LS1 Carburetor V.S. Computer Performance Test - Retro Modern Motivation

Is that Dwayne "The Rock" Johnson doing the eyebrow thing from the movie Be Cool? No, that's just Westech's "Hugene" striking a pose with the FAST LSX intake and our carbureted 5.3L LS test mule.

Is that Dwayne "The Rock" Johnson doing the eyebrow thing from the movie Be Cool? No, that

Who isn't a fan of the original 23-degree small-block Chevy? After all, it revolutionized the automotive aftermarket and has truly earned its legendary status. For those new to the Chevy scene, ask any small-block owner and chances are they have at least one cool story involving their beloved mouse motor. Never mind all the past racing success in nearly every form of professional and amateur motorsports, the original small-block continues to be a mainstay of the performance aftermarket industry, despite being phased out in favor of the modern LS family.

The LS engine series offers everything we knew and loved about the original and made it not only more powerful, but lighter and more environmentally friendly to boot. As much as we loved the Gen 1, the LS is certainly a worthy successor.

The LS looks bound and determined to make its own mark in history. Despite an impressive combination of power, mileage and low emissions, there are many Chevy enthusiasts who refuse to embrace the LS family for one simple reason: They were brought up on carburetors and electronic fuel injection is simply too complicated.

5.3L LS-Carb vs. EFI
In looking at the two graphs, it is easy to dismiss the carbureted combination since the FAST LSX offered so much more power, but there is more to the equation than simple plots on the curve. The carbureted combination offered exceptional power for a 9.5:1 street motor displacing only 324 cubic inches. Note that the carbureted induction system was tuned more for low-speed torque production, as it out-powered the injection up to 4,100 rpm, where a great many street motors spend their time. The carbureted combo is also considerably less expensive and many enthusiasts simply won't run injection on their small-block. Who can argue with an aluminum-headed LS motor that offers 462 hp and 413 lb-ft of torque? For the power-hungry individuals, the FAST LSX induction system offered even more peak power and torque, checking in at 482 hp and 436 lb-ft of torque (more than a stock 6.0L LS2). Where the carbureted combo offered over 400 ft-lb of torque from 3,900 rpm to 5,900 rpm, the FAST LSX extended this torque production from 4,000 rpm to 6,300 rpm.

5.3L LS-Carb vs. EFI In looking at the two graphs, it is easy to dismiss the carbureted

Having run untold numbers of both small-blocks and LS motors on both engine and chassis dynos, we can vouch for the fact that setting up any EFI motor is considerably more complex that its carbureted counterpart. From a sheer simplicity standpoint, it is tough to beat a carbureted engine. That ease of installation has carried over to the new LS engines, thanks in part to companies like Edelbrock, who have seen fit to produce carb conversions to replace the factory fuel injection. More than just bolting on a carbureted intake and calling it good, the Edelbrock conversion includes a plug-and-play ignition system that connects directly to the factory coil packs, cam, and crank sensors.

It is certainly true that simplicity is on the side of the carbureted combo, but does the modern EFI system have anything to add? In truth, a factory or even aftermarket EFI system has a lot going for it. That the OEMs have abandoned the carburetor in favor of electronic fuel injection should tell you something about its potential. The great thing about a sophisticated system is the ability to properly dial in the air/fuel ratio and timing curves for any combination of load and engine speed. The carburetor is very effective at metering fuel under most conditions, but it can never match fuel injection for precise metering under all conditions.

5.3L LS-Base vs Racing Tricks
After the FAST LSX induction system increased the power output to 482 hp, we couldn't help but wonder what it might take to reach 500 hp? Milling the heads was obviously an option as was wilder cam timing, but we wanted to test while the motor was still warm on the dyno. Reaching into out bag of racer tricks, we dropped the water temperature, changed the Lucas 5W-30 synthetic oil for some ultra lightweight 0W-10 Pro Stock oil and then replaced the 91-octane premium unleaded pump gas for some VP Q16 oxygenated race fuel. After bringing the oil temperature up by making a few hard pulls, we cooled the water temp and the peak numbers jumped right up to 501 hp and 452 ft-lb of torque. Some may argue that these numbers don't represent what can be achieved on a typical street application, but our goal here was to demonstrate what can be accomplished in full race mode (at the drag strip).

5.3L LS-Base vs Racing Tricks After the FAST LSX induction system increased the power ou

The one benefit carburetors often have over their fuel-injected counterparts is power production at wide-open throttle-assuming the same type of intake manifold is used. This advantage comes not from fuel metering as much as the position of the fuel supply. A carburetor supplies fuel to the top of the intake manifold, where it provides a significant drop in the inlet air temperature. Typical fuel injection systems (other than TBI) inject the fuel directly into the intake or head port (usually aimed at the back of the valve). This greatly minimizes the cooling effect offered by the carburetor.