Carburetor Vs.Electronic Fuel Injection - Tech

When It comes to carbs versus computers, this ain't exactly my first rodeo. Almost since the inception of the fuelinjected 5.0L Mustang, the carbureted contingent has taken exception to the fancy new fuel injection. They (of course) openly admit the fuelie 5.0L was responsible for ushering in a new era of Ford performance, and have no problem taking full advantage of all the latest cylinder heads, intake manifolds, and cam profi les. The "carbies" however, are still a little reluctant to embrace the electronics associated with EFI Fords, criticizing complication of the magic black box for their reluctance.

Backing up their position are a number of tests run by yours truly, illustrating the carbureted contingent certainly had a leg to stand on more often than not, as carbs have come out on top in a direct performance comparison. As antiquated as the carburetor may seem (compared to today's modern fuel injection), they remain a serious player in the hands of the right tuner.

As good as the carburetor is, however, there was more to the many comparison stories than simply carbs versus computers. From a basic standpoint, modern electronic fuel injection would certainly be able to equal or exceed the performance offered by a carburetor, if for no other reason than it provides the ability to precisely dial in the air/fuel and timing values to maximize performance.

Don't discount the drop in charge temperature offered by the atomization of the fuel through the carburetor. It is possible to get exceptional results with a carburetor and conventional distributor, but ultimately fuel injection could provide an ideal combination not only at every rpm run under full throttle, but an ideal combination run under every possible combination of load and engine speed. No matter how well tuned a carburetor and conventional distributor are, the same can't be said about that combination. All the carb jetting and advance weights and springs on the distributor can't match the precise tuning offered by electronic fuel injection (especially at the OEM level). Score one for modern technology.

With such an advantage offered by the electronics age, how can a carburetor possibly compete? In many of the previous carbs versus computers shootouts, power differences came not from the ability to dial in the air/fuel or even having timing control, but rather the differences in the intake manifold design associated with each system. Were we to run a carburetor versus injection on the same intake (say a converted Edelbrock Victor Jr.), we'd certainly see that the injection could provide the idealized air/fuel over every possible rpm and load combination.

But testing between a conventional carbureted intake versus a typical aftermarket 5.0L EFI intake often showed different results. Tested on the same motor, it was diffi cult for the typical long-runner EFI intake to best a carbureted Victor Jr. in terms of peak power. The long-runner intakes usually offered exceptional low- and midrange torque production, but the carbureted contingent usually took top honors in terms of horsepower. The majority of the credit for the impressive peak power numbers goes to the short (and large) intake ports offered by the single-plane carbureted intake. Optimized for high-rpm power production, a Victor Jr. carbureted intake is tough to beat.

The excellent results posted by the Edelbrock Victor Jr. intake in our past carbsversus- computers comparisons are exactly why we selected it for this shootout. After all, if you want to demonstrate the merits of your fancy new fuel injection, why not go up against the best?

Speaking of new injection, this Classic Fuel Injection from Dynatek Racing was so named for its combination of retro classic good looks and modern electronic sophistication. Any true Ford enthusiast should recognize it as a conditions. Keeping them in an optimized state of tune for every combination of engine speed, load condition, and temperature can be an exercise in frustration.

Understanding the limitations of the original Weber carburetors, Dynatek Racing decided to offer a system that provided all of the classic good looks of the 48 IDA downdrafts without all the tuning headaches associated with keeping them running properly. Externally, the Classic Fuel Injection certainly looks the part, with eight individual 48mm throats ready to feed each of the eight cylinders through billet-aluminum radiused air horns. Unlike the original Webers, the Classic Fuel Injection from Dynatek Racing is not carburetion at all, but rather a sophisticated injection system housed inside the retro throttle bodies. Hidden from view between the throttle bores, where you would originally fi nd the emulsion and jetting circuit on a Weber carburetor, are a pair of fuel injectors. Naturally, the injector sizing can be adjusted to suit the needs of your motor (ours relied on a set of 36-pounders). Continuing with the retro theme (for Cobra or street-rod owners wanting to further conceal their counterfeit carburetion), the Classic Fuel Injection is fed through the original Weber fuel inlets. Ours were sized to accept pipe fi ttings, but original-style (though high-pressure) banjo fi ttings can also be employed.

More than just a replacement for a set of original Weber IDA carbs, the Classic Fuel Injection offers improved performance over the downdrafts thanks both to precise tuning and enhanced airfl ow. The tuning aspect is fairly self-explanatory, as modern fuel injection (the system comes with a stand-alone management system) can provide precise tuning only dreamed of by the carbureted contingent. Additional power over a Weber setup is further improved with additional airfl ow. While retro in appearance, the throttle bodies supplied in the Classic Fuel Injection system are anything but. Each throttle bore outfl ows its carbureted counterparts by almost 90 cfm. That means the Classic Fuel Injection offers an additional 700 cfm over the original Webers, and this doesn't even take into account the differences in the lower manifold. After extensive testing, Dynatek saw the need to design its own lower intake for the 351 (other applications are in progress as well). Extensive work was needed on the original Weber intake to help match the fl ow potential of the throttle body. After all, what good does a 380-cfm throttle body do on an intake that fl ows only 250 cfm?

