CIS to ITB EFI conversion

[rwest]

Thanks Dan,

That really make sense. I was going to basically compare my datalog MAP and TPS and try and find common spots. Your method seems like it will save me time and get better results.

Rutager

[chrismorse]

Great write up Dan, I'm a long way from getting my 74, 2,8, twin plug/10.3 C/R, PMO rebuild running well, much less, optimized.
Can anyone recommend a dyno tuner, relatively close to Humboldt county, CA???

If my wife would just slow down on the Honey Doo List, i might actually be able to bring my dad's 12 year restomod to completion.

Thanks,
Chris

[dannichols1474]

Originally Posted by chrismorse

Great write up Dan, I'm a long way from getting my 74, 2,8, twin plug/10.3 C/R, PMO rebuild running well, much less, optimized.
Can anyone recommend a dyno tuner, relatively close to Humboldt county, CA???

If my wife would just slow down on the Honey Doo List, i might actually be able to bring my dad's 12 year restomod to completion.

Thanks,
Chris

Hi Chris,

The guy I use for dyno tuning is Gary Bains, Bains Tuning - he is in Fremont, CA but he can tune remotely via other dyno shops (he connects to the target ECU via internet, while the technician drives the car on the dyno per Gary's instructions). See Bains Tuning on FB, bainstuning.com, bainstuning_gary on IG. If he can't help you directly, he knows a lot of tuners and may be able to recommend someone near you.

[dannichols1474]

Originally Posted by Showdown

I had the same issue way back when with my kit- the TPS sensor was trash and causing all sorts of problems. In fact, I ended up replacing every component of my kit other than the ITB's with better, non Amazon-generic crap parts. Makes a big difference, whoda thunk it!

That's a really conservative AE. I'm surprised that you're adding so little fuel!

Hi Julian,

I have been adjusting my AE. Would you mind sharing your AE and how much fuel you are adding? I'm still pretty new to this EFI tuning game so knowing what others do is very helpful. Thanks.

[Showdown]

Hey Dan,

I'm using Accel Pump-AE (in Accel Enrich >> Accel Enrich Settings) as opposed to time-based. With 100% TPS.

This operates much like a carb setup where there's just one squirt of fuel- no time variables or percent variables and I've found it to work so much better than time-based.

Of course you gave to have a really well dialed in VE map before doing any AE adjustments.


I'm still playing with mine, but it's really snappy and sharp and I think I only need minor adjustments.

[dannichols1474]

Originally Posted by montauk

Is the stock BMW sensor a standard potentiometer? Is so, can you use a hall effect sensor? Non-contact sensors should last for a very long time.

For my TPS, I sourced the Variohm sensor from Digikey—it features a standard D connector and fit my BMW throttle motor. It's also dual sensing which is needed for DBW.

https://www.variohm.com/products/motorsports-sensors/rotary-position-sensors-for-motorsport/euro-xpd-d-shaft

https://www.digikey.com/en/products/detail/variohm/EURO-XPD-2832-812-214-911-00/22286984

Hi Montauk,

I just ordered the Variohm sensor from Digikey as well - I should have it in a week. Then I will be able to see first hand the difference in signal stability between the potentiometer based TPS and the Hall effect based TPS. Thanks for the info!

[chrismorse]

Originally Posted by dannichols1474

Hi Chris,

The guy I use for dyno tuning is Gary Bains, Bains Tuning - he is in Fremont, CA but he can tune remotely via other dyno shops (he connects to the target ECU via internet, while the technician drives the car on the dyno per Gary's instructions). See Bains Tuning on FB, bainstuning.com, bainstuning_gary on IG. If he can't help you directly, he knows a lot of tuners and may be able to recommend someone near you.

Thanks Dan, I'll give him a call.
chris

[TheBrokePilot]

Hi Dan,

What dwell settings do you have setup in Tunerstudio for triggering the MSD Streetfire?

