Re: V Max 200 EFI or HDPI?
The HPDI is a 2 stroke motor that complies with CARB three star pollution regulation. It introduces a high pressure discharge of fuel and air into the combustion chamber that is surrounded by air when the intake and exhaust ports are closed not permiting scavenging by the intake mixture pushing the end gas out the exhaust port and into the exhaust. It requires fuel vapor separators and coolers, the TCW 3 oil is injected into the motor via special nozzles that reach crucial parts, separated from the gasoline and therefore making the combustion cleaner and oil consumption slower. All sorts of electronics are used to monitor combustion and intake air temperature, pressure, etc. The main advantage over 4 stroke is power to weight ratio and not having to change motor oil at the specified intervals. There are no valves nor valve trains to wear, less moving parts. The heart is the high pressure fuel/air injector that injects an air-fuel mixture into a combustion chamber filled with air that slow the combustion and prevents the air-fuel mixture to burn prematurely, this is lean mixture produces less hidrocarbons. Examples of these motors are of course Yamaha HPDI, Evinrude E-Tec and FICHT and also Mercury OPTIMAX series.<br /><br />The EFI motor is a conventional two stroke where the fuel is metered via fuel injectors and the oil is pumped separately from the fuel increasing the cleaniness of the combustion. All sorts of electronics, sensors collaborate to introduce the best air-fuel ratio. However, the air-fuel mixture and oil scavenge the end gas and some of it reaches the exhaust. <br /><br />To me the EFI two stroke motor is an evolution step from the conventional two stroke motor and the HPDI. To me the HPDI is the way to go in terms of sophistication and envirinmental control, albeit an expensive option.
