Some info about injector :
Peak and Hold:
Peak/hold injectors are low impedance, usually in the 1-4 ohm range. When the ecu calls for fuel to be injected, it sends out voltage via the wire clips until a certain current level is reached (the peak part) (varies by injector size, company). For the duration of 1 pulse width, that current is slightly reduced and held (the hold part). Peak-and-hold injectors require a larger current (~4A) to open the injector and a smaller current (~1A) to hold it open.
Advantages of this design:
minimizes the injectors "on" time, resulting in faster response
Disadvantages of this design:
increases coil heat, which can lead to failure over time
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Saturated:
Saturated injectors are generally higher impedance than peak and hold, running in about the 10-15 ohms range. Unlike peak/hold, a saturated injector remains "on" for the entire pulse width. Saturated-circuit injectors use a constant current (typically 2A @ 12VDC) to open the injector and keep it open.
Advantages of this design:
reduces heat
Disadvantages of this design:
slower response time
can't handle large CC or lb/hr styles due to limitations in its speed.
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Sealing Mechanism Design :
Pintle – Bosch/Denso
- easy to clog not good with ethanol
- pintle weight 4 grams
- fuel atomization good ( good at low rpm & moderate at hi rpm)
Disc – Lucas
- good with ethanol
- disc weight 0.4grams = good respond
- still can flow over 100psi
- more direct spray pattern might also help cool intake valves in high horsepower applications
(not good low rpm )
Ball & Seat – Delphi/Rochester/gm multec
- Good with ethanol
- Cannot operate at very high pressure, the nozzle will stop inject fuel
- Cone mist atomization ( very good at low rpm )
- Use light weight material = maybe faster respond compare to disc type
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Minimum cycle time for most pintle types is 2.0 Ms. for Peak & Hold (OEM) and 2.5 for Saturated units. The Disc will cycle as low as 1.0 Ms. The Lucas Disc, and I assume RC Disc, weighs only 0.4 Grams. and the Bosch / Nippon -Denso pintle is at 3.9 to 4 Grams (Ten times heavier). The reduced inertial loading of the disc, allows the Disc to overcome the hydrostatic load at excitation quicker and return to it's seat faster, providing quicker response times and more consistent cycle-to-cycle values.
So why is this important. Well, it is not, most of the time. At 3000 rpm the intake valves open and close 25 times per second. Thus, each even is 40Ms in length. At 80% injector duty, the injector is "on" 32Ms and "off" for 8 Ms. This is plenty of time for both injector types to get their job done. During those last 4Ms, the pintle would only just get closed, when it is time to open again. Beyond 90% injector duty, the injector would start to become static (open all the time) or go "semi-static" (as in "lock-up"), which would have drastic consequences at WOT - this is why not to go past 85% Injector Duty.
Now, at 6000 rpm, the valves open/close 50 times per second. At 80% injector duty, the injector is "on" 16Ms and off 4Ms. Thus, at 6000 rpm, the injector pintle just gets closed, when it is time to open again. At 6500 rpm (redline), the valves open/close 54.16 times per second. At 80% injector duty, the injector is "on" 14.77Ms and "off" 3.7Ms. At 6500 rpm, the valve opens/closes 54.1667 time per second; at 85% injector duty, the injector is "on" 15.69Ms and "off" 2.77Ms. During those last 2.77Ms, the pintle would only just get closed, when it is time to open again; if the pintle is "slower" than the 2Ms stated above, the injector would start to become static (open all the time) or go "semi-static" (as in "lock-up"), which would have drastic consequences at WOT - this is why not to go past 85% Injector Duty.
Due the short time the pintle is open at 6500 rpm, the "ramp-up" time of the P&H vs. Saturated injector becomes critical as to how much fuel is injected. The 1-1.5 Ms quicker opening time of the P&H is significant in the amount of fuel injected. It is for this very reason and the reasons first stated (consistently and accuracy) that P&H injectors are used in turbo and performance applications.
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See some injector vid test :
YouTube - comparison of Lucas type disc injector to Bosch design III to the stock GM multec.
YouTube - 850cc to 1680cc
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my list to buy item is Injector Dynamic 2000CC hi impedance .. it very good injector, still can get good idle for 1.8cc engine with petrol ... google it if wanna get more info.
