5-111.bk Page 17 Monday, July 10, 2006 2:26 PM ASET™ AC Engine Technologies 6 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 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.
Figure 5 — CCRS “Phased” Fuel Injection 1. Pressure (bar) 2. Timing 3. CCRS Phase 1 4. CCRS Phase 2 5. Non-CCRS 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). 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. Page 17 DESCRIPTION AND OPERATION 1. Piston Crown 2. Re-Entrant Bowl