K&N Cone filter for 951
 

I was thinking about replacing stock air filter box with a K&N cone filter. Anybody know the filter size and/or K&N stock#?SmileWavy

Leave the factory airbox unless you put a MAF system in behind the drivers side headlight. A cone filter in the same spot of the airbox is picking up hot air from both the intercooler and radiator. The stock airbox picks up cold air from the fender area.

Thanks for the good advice.

You will lose noticable power with a cone filter. Stick with the stock setup. But go ahead and go with the k&n filter for it.

I started thinking about the cone filter when I saw some other 951 pics on-line w/ cone filters. So, being new to the 951 I thought, OK must be better.

Just goes to show you, be careful and ask. Thanks for your knowledge and experience.

why do you post this when you know several folks, here and rennlist, have done temp checks and the difference is minimal.:confused:

while i haven't checked on a 951, nor have i seen the measurements others have taken on it, on other cars there is a significant difference in intake temps when the filter is getting air from outside the engine bay at an unobstructed cold source like the front of the car - generally at least a good 20 degrees, which is a couple of horsepower - the trick in measuring temps though is to do it on the road - measuring intake temps sitting still won't be anywhere near an accurate reading - even the huge fans at the better dynos don't truly duplicate conditions

filter surface area is also a huge factor in the equation too - a cone filter even if placed in cold air may still not produce as much power as stock if the surface area is smaller

it's also pretty easy to isolate filters in most cars, and it doesn't take much in the way of a box to do it

Please do tell which folks on Rennlist have posted threads about there being minimal temperature difference.

Recently there was a post brought up about sitting idle in traffic where the tester saw temps as high as 180*F in the engine bay in traffic. Hello heat soak. And dont forget the part where he tested the temp depression between ambient and outlet air. True, my source is from an internet forum and i have done no empirical testing, but in my opinion its not hard to understand why so many people frown upon a cone filter on a stock AFM.

http://forums.rennlist.com/rennforums/showthread.php?t=456802&highlight=temperature

True, you may get close to ambient temperatures in the engine bay when the car is moving at speed, but the air filter is still positioned right behind the exit path of not one, but two heat exchangers.

i've spent a lot of time over the last year playing around with under hood temps, creating block off plates, diverters, and heat shields - i can definitely tell you that the proper airflow under the hood (this does not mean an increase) is critical to intake temps - no chance i want an air filter exposed to that heat, and i definitely want a divider of some sort between the intake air and the rest of the engine bay - intake temps have seen a very nice drop as a result of the new pieces, and i have more in mind

an airbox is one way manufacturers achieve some of this - many modern cars merely use a semi-sealed divider box - both are effective at limiting heat soak from reaching the intake air, and at a bare minimum, reduce the recovery time to cold intake air

but, all is for naught if the filter surface area isn't up to the job, or there is restriction in the path

manometers are very helpful in this quest, as are temp sensors placed throughout the engine bay

"search" is their friend.

180 deg in eng bay in traffic, no surprise there, the water temp is at least that hot, if not hotter.

I fitted a Pipercross hi flow foam filter in my standard airbox. Just personal choice instead of K&N, as I've used them on all my race cars.