Quote:
Originally Posted by Kodename47
So why not change the PI angle then, seeing as that injects the whole 720 degree cycle?
It's fine throwing out theories, but you have yet to show me why changing the DI angles is beneficial or makes any improvement. So you'd inject later in the cycle? Does this not impact on fuel mixture within the cylinder, which could have a negative impact on performance? How does that impact charge cooling (one of the main reasons for DI)?
@ Matt@Cosworth care to chime in seeing as you've done the most extensive testing?
FYI unburnt fuel doesn't throw off the O2 sensor, the lambda sensor measures oxygen gases. |
FYI unburnt fuel DOES throw off O2 sensors, because the oxygen that would have been used to burn it would have been converted to CO2. Since the fuel is unburnt, the oxygen is also unconverted, so, there is more oxygen present along with the unburnt fuel. The fuel isn't unburnt because there isn't enough oxygen, it is unburnt because the conditions for complete burning were less than optimal.
The DI angle is changed to compensate for the increased scavenging caused by lower restrictions in the Intake and Exhaust. An optimal angle will burn more of the fuel, so the combustion is more complete before being swept out by the Intake air. Since I have less restrictive Intake and Exhaust than OEM, I have more scavenging than OEM. AVCS timing is also as much as 30 degrees different than OEM, to give the charge better conditions to burn completely.
PI is great under low-load conditions at low engine speeds. It burns cleaner and is more efficient. But it knocks, bad, under medium to high-load and medium to high-speed conditions. DI cools the charge, is much less prone to knocking, but is limited by the size of the injector. PI for cruising, DI for accelerating, and 80/20 DI to PI at high-speed/high-load. I'll have a DI/PI table to show soon. Just working to smooth out the transitions now.