Jeep's '99 Grand Cherokeeoand its all new, SOHC 4.7-liter V-8oare among the most interesting of this yearis new sport/utilities. Yet, if our reader mail is any indication, there remains considerable interest in 5.2/5.9-liter Jeep/Dodge V-8-powered rigs. So even though this performance review involves a vehicle thatis just left the marketplace, itis still a popular one.
Performance Products doesnit just carry a few goodies for your Jeep; it has an entire catalog dedicated strictly to this brand. For its own test vehicle, PP raided its warehouse and bolted a bunch of go-faster, handle-better hardware to this i98 Grand Cherokee Limited 5.2. Supercharging is quite common these days, but not the choice of every enthusiast who wants a moderate power increase at an equally moderate investment.
Before any mods were performed, the Jeep was baseline tested by our crew. Then PP got busy with a naturally aspirated performance makeover using many name-brand products. The stock air-filter housing was removed in favor of a K&N Generation II performance kit. This kit not only allows the use of an open-element, high-flow K&N lifetime air filter, but includes a panel that insulates the air filter element from the rest of the engine compartment, reducing the temperature of the intake air. The plastic housing is also larger and smoother than the stock unit.
Most of the exhaust system also hit the dumpster, replaced by headers and a stainless-steel cat-back exhaust system from Borla Performance. The sound quality is impressive yet not annoying during daily commuter use. Finally, a JET performance module was plugged into the Jeepis engine management computer system. These ichipsi convince the stock computer to feed the engine a more aggressive ignition and fuel curve, intended to increase performance throughout the rev range. The system is further augmented by a Jacobs Magnum ignition and high-performance spark plug wires. Other than the above, the engine, transmission, and gear ratios remain stock.
Suspension modifications are minor, consisting only of H&R progressive-rate springs, and Edelbrock IAS gas-charged shock absorbers. These springs lower the Jeep about 2 inches overall, so a modicum of ground clearance is sacrificed while the center of gravity drops a bit for better on-road handling.
Performance was markedly improved. The engine exhibited only one minor bad habit, a stumble at redline as the rev limiter cut in before the 1-2 shift. We didnit notice this condition when shifting just prior to redline or at anything less than wide-open throttle, so itis not likely to be a problem by any means. Be advised that use of the JET module means premium fuel is now required. The suspension mods yield less body roll and a more controlled ride; we suspect further improvements could be gained with high-quality rolling stock.
Retail cost for all the engine and suspension modifications is approximately $2150 plus labor, and itis reasonable to expect that this combination of equipment would have similar effects on 5.2-liter-powered Dodges, as well.