CIS to ITB EFI conversion

[dannichols1474]

Hi Nick,

Looking good!

For the shielded twisted pair (black and white wires in grounded sheath), connect the white wire (pin 24, TACH IN) to the black signal wire from the Pertronix igniter. Leave the black wire (pin 1) disconnected. The wire sheath is already grounded at the ECU.

Connect 12V switched to the red, power-in wire from the Pertronix igniter and make sure you put a 1k ohm pull up resistor between the 12V switched power and the TACH IN signal wire so you get a good high/low/high... signal from the Pertronix to the ECU.

[dannichols1474]

Yesterday, I made the 1100+ mile round trip to Lake Havasu City, AZ to pick up my rebuilt transmission from California Motorsports (CMS).
It is a long drive, but I find the section through the Mojave National Preserve (from Barstow to the Colorado River along I-40) to be majestic.

Excellent spirit recharge.

I also took the opportunity to stop in at Ollie's Engineering to see how the engine case, crankshaft,... work is progressing - Tim says he is on track to complete the engine work by mid June.

Rebuilt Transmission:


CMS gives you all of the replaced parts:


Some clearly worn parts:



I had the original open differential replaced with a Wavetrac locking differential - here is the old unit:


I also had the differential side cover replaced with CMS's billet aluminum unit. Roger at CMS has seen many of the original magnesium side covers crack over time.

My cover is not cracked, but I had it replaced just to be safe.

[TheBrokePilot]

Hi Dan,
I was reading through your thread for the 20th time and I had a question about power for the EFI system. I was wondering why you chose to tie into the former blower fan circuit at the rear fuse block instead of something like the former CDI power lead? Thank you for writing up everything in such detail. It is really helpful.

Sean

[dannichols1474]

Hi Sean,
I chose the blower motor circuit because it was fused at 25 amps and ran off a relay which indicated to me that the wiring in the existing wiring harness was large enough to handle all of the circuits that would be attached to the EFI power panel especially the fuel injector circuits.

In hindsight, now that I am more familiar with the wiring in my car, the power wire to the original CDI module may also be suitable. But I would want to check the CDI module specs and see that its input current spec was in the 25 amp range before I tied the EFI power panel to it.

[dannichols1474]

Today I received the pistons and cylinders for my 2.7 rebuild (9.5:1 92mm JE pistons, 92mm Nickies). Thank you LN Engineering.

[dannichols1474]

Today I decided to fabricate the rod (Porsche tool P221) and chain (Porsche tool P222) holder tools that Wayne D describes in the engine assembly chapter of his 911 air cooled engine rebuilding book. I went down to the local Home Depot and purchased a 24in x 36in sheet of 28 gauge galvanized sheet metal and used the tool template dimensions on page 130 (figure 3-17).

The sheet metal cost $48 and I used 1/6th of the sheet, so the tools cost me $8 plus about 1 hour of time. Below are a couple photos of the process:

[NickW21]

Hey Dan! Things are looking amazing with your engine rebuild!! Quick Q: Did you end up cutting the length of the injector wiring that came with Al's kit? Those wiring harnesses are really well done, but are just extremely long for where they need to be connected. If you didn't cut them, did you just circle them up and zip tie them in the back somewhere? Not a ton of space in that engine bay and would love to not have tons of extra cabling just lying around back there...

[dannichols1474]

Hi Nick,

Sounds like you are on your way. Regarding the fuel injector and TPS wiring, I did trim the wires once I mocked up where the wires were going to be routed. I found that using scissors and cutting that stretchy fabric sheathing up its length, then pulling the wires out of the sheath and cutting off the excess sheathing worked well.

Yes, my engine build is coming along. I have (I think) all of the parts, supplies (sealant, lint free wipes, cleaner, etc.) and tools that I need to put the engine back together once Ollie's gets finish with the crankcase, crank, rods, etc.

I have been reading and studying the engine assembly chapter of Wayne D's 911 engine rebuilding book and asking Al lots of questions.

Al has been great, very supportive and has given me a lot of tips on procedure and suggested specialty tools to make the build go smoothly.

I have made multiple visits to Stomski Racing (stomskiracing.com) for specialty tools.

Have fun with your project!

[dannichols1474]

While I wait for parts... it's a perfect time to clean up the EFI wiring as there is ample room with the engine and trans out of the car.

I decided to replace the 8 bay and 6 bay connector blocks that connect engine side EFI wiring to the ECU side EFI wiring with moisture resistance connectors like I had installed back in December.

A 2 pin connector replaces the right connector block that make ECU ground connections for fuel injector banks 1 & 2.


The 8 bay connector block is replaced with a 2 pin connector for Pertronix power and signal (crank position signal) between the distributor and the ECU / EFI power panel and a 6 pin connector that handles engine temp sensor, O2 sensor, ignition trigger to MSD box, and the throttle position sensor.


Notice the 1 kohm pull up resistor between 12V and crank position signal. I soldered wire leads onto the resistor leads and covered with heat shrink tubing.






