Air Filter Restriction vs Boost On FI
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From: Texas
Air Filter Restriction vs Boost On FI Has anybody done a comparison of boost psi without air filter vs. boost psi with air filter ? It seems to me that in FI application air filter restriction would be just as, or more influential on power since FI moves so much more air. Case in point: ECS uses restrictor ring to limit boost in certain applications. I have never seen an air filter promoted or frowned upon by the FI community, but there has to be a difference between most restrictive to least restrictive. I was thinking about a vacuum gauge between air filter and supercharger inlet and wondering if anybody has experimented with this. I was not considering running without air filter, merely trying to establish correlation of intake restriction & boost. I may be fishing in a dry pond, but I have to ask 
here's my experience for what it's worth.
w/ an 8" long K&N cone filter, i was only able to build 10# in first, 12# in second, 16# in third, and 17-18# in fourth. took the filter off and built a homemade screen w/ 1/8" squares and slipped a K&N outerwear over that. first pass i could only build 10# in every gear. opened the hood and noticed the outerwear had sucked the screen in about an inch. removed the outerwear and just ran the screen.... 16-19# in every gear. i guess in some cars it doesn't matter, but it may depend on how big your filter is to begin with.
w/ an 8" long K&N cone filter, i was only able to build 10# in first, 12# in second, 16# in third, and 17-18# in fourth. took the filter off and built a homemade screen w/ 1/8" squares and slipped a K&N outerwear over that. first pass i could only build 10# in every gear. opened the hood and noticed the outerwear had sucked the screen in about an inch. removed the outerwear and just ran the screen.... 16-19# in every gear. i guess in some cars it doesn't matter, but it may depend on how big your filter is to begin with.
I dont know about turbo's , but on my D1SC I was tuned with the tube and filter on(ran perfect). My tube/filter came off while driving somewhere, and at 5500rpm I immediately had detonation(prob made another 2-3psi) I believe if my motor wasnt a forged build she would have been toast.
8 sec potential, 12 sec slip
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From: Savannah, GA
I am running the supplied 6" conical filter that my P-1SC kit came with. On my new setup, it is restricting me a LOT. With the filter on, it only makes 545 rwhp at 11psi. With the filter off, it makes 632rwhp at 14psi. It also goes lean with the filter off since it was tuned with it on. I am not sure if it is the filter by itself, or if it is the hat, but the combination of the 2 is horrible. Once I move the radiator forward, I am going to put a 90° elbow on the intake side of the P-1SC and get a bigger filter.
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Fresh off the dyno -
The only change was taking the Air Filter off....Had a stock ATI Procharger filter on it, we removed it and the elbow and picked up 30rwhp and almost 2psi.
Car went from 545 to 579.
The only change was taking the Air Filter off....Had a stock ATI Procharger filter on it, we removed it and the elbow and picked up 30rwhp and almost 2psi.
Car went from 545 to 579.
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9 Second Club
Joined: Nov 2003
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From: Norn Iron
Did tuning and AFR's remain the same ?
I recall kp having air filter issues....
In that his fell off !!! Pretty sure he said it made little-no difference off or on when making a pass ?
Obviously filter size and design will play a massive part.
K&N rate their filters at something like 1.8X n/a flow rating for a FI application.
ie 100bhp n/a filter is good for 180bhp FI.
But at the end of the day, is it really worth the potential debris damage when not running a filter ? I know I'll never take that risk ! A lot of these useless wire mesh screens probably restrict more than a suitable sized air filter !! and do nothing for filtration.
I recall kp having air filter issues....
In that his fell off !!! Pretty sure he said it made little-no difference off or on when making a pass ?
Obviously filter size and design will play a massive part.
K&N rate their filters at something like 1.8X n/a flow rating for a FI application.
ie 100bhp n/a filter is good for 180bhp FI.
But at the end of the day, is it really worth the potential debris damage when not running a filter ? I know I'll never take that risk ! A lot of these useless wire mesh screens probably restrict more than a suitable sized air filter !! and do nothing for filtration.
Nothing in the tuning changed, those pulls were back to back.
We are making a wire mech screen right now and will be testing it in a couple of minutes. We will later install a much larger air filter and see what happens.
We are not looking to pick up a ton of power, but rather, see what the differences are so that others can decide what they want to do.
I hope this information is helpful.
We are making a wire mech screen right now and will be testing it in a couple of minutes. We will later install a much larger air filter and see what happens.
We are not looking to pick up a ton of power, but rather, see what the differences are so that others can decide what they want to do.
I hope this information is helpful.
9 Second Club
Joined: Nov 2003
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From: Norn Iron
With no tuning, is it a fair comparison back to back ?
Shouldnt tuning be optimised for each ? or where changes in tuning and AFR's negligable ?
If the AFR's seen were different, this could affect boost slightly too...
Shouldnt tuning be optimised for each ? or where changes in tuning and AFR's negligable ?
If the AFR's seen were different, this could affect boost slightly too...
8 sec potential, 12 sec slip
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From: Savannah, GA
Originally Posted by stevieturbo
With no tuning, is it a fair comparison back to back ?
Shouldnt tuning be optimised for each ? or where changes in tuning and AFR's negligable ?
If the AFR's seen were different, this could affect boost slightly too...
Shouldnt tuning be optimised for each ? or where changes in tuning and AFR's negligable ?
If the AFR's seen were different, this could affect boost slightly too...
And the hat/ filter assembly did restrict the boost. I think the higher boost was what made my A/F go leaner. Plus, with the filter on, my MAF was not maxed out. It did max it out with the filter & hat off- so that clearly shows it was flowing more air.
Idealy, the filter would not restrict it at all. This means I need a bigger filter for my setup.
AFR did lean out SLIGHTLY but not enough to really affect HP that much.
I will print out a graph with all three AFRs/Boost and HP.
I think the power is coming from the change in boost...and even richening up the AFR with the no filter run would still gain alot of power...Maybe 25 instead of 30.
I will print out a graph with all three AFRs/Boost and HP.
I think the power is coming from the change in boost...and even richening up the AFR with the no filter run would still gain alot of power...Maybe 25 instead of 30.
8 sec potential, 12 sec slip
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From: Savannah, GA
Originally Posted by 70Stang
ChecyChad -
You went super lean! That is scary looking...!
You went super lean! That is scary looking...!
Glad it was only for a split second on a forged motor. Not sure if a stock motor would have survived that hit tho... 
I have purpously taken the filter/hat off and ran it back to back several times, it has fell off and I ran it over and it never ran any different lol, so I dunno. I have also tried various 90 degree elbows with the same results. Believe me if I could pick up even a couple hundreths it would be off and a screen would be on it, its not like I have any special attraction th the inlet hat. But I do have a HUGE filter mounted directly on it and another small filter on the bottom where the bypass hose goes..
On The Tree
Joined: Sep 2006
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Originally Posted by cablebandit
i have a tiny kn filter and put a screen on yesterday...i wonder if that was some of my huge boost increase that i wasnt expecting.....hmmmmm
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From: Texas
Originally Posted by 70Stang
Fresh off the dyno -
The only change was taking the Air Filter off....Had a stock ATI Procharger filter on it, we removed it and the elbow and picked up 30rwhp and almost 2psi.
Car went from 545 to 579.
The only change was taking the Air Filter off....Had a stock ATI Procharger filter on it, we removed it and the elbow and picked up 30rwhp and almost 2psi.
Car went from 545 to 579.