those differences fall well within the repeatability tolerances of chassis dynos which are about 2% (so 10hp in the case of a ~500hp engine) in back-to-back pulls with no other changes and a 15-minute cool down between them, I am willing to reluctantly accept those numbers as what could possibly be gained. Reluctantly because (a) they are well within the margins of error of the dynamometer (repeatability - not accuracy), (b) what is a more likely reason for the small gain you saw is that your differential fluid was a little warmer for the subsequent runs and thus less viscous and providing less resistance, and last but certainly not least, (c) the fact that the stock air boxes and filters already flow more air than an M156 can ingest at WOT even with a stage 3 supercharger.

Any potential gain of course comes as a result of reduced air flow restriction, NOT because of any spacers where all other things are the same. The air in the airboxes is turbulent (the MAFs themselves on the clean side provide much more of an obstruction than that corner of the paper element in the airbox), and how smoothly the air flows doesn't really come into play until you are well into the intake runners. It always comes out the same way through the air filters.

Thanks for sharing and doing the testing in the first place.

P.S. Another thread on the same topic: https://mbworld.org/forums/c63-amg-w...er-review.html

 

Ya that’s what I got out of it. The air filters already flow enough there is almost no restriction. I’m in the camp that can’t see how a spacer would add power in this situation as no filters entirely offers almost no noticeable difference.

 

car designs since mid 1930's have been about harnessing airflow, same thing that keeps aircraft aloft.

without the spacers, intake has inexplicable obstruction, akin to the boxy cars capone used to drive in 1920's.

couple hundred bux is not much and should only concern p31 guy who refuses to match.

 

There is no obstruction that they fix, a spacer might help if the air was being pushed into the engine, but since the engine is pulling vacuum then the engine is sucking air through the filter so there is no obstruction, ram air pressure will only overcome the vacuum at about 300 mph, so they might help if you can get them to add enough power to get you to 300mph.

 

Er - air boxes have indeed been designed as resonant systems for the last couple of decades, but the airbox in this case doesn't really begin until you are at the front of the intake plenum. And, even if the (plastic) airboxes were designed as resonant systems both for the purpose of minimizing noise and producing optimal air flow, by adding those spacers you have increased the airbox volume and thus completely buggered up how the air flows likely resulting in a loss of power at mid-range RPMs with no effect on peak power. Sorry, but you cant have it both ways.

If you want to read more about resonant airboxes, here's a good article (it is written mostly with motorcycles in mind but applies equally to both bikes and cars alike): https://motorcycleinfo.calsci.com/Airboxes.html