It's important to keep bend radius as large as
possible to prevent kinking. New hoes is relatively
stiff and kinking is usually not a problem. However,
after a few heat cycles the hose will soften up and
kinks (restrictions) will form if there is any residual
stress in the hose due to improper routing or
inadequate support.
control canister used to be. The can has two blow-by
hoses (one from each valve cover) and two vent
hoses.
rod end allows for tolerance adjustments and makes
the link moment free preventing undue stress on the
attachments. The aft side of the link is connected to a
plate I machined to cover the EGR port. Also
noteworthy is the autonomous IAT (Intake Air Temp)
sensor I modified to fit the #8 AN bunge I welded onto
the intake manifold. The sensor drives a dash
mounted gauge.
degrees F. It rarely goes beyond 130F. If I see it go
beyond 12 o'clock, I know I have a problem. The other
gauge is oil temp. With my twin coolers (see engine
section) I'm seeing about 230F max during a typical
track session.
configurations.
Top - Stock M90
Middle - M90S Model
Bottom - Magnum Power modified M90
The Eaton S/Cer has three distinct stages of
operation, Intake, Transfer, and
Backflow/Compression or exhaust. As you can see,
the more the port wraps radially the more duration in
degrees (time) the blower has to ingest a charge. In
addition, the larger the port is in height the greater
the airflow potential. Both dimensions have physical
as well as dynamic limitations. The height of the port
is limited in one direction by the bearings. Height
limitation in the other direction is limited by
operational dynamic conditions that make further
increases detrimental to volumetric efficiency.
Radially, limitations are more geometric as the rotors
lobes must seal off the intake from the outlet ports for
a minimum of 120 degrees. This is called "seal
time". The more seal time the better the low speed
volumetric efficiency (4000 blower rpm) but at the
expense of high speed VE (14,000 + blower rpm).
Therefore, the chosen configuration will usually be a
compromise. Since the minimum blower rpm I'm
interested in is about 6000 rpm (2 times engine rpm)
and the max 16,000 rpm, I'm working my way to min
"seal time".
outlet port (right) to a M90S outlet port (left) from both
inside the case and outside. From the outside (top
picture), the only visible difference is the chamfering
of the case at the bottom of the "V" outlet on the
"S"model. However, as seen in the middle picture,
the "S" model increases the outlet port timing by
again chamfering the inside edge of the "V". The
small rectangular ports allow the backflow
compression process to start earlier than otherwise.
This helps keep the typical blower pressure
fluctuations to a minimum, thus reducing blower
noise. This was foremost a consideration for
commercial auto applications where noise is an
important design constraint. For performance, they
hurt low speed VE somewhat as seal time is
reduced.
The bottom picture shows the Magnum Power case
which has been opened up to increase the backflow
compression phase and increase airflow potential. At
very high blower speeds it also increases thermal
efficiency as it allows more time for the normal
backflow compression cycle to take place. Note the
slight change in casings as the Magnum housing is
from an early model M90.
each. Theoretical displacement is 1.5L per
revolution. The rotors are twisted 60 degrees end to
end with an involute gear profile. Due to the twist,
inlet and outlet volumes remain relatively constant
compared to rotors with 0 or 30 degrees twist. This
has the affect of much smoother discharge flow out of
the blower. Twisted rotors also minimise losses in
VE due to carryback of high pressure air trapped
between rotor lobes. Later model M90s use Teflon
coating on the rotors which help tighten up tolerances
and increases volumetric and thermal efficiency.
Powers modified housing. Note the angle of the
outlet "V" coincides with the leading edge of the 60
degree twisted rotor. I'll eventually plug the
rectangular carryback ports on this housing as they
serve no purpose on a high performance vehicle.
set-up. Similar adapters and plates were used to
test the system end-to-end from Throttle body to main
manifold.
keep oil temps and piston temps within reason. More
pictures can be found in the "Thermal Control" section
