CIS to ITB EFI conversion

[montauk]

Nice work. I hope it gets better resolution for you. BTW, I found the plastic wire sleeves to be too difficult to fit particularly with tight bends. I've been using a combination of shrink wrap, abrasion-resistant wrap from Mcmaster Carr, and fabric tape.
https://www.mcmaster.com/catalog/131/1015/2649K521

[dannichols1474]

Originally Posted by montauk

Nice work. I hope it gets better resolution for you. BTW, I found the plastic wire sleeves to be too difficult to fit particularly with tight bends. I've been using a combination of shrink wrap, abrasion-resistant wrap from Mcmaster Carr, and fabric tape.
https://www.mcmaster.com/catalog/131/1015/2649K521

Thanks. I am going out for an auto tune session this morning and I'll record a couple of data logs to verify operation.

I agree with your assessment about the plastic wire wrap. I think I'll de-populate the wire connectors and try heat shrink tubing where ever possible. I'll also check the Mcmaster Carr wrap - thank you for the suggestions.

Update: I ordered some of the abrasion resistant sleaving from McMaster-Carr - I'll give that a go next. Thanks.

[dannichols1474]

I researched various wire wrap and wire sheath options. The heat shrink tubing I found is dominated by 3:1 shrinkage with an inner adhesive and I thought that would be more of a mess trying to remove in the case of a needed repair. I also looked at and ordered some abrasion resistant, length slit, wire sheathing from McMaster-Carr which I may install if the need becomes apparent. In the end, I settled back upon the method used by the factory for my 1975 Porsche: black electrical tape wrapped around the wires in long continuous lengths.

But first I removed and discarded all of the corrugated black plastic length slit wire sheathing - that stuff is bulky and didn't look right on my car. I also dismounted and laid over the EFI electrical panel and disconnected the EFI wiring connectors and I removed the fuel supply and fuel distribution hoses from the fuel pressure regulator to give me ample room to work on the re-wrapping of the EFI wiring bundles and sensor connection lines.

Once the wrapping was completed, I reconnected all of the EFI wiring, remounted the EFI electrical panel and reinstalled the the fuel lines.

Next will be to perform a fuel pressure / leak check, then start the engine and after warm up to perform an ITB flow balance check / adjustment.



Wire wrapping in process. I used small 4 inch cable ties to hold the wire bundles together, then removed them, one by one, as I wrapped along the length of each wire bundle and sensor connection line.

[montauk]

Nice job!!!

[winders]

Originally Posted by dannichols1474

I researched various wire wrap and wire sheath options.

The best stuff:

Raychem DR-25

https://www.milspecwiring.com/DR-25-Shrink_c_325.html

[Showdown]

Just be aware to if possible separate power and ground wires from signal wires and again, if possible concentric wrap your harness as it’ll make it more durable, flexible and so much neater.





Sent from my iPhone using Tapatalk

[montauk]

The Haltech harness uses shielded cables for the crank, cam and knock sensors. There's also separate ground sensor wires that go to the ECU but are not bonded to the chassis ground. 5VDC sensor power wires are included too. So far, I haven't had any wiring noise problems.

[dannichols1474]

Originally Posted by winders

The best stuff:

Raychem DR-25

https://www.milspecwiring.com/DR-25-Shrink_c_325.html

Agreed. The Raychem DR-25 heat shrink tubing is very good and available in many diameter sizes.

https://www.te.com/en/product-9908044002.html



Eurosensor uses Raychem DR-25 on the wire lead of their Variohm Hall effect rotary position sensor that I installed as a TPS.

[TheBrokePilot]

Originally Posted by Showdown

Just be aware to if possible separate power and ground wires from signal wires and again, if possible concentric wrap your harness as it’ll make it more durable, flexible and so much neater.

Stuff like that looks amazing and pretty but also looks like a pain to repair.

[TheBrokePilot]

Thank you again Dan for all your documentation in this thread. I finally got my CIS -> EFI conversion started for the first time today. Needs a lot of tuning and it’s not an ITB setup yet but it’s a start.

[Showdown]

Originally Posted by TheBrokePilot

Stuff like that looks amazing and pretty but also looks like a pain to repair.

