Ok Here is the old message.
-------- Original Message --------
Subject: Tracy's fuel injection system.
Date: Fri, 24 Jun 2005 07:46:06 -0700
From: Rotary Engine
<rotaryeng@earthlink.net>
I set up Tracy's system in the hangar to measure the injector pulse
widths using my oscilloscope. I removed the drive gear from a crank
angle sensor and chucked it into the drill press. Powered the whole rig
using a 12 Volt adjustable power supply. At 1200 RPM the whole system
drew about 2 amps. Ignition and EFI system. The current draw will go up
with RPM. In theory it will be about 4 amps at 2400 RPM and so fourth
and so on. 5800 RPM 8 amps.
I bought a vacuum pump at the auto parts store and plotted default total
injector pulse widths from about 5 inches of Hg to about 30 inches of Hg
or full atmosphere pressure. The hanger is 245 feet above sea level and
it was about an 85 degree day. Don't know the humidity but in SOCAL it
is generally below 25%.
This is total pulse width. Below about 15 inches of Hg only
the primary injectors work. Above 15 inches both sets of injectors fire.
Tracy adjusts the pulse widths so there is a smooth transition at 15
inches of Hg.
The three curves represent what happens when you change
the injector size in Tracy's Mode 3. The stock injectors default pulse
widths is the middle curve. When you increase or decrease the injector
size or flow rate the curves shift right or left.
Note; with the stock injectors you will run out of max pulse width
around 7500 RPM. That would be about the upper limit using the stock
injectors default pulse width. If the stock injectors will not flow
enough to provide the necessary fuel for your HP generated at that RPM
you will have to go up in injectors size or flow rate. This is why I
chose higher flow rate injectors for the P-port engine.
Paul Lamar
That is true, but don't forget about the other RPM end - at idle you
might have a problem with larger injectors because injectors will not
open reliably below 1 millisecond pulse width due to the mechanical
inertia of the pintle valve.
Chuck
Good point Chuck. I need to get some of those new skinny Bosch
or RX8 injectors and test them for dynamic range down below
1 ms or so. Anybody got one they can send me? Either that or I need
to talk Tracy into supporting six injectors like the high power
RX8 engine uses. Obviously Mazda ran into the same problem
with the high power RX8 engine that has a 9,000 RPM red line.
Paul Lamar
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