Your XJ Needs to Breathe Too

December 13, 2008 in Jeep Tech, Jeep XJ, Review by John W. | No comments

BreathingOne of the best things you can do for your XJ to increase horsepower and MPG is to allow your XJ to breathe better. Yes, your Jeep breathes. It breathes in through your air-box and out through your exhaust. You can help your Cherokee breathe by removing restrictions in the flow of this breathing process.

So, how do you remove restrictions? First things first, check your catalytic converter.  If this is going bad or broken then you’re already losing horsepower, wasting gas, and hurting your engine.

You can tell your catalytic converter is bad if:

  1. You’ve recently failed an emissions test.
  2. You’ve had a significant decrease in gas mileage.
  3. You’ve had a significant loss in horsepower, up hills, on the freeway.
  4. It feels rough during idle.
  5. You’ve experienced it stalling at idle.

If you’ve experienced any of these things you need to have an exhaust back-pressure check.

Performance Catalytic Converters

catconPrice: $100-$150

Performance Gains: 5-10 HP Increase

Websites like SummitRacing.com sell “performance” or “high flow” catalytic converters.  These have better flow than OEM catalytic converters and will reduce back-pressure throughout the engine.  Reduced back-pressure means increased flow and increased flow means more horsepower.  Upgrading your catalytic converter is a great way to help your Cherokee breathe better.

High Flow and Performance Mufflers

flowmaster_40_seriesPrice: $100-$450 Full Exhaust Systems

Performance Gains: 7-15% Increase HP

A great way to increase your vehicles “breathability” is to replace your OEM muffler.  OEM mufflers are designed to decrease sound more than they are to make sure your Cherokee is running at top performance.  You can purchase just a muffler or an entire exhaust system that contains a muffler, tail piping, tips, and hanging brackets.  The systems make replacing your exhaust a cinch and can be done in a matter of hours.   And again, this will reduce back-flow, increasing horsepower, and adding a great sound to your XJ.

Air Intake

Price: $30-250

Performance Gain: 5-10 HPxjairintake

Last but not least is your air intake.  What good is reducing all the backpressure if your not getting enough air into the engine in the first place.  Replacing your air intake with an open cone and tube design like the one on the right can take less than 10 minutes and give you a gain of 5-10 horsepower.

The stock box is restrictive and doesn’t allow the engine to get as much air as an aftermarket design.  Going with a company like K&N for your filter allows you to wash your air filter as well.  No more purchasing air filters every time you go off roading only to clog up your air filter with horsepower destroying dust and mud.  Check out Rustys Airtube it’s only$29.95 + $29.95 for the K&N Air Filter.

If you plan on going in some deep puddles, snorkels are also available.

All in All

Total Pricing:

  1. XJ Cat-Back Exhaust $150
  2. XJ Cat-Converter $100
  3. Air Intake $100
  4. Total Price: $350     Increased Horsepower: ~30 HP

Bottom line is reducing restrictive OEM parts and replacing them with aftermarket performance parts cannot only give you performance increases, but significantly increase your gas mileage as well.

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