Super Chevy | How-To - Engine and Drivetrain

Putting FiTech’s New Wallet-Friendly LS Induction System to the Test

LS Swap Solution

FiTech recently introduced a line of affordable and easy-to-install self-tuning induction systems for GM LS engines designed with both the do-it-yourselfer and the professional EFI tuner in mind. The fabricated sheet aluminum intake may be what grabs the eye first but it’s the rest of the kit that really stands out. It’s a complete system that comes with everything needed to finish the induction system of an LS engine and have it fueling accurately with little fuss and for minimal cash outlay—even with the super cool TIG-welded intake manifold. It wasn’t all that long ago that the only place you would see a fabricated sheetmetal intake was on an NHRA Pro Stocker or perhaps a highly competitive Comp Eliminator car. The rest of us mere mortals just couldn’t afford those enormously cool but ultra-spendy TIG-welded manifolds. But what was once an extravagance is now affordable.

FiTech garnered such significant attention with its self-learning throttle body fuel injection system that we covered it in the June 2017 issue (“Injection Inspection”) where we compared it to a carburetor on a 440hp 5.7L LS engine. That testing went so well that when we learned about FiTech’s Ultimate LS induction kit, we just had to try it.

Here’s the deal. FiTech has built a simple, short runner-length fabricated aluminum intake configured for both the 24x cathedral port (LS1, LS2) and the 58x rectangular port (LS3, L99) engines. FiTech calls it the Ultimate LS induction system and the base kit includes everything needed, including the intake manifold, throttle body, ECU, complete wiring harness, injectors (either 36 or 66 lb/hr), fuel rails, fuel hose, fittings, and nearly every sensor you’ll need to easily bolt the system onto an LS engine. This is great news for those with LS engines, either built or sourced from a salvage yard, who want an affordable way to get it running in their Chevy project.

The beauty of this approach is its simplicity. Once you’ve plugged in the wiring harness to the engine and powered it up, all that’s left is to input the engine size and your preference for idle speed, air/fuel ratios, timing, and a couple of other parameters and the engine is ready to run. It’s literally that easy.

It’s this simplicity that can make an LS swap into an older muscle car easy and affordable. FiTech even offers an option that includes software that will manage any of the electronically controlled GM LS automatics like the 4L60/65/70E, or the larger 4L80E. This means you don’t have to drop extra cash on a separate controller. The kit will include all the harness connections for the transmission so the shift points can be called up on the same handheld FiTech device that controls the engine.

The manifold itself is constructed of 3mm (0.118-inch or roughly 1/8-inch) sheet aluminum and is robust enough to handle reasonable boost pressures without distorting. One of the first things we did was peer inside the plenum with the throttle body removed to evaluate how the runners enter the plenum. The FiTech manifold actually extends the runners beyond the plenum floor and configures the tubes with a radiused entry to improve airflow.

While short runner manifolds look very cool, there’s more to this than just visuals. Intake runner length is one of the more critical aspects of engine design and this length is tied directly to the rpm band where the engine makes power. As you may know, longer intake runner lengths affect the reflected wave tuning to improve low-and mid-range power at the expense of top-end power. Conversely, shorter length manifolds sacrifice low-speed torque while improving the top-end power.

Even with the FiTech manifold runners extended into the plenum it appears that this intake would tend to enhance peak rpm power because the runners are significantly shorter (perhaps to help it fit beneath a broad range of possible hoods) than a typical LS factory manifold. As a point of comparison, LS6 intake runners measure roughly 22 inches while the FiTech comes in around 12 inches. We thought it would be interesting to test this new FiTech intake against a stock LS6 to see how it would fare. Knowing that the FiTech runners were significantly shorter, it was fair to estimate that the factory LS6 intake would probably make more torque in the lower and mid-range engine speeds while the FiTech would improve power from peak torque on up to peak horsepower. The only question that remained was how much peak horsepower the FiTech would add.

