[eschaider]

Excellent points, Tommy.

In a peak hp contest a properly tuned carburetted engine will give up little if anything to a properly tuned EFI engine. Where the injected engine will pick up an edge is in the various part throttle driveability metrics.

Because the carburetor relies on air bleeds, emulsion tubes, power valves and main jets to deliver the proper fueling over the engine's operating rpm range it provides an OK and sometimes even good fuel delivery performance. The EFI engine, which is continually monitoring the exhaust oxygen content in a closed loop fashion and in MAF based systems the pounds of air being consumed, the EFI system has the ability to immediately modify the fuel delivery to match the air available to the engine.

The net net bottom line of the contimuous process monitoring is a much closer to commanded (presumably correct) fuel dellilvery than the carburetted engine across the engine operating range. Where guys like us get flummoxed is in all the additional controls provided to deliver that fuel volume with a high level of precision and repeatability even in wildly changing atmospheric conditions.

EFI tuning is not that difficult and while better done on a dyno, it can be easily done on the street with an extra set of hands. As luck would have it, to produce 100 HP an engine, any engine, needs to process 10 lbs of air per minute. At what is referred to as Standard Temperature and Pressure (STP) air weighs 0.0765 lbs per cubic foot.

That means 1 pound of air, at STP, will be equal to 13.1 cubic feet of air. Now to make 100 Hp the engine will need to process (consume) 131 cubic feet of air per minute. If we have a 600 Hp engine it wll need to consume 131 * 6 or 784 cubic feet of air every minute.

When you consume 784 lbs of air and you are fueling to an AFR of 14.7:1 for Plain Jane gasoline you will need a little over 53 lbs of gasoline per minute. At 6.5 lbs/gallon (in round numbers) that means a fuel delivery demand of a little over 8 gallons per minute! Changes in air density require modificatins to that fuel delivery in real time. This is where the EFI systems shine.

An over 8 GPM consumption behavior is cruising fuel consumption at a 600 HP power level. If you are accelerating you will need to drop your AFR down to somewhere in the low to mid 11's (about 0.75 lambda) for max safe power. That will drive your fuel consumption up to a little north of 8 gallons per minute.

The transitions between different driving models is usually a complex problem with a comparable solution process. EFI systems are digital computers with sensors to tell the software program what is happening. The program along with your commanded fueling, air density metrics and injector flow characteristics determine when and how long to keep the injectors open to delivery the engine's required fuel.

A carb accomplishes essentially the same function but not quite as accurately because it does not have a closed loop feed back system like an EFI system. As a result the delivered fuel is 'in the ball park' but not exact.

Can you notice the difference in daily driving? The answer is yes if the fueling misss is big enough and usually but not always no if you are in the ball park. Most guys driving with carbs do not notice the difference unless the weather changes or there is an adequate whoops in the power valve or air bleeds or emulsion tubes or jetting.

These whoops are usually cumulative and except for some of the newer Holley and Holley like carburetors emulsion tubes and air bleeds are not changeable but main jets and powervalves are so there can be a correction possible and available — it just cannot dynamically change with the air.

With the EFI systems the correction capabilities are significant and can be overwhelming in number until you get familiarized. Once you are familiar with the location and naming conventions for the fueling variables your ability to tune is substantially increased.