An upgrade worth getting...

As much as I hate to admit it here, I swapped out my air box for a K&N Mass airflow kit. This is just the filter housing, and it's swapped for the truncated code style that gives 360 degrees of filter.

And I hate to say it, but you can hear that sucker sucking air. Sounds pretty groovy, and they boast a 10 hp gain at the flywheel.

It's too subtle to guarantee a difference, but I will say there surely is a difference between the stock box and paper filter and the K&N upgrade (I was already using a K&N square filter).
I know K&N are questionable, but in the time that I've had mine, after I fixed the injector problems, I've really noticed a stronger machine...I mean you can hear that sucker whistling as you gas it!




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Kurt B
1984 911 Carrera Cabriolet
75 914 1.8

I'm glad you like the enhanced induction music ... er, uh, noise level, but I'm not sure you really gained any power or torque from it. I'm not opposed to more 911 music on the streets at all, and I don't mean the kind speakers generate!

Personally, I feel the K & N folks have better ad copy writers than they do serious engineers that can analyze dyno data and actually make an improvement over factory hardware, whether it be from Porsche, Dodge, Ford, or GM!!! I have serious doubts that they have any dyno data to substantiate the claims of their ad writers, especially for our 911's.

But, that is just me, and I happen to think Bruce Anderson is a lot more than a guy who writes for a Porsche-oriented mag and has done a book and video about Porsches at Le Mans and a few other tracks around the world! He says the 'improved' air filters/boxes either show no increases or, in some cases, cost a couple of hp on CIS and Motronic engines, and his info DID come from the dyno! He also says the restrictions on the latest systems are always on the exhaust side of the heads, and smog-legal improvements there are hard to come by, and tend to be expensive to implement. My paraphrasing, folks, but still along his line of thinking for the past few years.

Again, nobody needs to take my comments personally, they weren't intended to insult or demean anybody!

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Warren Hall
1973 911S Targa

Well stated Warren, as usual.

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See Jerry Woods' dyno tests results of '84-89 Carreras with stock filter, K&N and no filter at all, in the current excellence.
Basically no difference, there was a tiny increase with no filter at all, but the K&N and stock were the same.
The problem is that the filter system is not the bottleneck. Therefore, no matter what you do to it (other than forced induction), it doesn't matter. The stock system already supplies a stock engine with more air than it can use. Woods recommends keeping the stock system, because the others don't increase HP and let in more dirt. His opinion, so if you disagree, complain to him (although I do agree with him).
Also, Kurt, what you got does not sound like the mass air sensor. A true mass air system might make a HP differnce, because it substitutes the "barn door" air flow sensor with a hot wire, "air mass" sensor. This can flow more air than the stock barn door system. It also costs around $1500-$2000, and while in theory it can increase HP, I don't know for a fact that it does in your application.
But, it does help to explain the situation. If your barn door can only flow X amount of air, and if your stock air filter system can flow X+1, it doesn't matter if you substitute a different filter that can flow X+2 or X+1,000,000.
What you got sounds like a simple, standard cone filter, not an air mass upgrade.

Hmm...well, the only way to tell any difference is to do a statistical test with some instrument more sensitive than way I have...And remember, the numbers given are for a stock car.

Where are the articles that challenge any claim of horsepower, and if it's been shown statistically that there is no significant difference, why hasn't their claim been challenged and pulled?

I actually had the privelige to put my car on a chassis dyno (86 Carrera). At the time all I had was my Racing Dynamics chip and I had bought the cone filter to measure before and after. I got 197 hp at the wheels with just the chip and 202 with the cone filter installed. On the road I couldn't feel the difference the filter made. After that I installed a B&B twin outlet muffler but haven't measured it since. It should be at around 210hp at the wheels.
Mike

Jerry Wood's in the most recent excellence is one example. Lots of others have tested cone filters in the past, and many have actually found decreases in power, because most factory air intakes are designed to, to the best extent possible, take in the coolest air possible in that particular application. Most (but not all, I'm not sure in your application) cone filters seem to take in more hot air than stock air filter systems, which leads to decreased power.

I have no idea of whether you are getting more power or not, but there are a TON of things out there that don't work, but don't really get challenged! Slick 50, lots of other cone filter systems, etc. etc. Just look at the claims made in most aftermarket parts catalogs. If you believed all of them, you'd have 300 hp with just air filters, spark plugs, wires, etc. I think MOST (maybe 90%) of aftermarket stuff is not as good as factory on a quality car like a Porsche.

Remember, Jerry Woods (in the current excellence) reported almost no gain with no filter at all (there was a little, but very, very little)! Mike the Mechanic's post above seems consistent with that. I don't think that your cone can possibly flow more than no filter at all.

As Wood's concluded, the stock paper filter system filters best. This is consistent with what most experts say. So, in his estimation, other systems are not worth the increased dirt intake. His conclusion: "Save your engine" use the stock paper filter.

In summary, my rule is this: In considering any mod, factory is presumed to be best, unless I am given undisputed information from a disinterested, reliable third party (Anderson, Woods, etc.)to the contrary. This is just a presumption, which can be overcome with good evidence. The basis for the presumption is that the engineers at Porsche are pretty smart and good at getting the most from the car. Its not an irrebutable presumption because any car co. has cost constraints, regulations, etc.

Others approach it the other way, that the aftermarket "mod" like a cone filter, splitfire spark plugs, oil additives, etc are presumed to be better than factory, unless proved otherwise. That is the approach that you seem to be taking. I'm not sure what the basis or explanation for that approach is, though.

I use to go to this drag strip until I got tired of hearing loud "open header" cars that were what I considerd slow (12-13sec. cars) lumbering down the track. What I eventually found interesting was the few turbo cars that were quiet but ran as fast or faster then the loud ones.

From what I understand the 911 is restricted on the Exhaust side not the intake side. So, unless it goes out faster it can't go in faster.

[This message has been edited by H20911 (edited 09-02-2000).]

This is my position also. Stock, or factory recommended upgrades like pressure tensioners. SSI. You know, the known quantities.

Nearly every other car on the planet is easier to upgrade than ours. To make one of those 'ordinary' other cars as track ready as a stock Porsche, thousands of dollars in upgrades would be absolutely required.

For example, if you wanted to get better wheels for your car, you'd have to spend A LOT OF MONEY. Fuchs are excellent wheels. To change shocks I'd be removing arguably the world's best shocks (Bilstien).

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'83 SC

Regarding the exhaust problems. I read an article in 911 and porsche world(August issue), that has an article about a company that makes a catalytic upgrade for the 3.2.
This seems like an obvious fix: to a newer cat design for the carrera owners. They say 27hp gain. Plus the guy with the mirror at the emission store will see what he wants(ours usually forget).
In Colorado, I was able to get a "collectors vehicle" plate for my car. Which means I only have to pass emissions once, and then send in the renewal slip every five years. No more emissions ever!
Which was nice considering how tough it was to get my tired old 2.2 to pass.
'70 911t w/'83 930/10