On paper, the new Dynatek injection system scored high marks in terms of looks and fl ow potential. I have to admit, I'm a sucker for multicarb induction systems, and havinga quartet of dual-throat carbs (or injection in this case) makes for one heck of a visual statement. On the cool scale, an individual-runner system, especially a retro-modern version, has to rank near the top, but how would this new system perform?

Given its obvious fl ow superiority to the original Weber system, we decided to test the new Dynatek injection against the tried-andtrue Victor Jr. intake. Feeding the impressive carbureted manifold was an equally impressive fuel mixer in the form of a Holley 750 HP carb. From a visual standpoint, the single four-barrel carburetor couldn't hold a candle to the more impressive quartet of throttle bodies, but owners don't always purchase their induction system on looks alone (though many do). On paper, the combined flow rate of the eight bores in the Classic Fuel Injection offered nearly 3,000 cfm. This compares to 750 cfm offered by the Holley carb, but when it comes to making power, airfl ow isn't everything. Intake design features such as runner length and port volume play a major role in determining the shape of the overall power curve.

There was only one way to demonstrate the power potential of the new injection system, and that was to actually run it on the dyno. Truth be told, the Victor Jr. had one more advantage in the form of porting. Though we wanted to run the test using an out-of-the-box Edelbrock intake, all we had was a ported version. The odds were certainly stacking in favor of the carburetor.

To properly test the merits of the two induction systems, we needed a stout motor. This came in the form of a 408 stroker (the CFI intake was designed for a 351W). The 408 short-block from Coast High Performance first was augmented with a Lunati Voodoo cam. The hydraulic roller profi le offered 0.600 lift on both the intake and exhaust along with a 241/249 duration split (measured at 0.050). The aggressive ramp-rate Voodoo grind also featured a 110-degree lobe separation angle. We wanted to make sure the 408 had plenty of power potential to tax the limits of the new CFI system.

The CHP short-block was topped with a set of AFR 185 heads. That this motor exceeded 540 hp is a testament to the impressive power potential of the AFR 185s. Credit the CNC porting program for the fl ow rates offered by the AFR 185 heads. You may remember that these heads came out on top of their category in our "Ultimate Guide to Cylinder Heads," and after this test on the 408, we can see why.

Since the Dynatek induction system required a small-cap distributor, we had MSD send us the appropriate electronic (billet) distributor. Both carbs and computers were run with this MSD distributor fi ring a set of MSD plug wires and Denso iridium plugs. Also present on the test motor were Crane Gold 1.6 ratio roller rockers, Hooker (barrier coated) Super Comp headers, and a CSR electric water pump. Before running in anger, the Milodon oil pan was fi lled with Lucas 5W-30 synthetic oil. Equipped with the Victor Jr. intake and Holley 750 HP carb, the 408 produced 528 hp and 523 lb-ft of torque. These were impressive numbers, and things weren't looking good for the injection system.

Installation of the Dynatek Classic Fuel Injection was as simple as performing an intake swap. Obviously, we had to install four throttle bodies and not just one carburetor, but the nuts and bolts portion of the equation was a no-brainer. The Dynatek injection included the necessary throttle linkage to ensure all four throttle bores opened simultaneously. Only minor changes to the single adjustment rod were necessary to get all the throttle bores marching in unison. The electronics portion was equally easy, as the injector harness was a plug-'n'-play affair. The usual EFI wiring was necessary, meaning connection of the positive and negative wires, MAP, and other associated sensors (all direct plug-ins). The fuel system consisted of a central fuel log (fed by the dyno EFI fuel pump) that distributed fuel to the four fuel fi ttings located on the individual throttle bodies. The vacuum source for the MAP sensor was fed by a common plenum located under the intake. This common vacuum source was fed by all eight bores (below the throttle blades) to ensure an accurate vacuum reading. This is critical on an individual-runner intake, as the surface area of the four 48mm throttles is the equivalent of a 136mm single throttle body.

The Classic Fuel Injection came with a dedicated harness and stand-alone management system that included closed-loop operation with the ability to self-adjust the mixture to a desired air/fuel reading. Since we were only interested in wide-open throttle for this particular test, we tuned the system manually and had things up and running in no time (after your idiot author fi nally fi gured out the correct direction of rotation of a Ford smallblock-the fi ring order was initially confi gured on the distributor in the wrong direction). After some quick tuning to produce the desired air/fuel ratio, we were able to run the motor again from 3,000 rpm to 6,300 rpm with the Dynatek CFI. All we can say is "Wow!"-as the new injection not only held its own against the Victor Jr., but the computer actually outperformed the carb. While the Classic Fuel Injection produced more peak power and torque, it also improved the power throughout the rev range (from 3,000 rpm to 6,300 rpm).

The trick individual runner system offered gains as high as 35 lb-ft of torque compared to its carbureted counterpart. Check out the graph to see for yourself, but it looks like Dynatek has solved the dyno dilemma-chalk up one more win for the computer geeks!

[Editor's note: Dynatek now has systems available for the 302, 351, 429, and even FE Fords. Tested recently on a stroker 427 Sideoiler, the Classic Fuel Injection produced 630 hp and outperformed a carbureted intake in the process.