[quote=baz-r;65838]fired up the tig today nd cut some alloy tubes to make my ford sandwich plate fit my zxr636 38mm throttle bodies.
i have removed the ecu controlled butterflies and im not sure witch set of injector im going to use yet ford or kwack? im thinkin ford as there right at the port and i dont want drop out probs at idle hope 195cc/min will be enough?
The below is to calculate inj size at 100% duty cycle but when I spoke to dave walker at emerald he reckoned dont run much past 80%. Hope its of some use.
Bob
Fuel Pressure and Injector FlowThe pressure at which an EFI system runs affects the flow of an injector. Most fuel injectors are rated at 43.5 PSI. Increasing the pressure above this increases the flow and lowering it decreases the flow. If an injector does not flow enough at 43.5 PSI, the fuel pressure can be raised to increase the flow rather than having to change to a larger injector. It is best not to raise the fuel pressure much above 60 PSI. Certain injectors will not open properly at higher pressures. Fuel pump flow also decreases at higher pressures, so make sure your fuel pump flows enough if the pressure is raised. Remember that on a supercharged or turbo-charged engine the fuel pressure will be raised above the base fuel pressure by the extra boost that is produced. In other words if the base fuel pressure is 43.5 PSI and you have 10 PSI of boost, the total fuel pressure will be 53.5 PSI.
The following equation is used to calculate the flow if the fuel pressure is changed:F1 = P1F1 = rated mass flow of the injector at fuel pressure P1 in lb/hrF2 = P2F2 = new mass flow of the injectors at new fuel pressure P2 in lb/hrP1 = rated fuel pressure in PSI (usually 43.5 PSI)P2 = new fuel pressure in PSI
ExamplesRated flow = 24 lb/hrRated fuel pressure = 43.5 PSINew fuel pressure = 55 PSI
Raising the fuel pressure of a 24 lb/hr injector to 55 PSI raises the flow to 27 lb/hr.
Duty Cycle -The duty cycle is the maximum amount of time you want the injectors to be open at a certain horsepower and injector size. Under most circumstances you don't want an injector to be open more than 90% of the time at the most. Marine applications shouldn't exceed 80%. Injectors are rated at 100% duty cycle (static flow).
When calculating injector size, round up to the next nearest size needed. For example if you calculate 26 lb/hr and have a 24 lb/hr and a 30 lb/hr to choose from, select the 30 lb/hr injector.
Examples400 HP street engineNumber of injectors = 8
Injector size = (400 HP) x (0.5 BSFC) = 27.7 lb/hr (8 injectors) x (0.9)
600 HP Supercharged engineNumber of injectors = 8
Injector size = (600 HP) x (0.57 BSFC) = 47.5 lb/hr (8 injectors) x (0.57)
Injector HP Chart for Typical Performance EnginesThe following chart indicates recommended injector size for typical naturally aspirated V8 performance applications. A BSFC of 0.45 and duty cycle of 90% is used for the following recommendations. Use the formula above to calculate your injector size if a different BSFC and duty cycle is required.
14 lb/hr up to 225 19 lb/hr 225-300 24 lb/hr 300-385 30 lb/hr 385-480 36 lb/hr 480-575 42 lb/hr 575-670 50 lb/hr 670-800
And heres an easy one.
http://www.witchhunter.com/injectorcalc1.php4 Looks like those injectors will support about 120bhp.
Bob