FiTech’s Ultimate LS kit includes everything you need on the induction side to finish practically any (from a stock 4.8 to our big-inch stroker) LSX long-block. This kit definitely passes the eyeball test with its good looks, but we plan to put it to the test on the dyno. This is a fresh build, but we’re betting the Ultimate LS kit will also be a big help for anyone looking to swap an LSX engine into a car that never came with one.
We put FiTech’s Ultimate LS System to the Test on the Dyno
Let’s get right to straight facts: The LS engine platform is one of the greatest power producers ever created by the hand of man. But that doesn’t mean everyone wants to run the exact same engine. FiTech Fuel Injection is probably most commonly known for their fuel-injected throttle bodies that allow car guys (and girls) to easily replace their carbureted setup with fuel injection. But the company has also developed a wide range of port fuel-injected intake setups for LS engines that never came with carbs. And it’s turned out to be a pretty comprehensive kit as well as a great way to improve performance.
Here’s the specific FiTech Ultimate LS kit we are using. As you can see, it’s pretty comprehensive with an intake, big 102mm throttle body, computer, handheld touch-screen controller, fuel pressure regulator, injectors, fuel rails, braided crossover line, fuel pump, coils, and a wiring harness. Not pictured are several included sensors and a lot of brackets and other assorted hardware.
It seems like FiTech’s Ultimate LS kits will be a best bet both for anyone doing an LSX swap into a car or building a new engine from scratch. That’s because it includes FiTech’s self-contained engine control unit that is self-learning and also quite customizable. FiTech also packs in a custom wiring harness that includes all the fittings you need and none of what you don’t. That’s actually a big deal because in our experience it’s not the mechanicals that trips up most people doing LS engine swaps, it’s the confusing task of modifying a stock wiring harness that can leave you pulling your hair out.
We decided to put the 750hp kit to the test on a big-inch stroker LS build, although we expect most users of the FiTech Ultimate LS kit will be using it to help simplify LS swaps. The block is a 6.0L iron LQ9 we pulled out of a Cadillac Escalade in a junkyard, but it has been fully machined at Automotive Specialists with the bores punched out to 4.070 inches.
In addition to the ECU and wiring harness, there are a number of options to choose from depending on what you need. For a stroker LS1 build we have going together, we went with a nearly complete kit that also includes a long-runner fabricated intake, big 102mm throttle body, fuel injectors, fuel rails, fuel pressure regulator, handheld controller, fuel pump, coils, and a ton of sensors, connectors, fittings, and everything else needed to get it all working. As a system, our kit is designed to be able to handle up to 750 hp.
Of course, a one-size-fits-all solution never works for everyone, so FiTech has several different part numbers with variations on the kit. For example, we chose the long-runner intake to help generate lots of low-end torque, but if hood fitment is an issue you can go with a short-runner intake that’s just 6.5 inches tall. You can drop the coils if you already have your own; go with a kit designed for a maximum of 500 hp, which should work better with a stock 4.8- or 5.3L engine, or even add in an integrated electronic transmission controller.
For the pistons and rods, we’re using a set of Wiseco 4.070-inch forged pistons with a bit of a dish to keep the compression ratio right at 10:1 so we can use pump gas. The connecting rods are K1 H-beam forgings that are 6.125 inches from center to center.
What we really liked is all the components have already been scienced out as a package so you can be confident everything fits and works well together. That eliminates all the head-scratching that often comes from mixing and matching components from different manufacturers. Plus, that fabricated aluminum intake manifold just looks sweet. Obviously, looks are not a primary consideration when it comes to an engine build, but let’s not pretend that looks don’t matter at least a little bit. After all, everybody wants a little eye candy when they pop the hood with your friends standing around.
A K1 forged crank rounds out the rotating assembly spec’d to be able to handle plenty of power. The crank has a 4.00-inch stroke, so combined with the 4.070-inch bore that makes total displacement 416 ci (6.8 liters). This is an LS1 build with a 24X reluctor at the back of the crank, but the FiTech ECU can work with 24X and 58X systems equally well.
We’re sure you are ready to get to it, so we won’t waste more time yapping. Follow along as we assemble one of FiTech’s Ultimate LS kits on a big-inch stroker build and then put it to the test on an engine dyno.