Sean

[dannichols1474]

Originally Posted by TheBrokePilot

Hi Dan,

What dwell settings do you have setup in Tunerstudio for triggering the MSD Streetfire?

Sean

Hi Sean,

I'm using the default settings in TunerStudio. Honestly, I don't know enough about dwell time with CDI ignition to experiment - I have read 3 ms is pretty typical for a running engine.

[dannichols1474]

While I am waiting for the Variohm Hall effect TPS to arrive, I decided to add an intake air temperature sensor (IAT also referred to as MAT - manifold air temperature in MS / TunerStudio documentation) to my ITB EFI set up. The conversion kit from Al at x-faktory.com doesn't use the IAT sensor and my system worked without it, but without the IAT sensor data the MegaSquirt ECU assumes the intake air temp is 70 deg F and does not adjust fueling to compensate for air density changes as temperature rises and falls.

The first order of business was to carefully remove the vinyl electrical wrapping I had applied to the ECU wiring harness back to the point where I separated signal / sensor wires from power / ground wires.

The short orange wire is connected to ECU connector pin 20 - MAT (IAT) sensor. I joined a 3 foot length of orange 16 gauge wire with a crimp connector.



The IAT sensor has an orange signal wire and a black ground wire which is connected to ECU pin 7 sensor ground which is also used for the TPS, so I used a crimp connector with 1 wire in / 2 wires out to split off the sensor ground for both the TPS and the IAT sensor.



This time instead of re-wrapping the wiring bundles with vinyl electrical tape I decided to use 3/8 inch plastic split wire wrap.





Close up of the IAT sensor with connector and pigtail. This is a GM unit and supported with calibration setpoints in TunerStudio. I found this listed on the diyautotune and summit sites.



The IAT sensor mounted on the base plate of the air filter weather hat on the 1,2,3 bank ITB's.



I updated my EFI documentation for the addition of the IAT sensor signal and sensor ground connections.



With my notebook PC running TunerStudio and connected to the powered up MegaSquirt2 ECU, I unlocked the temp sensor calibration tables and selected "Burn". Then I opened "Calibrate Thermistor Tables", selected "Air Temperature Sensor", selected "GM", then selected "Write to Controller". Then I locked the sensor calibrations and selected "Burn". Now the IAT sensor is calibrated and reading the correct air temperature and ready to use.

[Showdown]

I also installed one this winter. I haven’t seen any massive benefit yet, but it’s not yet hot or cold enough to really make a difference. Either way, it’s a good piece of data for tuning and understanding what the engine wants/needs.


Sent from my iPhone using Tapatalk

[montauk]

I haven't driven my car or even started it in particularly hot or cold weather. Once warmed up, the IAT stays around 25°C. Mine is mounted in the old MFI type air filter so I think it's getting an accurate sample of the intake air.

Before I put the MFI filter on, I ran the car with the IAT loose near the front of the engine and no air filters at all. I thought the MFI filter might make a slight difference because all six cylinders would be getting air at the same temperature from the back of the engine. So far, I can't see any difference.

[winders]

You should have intake air temperature and intake air pressure sensors along with fuel pressure and fuel temperature sensors. Well, I hope the EFI system you are using adjusts for changes in fuel pressure and temperature...

[Showdown]

Originally Posted by winders

You should have intake air temperature and intake air pressure sensors along with fuel pressure and fuel temperature sensors. Well, I hope the EFI system you are using adjusts for changes in fuel pressure and temperature...

Does/did the 1977 CIS adjust for fuel pressure, fuel temperature and air pressure and air temperature.

Not a sarcastic comment, I really want to know- I can't remember since it's been a while since I had a CIS...

[dannichols1474]

Originally Posted by Showdown

Does/did the 1977 CIS adjust for fuel pressure, fuel temperature and air pressure and air temperature.

Not a sarcastic comment, I really want to know- I can't remember since it's been a while since I had a CIS...

