DESCRIPTION AND OPERATION
Page 17
ASET™ AC Engine Technologies
The ASET™ AC engine uses current controlled
rate shaping (CCRS) phased into production
during 2001. Current controlled rate shaping
provides a modulated two-phase injection of fuel
into the cylinder. With the two-phase method, a
small volume of fuel is injected into the cylinder
prior to ignition followed immediately by the
primary fuel charge after ignition (Figure 5). This
phased injection of fuel effectively helps to lower
NOx emissions and improve stability at idle.
5
Figure 5 — CCRS “Phased” Fuel Injection
The port design of the cylinder heads, the valve
seat inserts and the piston crowns have been
redesigned to change the swirl characteristics of
the inlet charge. The redesigned piston is cast
with a re-entrant bowl shape that is narrower at
the top and widens as it curves deeper into the
crown (Figure 6).
6
Figure 6 — Redesigned Piston Crown
In addition, both the inlet and exhaust valve seat
inserts are of a new design that has a smooth
rounded radius (Figure 7) to achieve the optimum
flow of air and exhaust gases in and out of the
cylinders. With these changes, swirl is generated
within the cylinder where it is needed to
effectively mix inlet air, fuel and recirculated
exhaust gas. Along with swirl characteristics,
compression ratios have been changed for
combustion efficiency, improved cold-start
capability, faster warm-up and improved idle
stability. Also, the top compression ring face
coating has been revised to provide long life and
less cylinder bore wear.
At the base of the valve seat insert radii, the
contact surfaces with the valves are 30 degrees
and 20 degrees, respectively, for exhaust and
inlet valves. This is the same as current engines.
However, the new design of the seat inserts
prevents their removal in the traditional manner.
A revised procedure for replacing the inserts is
covered in the REPAIR INSTRUCTIONS section.
1. Pressure (bar)
2. Timing
3. CCRS Phase 1
4. CCRS Phase 2
5. Non-CCRS
1. Piston Crown 2. Re-Entrant Bowl
5-111.bk Page 17 Monday, July 10, 2006 2:26 PM
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