The camshaft is a hydraulic roller from Comp Cams. It has been ground with an eye toward overall street performance and not just peak horsepower. Duration is 247 degrees for the intakes and 255 for the exhausts at 0.050-inch tappet lift. The lobe separation is 113 degrees and with stock ratio rockers—gross valve lift will be 0.637 inch for both the intakes and exhausts.For cylinder heads, we wanted something that was capable of moving plenty of air and making power. So, we went with a pair of fully CNC-ported heads from Brodix. They came fully assembled, but here we’ve disassembled them for a full inspection. The valves are sized at 2.100/1.600 with a 70cc combustion chamber to help keep the combustion ratio manageable with the big 4.00-inch stroke.When trying to make big power, it’s just easier if you go with the LS3-style square-port heads. But we wanted to stick with LS1-style cathedral ports because a lot of people are still using the Gen III 5.3 and 4.8 engines with the cathedral ports for engine swaps because they are cheap and plentiful (FiTech makes intakes that fit both cathedral- and square-port heads). Anyhow, it is cool to see that Brodix is still developing cathedral-port programs for its customers. These 245cc intake ports are actually a new design that flows a healthy 370-plus cfm!The FiTech ECU can use the stock knock sensors. Some like this, but since we’ve made so many changes (cam, valvetrain components, displacement, rpm operating range) we feel the stock knock sensors won’t be much use. The FiTech ECU will work just fine without the knock sensors, so we also took the opportunity to swap out the stock valley cover with the two large depressions that tend to collect oil, moisture, and dirt and replaced it with a super sanitary valley cover from ICT Billet.The intake manifold that FiTech has designed includes nice, thick flanges. O-rings replace intake gaskets like on most other LS systems and makes installation a breeze.The fabricated intake is definitely a beautiful piece with really nice black anodizing. Even though the sheetmetal is 3mm-thick aluminum, FiTech says it is good for up to 30 psi of boost.Here’s a look at the inside of the intake. The plenum volume seems a bit small, but each runner is bell-mouthed to help improve airflow into the combustion chambers.The throttle body bolts up with plenty of clearance for the Holley mid-mount front drive system we’re using. The idle air control (IAC) and throttle position sensor (TPS) are included in the kit and already installed on the throttle body for simplicity.FiTech packs in a set of 55-lb/hr injectors for the 750hp kit to fit into the billet fuel rails. For the 500hp kit they are more appropriately sized at 36 lb/hr. A really nice touch is the AN fittings are already installed on the braided hose for the fuel crossover, saving time and trouble.Here, we’re installing the fuel crossover line, but you can also get a good look at the big 102mm cable-operated throttle body, which can move a ton of air. For the 500hp kit the throttle body is a bit smaller at 92 mm.The included manifold absolute pressure (MAP) sensor mounts up conveniently out of sight at the back of the manifold. The included unit can handle up to three bar, which is nice.At this point we’ve moved onto the engine dyno, and Automotive Specialists’ Jeff Dorton is hooking up the wiring harness and the fuel lines. Since the dyno uses its own fuel pump and fuel pressure regulator, we weren’t able to test the units in the FiTech kit. That will have to wait until we’re able to put everything into a car. FiTech does, however, recommend you be able to provide a steady 58 psi of fuel pressure to the injectors.Another great feature we appreciated is the FiTech ECU can read wideband O2 measurements from both banks of the exhaust and not just one. This helps provide better fuel management under a variety of conditions. The wideband O2 sensors are part of the kit.The ECU is a self-contained unit that’s small enough that it can be mounted just about anywhere. Downloading changes from the handheld controller were simple and easy.Speaking of the handheld controller; here it is. We used it exclusively for the dyno tuning session and it worked perfectly. Here, we’re setting up the engine parameters so the self-learning ECU can do its thing on first fire-up. Notice that the engine displacement isn’t right yet (it’s 416). The ECU made it a piece of cake to adjust the rev limiter as we slowly worked our way up the range. An engine dyno causes too much drag for an engine to idle cleanly at lower rpm levels, but the controller made it easy to bump up the idle rpm so the engine will be happy. Bringing it back down once the engine is in a car will be a task of about 10 seconds.Here, you can see the easy-to-read labeling for every connector on the wiring harness. Once everything is in your car you can rip off the labels to clean up the look, but they definitely make life a lot easier when you are trying to make heads or tails of a new wiring harness. Also notice that the oil pressure sensor (beside the cam sensor) isn’t used by FiTech. You will need to hook up your own gauge to be able to monitor oil pressure.The FiTech coils have an interesting feature: An LED that lights up when the coil is firing. In this shot the engine is at idle and you can see that while the shutter was open, the coils for cylinders 1, 5, and 7 all fired, but 3 has not. If your engine is running rough, this is a quick-and-easy way to make sure all your coils are operating correctly.The handheld controller isn’t meant to be a replacement for a gauge cluster, but it does have the ability to monitor a few functions in real time. You can choose what shows up on the screen, but we think being able to watch actual versus target air/fuel levels in real time, along with the rpm, will prove really useful.On the dyno, the FiTech system had the engine fired up and running smoothly surprisingly quickly. We tried a few different changes with the air/fuel ratio and some other things, but, generally, we allowed the self-learning ECU to run the show. As you can see, we had the serpentine belt off and an electric water pump moving coolant through the engine. We also didn’t use a velocity stack on the intake, but we did have a hood (not shown in this photo) blowing fresh air into the intake. We saw peaks of 521.2 lb-ft of torque at 5,300 rpm and 597.3 hp at 6,700. We were dying to break the 600hp mark, but the engine just didn’t want to do it and we weren’t willing to get into cheesy magazine fakery to get there. Peak numbers are nice for bragging rights, but they really don’t tell you how much fun a car is going to be to drive. What we are really stoked about is the power across the range. From 4,500 to 7,300 rpm we averaged a very impressive 486.4 lb-ft of torque and 486.39 hp while burning pump gas!
