Cold-Air Induction System

• cool ambient air (instead of air from the hot engine compartment) is directed through an inlet in the left front fascia and ducted to the air intake
• can deliver ambient air temperature that is as much as 15 degrees F cooler than the engine compartment
• new induction system flows 40% more air than Premium '03 TL and 4% more than the '03 TL Type-S

• dual-stage intake manifold divided into two banks with 3 cylinders fed by each bank
• at low engine speeds the valve between the two banks are closed and so each separate bank of the manifold is tuned to maximize the resonance effect of incoming air
• at high engine speeds, the resonance effect fades and the valve between the two banks are opened and the resonance from individual pressure pulsations is eliminated
• an inertia effect helps the mass of air rushing down each intake passage providing more air than each cylinder would normally ingest
• more than 75% of the peak torque is available from 2100 rpm to 6500 rpm

• ignition spark timing varies based on engine's load, rpm, temperature, etc.
• acoustic detonation knock sensor mounted on the engine listens for impending knock and powertrain control module pulls back timing incrementally
• platinum-tipped sparkplugs used with individual coil units; 105,000 mile service life on sparkplugs

• PGM-FI tracks throttle position, intake air temperature, water temperature, intake manifold pressure, etc. and monitors the exact state of the exhaust gas
• based on these inputs PGM-FI knows when to trigger and how long to keep open the high efficiency multi-hole fuel injectors

• drive-by-wire converts acclerator pedal into digital commands and eliminates throttle cable
• the relationship between the pedal and the throttle body's butterfly valve is varied depending on the driving conditions like: current pedal position, throttle position, road speed, engine speed, and gear position
• at low speeds, the pedal to throttle relationship has lower "gain" enabling smoother engine response and launches
• at high speeds, the pedal has progressively higher "gain" for more urgent acceleration
• engine's throttle is now fully integrated with the 5AT and the Vehicle Stability Assist with traction control

• exhaust manifolds are cast right into the cylinder heads, saving weight and positioning the two primary catalytic converters as close as possible to the exhaust ports
• primary catalytic converters are 900-cell per square inch high efficiency units positioned directly to the exhaust port for quick converter light off after the engine starts
• eliminated the need for traditional exhaust header pipes, saving 17.6 lbs.
• new hydroformed 2-into-1 collector pipe directs exhaust into a 350 cells per inch secondary catalytic converter
• dual silencers further reduce backpressure and is 11% lighter than the '03 Type-S arrangement

Source: Honda PR