The goal is to plan sufficiently such that you don’t ever have to cut into your harness to make modifications. If you have to alter the wiring after install, the prep was insufficient.

Tidy wiring is much easier to repair if ever that’s needed than rats nests.


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[930cabman]

I am close to dumping the CIS on my 1975 911S, but will go to Weber triples.

I like simple

[Wizoftk]

Awesome write up! Dan what fuel pressure regulator are you using? Can’t make it out from the pictures and also at what PSI do you currently have it set at? I’m chasing down some fuel issues and just trying to verify few numbers. Thanks

[dannichols1474]

Originally Posted by Wizoftk

Awesome write up! Dan what fuel pressure regulator are you using? Can’t make it out from the pictures and also at what PSI do you currently have it set at? I’m chasing down some fuel issues and just trying to verify few numbers. Thanks

The fuel pressure regulator is from K Motor Performance:

https://kmotorperformance.com/shop/universal-adjustable-fuel-pressure-regulator-kit-an6-6an-fittings/

I set the fuel pressure to 40 psi static and it drops to 38 psi when the engine is running.

[montauk]

Originally Posted by dannichols1474

The fuel pressure regulator is from K Motor Performance:

https://kmotorperformance.com/shop/universal-adjustable-fuel-pressure-regulator-kit-an6-6an-fittings/

I set the fuel pressure to 40 psi static and it drops to 38 psi when the engine is running.

Dan,
I went with the Bosch 0280155831 injectors—same ones you used—mostly because you did. I’ve set them as close as I can to the spec’d 43.5 PSI (3 Bar), but my data logs show 45 PSI. I noticed you ran yours at 38 PSI (2.6 Bar), which is over 10% lower. Any particular reason for choosing that pressure?

One odd thing I ran into: accurate injector data is surprisingly tough to find. I couldn't track down the dead time versus voltage specs online. Then it hit me to check the Maxxecu software (which had made my shortlist of ECU options), and sure enough, the data was right there.

Here’s what I’m using:
Dead Time (ms): 1.96, 1.43, 1.11, 0.94, 0.82, 0.71
Voltage (V): 8, 10, 12, 14, 16, 18

[winders]

This is a fantastic FPR with a damper built in. This worked flawlessly on my race car:

https://www.radiumauto.com/FPRD-RA-Fuel-Pressure-Regulator-Damper-P2751.aspx

P.S. You want a damper....

[dannichols1474]

Originally Posted by montauk

Dan,
I went with the Bosch 0280155831 injectors—same ones you used—mostly because you did. I’ve set them as close as I can to the spec’d 43.5 PSI (3 Bar), but my data logs show 45 PSI. I noticed you ran yours at 38 PSI (2.6 Bar), which is over 10% lower. Any particular reason for choosing that pressure?

One odd thing I ran into: accurate injector data is surprisingly tough to find. I couldn't track down the dead time versus voltage specs online. Then it hit me to check the Maxxecu software (which had made my shortlist of ECU options), and sure enough, the data was right there.

Here’s what I’m using:
Dead Time (ms): 1.96, 1.43, 1.11, 0.94, 0.82, 0.71
Voltage (V): 8, 10, 12, 14, 16, 18

Hi montauk,

I set the fuel pressure based on my observation of the fuel pressure running on other cars I have owned or worked on and not on any engineering calculations. When I initially installed the ITB EFI system on my stock CIS motor and checked the fuel pressure, the fuel pressure regulator adjustment was screwed all the way loose so I saw the max pressure of the fuel pump at 90 psi and turned it down to 40 psi and left it there.

Since the stock CIS motor with ITB EFI was making 205 hp (crank) on the dyno before I rebuilt the motor, I was way below the estimated max hp for the given injector size (I remember reading the 30 lb/hr injectors would be good for 288 hp), so if I was running the injectors with 38 psi versus 43.5 psi I wasn't in danger of running out of injector capacity. But now with rebuilt motor making 274 hp (crank) I am much closer to the edge.