It might also be useful to mention that any of these FiTech systems can be upgraded with larger injectors if future upgrades require more fuel flow than the originals can supply or tuned with custom maps. As long as the injectors are high impedance versions, increasing the injector size requires no more effort than merely inputting the information into the base configuration. For example, adding 85 lb/hr injectors so you could run this configuration on E85 is as easy as changing the injector size on the configuration screen.

Another attractive feature offered by the LS Ultimate induction kit is knock detection. FiTech has employed a rather sophisticated algorithm that once it detects knock, it can pull an adjustable amount of timing either across all cylinders or just from individual holes that experience knock. The total amount of retard is adjustable along with the retard’s maximum rpm. As you might expect, it is also adjustable for sensitivity since there’s lots of other noisy components that can trigger the knock sensor. All of these features offer protection for the engine, which allows the tuner to be a bit more aggressive in the tune—especially at part throttle.

For our test, we chose to use editor Rupp’s budget 5.7L iron block, cathedral port LS engine as our test mule. If you recall, this engine started life as a Summit 5.3L LS block that was bored to the larger 3.89-inch 5.7L bore size using stock replacement pistons and a stock 5.7L 3.62-inch stroke crank. The only real performance addition was a Comp XFI RPM hydraulic roller measuring 216/220-degrees of duration, at 0.050, with 0.525/0.532-inch valve lift, and a lobe separation angle of 114 degrees. As you can see, this is a pretty mild cam, which should deliver decent mid-range and peak power while still offering excellent street manners.

We began our baseline with the LS6 intake using the FiTech 500hp kit’s 36 lb/hr injectors, controller, wiring harness, and software. This was the best way to perform the test so we could evaluate just the effects of the manifold without adding the variable of a different EFI control system. We experimented with the air/fuel ratio but finalized it at 12.8:1 and maintained the same settings for both manifolds.

It only took a few minutes and less than a half-dozen dyno pulls to give the FiTech ECU enough tuning time to stabilize the power with the stock LS6 intake and OE 78mm throttle body. As you can see from the numbers, the combination of a decent length intake runner put max torque at 417 lb-ft at 4,800 rpm and pushed peak horsepower to 426 at 6,200. That placed the powerband at 1,400 rpm, defined as the rpm spread between peak torque and peak horsepower. Ideally, we’d like to have as wide a powerband as possible for street engines. Typical powerbands are generally around 1,500 rpm, so the stock manifold is relatively close.

It didn’t take long to swap over to the FiTech Ultimate LS induction system intake because LS engines don’t require draining coolant or installing new gaskets. In far less than an hour, we were back up and running. Besides the change to the sheetmetal intake, this swap also incorporated a larger 92mm throttle body that comes standard with the 500hp kit.

After only a few pulls, the power stabilized and the results pretty much followed our expectations. The shorter FiTech runner length did give up some low and mid-range torque to the LS6 intake with the greatest differential being 13 lb-ft at 3,800 rpm. But once the engine crested 5,300 rpm, the torque and horsepower numbers began to exceed the LS6’s achievements, with the FiTech making 17 more horsepower with 443 at 6,200. Comparing peak torque numbers, the FiTech was down from the LS6’s 417 lb-ft to the FiTech’s 405 lb-ft peak.

Essentially, the FiTech manifold traded torque for horsepower by using the shorter runners to improve the numbers above peak torque while experiencing losses in torque at the engine speeds below peak torque. If we look at the average torque and horsepower numbers, they are within less than one percent.

Just for fun we also referenced the power numbers from the FiTech throttle body test. We looked at both the carbureted single- and dual-plane intake numbers and the LS6 intake numbers are very similar to the dual-plane TBI results. As you might expect, the Ultimate LS intake’s power curve was similar to the single-plane carbureted manifold.

As a final test, we tried the larger 102mm throttle body that’s used on the 750hp Ultimate LS kit to see if it might be worth some power. The results proved to be inconsequential, which means for this application the larger throttle wasn’t necessary. Had our engine been capable of near 700 horsepower, then the larger throttle body would be of value.

