Any wiring tips for XDI crank fire system?

[MST0118]

Hey Guys,

I'm planning to install the XDI2 crankfire ignition dual plug set up and had questions on the best way to wire it.

I talked with Clewett a couple times and he suggested installing a dual 30 amp relay in the passenger compartment where both the DFUs are wired into it and then I would need to run a ground and a wire from the ignition switch as well as a direct wire from the battery. Picture of the relay wiring is just below.

Here's my questions.

1. Is there a source for 2 amp fuses that can fit in our standard fuse boxes?

I have the standard 1972 911 fuse boxes (10 and 8) in the trunk and the small 3 fuse box in the engine compartment. The smallest amp fuses that I have are only 5 amps. Does anybody know where to get the 2 amp ones?

2. I need to run a wire to the ignition switch from the relay in passenger compartment. Can anyone suggest a preferred way of doing that?

3. Is it possible to run that ignition switch wire through the fuse box in the trunk to the relay or should it wire directly from the ignition switch to the relay?

[fred cook]

Originally Posted by MST0118

Hey Guys,

I'm planning to install the XDI2 crankfire ignition dual plug set up and had questions on the best way to wire it.

I talked with Clewett a couple times and he suggested installing a dual 30 amp relay in the passenger compartment where both the DFUs are wired into it and then I would need to run a ground and a wire from the ignition switch as well as a direct wire from the battery. Picture of the relay wiring is just below.

Here's my questions.

1. Is there a source for 2 amp fuses that can fit in our standard fuse boxes?

I have the standard 1972 911 fuse boxes (10 and 8) in the trunk and the small 3 fuse box in the engine compartment. The smallest amp fuses that I have are only 5 amps. Does anybody know where to get the 2 amp ones?

2. I need to run a wire to the ignition switch from the relay in passenger compartment. Can anyone suggest a preferred way of doing that?

3. Is it possible to run that ignition switch wire through the fuse box in the trunk to the relay or should it wire directly from the ignition switch to the relay?

I basically followed the instructions that came with the system. However, I put the two 30 amp capacity relays on the power board where the Bosch CDI was originally mounted. Then, I ran the necessary wires into the cockpit where I mounted the control module. It (the module) is mounted on the vertical surface behind the passenger seat. I also made a mounting bracket that allows a bit or room between the timing control module and the carpet for ventilation. I pulled the main power supply off the starter, used the small red switched wire that was in the CDI master plug for the relay trip wires and attached the ground wire to both the chassis and to the engine (just to be sure!). I made a mounting bracket for the coil units and mounted it on the small shelf between the engine and the back seat firewall. Be certain to make very good grounds for the coil modules or you could damage the system or get a super shock! Also, once I got the timing wheel sensor correctly spaced, I put a small hose clamp on the sensor so that I could remove and install it without using a feeler gauge. Once the rear sheet metal is in place, it is difficult to get a feeler gauge down there!

Coil Packs mounted


Timing controller w/mounting bracket


Timing controller mounted in cabin


Engine installed. Note lack of distributor and backdated heat ducts.


The engine is a 3.3SS w/Mahle 10.5:1 pistons, KN Engineering 100mm cylinders, 964 Cams, SSI exhausts, Carrera twin plug heads, a large port 1978-9 SC airbox and some other misc. goodies.

[MST0118]

I like how the the timing controller is mounted in the rear part of the cabin and may do that as well. Did you use the fuses on the relay board in the engine compartment for the XDI system or somewhere else?

[fred cook]

Originally Posted by MST0118

I like how the the timing controller is mounted in the rear part of the cabin and may do that as well. Did you use the fuses on the relay board in the engine compartment for the XDI system or somewhere else?

According to the manual, the max load per coil pack is 10 amps. Roughly 1 amp per 1000 rpms. So, I used one 20 amp fuse to power both relays. My ignition cutout is set at 7500 so that would be about a 15 amp draw. I made a 4 fuse panel to replace the 3 fuse original and set it up to use modern ATO fuses. I did not fuse the low amperage leads that act as the relay triggers. That load is probably about 1 amp per relay or less. Here is a picture of my mini fuse panel. The larger panel is a replacement for the main fuse panel in the trunk w/headlight relay kit.

[Gordo2]

Single plug setup - Engine Harness / Multi-pin Connector for Carb Conversion '83 SC

I used a relay - ignition source from original wire harness, DFU power from the starter power wire (I think).


Good luck - great systems.

Gordo

[MST0118]

Thanks Fred and Gordo for the great tips! Just what I was looking for.

[gumba]

I used a "Painless" 8 fuse block mounted in the engine compartment. Power direct from the battery. Four fuses come on with the ignition key and three are constant 12 v.

[MST0118]

Yeah, Richard also recommended running a 10 gauge power line directly from the battery to the 30A relay. He also said no need to fuse it, but if I did, he recommended a 30A fuse instead of a 20A or two 10A fuses.

He also recommended installing a 2 amp fuse on the yellow wire that runs to the XDI2 unit which is consistent with the installation instructions. I haven't been able to find a 2 amp use that fits in the stock fuse box, however. I think 5 is the smallest that I can find. Could I get away with using 5A? If not, thinking I may have to go with a single 2A ATO fuse.

[florent78]

Hi

I want to use the power connecting directly on the starter +12V

it's already having a good power line, and much easier to connect

for me, appart of the 5 sec start engine, the starter is not working so the +12V should be "clean"

do you agree ?

thanks

[911pcars]

Originally Posted by florent78

Hi

I want to use the power connecting directly on the starter +12V

it's already having a good power line, and much easier to connect

for me, appart of the 5 sec start engine, the starter is not working so the +12V should be "clean"

do you agree ?

thanks

The entire electrical system "sees" whatever voltage is available during engine cranking. But yes, the bat. terminal on the starter solenoid would be one take off point. Better yet, reduce/avoid any possible voltage drop (albeit low) from that location and route a 12-14 ga. path from that location to a relay in/near the engine compartment, then to the XDI box. Since the voltage at the starter solenoid isn't switched, Route another ign. ON path to energize the relay to control voltage to the XDI box.

Sherwood

[florent78]

yes

I want to use the +12V on the starter as power ignition on the relay


and I will use the +12V coming from the HKZ plug (no more HKZ) as "excitation" on the relay

seems to be a correct fit for me