Weber Look A Like Fuel Injection!

[Cobra #3170]

We dynoed my engine back to back with a 1050 Dominator and a 1650 cfm Wilson throttle body (with spacer). The manifold was a highly modified Victor Jr. The Dominator made 819@7600 and the EFI made 806 @7600. The theory was that the additional cooling provided by the fuel vaporizing upstream with the carburetor may have been responsible for the improvement. Formula 1 engines (several years ago, I am not sure what they do now) had the injection nozzles above the intake trumpets in the plenum probably for the same reason. The location of the EFI nozzles in the intake track on my manifold were not optimum due to packaging which may also account for the difference. The EFI did have a fatter more consistent torque curve and does not crap out under high G stops and cornering. That is the main reason I went with EFI. It also starts much better because it doesn't flood the engine when you move the throttle like those twin 50cc accelerator pumps do.

Originally Posted by fkemmerer

Some additional thoughts on the EFI vs carb question. In many cases, an EFI setup (when properly tuned) can be bolted onto an engine build for a carb and performance and drivability will improve. This is due to the EFI motor's ability to deliver an broader and more ideal range of fuel and timing in any give range of engine load and RPM (as well as responding better to transient conditions like mashing the throttle at low loads/RPMs). EFI is also very helpful in solving difficult tuning problems like big cams with short individual carbs or throttle bodies.

Something to consider is what happens when a motor is built with EFI in mind in the first place. Carbs need a strong vacumn signal to work. This is especially true at low RPMs and idle (this is why cam selection is critical with webers for example). This forces an engine builder to pick a cam that can provide some level of idle vacumn. EFI systems do not need this and therefore cam selection, intakes, etc. can be tuned for maximum power and torque without these compremise. This coupled with that fact that all restrictions required to create lower pressures to atomise fuel in a carb are eliminated give the EFI system a decided advantage in high performance applications.

- Fred