Jeep 4.0L Wrangler Sahara (A)
Gas Flowed Big Valve Cylinder Head | Unichip Power Tuning

The Jeep Wrangler is the archetypal compact sports utility vehicle, but in the South African high altitude / high ambient context its overall performance is impaired by two shortcomings – both of which can be addressed by tuning gurus, Steves Auto Clinic.

A combination of absurdly long gearing and a conservative, closed-loop engine management system have resulted in poor acceleration and excessive fuel consumption – particularly in the automatic version – which has limited its appeal as an affordable SUV.

These problems have been exacerbated by a tendency for Jeep owners to customise their Wranglers, often with a combination of bigger wheels and tyres, and accessories which add both weight and aerodynamic drag.

SAC started an intensive process of research and development on the current generation Wrangler late last year, and came up with a development on the 4,0 litre straight six engine which dramatically improved the performance, enabling a 0 – 100 km/h sprint in 11.4 seconds and a 176 km/h top speed despite the brick-like aerodynamics.

The lazy six-pot certainly lends itself to some tweaking, and SAC Engineering discovered that getting the air and petrol into this particular engine was the key, and to that end the SAC mule was enhanced with a six pack of enlarged inlet valves, a fat 63 mm throttle body, and a Sportflo air filter element in the original airbox, which has had an aluminium venturi moulded into it to optimise airflow.

The final part of the conversion comprises a tubular branch manifold and a stainless steel, free-flow exhaust.

On a dynamometer, the engine can now make up to an additional 25 percent more power than standard, as well as increased torque from lower engine speeds, translating into swifter overtaking and a vast improvement in towing ability.

More recently – and it’s a development which has enabled SAC to take the conversion into the marketplace with total confidence – was that the hard work with the engine management paid off when an SAC engineer finally managed to access the newer, more conservative electronic engine control units fitted since the beginning of 2005.

This enabled the fuelling parameters to be fully optimised via a piggyback computer -- in a similar way to which they have long been able to do on older versions of this engine -- resulting in significant improvements in fuel consumption.

In local tests simulating mixed urban/highway driving, the two-pedal Wrangler used for R&D realized a saving of approximately 15 percent.

“The focus of this, our latest conversion, has once again been on driveability and refinement,” commented Steve Fischer of SAC Holdings. “We could have made more power, and in fact we did have a bit more with a fabricated airbox, but testing revealed that induction noise was an issue, so we reverted to the original 'box'."

“The overall efficiency of the engine – rather than just peak power – has been our objective all along, and that is certainly greatly improved.

The Wrangler has become something of a fashion icon thanks to its iconic looks, and now it can really combine its excellent off-road ability with decent cruising manners and acceptable fuel consumption.”

A similar conversion can be carried out at any of SAC’s 12 outlets nationwide, and can be tailored to the customer’s needs and requirements: this can extend as far as offering revised differential ratios – a recommended change for those who intend using their Wrangler as a tow vehicle.