When the new 1.7L 60 degree V4 115HP E-TEC engine was announced with the 2007 model year line-up it received rave reviews for its lightweight, low-profile design and sparkling performance.
It was not long before there were calls for a larger version of the same engine to fill the gap between 115 and the next engine up the range, the 150 HP 2.6L V6. Traditionally an engine around 130HP was very popular in the trailer boat market and previously there were several 135HP versions of the 150 HP V6 intended for this market. However, those V6 engines tended to be rather heavy and not as popular as the older, smaller V4 engines of the same power.
What was needed was a modern, low emission, lightweight V4 engine around 130HP and Evinrude announced a 130HP E-TEC was under development. Getting the 1.7 Litre 115HP engine up to 130HP would not be difficult, as there had been 130HP V4’s before, but they were not E-TEC’s with their 3 year/300 hours dealer service intervals, 3 star emissions, and very quiet operation, while retaining that desirable 2-stroke performance. The new 130HP E-TEC would have to wait for some new developments, until now! The new 130 HP E-TEC will be available in two very similar engines, a 115HO (High Output) model to give maximum performance to boats rated at 115HP, and a 130 HP for boats able to handle 130HP. Both engines are 1.7L V4’s, just like the current 115HP, but feature newly developed electronically controlled tuned exhaust systems and a new ducted cold air intake.
The current E-TEC 115HP V4 utilises a dual-length tuned exhaust system in the engine’s mid-section, with an electronically controlled valve that switches the tuning to suit the engine speed. Higher HP from the same size engine, while maintaining low emissions, meant getting even more use out of the energy in the exhaust system, so the new 115HP and 130 models feature a new mid-section that now incorporates two complete larger tuned exhaust systems. One for lower speeds that provides best power and torque below 4000 rpm and one for higher speeds that boosts top end power above 4500 rpm.
The tuned exhaust systems on V4 engines use the energy waves created inside the exhaust system when an exhaust port opens on one side of the engine, to raise the pressure in a cylinder on the other side of the engine, just before its exhaust port closes. Higher pressure inside the cylinder, after port closing, equals higher power output. The secret to getting maximum use of the pressure waves in the exhaust is to get them to arrive at the port at the correct time. Because pressure waves travel at the speed of sound, their speed is fixed and therefore their arrival time depends on distance travelled. So most tuned systems work best at only one speed, but not the new E-TEC. With two complete systems exhaust tuning for better power and torque now occurs over a wider operating range.
The illustration shows only the starboard half of the engine’s mid-section for clarity. Tuning pulses or pressure waves (red arrows) enter at the top and travel to the far end of the system where a port allows the pulses to cross over into the other half of the system (port side in this example). There they travel up to the exhaust ports on the port side cylinders. The exhaust gasses travel much slower than the pressure waves and exhaust through a separate smaller passage (yellow arrows).
At speeds below 4500 rpm the low speed system is in action. Its longer tuned length provides the strongest exhaust tuning in the 3000-4500 rpm region for best acceleration and good part throttle economy. At speeds above 4500 rpm the electrically driven exhaust valve (shown in black near the upper end of the system) switches over to the much shorter high speed system shown on the right in the above sketch. Now tuning pulses arrive much earlier and provide best power over 5000 rpm. The change over from low to high speed systems is controlled by the Engine Management Module, together with the fuel mixture and spark timing changes required to make the changeover smooth and seamless to the operator.
Getting this new much larger tuned exhaust into the same space as previous systems required designing a completely new one-piece casting using the “lost-foam” method. Inner and outer housings, exhaust passages and water passages are now all incorporated into a single casting, replacing many previously individual components.
The new 115HO and 130 HP models also feature a new cold air intake system in the motor cover. Engine intake air enters at the rear, as it does on all E-TEC models, but now it travels through a separate duct inside the top of the motor cover. This provides a straighter, less restrictive path to the engine’s intake, and keeps the air cooler for better top end power, when you need it. The new motor cover is only slightly taller than the 115 (about 35 mm) to retain the very desirable low profile enjoyed by V4 engines.