Next up will be to replace the 10 gauge main power and ground wires that were left overs from my home solar power project with some automotive grade 12 gauge wire that will be more flexible and better able to handle vibration.

[dannichols1474]

With new moisture resistance connectors installed, I turned my attention to the main power supply and ground wires for the EFI; as well as, the high current power and ground wires for the MSD CDI box.

When I originally installed the ITB EFI system I used 10 awg solar system wire that I had left over from the solar power installation at my house. The solar wire has high heat and UV tolerance and plenty of dielectric stand off strength, but the insulation is thick and pretty stiff so it was hard to work with. In its place I used 12 awg automotive grade copper wire.

Unfortunately, the main wires were buried beneath the rest of the EFI wiring so replacing them meant unwrapping and taking apart the EFI wiring. The upside is I get to improve the wiring layout and should end up with a more tidy installation.

Following are photos of the tear down and re-assembly:





EFI wiring harness unwrapped and main EFI power wire removed:


Removed the fuel filter and disconnected the MSD CDI high current wires:




Old MSD CDI high current wires are removed:


Main EFI ground wire where it attaches to the chassis ground lug behind the fuel filter:


Old main EFI ground wire removed:


New MSD CDI high current ground wire installed at chassis ground lug next to the transmission shift rod tunnel:

[dannichols1474]

More photos:

New MSD CDI high current ground wire installed:


New MSD CDI high current power wire installed:


New EFI main ground wire connected to chassis ground lug behind the fuel filter:


Starting to re-assemble the EFI power panel and wiring:

[dannichols1474]

More photos:

Old tach wire connection to MSD tach out wire:


New tach wire connection to MSD tach out wire:


Tidied up the ground connections at the left rear engine compartment electrical panel:


Getting the EFI engine harness straightened out and held in place with cable ties:


Making power and ground connections at the EFI power panel and re-wrapping the EFI engine harness:


The EFI engine harness is wrapped and secured in place. I decided to keep the new EFI power wire outside the wrapped harness for easier access:


EFI wiring all back in place with new moisture resistant connectors replacing the original connector blocks. The fuel pressure regulator, fuel supply, and fuel return lines are re-installed. The back of the engine compartment is still pretty busy, but at least to me it is more organized. Now I will update my EFI wiring documents to match the new configuration:

[Old H2S]

Hey Dan, That is not a good ground location..Yes Porsche used it but was the cause of the CDI box failing when these cars were new, lots of headaches for PNA. I was a tech at HBL Porsche at the time and got to drive home a new 911 everyday to check for faults.

[PeteKz]

Old H2S: Are you referring to the ground stud that's just forward of the relay panel? On my 1973, that stud is brazed to the body, so it "should" be a very good ground point. Not so?

[Old H2S]

No Pete, that forward stud is good. I was looking at the picture of the wires attached to the mounting panel using a long bolt through the panel into the sheet metal behind it. Porsche did the same thing grounding the CDI to the panel rather than a wire to the grounding stud that was 6" away.

[dannichols1474]

Hi H2S,

Thank you for your concerns about CDI module grounding to the sheet metal electrical panel.

While the original CDI box used this point for ground, after the CIS to ITB EFI conversion the original CDI module was replaced by an MSD CDI module and the main ground for it is taken at the grounding stud on the chassis next to the transmission shift rod tunnel (see photo #3 below).

The main ground for the rest of the EFI system is taken from the grounding stud on the inside of the chassis beneath the fuel filter (see photo #2 below) - also note the webbed ground strap directly beneath my new black ground wire.

The ground wires I was referring to in the photo below (photo #1) are for 2 low current circuits and not the ground for the MSD CDI module - note the webbed ground strap beneath my ground wires which is originates at the chassis ground stub in photo #2).

Photo #1:


Photo #2:


Photo #3:

[pmax]

Originally Posted by dannichols1474

...
Photo #3:

That's one amazing clean underbody, in white to boot.

[dannichols1474]

Hi pmax,

I had the underside of the car steam cleaned like 10 years ago and I stopped driving it in wet conditions so it has stayed pretty clean.

[dannichols1474]

Deciding to rebuild my engine and transmission 1 year after I converted from CIS to ITB EFI has given me the opportunity to go back and review / modify / improve the EFI wiring connections.

For anyone thinking about or in the process of this conversion, I will share documents I used with the EFI wiring.

In the software documentation that Al @ x-faktory.com provided with the CIS to ITB EFI conversion kit there are 2 documents that I have found to be very helpful in properly wiring up the EFI so it plays as advertised:

1. The EFI wiring schematic:

[dannichols1474]

2. The Megasquirt2 (ECU) pin out definitions:


And then I documented how I actually made the wiring connections between and ECU wiring harness and EFI engine wiring harness.

Here is the original wiring connections from June 2023 using the wire connector blocks:


And here is the new wiring connections from May 2024 using moisture resistant wire connectors:


In my opinion, clear documentation is a must for success.

Good luck with your DIY project!