Thread: Carb to EFI
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Old 02-21-2015, 10:52 AM
olddog olddog is offline
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Join Date: May 2006
Location: St. Louisville, Oh
Cobra Make, Engine: A&C 67 427 cobra SB
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Default But what EFI?

EFI encompasses many different technologies.

Throttle body - pretty much an electronic version of a carb.
Multi-port - an individual injector at every intake port.
direct injection - the newest from the manufactures.

But how is it controlled?
Speed density - MAP sensor to estimate the air flow
Mass Flow - a meter to directly measure the mass air flow
Alpha-N - a wild ass guess at what the air flow is based on rpm and throttle position

The most important question of all is what is the tuners access to collect data, and what is the tuners access to change tune parameters? If you cannot tune it yourself, how many tuners are there that can work with your system.

Many respected experts with real experience on this site will tell you that a carb will make more power than EFI, even though the EFI will give better overall behavior/manors.

From my perspective, theoretically if the AFR and timing is the same, the only way for an engine to make less power is if it flowed less air or burned less of the fuel. A carb must have some pressure drop to work, and fuel/air mixture flows through the entire manifold. Where MP EFI needs no pressure drop across the throttle body and the intake runners are dry. So in theory the MP EFI should flow more air, unless the injector is causing a flow disturbance at the port. If combustion was less complete for EFI, you would tend to think the manufacturers would not have went to EFI for better emissions. But cruising and WOT max Hp may be totally different results.

Once you get access to the EFI CPU, you have so much more control over the fuel and timing parameters than the old school carb and distributor, that you are in a totally different league. You can fine tune the fuel and spark over the rpm range. You certainly should be able to improve the torque curve over a carb, even if you cannot make the same peak Hp. I don't understand why you could not make the same peak Hp, but respected people who tried failed to.

I will say this. You can sit at the London Ohio Cobra show and watch the 1/8 mile burnouts. You will hear quite a few carb cars stumble bad after the launch. I expect its the fuel sloshing in the bowls, and there are things that can be done to prevent it. You will see a lot of carb issues. The EFI engines seem to run perfect every time. True a good carb tuner could correct the problems, and you can screw up EFI. I do feel EFI tends to run better.
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