Event Coverage The Day Of The Drags - 2011

BLAKE · Oct 4, 2011

alkydigger said: ↑

There is a popular new trend toward raising the fuel pressure in mechanical injections by installing nozzles that are smaller than those recommended to achieve enough pressure to work properly.
This subject is so broad that it is difficult to type enough to cover the combinations that might exist.
First: Mechanical injections need different pressures for different air inlet areas as well as different kinds of fuels.
Methanol likes to be injected in more of a liquid and near the valve head, so air does not disrupt the flow of methanol as it enteres the air stream from the tip of the injector. It will remain cooler, and achieve more density by being closes to the valve head.
Gasoline and to a lesser degree E-85 responds better to introducting it in more of a fog ( high fuel pressure) up higher in the port, and into the air stream.
You can usually install a nozzle one size smaller than recommended and install a by pass jet (pill) about .005" to .010" smaller to attempt to make the pump push more pressure through a smaller orfice , thus making more of a fog than a stream of fuel. This works in moderation, but beware of trying it to extream. There is an exponential problem with the fuel supply not being uniform enough during idle and part throttle settings and at wide open throttle. On a gas powered drag car or spring car with a high stall converter, or seldom dropping under 4000 rpm, you can easily drop two nozzle sizes and go .020" or .030" smaller on the main jet assuming you have the type of fuel pump that will continue to raise fuel pressure. If you have a weak , untested, or very old 150A style pump you might lean out the engine and cost yourself a lot of money and time. At the same time consideration has to be lent to how many square inches of air flow you have available. Just as a 500 Holley carb cannot be a 750, a 1 13/16" Hilborn or small 2 1/4 " Enderle injector cannot achieve the correct flow/pressure differential if your engine needs a 2 7/16" or 2 5/8" dia butterfly. One injector simply cannot be everything to every engine. Normally- about 45-60 lbs of running pressure is more than sufficent to atomize methanol, gas, or E-85 in an unblown engine. With a blower, or with some % of Nitro, the engine can benefit from much larger nozzles, and more fuel pressure. Do not be talked into trying to raise the fuel pressure to 150 lbs just becasue some uninformed or misinformed person heard that the smaller the nozzle , the better. Try putting out a house fire with a garden hose with 150 lbs of pressure,,,,a crude anology perhaps , but you get the idea.
We have several Injection hints posted on our "Technical" area at www.Alkydigger.com . I'm always available to help anyone who cares to call me . Mike Chilando 615-483-6830
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'Planking' is also a popular new trend, and it, too, has little-to-nothing to do with this discussion.

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Event Coverage The Day Of The Drags - 2011

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