Overall, our test was a complete success. The one thing this test really doesn’t indicate however, is this manifold’s ultimate potential for airflow. FiTech rates the larger unit with its 66 lb/hr injectors at 750 hp, which could easily be possible with enough cylinder head and camshaft. The LS software also will control nitrous if you’re so inclined. Also note that all of the FiTech components are offered a la carte, so if want the harness and computer, or any part of this kit, separately then FiTech can hook you up. This is great news if you have a complete LS and just need the easy-to-install computer and harness.

All of this means the FiTech manifold has plenty of potential as a performance manifold in lots of configurations and displacements. Stuff a 427ci rectangular port version under this intake with an aggressive cam and you could expect 625 to 650 hp potential without losing any sleep over whether you’d make enough power. Combining lots of power potential with an affordable price (kits start at $1,495) and it’s a deal that will make both your car and wallet pretty happy.

1. Here’s the Ultimate LS induction system. The manifold comes with injectors, fuel rail, throttle body, complete wiring harness, and most of the sensors, including the TPS, MAP, and coolant sensors plus the idle air control motor and the wideband oxygen sensor. The manifold is barely 7.5 inches tall from the valley plate to its highest point, which is just 0.5 inches taller than an LS1 intake.

2. This inverted view reveals four separate pipe thread holes available for any vacuum requirement like power brakes or PCV. Our test engine was a cathedral port Gen III engine but a nearly identical version will bolt up to rectangular port Gen IV engines.

3. Here, FiTech’s Jeremy Schmidt (left) and Jason Oberhelman (right) slide the Ultimate LS manifold in place. Note that the manifold comes with a -6 AN crossover hose that ties the two fuel rails together.

4. FiTech’s throttle body systems incorporate the ECU into the throttle body, but with the LS system, the ECU is a separate box that can be mounted almost anywhere

5. This rear view reveals where the MAP sensor is placed. This manifold’s low profile makes it a great addition for any car like a third-generation Camaro or Firebird with a very low hood line.

6. The handheld display is the same as used on the FiTech throttle body systems. The device uses a combination of touch screen and that small button on the right to make navigating through the inputs and tuning screens really easy.

7. The 500hp Ultimate LS package comes with a cable-operated 92mm throttle body while the 750hp packages come equipped with a slightly larger 102mm throttle body. We experimented with the larger 102mm throttle body on our mild LS engine but it didn’t improve power.

8. This is a shot inside the plenum with the throttle body removed. Note how the runners extend inside the plenum to increase length while maintaining a relatively low profile. Also note how FiTech radiused the inlets for each runner to improve airflow.

9. Here you can see the stock LS6 intake we used for the baseline manifold. It made more torque due to its slightly longer runners but fell short in peak horsepower.

10. The LS6 intake made as much as 13 more lb-ft of torque at 4,200 than the FiTech but the lines cross after 5,200 rpm and the sheetmetal intake’s shorter runners produced as much as 19 more horsepower at 6,400 rpm. The average power numbers are nearly identical between the two manifolds.

Power Chart
RPM LS6 TQ LS6 HP FiTech TQ FiTech HP Diff TQ Diff HP
3,000 377 215 364 208 -13 -7
3,200 381 232 370 225 -11 -7
3,400 386 250 378 244 -8 -6
3,600 392 269 385 264 -7 -5
3,800 402 291 392 284 -10 -7
4,000 410 312 399 303 -11 -9
4,200 413 330 400 320 -13 -10
4,400 413 346 403 337 -10 -9
4,600 416 364 405 355 -11 -9
4,800 417 381 405 370 -12 -11
5,000 414 394 403 384 -11 -10
5,200 408 404 402 398 -6 -6
5,400 400 412 402 413 2 1
5,600 393 419 400 426 7 7
5,800 383 423 395 436 12 13
6,000 373 426 386 442 13 16
6,200 361 426 375 443 14 17
6,400 347 423 363 442 16 19
AVG 393.1 353.8 390.3 353.1 -2.8 -0.7