Modification of OEM Air Box

Kfd405

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Sep 27, 2021
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Tennessee
I have a 1998 TJ 4.0L. Instead of spending a few hundred dollars on a high flow new air filter/intake, I opted to modify my existing OEM box. Recognizing that the restriction to air flow was coming from the relatively small mouth of the OEM intake, I removed the bottom box all together. I then loosened the pipe collar, inverted the top of the air box upside down, and secured the rectangular OEM air filter into place with large zip ties. Seems to work amazingly well. Marked improvement in power. Does anyone have any experience with having done this? Any potential pitfalls?? Not planning to submerge my TJ do I don't feel water incursion will be an issue.
 
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I have a 1998 TJ 4.0L. Instead of spending a few hundred dollars on a high flow new air filter/intake, I opted to modify my existing OEM box. Recognizing that the restriction to air flow was coming from the relatively small mouth of the OEM intake, I removed the bottom box all together. I then loosened the pipe collar, inverted the top of the air box upside down, and secured the rectangular OEM air filter into place with large zip ties. Seems to work amazingly well. Marked improvement in power. Does anyone have any experience with having done this? Any potential pitfalls?? Not planning to submerge my TJ do I don't feel water incursion will be an issue.
Venturi, learn it. Stops you from making silly assertions.
 
Marked improvement in power? Have you dyno tested this?
A number of years ago, I put my TJ on the chassis dyno at my old shop. I tried several mods on it
1) larger injectors
2) CAI
3) a couple different programmers.
Numerous passes later, we found no real increase in HP/Torque #'s
I do remember that you lost a lot of HP through the drivetrain.
If memory serves me correctly, I think I was anly getting like 98hp at the rear wheels.
The fun part was putting 75hp shot of nitrous thru it, which only netted like a 30ish hp gain at the rear wheels.
 
A number of years ago, I put my TJ on the chassis dyno at my old shop. I tried several mods on it
I do remember that you lost a lot of HP through the drivetrain.
Not surprised at all. Especially on the automatics. Not efficient at putting the power to the ground by any stretch. 20-25% drivetrain losses for sure.

I'm sure a good dyno tune via hp tuners with some street fine tuning would net efficiency and power gains...but for the cost involved one would have to figure out if it was worth the investment.
 
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Recognizing that the restriction to air flow was coming from the relatively small mouth of the OEM intake.

You recognized wrong. There is no restriction whatsoever from the factory airbox. Every thing you just did is a complete waste of time and will gain you nothing whatsoever. Sorry to be blunt, but someone had to.

TJs DO NOT suffer from restrictive air intakes. That is a cold, hard fact.
 
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Not really. The amount of air the engine needs is determined by the position of the throttle body butterfly. Even at wide open, the stock air box delivers more air than the engine can use.
Sorry, that's what I meant. PEOPLE THINKING more air = more power
 
I really want to see this with the zip ties holding the filter in place…
Ok. Some of you need some basic manners. Seriously. Attached is a photo of what I did. All I can say is that driving the TJ with same barometric pressure, same air temperature, humidity, and same fuel,..... with this modification, my TJ doesn't seem to bog down at 1500 rpm and it now maintains 90 MPH on the highway. Before the modification, I had the peddle to the floor (literally) to hold 78 MPH. So,..it is what it is.
Cheers
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