I did a quick AI internet search:

Calculating Maximum Power for a Given Fuel Injector Size
To determine the maximum power a given fuel injector can support, you'll need to use a variation of the fuel injector sizing formula. The key components are:

• Injector Size (lbs/hr or cc/min): The flow rate of your specific injectors.
• Number of Injectors: The number of injectors in your engine (e.g., 8 for a V8).
• Brake Specific Fuel Consumption (BSFC):This represents the amount of fuel an engine uses to produce one horsepower per hour. BSFC values vary depending on the engine type (naturally aspirated vs. boosted) and fuel type (gasoline, E85, methanol). (0.5 for naturally aspirated gasoline engines)
• Maximum Injector Duty Cycle: This is the percentage of time the injector is open and flowing fuel. It's generally recommended to use a maximum duty cycle of 80-85% for safety and consistent fuel delivery.

Formula: Estimated Crank HP = [(Injector Size in #/hr x Number of Injectors) ÷ BSFC] x Maximum Injector Duty Cycle

For 30 lbs/hr: Est HP = [((30 x 6) / 0.5) x 0.80] = 288 hp

For 31.4 lbs/hr (43.5 psi): Est HP = [((31.4 x 6) / 0.5) x 0.80] = 301 hp

Now assume those injectors at 38 psi flow only 27 lbs/hr (down 10%),

For 27 lbs/hr: Est HP = [((27 x 6) / 0.5) x 0.80] = 259 hp (80% injector duty cycle)

For 27 lbs/hr: Est HP = [((27 x 6) / 0.5) x 0.85] = 275 hp (85% injector duty cycle)

Now, with more experience and considerably more thought, I see that I should turn the fuel pressure up so that when the engine is running the fuel pressure will be at 43.5 psi to take full advantage of the Bosch 62672 (0280155831) injectors that are rated at 31.4 lbs/hour at 3 bar (43.5 psi).

But unlike your Haltech ECU, the MegaSquirt2 ECU doesn't monitor fuel pressure nor fuel temperature directly, so if I adjust fuel pressure, then I will need to re-run auto tune to adjust the values in the VE table since for a given injector pulse width the injectors will deliver more fuel per shot at the higher fuel pressure.

Another thought: My motor makes max hp at 6600 rpm and that carries flat out to 7200 rpm and I have the rev limiter set to 7500 rpm. The ECU fires each bank of injectors once every 2 revolutions, so a given injector fires 3750 times per minute which works out to firing every 16 ms. Per your dead time data and given my Anti-Gravity battery is at 13.2 V (13.8 V while running), my injector dead time is about 1 ms which leaves 15 ms for the injector to deliver fuel at 7500 rpm. At 85% duty cycle, that translates to 12.75 ms maximum pulse width available at 7500 rpm. I need to go look at a recent data log with the a 100% TPS pull to 6000 rpm and see what injector pulse width the ECU was calling for - I wonder if I'm already at the wall?

Thank you for asking the question.

[TheBrokePilot]

Hi Dan and the rest of the thread,

Just to add on to the chat about injectors. Today I tested my injectors for dead time in preparation for tuning. The setup I have is 986 Boxster Fuel Rails with built in Fuel Pressure Regulator(FPR) that is calibrated for 3.8 Bar(55 PSI). I am using stock Bosch 0280156053 injectors rated at 260cc but with the stock 3.8 bar fpr they are theoretically rated at 294cc.

I did some testing today for dead times and with the stock FPR and stock replacement CIS Bosch Fuel pump they output 310cc with the FPR verified at 55 psi. When checked at different voltages and pulse widths in TunerStudio I ended up with a .81ms dead time. This is on a stock but tired old 77 2.7 CIS engine.

Sean

[winders]

Dan,

The Bosch injectors will have an improved spray pattern if you bump the pressure up to 60 psi and will also decrease the duty cycle which would be a good thing in your case.

If you don't have a fuel damper, I would recommend installing one. When I installed the FPR I listed above, my MoTec M150 traces for fuel pressure smoothed out.

[montauk]

Dan,

You have invested a lot more time in figuring this stuff out than I have. Great work. I was thinking about the dead times. Those are at 3 bar. If you're running at a different pressure, you'll need to determine what the dead times are. Or doesn't Megasquirt allow for dead times?

