MembersPage/KarlBuchka/Fuel

Original intentions of running Delphi 1000cc injectors was scrapped. A friend offered me a set of used Siemens DEKA 1 795cc Low-Z injectors for a great price. Specs (from http://www.racetronix.com/3145FM.html)

Static Flow Rate: 74.7 lb/hr = 9.42g/s = 769 cc/min (+/-4%)

Dynamic Flow Rate 2.5ms PW @ 100Hz: 16.9 mg/pulse (+/-4%)

Coil Resistance: 2.35 Ohms / Low Impedance / Low-Z (Peak/Hold driver circuit required)

Spray Pattern: Pencil

Connector: Minitimer (Bosch EV1)


MembersPage/KevinBlack/InjectorSpecDatabase has a complete looking set of these numbers for the Delphi 95lb/hr injectors. Mirrored here:

Delphi Low-Z 95#/hr (with 30v TS diode and 6R8 resistors)

Barring any new information I will use these as base values for the Siemens injectors. Any suggestions on the figures?


The low-z injectors will require power resistors. As mentioned earlier, I can source them in almost any spec I want. I understand the resistors are used for current limiting, but how much current am I aiming for? A couple of quick calculations yields a 12ohm resistor for a current of 1A and 5ohm for 2A (both assuming 2ohm injector resistance and 14V supply).

PhatBob?'s UserGuide? states that 6.8ohm/50W power resistors yielded good results on 'Delphi 1000cc injectors'.

I have opted for 6R 50W power resistors due to cost and availability.


Injector wiring and setup

Cylinder Inj. channel ECU Pin Mask pattern number [hex]
1 Injector1 EC36/7 1
2 Injector2 EC36/19 2
3 Injector3 EC36/8 4
4 Injector4 EC36/20 8
5 Injector5 EC36/9 10

Since the injectors are going to be fired sequentially I want them to trigger on the intake stroke of each cylinder.

Assuming the intake stroke starts at 0 crank degrees, when each cylinder is at TDC of it's compression stroke (360 crank degrees later), all the other cylinders will be at the following positions:

  Cyl. 1 TDC Cyl. 2 TDC Cyl. 4 TDC Cyl. 5 TDC Cyl. 3 TDC
Cyl. 1 pos. (360) 504 648 72 216
Cyl. 2 pos. 216 (360) 504 648 72
Cyl. 4 pos. 72 216 (360) 504 648
Cyl. 5 pos. 648 72 216 (360) 504
Cyl. 3 pos. 504 648 72 216 (360)
(Arranged in firing order, not numerical order)

Because the injectors have to be fired at the same time as the coils fire, we need to sync each cylinder's spark event with an injector event on the intake stroke of another cylinder. The table above assumes that the intake stroke occurs during the first 180 degrees of crank rotation. Looking at where the values fall, cylinder 4 should be on it's intake stroke as cylinder 1 is firing, cylinder 5 as cylinder 2 is sparking, etc.

Going over to MembersPage/KarlBuchka/Trigger, we can match the reference tooth array (h[1]) to the injector output array (h[0]) as follows:

h[0] = 08 02 01 04 10 00 00 00

I calculated req_fuel to 3.75 using (6.49 * 2300[cc] / 5[cyl] / 795[cc/min]).


As of now I plan to use my current Megasquirt fuel map (with values scaled) as a base map.