Terribly sorry we've been away the past two months, but Top Truck Challenge and summer trail coverage have required more than our undivided attention. (Speaking of Top Truck, we can't start our first post-TTC "Teal J'' story without congratulating Phil Smith and his TJ on an impressive Second-place finish.)
Now, on to this month's subject.
A 4.10:1 ring and pinion and 33-inch tires have long been thought the "perfect combination'' for nearly any vehicle equipped with anything larger than a four-cylinder. Rpm-wise, the 4.10:1s are indeed just about right for highway cruising in Fifth gear. However, in Teal J, when that freeway becomes inclined five or seven percent, power seems to drop off and we're forced to downshift. Likewise, off-the-line acceleration and passing power are a bit more sluggish than stock. So what to do?
We could swap to 4.56:1 gears, but we'd already invested in the 4.10:1s, and 4.56:1s might actually rev a bit too high on the freeway. A V-8 swap was contemplated (dreamed of, actually), but that would require an axle and transmission upgrade to maintain durability. In addition, we would have sacrificed our factory warranty.
A more practical solution to increase power in the stock motor came from the folks at Turbo City. We didn't add a turbo, but we did install Turbo City's new TJ Performance Kit.
Old School Tricks
There's nothing ground-breaking about Turbo City's kit. It amounts to a collection of simple hot-rodding tricks-increase the air/fuel mixture up front and decrease the restriction out back. The Performance Kit comes with a K&N filter, modified throttle body, a cat-back exhaust system and a new thermostat.
To give the intake a boost, Turbo City gets rid of the stock TJ airbox along with some of the power-robbing tubing, and mounts an exposed K&N open air element. A washable K&N filter on its own is one of the easiest and best modifications you can make to a vehicle. And the fact that, as of press time, K&N didn't have a filter to fit TJs is almost reason enough for the Turbo City Kit. Just one look at the new filter arrangement says there's more air getting to the engine. To make the most of the increased airflow, there's also a replacement throttle-body fuel injection.
Turbo City mildly bores the stock TBI just enough to increase power without hurting low-end torque. And finally, to expel the gases more efficiently, a cat-back exhaust is included. The entire kit is straightforward to install, street-legal, and took the tech guys at Turbo City less than two hours to install.
Sum Of The Parts
When we add an aftermarket exhaust, psychological horsepower is usually far more than the actual gain. The growlier exhaust note from these systems just can't help but make us think we're driving something significantly quicker, and usually these systems are good for single-digit horsepower gains. Because the Turbo City Kit sounds so throaty, we were once again in the same boat. However, the difference this time was, we really felt it. Bottom line, this kit creates a pronounced increase in throttle response and First-gear acceleration as well as off-idle torque. Still, just to make sure we weren't overestimating our seat-of-the-pants reaction, we measured the improvements on a dyno.
At K&N's new Dynojet dynamometer, we recorded an increase of 15 horsepower and 15 lb.-ft, of torque at the rear wheels. Though these numbers don't suddenly loft us into V-8 territory, they do have benefits for street and trail. At 1,000 rpm, a typical low-range 'wheeling engine speed, we gained a full 13 lb.-ft. of torque. This is quite noticeable on the street as well, in First-gear acceleration; where the TJ used to bog a bit until about 2,300 rpm, it now jumps off the line. This also has a lot to do with throttle response, which is noticeably improved. In fact, across the entire rpm range we consistently picked up eight to 10 horsepower and lb.-ft.
The kit now gives us just enough power to maintain speed in Overdrive on the shorter freeway grades. The long ones, though, still require some downshifting. This problem, we feel, is something we could only overcome with a larger motor.
Noticeable gains from mild engine tweaks are welcome nonetheless. We now have a livelier motor, a downright awesome-sounding exhaust note, and the K&N filter we've wanted for a year, all at no apparent cost to fuel economy or reliability. In addition, our OBD II computer hasn't made a peep.
As of press time, the Turbo City Performance Kit was available for about $400. Applications also include older YJs in addition to four-cylinder YJs and TJs.
Next month, we'll give all the modifications made over the past few months a good workout when we test them at Arizona's annual association run.
Fifteen horsepower not enough? How about a stroked 4.7-liter kit putting out 260 horsepower and 305 lb.-ft. of torque (measured at the flywheel)? Hesco has a 4.7-liter Stroker Conversion Kit available for 1997-and-later Jeep TJs and all 4.0-liter Jeeps. The kit includes a new Stroker crankshaft, performance rods with ARP rod bolts, forged pistons, performance moly piston rings, new main and rod bearings, RV camshaft and lifters, and a three-piece roller timing chain. According to Hesco, all the customer has to do is assemble the motor, once the machine shop performs a simple bore, and hone of the cylinders.
A few extra performance parts were used by Hesco to achieve the above dyno numbers, including an ECM upgrade, adjustable fuel pressure regulator, 20-percent-larger fuel injectors, a high-flow catalytic converter, 62mm throttle body and a 3-inch exhaust system. We checked out Hesco's Stroker kit on Ken Rosser's CJ-8 when we were on the Appalachian Adventure Expedition, and can report the performance is impressive.
If the Stroker Kit still isn't enough, Hesco offers additional supercharger kits for the 4.0-liter tailored to each owner's individual needs. One particular 4.0-liter YJ improved its 0-60mph times from 9.2 seconds down to a Z/28-like 6.2 seconds. For more information, contact: Hesco, Dept. FW, 1329 4th Ave S., Birmingham, Alabama 35233, 205/251-1472, 205/251-8358 (Fax). -Ben Stewart