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Re: F.I. Tech (was BSFC)

To: 3liter <>
Subject: Re: F.I. Tech (was BSFC)
From: Dave Dahlgren <>
Date: Mon, 22 Sep 2003 04:43:36 -0400
Think of what we are trying to do here. We are burning the fuel.. With finer
drops you have more surface area. To make an analogy as painfully simple as
possible .. would you rather start a camp fire with some twigs or a pile of
12X12's?? As rpm goes up the drops have to be finer or you will be passing a lot
of unburned fuel through the engine. 

When I have played around with mechanical FI I have always used small nozzles
and big pump pressure and never been disappointed as well.

I have no clues as to what was theorized in the 60's either nor do i care. I
hope this was not the same guys that said you could only go X fast in a 1/4
mile.. I think the amount of time you have to oxidize the fuel is most
important. You would want to optimize for BTU's released per unit of time rather
than most complete combustion or cleanest burn.

3liter wrote:

> Dave, does that mean since the Classic category is restricted to mechanical
> fuel injection it might be beneficial to start experimentation with the
> Hilborn pump pressure, and corresponding nozzle sizing?
> Also, I remember reading many years ago about "droplet chemistry" for nitro.
> If I understood it correctly I think nitro needed larger drop size to burn
> efficiently.  I think surface area of the drop had something to do with it
> rather than a homogeneous mix of many small drops. Fine atomization did not
> work as effectively as large drops. The article might have been by Dr. Dean
> Hill in Hot Rod during the 60's. Not sure about that reference though. There
> also has been a lot of research in the aerospace community on the very same
> thing for propellants. One thing is clear, different materials react
> differently to droplet size. It is not always intuitive.
> I am assuming you were talking about gasoline and agree with you for that
> fuel.  More in Part 2. . .  -Elon

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