firing angle Formula? 03cobra

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firing angle Formula? 03cobra

Postby ultraspeed » Thu Feb 26, 2015 10:09 am

Okay so I have a 03 cobra whipple setup and im trying to figure out what the injector firing angle would be. Id like to fire the injector on the back side of the intake valve right at opening.


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Re: firing angle Formula? 03cobra

Postby HaltechMatthew » Fri May 01, 2015 4:16 pm

For a Port injected engine usually you would time for the closing of the valve, not the opening. Timing for the opening can cause not all fuel to make it into the engine on that cycle if the injector is still open after the valve closes. The same goes for spraying fuel when the airflow has all but stopped, even though the valve is still slightly open.

Depending on the injector location, and a gazillion other factors, around the 400BTDC mark is a good starting point. If the location is close to the valve you may be able to get down closer to the 360BTDC range, and conversely if the injectors are far you will need to advance the timing to a higher value. Go too retarded and you end up with flat spots on acceleration as the main side effect, as fuel is held off until the following cycle. Fire too early and poor atomisation will make the engine feel slightly flat, but this is better than being too retarded with the timing and why I would say to start high and work your way down.

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