Out with the old, in with the new...air filters


fjpikul

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Jan 4, 2006
11,704
Belleville, IL
I just got my new air filters from Torrie on Friday. Pulled the air box today, pulled out the old, orange colored filters, and tried to install the new black colored filters. One filter fit, and the other didn't. They are exactly the same. Apparently, one side of the air box is just slightly less wide than the other. I shaved off about 1/8 inch of the foam with a razor blade and it fit just fine. Later on in the day, I talked to ShadowMan who feels it might be a new supplier with slightly different tolerances. This is an FYI for those who might run into this probelm again.
 

Kingman

GT Owner
Mark II Lifetime
Aug 11, 2006
4,072
Surf City, USA
Thanks for the FYI Frank!:thumbsup
 

RALPHIE

GT Owner
Mar 1, 2007
7,278
Been doing that since I got my car. I've never seen replacements the same color as the originals, and have trimmed them to fit.
 

BlackICE

GT Owner
Nov 2, 2005
1,416
SF Bay Area in California
Been doing that since I got my car. I've never seen replacements the same color as the originals, and have trimmed them to fit.

I wonder if one of the after market air filters fit better without having to trim one.
 

Rockstar

GT Owner
Jun 30, 2009
139
Golden, Colorado
I cannot say that I have had a problem getting my filters to fit. But what I want to know is who has the best flow filter, K&N ? I do know that Dustin at Whipple is working on another filter and Kip is going to do testing on the GT air box. In the mean time what should us 4.0 guys use? Here is the mod that I have done to help flow untill we get some solid answers.
 

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fjpikul

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Jan 4, 2006
11,704
Belleville, IL
Now's a good time to bring it up RALPHIE. Go back to driving off bridges. Now just how many times could you have changed filters by now?
 

RALPHIE

GT Owner
Mar 1, 2007
7,278
Now's a good time to bring it up RALPHIE. Go back to driving off bridges. Now just how many times could you have changed filters by now?

On my 4th set.

PS - I stored my originals as they weren't that dirty, as I don't think you'll ever see those for sale by Ford. Might come in handy at a Concours in 40 years.
 
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fjpikul

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Jan 4, 2006
11,704
Belleville, IL
Ralphie, where have you been driving? Four sets already? I thought mountain air was crisp and clean?
 

RALPHIE

GT Owner
Mar 1, 2007
7,278
Ralphie, where have you been driving? Four sets already? I thought mountain air was crisp and clean?

Over 30,000 now. When traveling across the desert areas, if there is wind, a lot of dust can be in the air. Also, they have been doing a lot of road "improvements" on US 395 (the link to SoCal or Rano) which also stirs up quite a bit of dust.

If I was like EP, none of this would bother the GT, 'cause it would never come out of the garage. However, I can't resist driving it.
 

TO AWSUM

Ford GT Owner
Mark II Lifetime
Jul 4, 2007
1,512
Niceville FL
I'm sure the 4L Whipples require more air, but I don't think I'd substitute more air flow for less filtering ability. Hopefully, Kip will be testing the particulate size at the same time as he is testing air flow. :biggrin I'd hate to see owners lose engine longevity to gain a little more horse power when there may already be too much so some are looking at adding traction control to take advantage of the power adders.

Then again, can you ever have too much horse power? Maybe not.:willy
 

paul b

GT Owner
Nov 2, 2006
810
I cannot say that I have had a problem getting my filters to fit. But what I want to know is who has the best flow filter, K&N ? I do know that Dustin at Whipple is working on another filter and Kip is going to do testing on the GT air box. In the mean time what should us 4.0 guys use? Here is the mod that I have done to help flow untill we get some solid answers.

I always thought the inlet side of the air box was the cause of the inlet tube collapsing and what you did was the easiest solution. Now that its been done, can you feel any difference in performance or driveability?
 

AZGT

GT Owner
Mark IV Lifetime
Dec 20, 2005
1,354
Scottsdale, AZ.
Just changed mine. Also different than the orange rim originals. They wanted to "pop up" in the enter just a little, but I figured when I cranked them down it would make a snug fit and make them conform. They did fit.

FYI - the filter code on the (my) originals (just to document in case they are cheaper elsewhere like the oil filters were) is XL 3U-9601-AC-RR.
 

w.a.nelson

GT Owner
Mark II Lifetime
Feb 29, 2008
1,119
Asbury, NJ
Just installed K&N filters. Don't know if they really flow better or not, but thought it was worth a try. They are supposed to be "lifetime" - can be cleaned and re-oiled. They fit perfectly into to the airbox in the space occupied by the original orange filters. Don't know how they compare in price to Ford or other OEM replacement - they were $43 each.

K&N also offers an oil filter cartridge for around $ 10.
 

Rockstar

GT Owner
Jun 30, 2009
139
Golden, Colorado
I always thought the inlet side of the air box was the cause of the inlet tube collapsing and what you did was the easiest solution. Now that its been done, can you feel any difference in performance or driveability?

I think what I have done has not completely solved the problem but helped air flow. What I should of done is dynoed the car before the modification and then after the mod. Before I go back to the dyno with the 4.0 we are changing the injectors to 1000 cc. Also replacing the 3.25 pulley with a 3.0. After we get it tuned on the dyno runs we are going to pull out the K&N filters and see what changes. We truly believe there is some restriction in the air filters.
Talking with Scott Fisher at Fisher Motorsports, he is in the process of looking into building an oval throtal body. After that he wants to double the filter space by enlargening the air box. The 4.0 is uncharted teritory and the air demands are much larger then the Gen 2. There are other items on the GT we are talking about to make the 4.0 achieve 900 to 1000 RWHP on pump & race fuel. This will take some time and we will keep you posted.
 
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