I was wondering if an aftermarket air intake would be good for my car, or should I just stick with the old stock air box.
I have a 1984 300D turbo 125,000miles

I bought an aftermarket air intake from a friend and I put it on my car, and I will have to admit my car is alittle bit faster and I do get resonably better MPG.
But I hear my turbo working more than i think it is used to.

The air filter came w/ the chrome pipe some fittings and an oil seperator, and a reusable filter.
\


I know these cars are not meant for racing, they are meant for cruising. I only bought the air intake in hopes of improving my gas mileage from 20mpg to maybe 23-25 mpg or more.But if it is going to decrease the life of my turbo or my engine then I will put the old air box back in.
I do oil changes about every 3,500miles

Stick with the stock airbox. I'm guessing that your aftermarket air intake draws air from underhood which of course is hot air. The stock airbox pulls nice cool fresh air from next to the headlight. Hot air is not as dense as cold air and therefore does not provide as much oxygen for the engine to burn.

Also, your car was designed such that it gets all the air it needs, to make it go faster you don't need more air, you need more fuel. Unless you've turned up your boost pressure and/or adjusted your ALDA I guarantee you your car is not any faster, it is probably slower.

The reason you think that the car is going faster is that your aftermarket intake is letting alot more sound out of the engine because it probably is a conical filter that does not have an air box. The stock airbox acts like a muffler on the intake and greatly reduces the noise level coming out of your intake. That is also why you hear the turbo more, everything is just louder.

Additionally, your aftermarket air filter is probably a K&N style filter which does not capture fine dust particles as effectively as a stock filter. The small particles getting run through the engine will take a few miles off of the overall engine life.

And last but not least, MB designed the stock airbox, could you ask for better engineering than that? Not in my book.

__________________
1987 300SDL 167k
1992 Volvo 740 140k
1990 Volvo 740 250k
1989 Volvo 240 269k

Anyone want to trade an old Volvo for an '87 300sdl?

I get 25-27 mpg with the original equipment. '82 300D.

I agree with the previous post. A conical flter from K&N will likely not give u the type of performance improvement you think you might want. If you check the graphs of horsepower "improvement" claimed by most aftermarket filter manufacturers- you'll find that the improved figure is for "flow" not HP or Torque. What's more if there is a graph showing hp increases- there is usually not an indication of the other mods that have been done. A filter will not give you 25 HP- even at WOT.

A clean filter and factory cold air intake should give your factory set up what it needs. If you start swapping cams and exhaust on a big block motor with a blower- then YES you'll need more airflow to wind that sucker at 6000 rpm, but a benz diesel shouldn't need that kind of "flow," even near it's redline. I'd stick with a stock set up.

You're right about the graphs and what's even worse is that if you read the fine print on the side of a panel filter K&N box you will find that the restriction at max flow was not tested but instead was calculated. K&N literally made up some equation that basically says if the airflow is X at 100cfm then it must be Y at 350cfm. Their equation is complete garbage and was obviously created to fake the results they wanted. Why couldn't they just flow the filter at 350cfm rather than calculating it? Can K&N not afford a flow stand that goes to 350cfm? Yeah, right.

I have five years experience as a product design engineer for air induction systems and I can tell you that a treated paper panel filter typically only adds about 2" of water restriction at 300cfm. 2" of water restriction equates to roughly a 0.66% horsepower decrease (on a gas engine). So if you took the filter completely out of the system you would be lucky to improve a 200hp engine by 1.32 horsepower. In other words, trying to get horsepower out of a filter is a complete waste of time.

__________________
1987 300SDL 167k
1992 Volvo 740 140k
1990 Volvo 740 250k
1989 Volvo 240 269k

Anyone want to trade an old Volvo for an '87 300sdl?

New2MB:

Though I'm all for anything that involves sticking with the cheapo stock filter setup and saving $$, why is it that so many racing applications feature a K&N type system versus a paper filter? I know money seems no object for race car preparers, but if they can save a buck here and there, I imagine that they would.

I always assumed that since its easier to breathe through a piece of gauze (K&N) versus a piece of felt/paper (most other filters), that K&N would, logically, be less restrictive and possibly make things a little more efficient. You say this is not true, or at least of negligible benefit.

I agree with the reasons why one should stick with a stock airbox setup on a turbo - cold air from the grille is a lot denser and better for the turbo than is hot air under the hood. Why not use a K&N insert into the stock box? I've put one off only because I figure the oil being dumped all over it from the re-breather would make short work of a $40 K&N filter - I'd rather replace a cheap filter than keep cleaning an expensive one.

Barring a K&N, is there a preferable brand of paper filter or are they more or less the same (I know lots of people will say Mann - or Wix, that is if Dana Corporation survives their recent bankruptcy).

Thoughts?

__________________
Gil

2004 ML350
1984 300CD; Ivory (sold)

There are K&N's made that will fit the stock box. HERE is the K&N you would need. Applications

Yes, they flow slightly more air. Enough to push a 0.15oz pingpong ball 3" higher than a stock Fram in a test tube.

Here's a test. Do a 0-60 time with a clean, OEM paper air filter. Then, do a 0-60 time with no filter at all. The 0-60 times will be exactly the same. This goes to show you that the OEM filter is not restricting your air intake flow in any way, and all a K & N filter does it allow more dirt and particulates to enter and wear out your engine faster.

__________________
'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

I'd look for power elsewhere, I think full load stop + ALDA will limit much turbolag.

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

I disagree. My filter restriction gauge shows a max of 2" vacuum at the start of the u-tube (closest to the airfilter). Even with a new Fram filter, it's not flowing perfectly.

Granted, 2" H2O of vacuum is a far cry from the 11" H2O "limit". The stock box is not the best design. The two sharp 180* turns in the air stream will restrict the air flow no matter what.

Yeah, I can see that, but we're talking about two totally different components here. You're referring to the u-tube, I was talking about filters when you quoted me.

__________________
'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

For the record, it has been noted many times that even though there are some restrictive 180 degree bends in the air intake system, it still provides more than sufficient air for the turbocharged diesels. That's why I'm leaving my OEM setup alone, and have never considered a cone type or K & N straight replacement paper air filter.

__________________
'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

Air traveling through a tube with a 180 degree bend has no more restriction than air traveling through the same length of straight tube of the same diameter.

The 180 degree pipe will be slightly more restrictive. I doubt you could measure it readily availible equipment though. The turbulence the bend causes _might_ have more of an effect than any restriction it imposes however. ( Refer to this flame war thread http://www.peachparts.com/shopforum/showthread.php?t=146364 )

Personally If I was that worried about airflow I would run a second filter in parallel with the stock air box.

__________________
green 85 300SD 200K miles "Das Schlepper Frog" With a OM603 TBO360 turbo ( To be intercooled someday )( Kalifornistani emissons )
white 79 300SD 200K'ish miles "Farfegnugen" (RIP - cracked crank)
desert storm primer 63 T-bird "The Undead" (long term hibernation)

http://ecomodder.com/forum/fe-graphs/sig692a.png