As far as running at 60PSI, per Scott's suggestion, I did find one chart that lists flow at 55PSI, 334 cc/min versus 297 cc/min at 43.5PSI.

Stan Weiss' - Electronic Fuel Injector (EFI) Flow Data Table

Dave

Originally Posted by dannichols1474

Hi montauk,

I set the fuel pressure based on my observation of the fuel pressure running on other cars I have owned or worked on and not on any engineering calculations. When I initially installed the ITB EFI system on my stock CIS motor and checked the fuel pressure, the fuel pressure regulator adjustment was screwed all the way loose so I saw the max pressure of the fuel pump at 90 psi and turned it down to 40 psi and left it there.

Since the stock CIS motor with ITB EFI was making 205 hp (crank) on the dyno before I rebuilt the motor, I was way below the estimated max hp for the given injector size (I remember reading the 30 lb/hr injectors would be good for 288 hp), so if I was running the injectors with 38 psi versus 43.5 psi I wasn't in danger of running out of injector capacity. But now with rebuilt motor making 274 hp (crank) I am much closer to the edge.

I did a quick AI internet search:

Calculating Maximum Power for a Given Fuel Injector Size
To determine the maximum power a given fuel injector can support, you'll need to use a variation of the fuel injector sizing formula. The key components are:

• Injector Size (lbs/hr or cc/min): The flow rate of your specific injectors.
• Number of Injectors: The number of injectors in your engine (e.g., 8 for a V8).
• Brake Specific Fuel Consumption (BSFC):This represents the amount of fuel an engine uses to produce one horsepower per hour. BSFC values vary depending on the engine type (naturally aspirated vs. boosted) and fuel type (gasoline, E85, methanol). (0.5 for naturally aspirated gasoline engines)
• Maximum Injector Duty Cycle: This is the percentage of time the injector is open and flowing fuel. It's generally recommended to use a maximum duty cycle of 80-85% for safety and consistent fuel delivery.

Formula: Estimated Crank HP = [(Injector Size in #/hr x Number of Injectors) ÷ BSFC] x Maximum Injector Duty Cycle

For 30 lbs/hr: Est HP = [((30 x 6) / 0.5) x 0.80] = 288 hp

For 31.4 lbs/hr (43.5 psi): Est HP = [((31.4 x 6) / 0.5) x 0.80] = 301 hp

Now assume those injectors at 38 psi flow only 27 lbs/hr (down 10%),

For 27 lbs/hr: Est HP = [((27 x 6) / 0.5) x 0.80] = 259 hp (80% injector duty cycle)

For 27 lbs/hr: Est HP = [((27 x 6) / 0.5) x 0.85] = 275 hp (85% injector duty cycle)

Now, with more experience and considerably more thought, I see that I should turn the fuel pressure up so that when the engine is running the fuel pressure will be at 43.5 psi to take full advantage of the Bosch 62672 (0280155831) injectors that are rated at 31.4 lbs/hour at 3 bar (43.5 psi).

But unlike your Haltech ECU, the MegaSquirt2 ECU doesn't monitor fuel pressure nor fuel temperature directly, so if I adjust fuel pressure, then I will need to re-run auto tune to adjust the values in the VE table since for a given injector pulse width the injectors will deliver more fuel per shot at the higher fuel pressure.

Another thought: My motor makes max hp at 6600 rpm and that carries flat out to 7200 rpm and I have the rev limiter set to 7500 rpm. The ECU fires each bank of injectors once every 2 revolutions, so a given injector fires 3750 times per minute which works out to firing every 16 ms. Per your dead time data and given my Anti-Gravity battery is at 13.2 V (13.8 V while running), my injector dead time is about 1 ms which leaves 15 ms for the injector to deliver fuel at 7500 rpm. At 85% duty cycle, that translates to 12.75 ms maximum pulse width available at 7500 rpm. I need to go look at a recent data log with the a 100% TPS pull to 6000 rpm and see what injector pulse width the ECU was calling for - I wonder if I'm already at the wall?

Thank you for asking the question.