FAST EFI’s new E-Z EFI is...
FAST EFI’s new E-Z EFI is the latest of a new breed of EFI systems that take the difficulty out of an EFI without compromising performance for the vast majority of muscle cars and hot rods.
Tuning EFI Requires A Pro
There are systems intended for pro racers and tuners that will probably require professional help, but the latest trend in consumer-level EFI systems is super user-friendly tuning requiring little to no previous experience to dial the system to near perfection. Matter of fact, some of the kits in EFI For Every Guy in the October 2010 issue of PHR are designed to be completely self-learning, meaning the only tuning they need is to be driven. The software will adjust itself to the engine’s demands based on sensor readings and your driving style. To be perfectly honest, it’s actually much more difficult to truly tune a carburetor to peak efficiency with highest possible emulsion and correct air/fuel ratio and keep it there. That’s why high-end race carbs cost much.
Perhaps the best of both worlds,...
Perhaps the best of both worlds, individual runner style EFI systems offer the ultimate in fuel distribution and tenability.
Carbs Make More Horsepower
Depends on how you look at it. In naturally aspirated form, well-designed and perfectly tuned carbs usually do make a bit more peak hp due to better fuel atomization and emulsification properties vs. EFI, and on some combinations a noticeable amount of fuel cooling due to the Joule-Thomson effect. On the flip side, properly designed and tuned EFI will create nearly the same peak power as well as a generally broader, flatter torque curve that begins earlier. Those are typical results, but given the skill of the builder and tuner it really could go either way. The 4.6 Ford used in Final Answer in the October 2010 issue is a great example; despite having a carefully dialed in carb for the Engine Masters competition, it actually made more horsepower with port injection style EFI.
The real difference is that a carb cannot adjust itself for changing atmospheric conditions, but EFI does so continuously and as such will always deliver more precise air/fuel ratios no matter what the altitude or weather. So, while a carb is technically only perfectly tuned for a given set of atmospheric parameters and must be readjusted to compensate when things change, EFI is always in peak tune so the power and performance are optimized. That’s why racers looking to stay in the best possible tune usually have mini weather stations set up to monitor conditions and jetting correction tables for weather and altitude changes along with all potential jet combinations for their combination.
Here’s the before and after...
Here’s the before and after chassis dyno runs from an EFI swap we performed previously on a near stock 351W. The before run was with a perfectly tuned Holley 650HP double pumper (blue line), the after run was with Professional Products’ Powerjection system (red line). The graph shows a near perfect overlay with the Powerjection picking up a little torque below 4250rpm and the Holley squeaking out a little more horsepower above 4750rpm. In the mid range, it was essentially a wash.
Carbs Are As Fuel Efficient As EFI
Rarely. EFI almost always offers greater overall fuel efficiency because day-to-day driving conditions are not the same year round, and neither are day-to-day driving activities. Are we cruising at 70mph or trudging through stop and go? Humid or dry? Mountains or sea level? EFI, however, can compensate for each condition. Plus, as the OEMS have known for some time, EFI also offers the benefit of being able to tune and adjust at differing engine loads (and even for different octane ratings when used with a knock sensor). For example, an engine doesn’t need nearly as much fuel to cruise at a steady speed under light throttle as it does when you stomp the throttle to pass. EFI can be programmed to lean out at cruising for increased mileage and then get right back into the proper air/fuel ratio for optimum power when you need it. We’ve personally picked up over five mpg using this trick on a project car retrofitted with EFI. Or, if you really want to take the concept to the extreme, with advanced EFI systems cylinders can be deactivated under low load such with GM’s latest Active Fuel Management technology and instantly be reactivated when needed. Try that with a carb.
If you really want to nit-pick, fuel evaporates out of carburetor bowls as well when your rod is parked (known as evaporative emissions, it’s the reason for carbon canisters and sealed fuel systems on new cars) so you’re losing a tiny there as well.