991.1 GT3 RS Service Bulletin to Replace Air Filters?
10-09-2018, 01:24 PM
#16
Addict
Rennlist Member
Rennlist Member
So, if using BMC filters for better performance make sure to clean or replace very frequently. Since this means removing the rear bumper, I'm satisfied with using paper...
10-09-2018, 01:39 PM
#17
Nordschleife Master
Originally Posted by GrantG
So, if using BMC filters for better performance make sure to clean or replace very frequently...
10-09-2018, 04:37 PM
#18
Addict
Rennlist Member
Rennlist Member
I did read an investigation of K&N vs. Paper filters years ago (maybe BMC is better?) that showed a small advantage of K&N over paper for CFM flow, but the paper flowed better than K&N after a modest amount of use.
10-09-2018, 05:00 PM
#19
Nordschleife Master
Originally Posted by GrantG
I have no idea how much better (if any) the BMC's flow when new than paper. My point is that if someone is using the BMC's because of a real or only hoped for improvement of airflow and performance, that any benefit would be gone once the filter becomes even a little dirty. So, that's why I said to clean or replace frequently if performance is the motivation for using them.
I did read an investigation of K&N vs. Paper filters years ago (maybe BMC is better?) that showed a small advantage of K&N over paper for CFM flow, but the paper flowed better than K&N after a modest amount of use.
I did read an investigation of K&N vs. Paper filters years ago (maybe BMC is better?) that showed a small advantage of K&N over paper for CFM flow, but the paper flowed better than K&N after a modest amount of use.
I remember seeing a couple of Dyno runs posted over the years. I wish I remembered where they were posted,but they seemed fair : same day,same car,same temperature. The only thing they've changed between the runs was the air filter : all runs were between -1 --> +1. So negligible.
Also if I'm not mistaking, BGB(which is one of the tuners I really trust) said the same : don't expect an increase in performance from filters alone. Add a tune and a better flowing exhaust and now we're talking!
10-09-2018, 06:33 PM
#20
RL Community Team
Rennlist Member
Rennlist Member
Thanks.
I remember seeing a couple of Dyno runs posted over the years. I wish I remembered where they were posted,but they seemed fair : same day,same car,same temperature. The only thing they've changed between the runs was the air filter : all runs were between -1 --> +1. So negligible.
Also if I'm not mistaking, BGB(which is one of the tuners I really trust) said the same : don't expect an increase in performance from filters alone. Add a tune and a better flowing exhaust and now we're talking!
I remember seeing a couple of Dyno runs posted over the years. I wish I remembered where they were posted,but they seemed fair : same day,same car,same temperature. The only thing they've changed between the runs was the air filter : all runs were between -1 --> +1. So negligible.
Also if I'm not mistaking, BGB(which is one of the tuners I really trust) said the same : don't expect an increase in performance from filters alone. Add a tune and a better flowing exhaust and now we're talking!
Some years ago, I had a tuned Volvo V70R. Some friends of mine and I got a commercial grade manometer and hooked it up to the intake tract at various points. What we found was that once the car was tuned, a slight vacuum developed in the airbox under full boost. We solved this by developing a true cold air intake from behind the lower bumper near the foglight.
While we were doing this testing, we also tested the difference along the intake manifold downstream from the filter. The BMC filter was at the time a popular upgrade (I ran one). The stock Volvo filter was cylindrical, about 10" by about 3 or 4 inches in diameter. The BMC replacement was a direct bolt into the factory airbox.
What we found was that once we solved the intake issue upstream of the filter and we were running our CAI, that there was almost NO difference in pressure in the intake runner downstream of the filter whether the BMC or the OEM paper filter was used. We're talking so small as to be within the margin of error from other factors (Boost, IAT, etc). Less than 5" of water difference (which is 0.18 psi) separated the tests. Furthermore, those running oiled filters began to see premature MAF failures from over-oiling.
Conclusion was that the BMC filter could not offer any performance benefit over the standard paper filter, which was of excellent design. Sounded good though...
10-09-2018, 06:54 PM
#21
Nordschleife Master
Originally Posted by Needsdecaf
(I realize that this is only directly relevant).
Some years ago, I had a tuned Volvo V70R. Some friends of mine and I got a commercial grade manometer and hooked it up to the intake tract at various points. What we found was that once the car was tuned, a slight vacuum developed in the airbox under full boost. We solved this by developing a true cold air intake from behind the lower bumper near the foglight.
While we were doing this testing, we also tested the difference along the intake manifold downstream from the filter. The BMC filter was at the time a popular upgrade (I ran one). The stock Volvo filter was cylindrical, about 10" by about 3 or 4 inches in diameter. The BMC replacement was a direct bolt into the factory airbox.
What we found was that once we solved the intake issue upstream of the filter and we were running our CAI, that there was almost NO difference in pressure in the intake runner downstream of the filter whether the BMC or the OEM paper filter was used. We're talking so small as to be within the margin of error from other factors (Boost, IAT, etc). Less than 5" of water difference (which is 0.18 psi) separated the tests. Furthermore, those running oiled filters began to see premature MAF failures from over-oiling.
Conclusion was that the BMC filter could not offer any performance benefit over the standard paper filter, which was of excellent design. Sounded good though...
Some years ago, I had a tuned Volvo V70R. Some friends of mine and I got a commercial grade manometer and hooked it up to the intake tract at various points. What we found was that once the car was tuned, a slight vacuum developed in the airbox under full boost. We solved this by developing a true cold air intake from behind the lower bumper near the foglight.
While we were doing this testing, we also tested the difference along the intake manifold downstream from the filter. The BMC filter was at the time a popular upgrade (I ran one). The stock Volvo filter was cylindrical, about 10" by about 3 or 4 inches in diameter. The BMC replacement was a direct bolt into the factory airbox.
What we found was that once we solved the intake issue upstream of the filter and we were running our CAI, that there was almost NO difference in pressure in the intake runner downstream of the filter whether the BMC or the OEM paper filter was used. We're talking so small as to be within the margin of error from other factors (Boost, IAT, etc). Less than 5" of water difference (which is 0.18 psi) separated the tests. Furthermore, those running oiled filters began to see premature MAF failures from over-oiling.
Conclusion was that the BMC filter could not offer any performance benefit over the standard paper filter, which was of excellent design. Sounded good though...
I also think that if there was a real performance difference between paper and oily(any brand...I am not here to put down a specific manufacturer) filters,then manufacturers will start using them from the factory,whether you are talking a regular sedan or a high performance machine. And as I said before,yes I am aware that Porsche is using BMC from the factory on the RS! But I believe they are doing it for the increased intake noise that AP was talking about at high speed due to the RAM effect.
10-14-2018, 11:06 AM
#22
Rennlist Member
Originally Posted by 911therapy
Hey Matt - I cant answer your question about porsches new service interval for the filters. But, the BMC filters can be bought for less than $150 and, as handy as you are, you would have no problem just pulling the bumper cover and dropping them in once a year. It would make more sense to just replace instead of trying to clean them (and then have the worry of over or under oiling them).
I do know the BMC filters on the RS are oiled filters and some say those tend to collect more dust/grime than the paper filters. Maybe thats why porsche recommended the quicker service interval. I run the BMC's in my GT3 and swap out annually, unless I am in a dusty area or dusty track....and then I swap every 6 to 8 months...
I do know the BMC filters on the RS are oiled filters and some say those tend to collect more dust/grime than the paper filters. Maybe thats why porsche recommended the quicker service interval. I run the BMC's in my GT3 and swap out annually, unless I am in a dusty area or dusty track....and then I swap every 6 to 8 months...
