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Old 04-01-2012, 10:00 PM   #104 (permalink)
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Originally Posted by Old Tele man View Post
The purpose of EFI is to more precisely 'control' both the quantity of fuel injected and the timing of its injection...two aspects of fuel economy (FE) and power (HP) that the common pressure-differential carburetor cannot match...perform reasonably well? Yes, but match or exceed, NO WAY!

First, the carburetor functions on pressure difference--vacuum--which means its susceptable to atmospheric and altitude changes...EFI is a VERY stable constant volume and pressure device, albeit a computer-controlled system. Typical, normal-aspiration engines only achieve about 14.7 psi differentials at best, whereas a pressure-differential of over 2000-2500 psi is possible/common with today's EFI high-pressure piezo-injector systems. It's like the HUGE difference between raindrops and weather's mist!

Droplettes of gasoline don't burn very well nor very fast, resulting in less HP and even less fuel economy...while, the closer the gasoline volume within the air-fuel mixture is to a 'true' vapor, the more HP and better fuel economy...with LESS gasoline going out the tailpipe as emissions.
Hi Tele,

You make some very good points here!

Also, carburetors can run lean on high pressure days, and rich on low pressure days.

There was a very well known spark plug tuner namely Bobby Strahlman, who usually showed up at Daytona during Motorcycle Week back in the early 70's.

There were tuning issues with carburetors, where main jets were being changed in the morning, due to cool ambient temperatures, and then later in the day when the sun heated the surrounding air, again, main jets needed to be leaned back out.

With all this fine tuning going on during changes in temperature during the day, just imagine how "course" the tuning is on any old carbureted engine where the jets are never changed or optimized for best fuel economy. In fact, most of these carburetors are run on the rich side, to cover all the bases regarding worst case barometric/temperature swings during normal operation.

A fuel injected engine is vastly superior to this!


Last edited by 3-Wheeler; 04-01-2012 at 10:24 PM..
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