Can anything be gained by doing away with the funnel downed air intake on the S4 and makeing it all the same size?? Looking at it it looks like one could move more air if the tubing was all the same size it looks to be about 3 inch tubeing.

Cliff 87 S4

 

No difference. Plenty of discussion over the years on this issue, and other related air intake ideas.

Rich

 

Tim Murphy could supply you with a nice "air intake system".

 

I have 3" tubing all the way. there is (or theoretically could be) a loss across the venturi area, but the air flow throught the two tubes is fairly low. 250cfm max per tube (like a high powered computer fan) and with the leaky areas, some of the air is still coming in from the sides of the air box. (already proved this) so, certainly if you want to gain as much power as possible and keep hot air out, use sealed 3" tubes, and further clamp down your air box. probalby a few hp for doing this. However, you need to vent the back of the air box, because sealing the air box, just increased restriction by .5psi!!! so even though you have cooler air, the pressure drop due to the restriction of the system is a greater loss than the temp loss. Thats why i have the 3" tubes and a vented air box to the rear high pressure zone!

Mk

 

The air intake doesn't seem to have any level of restriction even on a race motor at WOT, Kibort measured a static pressure at 100 mph of +0.10 psi, which dropped to +0.07 at WOT, ie nothing lost.

Some talk about insulated hoses to keep the intake air cooler, but that doesn't really seem like much of an issue for a street car.

As soon you get past the air filter I think some flow restriction issues may show up, but I don't really know.

Something to consider is that increasing power may not change the character of the power much. You get a faster car with more traction and ticket issues, but maybe not that much change in how it feels to drive except at WOT.

 

If you get the right hoses, it can look real cool. GTSs have insulated full bore hoses BTW. My 80 came with full bore uninsulated hoses. I think the venturi design was to help clear the big intake manifolds of the 85 - 86 32V engine

 

I was told the venturi design was to keep the noise level of the intake down in Europe where loud cars are frowned upon. Can't remember where I heard that, might have been out of my ****..

 

78-80 had the corregated paper hoses. 81 was the first year of the intake muffling venturi, plastic hoses.

85-86 have special (NLA new, AFAIK) hoses with a much longer taper to fit alongside the plenums. The venturi section is just before the TB cover opening, and angled towards the fan shroud funnels. I would say that the 85-86 are the most restrictive of the various hoses.

 

thats .07psi, even with the rear of the intake air box vented with a couple of large openings to the base of the windshield. the real issue is, are the tubes sealed? if not, its not an issue, especially on a street car. if they are, then there is a sizeable restriction with the neck down venturi tubes. only way to test this would be to have a sealed air box. (based on what i know, im the only one that has really sealed the air box) and sealed air intake tubes. then, dyno runs with and without the venturis. i dont know the exact diameter, but since you have 2 inlets, even if it is half the diameter, two inlets of 1.5 " is still a lot of a inlet diameter to feed the air box. but, its like having 2 x 1.5" diameter inlets. probably more like two. i forget the reduction in diameter size.

i think its mainly a "looks" thing anyway.

mk

 

I went to a couple Mercedes dealers today, bought 3 from the first, one from the last, of 1980 something 380 sedan air cleaner hoses, part number 117 094 03 82 $9.12 each (various online sources are $6 or less, but I wanted it NOW), then a stop at a bug shop for a $16 foot of 3" silicone hose. Providing I can cut the hose and keep all my fingers and make it straight and tidy, 3" sections will couple the slightly smaller end of two of the Benz intakes and make one 928 intake. I see if it fits tomorrow.

 

I agree on the looks thing, I "may" just opt for silicone hose all the way, but all they had was blue, and I haven't settled on a under hood color scheme.

 

Does anyone know where an aftermarket MY 85-86 airintake tubes can be acquired? or fabricated? It is true that they are NLA....

 

As far as I know, no one makes them. They were the first thing I sold off the parts car and had many requested about them afterwards.

 

Thanks Imre - I bought your last one recently.. I'm just trying to find a place that will make new ones, as I begin the process of full restoration.....