K&N air filters experience

Yes, you shoudl be banned for asking such a question!
And nobody's ever going to manage to overtemp their cats with the little bit of extra airflow from a K&N. Your cat temps might go up by 5 deg F. So if you ran your car at track days every weekend of the summer your cats might lose 1% of their effectiveness at 100K miles. But you'd still pass emissions. Manufacturers are always conservative. Even Ferrari. They don't want to be hit with a recall!

 

if you run rich you will actually overheat the cat!!

the extra air in fuel injected cars it's measure by the mass sensor and the correct amount of gas will be provided by the injectors to correct the mixture so you will get and hp increment but the computer can correct up a to certain quantity of gas, after that you run lean and break the thing, a kN filter will work properly on fuel injected cars, on carbed cars you need to adjust the mixture

 

this is not true
if they can do it, they would have also change the cams to more agrresive ones, at NO cost becuase i'm pretty sure it costs the same to make a normal cam than a special one, just a little more on develoment

they don't try to squeeze as much power as they can because service intervals would be closer, so not good for costumers and also some plution issues

 

This is a valid issue. It points out the difference between a road car and a race car. Compromises are made for streetability as well as maintainence (i.e. you can't need to rebuild a street engine every week like a race engine). I touched on that point earlier.

I should have said, "They try to squeeze as much HP out as they can WITHIN THE PARAMETERS OF A ROAD CAR". Sorry it wasn't clear that was implied. Yet my point still holds: if you can *safely* add HP with a less restrive filter, it would already be on the car. Either Ferrari et. al. already get the optimum air flow already, or getting more will hurt the car in other ways that the factory deemed unacceptable.

Ken

 

another thing with high perfomance air filters is MPG's

if you install one you'll benefit from it

i've seen it happen before, one example, on a ford explorer sport trac from a friend of mine, i installed a filter on it, it whent from making 320km per tank to making 340 350, they i added a flowmaster exhaust and a KN fuel injection performance kit for it and it whent to 380 km per tank

 

its also about how quickly the combustion chamber fills.

so a filter that flows more air will provide some benefit.

 

You have to go much too rich to overheat the cat. The ECU will indeed measure the airflow and then it gives a programmed air/fuel ratio. This is a function of pedal position (in addition to many other parameters). At part throttle, it's programmed to give stoich, or about 14.6:1. At WOT it will be programmed to differing values at different RPM, sometimes with a timer function as well. It's quite possible for a manufacturer to program a vehicle to run at a better air/fuel ratio long enough to get a quarter mile run in, then go to a safer, richer level for long durations such as trailer pulling. Building a car is full of compromises!

 

actually , these are known as open vs. closed loop fuel monitoring.

at idle , the ecu relies on the lambda sensor to maintain the correct AF ratio.

at anything above idle , the ecu relies on pre-programmed fuel maps.

.

 

No, actually.
Any ECU from the last 20 years will perform part throttle fuel trim adjustments. These are known as "KAMs", "trims", etc by various manufacturers. As early as the mid 80s GM had about 6 cells divided into low & high RPM at low, mid & high throttle openings (I think that was the breakdown). In modern cars this matrix has been expanded by a factor of say 2 or 3.
At least that's the way it's been at the two members of the "Big 3" that I've done powertrain calibration at.

 

Many factory air cleaners are an overly restirctive deisgn because they also serve to lower intake noise... if that's not a function you desire, most any design can be improved on. (Read the long thread about the restrictions found in the carbed 308 airbox and the dyno improvements made by removing them.)

On my carbed 308, I went to individual K&N's... which required me to rejet the carbs. I can readily tell you that the performance, sound, and throttle reponse all improved noticeably... even though in theory inducting warmer air would hurt performance more than the unrestricted intake would help it...

The argument that air filters don't add performance is similar to saying that replacing the factory exhaust system wouldn't help either... both the exhausts and intakes in production cars are design compromises. I do think the changes are more noticable in carbed cars over injection cars, but only because the intakes in injection cars are better designed to begin with, using a couple decades of improvements in technology.

Does a K&N let in too much dirt? That's the charge and there is some decent evidence for it...

Bill

 

Where can one get these??? (green cotton or BMC) For a 1997 F355 spider.

 

Here's one from the archives: Rob ran his 328 on a dyno with a stock and a K&N filter, 18hp gain.

http://www.ferrarichat.com/discus/messages/6532/13916.html

 

So it really comes down to dirt.

Ferrari uses the exhaust they do as a compromise between noise, emissions and power. Aftermarket systems may give more HP at the expense of noise (and emissions). These posts all lead to the conclusion air intake is the same idea: a compromise between a clean engine and HP. I'll conceed from the evidence a K&N gives more HP, the only remaining question is at what cost to the engine.

Ken

 

like squeezing blood from stone .....

 

THEY work for me in my F512M put some in 15 months ago better throttle response if you search the archives the ones made for a VW fit the 512tr/f512m and they are lots cheaper than the ferrari ones if anybody needs the number i have it somewhere but did post it on here done the search its part no 33-2069 which is a VW filter

 

FWIW, 355 use the same filter as 550 and 456 too.

Green Cotton are made in France. i stock them but I have no idea where your nearest supplier would be. BMC are sold by numerous outlets, including several Fchat sponsors....

 

I think the bigger issue is that a K&N requires care and effort for it to work properly. It needs to be oiled periodically and applying too much oil creates a problem. That's probably the biggest reason a car manufacturer does not spec these as OEM, the average car owner does not want the hassle of caring for it properly and the manufacturer does not want to fix mass airflow sensor problems caused by an over oiled filter.

Cared for right, the trade-off may not be so large. You have to ask yourself if you are willing to spend the time and effort to provide that care.

 

There is a recharger kit that is fairly cheap, but K&N filter should last 50,000 miles. For $49 I think I will just replace it at that point. Hell compared to oil change I might just replace it every other year!

 

Oh, then it's perfect for my Lotus; it's self oiling!

Ken

 

Hi, you mentioned a good point about these K&N filters! It happenned to me, I had to replace the airflow sensor in my Boxster once because of it, at least according to my Porsche mechanic. But I still have K&N's in all most of my cars, including a 77 308GTB , which do run a little faster and smoother with it.
Si

 

Okay, this whole mixture vs. VE and air-flow has me tossing my hands in the air screaming, 'Aaaaarrrrghhhhh!!!!!'

I mean, for "practicalities sake"; Who has ever tried adjusting the carbs on a 308 (for mixture or balancing) with the air filter still attached?

Anyone? Bueller? Bueller? Bueller?

C'mon.... If anything can be said definitivley about the difference between a K&N that has (for arguments sake) a better air flow than the stock unit, it would be, "...that the K&N makes the mixture run closer to the condition the car was in (i.e., no filter attached!) when the mixture was originally set and deemed to be correct".

Just my 2-sense....

 

Great post, someone buy this man a beer. Another thing. Just because it flows more air, does not inherently mean its letting through more dirt. In fact it could be quite the opposite.

Imagine you have a sheet of burlap, and a sheet of fabric from say a nice bed sheet. The burlap has far less threads per inch, larger holes, and not very many holes per square inch. Maybe 25 threads per inch, maybe 100 holes per square inch. A good bed sheet can be over 200 threads per inch, over 400,000 holes per square inch. The square inch of bed sheet could potentially flow more air under equal conditions, while filtering out particles far smaller than a peice of burlap. Dont let higher flow rates fool you into thinking it has less filtering ability.