If you are not able to login to the forum, please Contact Us here to let us know. Thanks!

Support FSC and see no ads! - Click Here
Results 1 to 8 of 8

Upside down air filter cover: Good or Bad Idea

This is a discussion on Upside down air filter cover: Good or Bad Idea within the Technical / Maintenance forums, part of the General Discussion category; Not sure where I read it or saw it, but someone was claiming better performance and better mpg's with the ...

  1. #1
    Registered User
    Join Date
    Nov 2011
    Location
    Angola, IN
    Posts
    118

    Upside down air filter cover: Good or Bad Idea


    Support FSC and see no ads! - Click Here
    Not sure where I read it or saw it, but someone was claiming better performance and better mpg's with the cover of their air filter turned upside down.

    This basically just leaves you with an exposes filter so air can enter in from all direction, rather than from the stock intake.

    I did it last night. My check engine light came on when I started the truck. At idle it was initially surging up and down a little bit for like 20 seconds, then smoothed right out. SES light went off.

    Did the same thing this morning. I was trying to get another mpg out of this TBI. Is this bad idea to try?

    what would be causing the surging and the SES to flash on? It's not like this 1990 5.7L TBI has a MAF or anything in the intake.

    Thanks in advance for your help and input.

  2. #2
    Registered User
    Join Date
    Jan 2012
    Location
    Indian Head, MD
    Posts
    428

    Re: Upside down air filter cover: Good or Bad Idea

    I'm not sure what would have caused the light to flash or the engine to surge. I think mine surged a little bit when I flipped the lid and the engine was cold. I've tried flipping the lid, but can't really say if it improves performance or mileage. The one thing it definitely does is increase the noise from the intake when you really get on the gas. The biggest factor I've found in mileage thus far is outside air temps and the number of heat cycles the engine goes through per gas tank. I've been religiously calculating mileage on each fill up since December. My truck is in tip to running condition despite its mileage. What I've found is that the worst mileage occurs when I do a lot of short trips, with cold starts, in cold weather. My mileage drops to about 14. Last week, I did a mix of short and long trips, and the outside temps were much higher than they were in December. The difference in warm up time when it's 25 degrees versus the time when it's 65-70 degrees is huge. At 25 degrees it takes about 4 miles to get up to normal temperature. At 65-70, it takes about 1 to 1 1/2 miles. That's a tremendous difference.

    Back to the filter cover. We know that the snorkel from the fender to the filter housing is barely suitable. At the same time, it is a "cold air intake." But the cold air is heated by that valve on the snorkel that pulls warm air off the exhaust manifold. Every time you get something good, you get something bad it seems.
    1. A cold air intake that's too small in any condition.
    2. An open air filter element draws in the hottest air possible in warm weather.
    3. An open air filter element in cold weather may cause the engine to take even longer to heat up which may reduce your mileage even more.
    4. The valve on the snorkel helps the engine heat up on the stock air intake. Unfortunately, most of them never work properly. They seem to be either closed fully, or partially open. They never fully open. So air intake is further restricted.

    On mine, I leave the cover in the proper position. The only change I made was I removed the valve/wax pellet assembly from the snorkel and sealed the hole with that tape that's like aluminum foil with an adhesive backing. With the warmer weather, I'm seeing 16-17MPG. I don't think it will get better than that.

  3. #3
    GMC RULZZ NEUMANNZZ's Avatar
    Join Date
    Mar 2005
    Location
    San Diego
    Age
    48
    Posts
    20,746

    Re: Upside down air filter cover: Good or Bad Idea

    put it back to stock.
    O2 GMC RCSB 4.8L V8 AUTO 3.73's
    rebuilt/beefed up 4L60E(at 43,000miles)
    Matching Ninja 500r


  4. #4
    Registered User
    Join Date
    Oct 2007
    Location
    TN
    Age
    31
    Posts
    7,842

    Re: Upside down air filter cover: Good or Bad Idea

    The idea is for more power, think everything has basically been covered.
    I have done this to a Carbed truck I used to have.
    The down side, you pull hot air from the engine in, the snorkle pulls in cooler air. If your in a dusty area your filter will get dirty real quick too.
    Really I don't think their is an advantage for a dd.


    03 Silverado ECSB, Dmax, Allison, 3.73 G80
    96 Silverado ECSB, 350, 4L60E, 3.73's Powertrax Locker
    05 Cavalier
    74 Corvette Stingray, 350, 4 speed
    49 F-1, flathead 6, 4 speed, 2wd, unknown rear end. Old rust bucket.

  5. #5
    Registered User ToyHauler's Avatar
    Join Date
    Jun 2006
    Location
    Western NY state
    Posts
    4,664

    Re: Upside down air filter cover: Good or Bad Idea

    i was getting 20-22mpg from my tbi 350, the only thing i did to the air intake is fix that valve all the way open
    99 GMC Yukon SLE 4dr
    KYB monomax, air lift, tekonosha, reese dual cam, bfg at/ko

    87 Firebird, 07 Monte Carlo lt, 98 Bonneville SSE, 04 F550 CC 4wd service body

  6. #6
    Registered User 19silverado94's Avatar
    Join Date
    Jun 2006
    Location
    Mississippi
    Posts
    246

    Re: Upside down air filter cover: Good or Bad Idea

    Phishin, I think your '90 intake/snorkle system is the same as on my '94. What I did was take off the flex tubing on the bottom of the snorkle and remove the butterfly, then I closed off the hole where the flex tube entered the snorkle. Now all air intake comes through the oem parts via fender, also taped off all holes in the right fender, trying to get more cool/ram air.

  7. #7
    Registered User
    Join Date
    Oct 2007
    Location
    TN
    Age
    31
    Posts
    7,842

    Re: Upside down air filter cover: Good or Bad Idea

    Toyhauler and 19silverado94 did the same thing.
    I would recommend the way Toyhauler did it though. It will be a smoother path for the air to flow, less turbulance, more air to the engine with less work.
    Either way you really won't notice much diffrence though.
    19silverado94 that flex hose is to heat the intake when it's cold, gets the engine up to temp and out of closed or open loop for better mileage quicker. (can't ever remeber which is closed or open loop)
    If it works correctly it's not a bad thing to have.


    03 Silverado ECSB, Dmax, Allison, 3.73 G80
    96 Silverado ECSB, 350, 4L60E, 3.73's Powertrax Locker
    05 Cavalier
    74 Corvette Stingray, 350, 4 speed
    49 F-1, flathead 6, 4 speed, 2wd, unknown rear end. Old rust bucket.

  8. #8
    Registered User Srabai47's Avatar
    Join Date
    Dec 2010
    Location
    Toledo
    Posts
    575

    Re: Upside down air filter cover: Good or Bad Idea

    I flipped the lid over 2 years ago and it hasnt hurt anything. Mileage is the exact same and the only reason i keep it is because the hissing air sounds cool. I have a K&N filter as well. it doesnt help my truck. but ill never have to buy a new filter again. your pretty much stuck with your mpg. these trucks will never be known for good gas mileage.
    1994 Chevrolet C1500 Suburban 5.7 260,xxx miles.

    1994 Chevrolet C1500 SCLB W/T 4.3 TBI NV3500-(Rebuilt 02/23/12) 3.42 --268,xxx miles -Blew motor (3/20/13)



    1992 Toyota Celica (182,000miles) - Sold

 

 

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •