Torker II MPFI Build

Here is some more Megasquirt variable setup stuff on injector timing to an open valve: forget it above 2300 RPM! There is just not enough time to inject enough fuel above 2300 RPM into an open intake valve. Larger injectors help, but its a pipe dream to think you can do this 100% of the time.

".....However, sequential injection does not necessarily mean you are injecting into an open intake valve all the time. The intake valve is only open less than 30% of the time in a typical 4 stroke engine. Once you are trying to produce more than about 25% of maximum HP your injectors are firing for longer than the intake valves are open. If your maximum HP is correctly calibrated to a safe 80% duty cycle, your injectors are injecting well over 50% of the time on closed valves.

At higher rpms, it becomes increasingly difficult to inject while the valve is open. For example, if your Req_Fuel = 15.0 ms, and your maximum duty cycle is 85% then the interval between injections cannot be closer than 17.6 ms. The time available to inject during the entire 4 stroke cycle is:

timecycle = 120/RPM
the intake is typically open for less than 240° of 720° in an engine cycle in a hot street engine, about 1/3 of the time for a complete cycle. So:

timeinject = 40/RPM
and

RPMmax = 40/timeinject
Using the numbers above,

RPMmax = 40/0.0176 = ~2300 rpm
Above this RPM, it is not possible to inject the entire amount fuel through the open valve at 100% VE and 100kPa. At idle, however, VE may be 30%, and kPa might be 35 kPa, yielding a pulse width of ~1.8 milliseconds, which certainly could be injected during the intake valve opening. So sequential injection is primarily effective at idle, and not much different from batch injection as pulse widths get larger at higher engine speeds and loads.

In any case, when fuel is injected while the valve is closed, it will simply stay in the port until the valve opens. In some cases, this period of time may allow enough heating of the mixture to better vaporize the liquid fuel, improving efficiency and emissions..."


I understand that is the best place to mount the injectors, like where else would you put them? In a pinch, I suppose you could make a 1" spacer under the TB and add 2 injectors per side ala Wilson "V-power" and bank fire them but they would have to be pretty big for a warm V8. like 4 X 54 lb/hr for a 450 HP motor (taking the 8 X 27 lb/hr injectors from a Edelbrock system) Looks good. I hope I can get mine as angled and not straight in.