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SA4x4 Clinic got a technical query

Chips And Cats

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Question by: Johnny Viljoen Answer by: Justin Bennetts & Arnold VenterI have an ’08 Jeep Wrangler Sahara V6 AT. I want to remove the vehicle’s catalytic converters but someone told me I’ll experience engine management problems and that the warning light will remain on. Is there a solution to this problem?
Secondly, I was told to steer clear of a super-chip conversion. Rumour has it that the piggy-back system will confuse the ECU. Is this true?
Johnny Viljoen

THE EXPERT’S OPINION (ONE):
The advice you’ve been given is entirely correct. Later model Jeeps (’05 onwards) are incredibly sensitive to having their catalytic converters removed and will often report engine faults. Previous models were far more forgiving.
Your Jeep has four lambda sensors: two situated behind the catalytic converters and another two stationed on each bank of cylinders. Once you remove the catalytic converters the after-cat sensors will send an incorrect signal to the ECU causing the engine management light to come on and a diagnostic fault reading (emission control) to occur.
There are two possible ways to solve this problem. Your first option is to remove the cats and simultaneously fit a Unichip with ‘lambda fooling’ function – this will override the signal from the rear lambda sensors and tell the ECU that everything’s fine with the exhaust. Alternatively, you can opt for an aftermarket high-flow catalytic converter, but we haven’t seen a significant performance difference between these units and the OE-fitted ones.
As mentioned before, modern Jeeps are particularly sensitive to having their cats removed and in this vehicle’s case I would refrain from performing such a modification. If the OE units are completely blocked and you can’t afford replacement parts, consider the Unichip solution. Otherwise, stick with a recognised replacement part.
Justin Bennetts
Powerflow Exhausts (Tokai)
(021) 701 5513


THE EXPERT’S OPINION (TWO):
As explained in previous Clinic responses: if there’s a problem with a performance chip conversion it’s almost always instalment related. In other words, if you know of a vehicle that has engine problems due to a chip conversion it’s because the company that installed the unit did a poor job setting it up.
Performance chips manipulate the ECU at different engine speeds; they have no impact on the ECU’s standard functions. We’ve conducted countless performance chip conversions on the Jeep V6 engine and have never had a problem.
Arnold Venter
CRD (4×4 fitment & repairs)
(011) 907 0580 / arnold@crd.co.za

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