1978 Porsche 928 body

1989 5.0L 32V V8 engine

78 2.75 drive ratio rear mounted transmission

V-1 Vortech Supercharger

Engine Build:

Swaintech coated pistons, ARP Rod bolts,

ARP head studs switched from OEM head bolts

Cometic Headgasket

Forged early 928 rods

944S2 valve springs

928 S3 (928 from 85-86) Cams (Shortened and bearing surface moved by Elgin Cams)

Planned: Side plates on dual resonance intake for more volume


IGNITION: Porsche Cayenne Coils fit PERFECTLY into the 928 32V heads, almost as if they were meant to there.

PNA- 721 043 00 430 “Car Tool 9” 26.01 and this is a pack with two male plugs for the coils. They are without wires, and you would need 4

948 602 104 03 “Pencil Coil” 12.21(!) dollars

PNA 721 043 00 504 “Harness Re” 67.44. Its enough terminated wires for two plugs, so you need 4. They are crimped onto the metal female receivers that slide into the plug itself, and have rubber gromits and about 12 inches of wire.

Partial Description of Wiring diagrams for Coils:

I took some time to analyze the drawing. The coil plug has 4 wires and they are labeled A1, A2, A3, A4. On the drawing, the wires come out of the plug, left to right, A1, A4, A3, A2. A1 is ground. A4 is the pulse input. A3 is +12 volts. the function of A2 is sort of a mystery. It's a small wire only 1mm in diameter. The color as near as I can tell is brown/black. It goes to something called MM1 as near as I can read the drawing. Four coils go to MM1 and 4 coils go to MM2. Since this wire appears to be connected through a diode internally in the coil to the low side of the secondary winding, it may be a sense line to feed back some spark signal characteristic to a "black box" ignition control unit. I know some ignition units sense the ionization characteristics of the spark to determine if detonation is occuring. The drawing if the coil internals is quite basic with not enough detail to know what's really going on in there.

  • it is very common nowadays with non-logic-level (but power input CDI capable) ignition transformers that the secondary has a return signal. This return signal is suitable for IonSense current measurement (when connected to a 100V supply). You can simply connect the return signal to ground (secondary current is small, 0.5mm2 wire is more than enough).
That pin 2 brn/blk wire just goes to a ground. The MM1 and MM2 is a ground terminal point. So it all looks pretty simple.

It is probably secondary winding return to ground signal. You can connect to ground. IonSense applications probably return to an articicial (80..300V) potential through a resistor so ion current can be maintained and measured.

I am trying to get the PDFs of the wiring diagrams up on photobucket so I can post here. Also, measure resistance between all pin-pairs, in both direction.

The v3harness is for 4cyl (4 injectors) by default (though more ignition and misc channels, suitable for upto 8 cyl). Regardless of the VEMS assembled controller options, you have to write an order note to request 6 or 8-injector version loom. The 6 cyl is suitable for 5 as well. The 8-injector is split to 2x4.

How is the injector split 2x4 if they are sequential?

Since the different V8 (and W8) engines have different firing order, it is not feasible to insert the EC pins during manufacturing. The recommended method is to use the

h[0]=01 02 04 08 10 20 40 80

and assign the cylinders to H,G,F,E,D,C,B,A as in the firing order. You can of course rotate the h[0] injector sequence later, but at least it is trivial to spot mistakes. (while if one does it the not-recommended way, cyl1..8 to injout A..H than the h[0] will be messy, harder to spot mistakes later).

I have also found some three pin plug pigtailed Knock sensors, the same ones used for the OEM config on the car. I need to find the recieving end of the plug for the loom end.

Do you have the pinout for your knock-sensor ? Did you verify the knock-sensor and record with a notebook while clinging the side of the block with a wrench ?

Specs of unit that are published: Manufacturer: BOSCH

Newark Part Number: 68C2834

Manufacturer Part No: 0261 231 018

RoHS? Compliance :



* Capacitance, max:1600pF

* Capacitance, min:800pF

* Diameter, external:28mm

* Diameter, internal:8.4mm

* Frequency response, lower limit:1kHz

* Frequency response, upper limit:20kHz

* Impedance:1MR


Now info: I have chosen to run E85 fuel. Easy to get here, and cheaper. While I have to now nickel plate or anodize the fuel rail (aluminum), I already bought High Imp. 72lb injectors because I didn't like the issues with low impedance.

Well, now that I will run ethanol, and will need up to 40% more fuel, I may need even more than the 72lb injectors at high boost and high rpm, since sequential, per A. Graham Bell's "Four Stroke Performance tuning" book must be run down to 65-70% duty cycle, or there is no real advantage in power.

There are 160lb metahnol compatible injectors which would be better for the ethanol, but they are always low imp.

Q: I suppose I can just order the unit with the low imp. option, but will that then limit me in the future?

Q: Will I have enough control to run the 16olb injectors at idle?