On the Z (ls motor) my oil analysis showed huge levels of silicon with the k&n. After switching to an aem dryflow, these #'s dropped by 260% for the same mileage interval.....no more k&n for me in any car.

 

Thanks everyone for all the insight on this issue although its been visited many times, appreciate the help!

 

Why would you run a K&N filter on a car that only uses 1/3 of the paper filter, stock element? Looks?

It doesn't make more power and it simply ingests more heat (unless shrouded).

 

I sort of hate those blanket statements, especially unsupported.

An intake - not necessarily the K&N, but an intake - can help an engine produce more power. So can an exhaust. So can a remap. Car companies themselves use these tricks all the time when they uprate an engine as part of an option package, for example. An engine does not come from the factory optimized for power. It comes optimized for power + economy + emissions + noise + drivability + durability and reliability + cost targets, mashed up into a compromise that fits the most typical consumer in the most typical driving environment on typical fuel. With most modern engines, there is all sorts of power on the table if someone is willing to sacrifice one or more of those things (a recent example I read was the Toyota motor that Lotus buys. Toyota got 18 hp out of it with just a remap. Why? Because a Lotus driver is willing to put up with more NVH than a Corolla driver is).

Now, how, someone will ask me, do you explain the X51 kit? And the answer is that Porsche couldn't or wouldn't sacrifice any of those things except for cost. So to get a motor that meets noise, emissions and fuel economy regulations, is no less durable or reliable than the standard engine, is equally drivable and easy to live with and will run on regular fuel if necessary, they spent a ton on internal efficiency.

Engineering is all about choosing compromises. There are no two dimensional scales. So I don't think there's much value in making people feel stupid for wanting to mod their cars.

My .02, anyway.

 

It could not have dropped by 260%. 100% is the maximum.

 

Flow is greater than stock filter. A simple reading of your MAF flow will show you the difference.

 

I really should save this as a cut and paste file. Yes a K and N can flow more air. Without getting into the fact that with the same surface area a filter that allows more air through it will allow more dirt too.

Here's the point - our engines only need and can only use a certain amount of air. How much? How about 3.6 liters x the rpm of the engine. At say, 6000 rpm that 21,600 liters per minute. The stock air filter can flow three times that amount. The margin is to allow for dirt which accumulates on the filter over time. If anyone thinks that Porsche left 10 or more horsepower on the table by using an undersized filter on the water cooled cars, you are probably delusional.

The only exception I know of was the 993 - don't mess with the filter it has more than enough capacity. It has been shown that by drilling 5 one inch dia. holes in the airbox you get a measurable increase in power. That's because Porsche had to compromise the air intake system to meet euro noise specifications. This is not an issue on any of the water cooled cars.

 

With all due respect, if you think that the only factor in getting air into an engine is how big the hole is - I won't accuse you of being delusional, which seems a bit mean-spirited - you are oversimplifying what a car's intake does.

Anyway, this kind of debate quickly takes on a shrill irrationality on message boards like this, for reasons I can never quite understand. Anyone who has seen the process of designing an engine for the street would never argue for a second that a passenger car engine is optimized for power. I'm sure car companies would love to live in such a simple world, but they don't.

 

Well, good call....that's what I get calculating and posting from my phone. Basically what I was trying to illustrate was that using the given universal average my Silicon level with K&N was nearly double the universal average. Then with the AEM Dryflow, I dropped to well below (less than half) the universal average, so I was considering the universal average to be zero and less than that to be negative

 

Bruce, I am not trying to over simplify the effects of an intake system, but I believe the question was about the advantages of using an oiled filter such as the K and N versus stock. Having seen multiple before and after runs with stock versus B&M, and K and N filters, I know that there is no performance gain. A little more intake noise, yes. Power? no. I have seen power drops when people suckered for a silly cone filter setup which sucked hot air into the engine.

Regards,

 

No disagreement with anything you said in the latter post. I, too, doubt the benefit of a drop-in oiled filter on this car.

I guess I got distracted by your mention of the 993 box, since it kind of proves the point that intake systems are always compromises. In the 993's case, the effort to meet Euro noise regs caused pumping losses (as opposed to 'restriction'). I've got no basis on which to argue with people who say the 996's is as efficient as Porsche could make it - maybe it is and maybe it isn't - but I think people who make blanket condemnations of all aftermarket CAIs don't know their butts from a hole in the ground and should be called on it once in awhile.

I guess you weren't one of them after all.

 

You went way off topic Mr. Bruce. The M96 factory paper element will easily support 296-320hp. If you look under a factory element, you will see it only draws air through roughly 1/3 of the filter.

So, what is the point of letting more dust/dirt into the engine?

 

Ok, what is the reading difference then and what does that translate into hp #'s?

 

Um, I think we have that covered. I wasn't defending the filter. Read my post above. Bob mentioned the subject of intakes in general, and I further hijacked the thread. These things happen.

Again, I think we're all in agreement that a drop-in oiled filter is not superior to the OE paper filter in the stock intake. Nolo contendere.