Hi Julian,

My 75 CIS system did not monitor and adjust for air temp, air pressure or fuel temp, but the CIS system is controlled by fuel pressure and there were no O2 sensors, so no Lambda control.

I read Scott's (Winders) comment to be directed toward the EFI ECU control capabilities. I am running a MegaSquirt2 ECU so air pressure (BARO) is measured by the MAP sensor when the engine is key on / engine off, the air temperature is measured by IAT sensor, and both air pressure and air temp are compensated for in the fueling pulse width calculations.

Fuel temp and fuel pressure are not monitored directly, although air temp could be considered a proxy for fuel temp as delivered to the injectors (not accounting for cooling effects due to the latent heat of vaporization when the injector sprays fuel into the intake port).

On the flip side, my system is running closed loop (when it is warmed up and within upper / lower limits of MAP and TPS) as I have the EGO (exhaust gas oxygen) Correction enabled and the ECU monitors the actual AFR against the target AFR and makes corrections to the fuel injection pulse width in real time.

[winders]

Originally Posted by dannichols1474

Fuel temp and fuel pressure are not monitored directly, although air temp could be considered a proxy for fuel temp as delivered to the injectors (not accounting for cooling effects due to the latent heat of vaporization when the injector sprays fuel into the intake port).

On the flip side, my system is running closed loop (when it is warmed up and within upper / lower limits of MAP and TPS) as I have the EGO (exhaust gas oxygen) Correction enabled and the ECU monitors the actual AFR against the target AFR and makes corrections to the fuel injection pulse width in real time.

Air temp is not a proxy for fuel temp. Fuel temperature affects fuel density so an EFI system monitoring fuel temp can compensate for changes in density. Changes in fuel pressure need to be compensated for as well.

A closed loop EFI setup can compensate for only so much variance. Changes in air density, air temperature, fuel temperature, and fuel pressure can easily exceed the limits of compensation when running in closed loop.

[montauk]

I'm monitoring fuel pressure, IAT, MAP, cylinder head temperature, oil pressure and oil temperature. I can add fuel temperature since it's built into the same sensor that monitors fuel pressure. Maybe I'll do that and see what the results are. I've got a few unused inputs left.

Scott - how much variation are you seeing in fuel temperatures?

[dannichols1474]

Originally Posted by winders

Air temp is not a proxy for fuel temp. Fuel temperature affects fuel density so an EFI system monitoring fuel temp can compensate for changes in density. Changes in fuel pressure need to be compensated for as well.

A closed loop EFI setup can compensate for only so much variance. Changes in air density, air temperature, fuel temperature, and fuel pressure can easily exceed the limits of compensation when running in closed loop.

I stand corrected, the MegaSquirt2 ECU has limited capabilities which in turn limit its capabilities to control AFR, see below from a quick AI search of the internet:

Fuel temperature and intake air temperature are often different in an engine's fuel injection system due to several factors:

Heat Transfer: Components within the fuel injection system, such as fuel lines, pumps, and injectors, are located near the engine's heat sources (like the engine block and exhaust system). This heat can be transferred to the fuel, raising its temperature.

Fuel Recirculation: Many fuel injection systems have a return line that sends unused fuel back to the fuel tank. This recirculated fuel has been heated by being in the engine compartment and can increase the temperature of the fuel in the tank and lines.

Intake Air Source: The intake air is drawn from the ambient environment, often through a cold air intake system designed to minimize its temperature, to improve air density.

Different Paths: Fuel and intake air travel through different parts of the engine compartment. The fuel path is near the engine, while the intake air path is typically routed to avoid heat.

Ambient Conditions: The temperature of the fuel in the tank is affected by the ambient air temperature, whereas the intake air temperature is directly influenced by the ambient air temperature at the point of intake.

These factors contribute to a difference between the fuel temperature and the intake air temperature, even though both can be influenced by the external environment. The ECU monitors both temperatures to ensure the correct air-fuel mixture is delivered for optimal performance and emissions control.

[winders]

Originally Posted by montauk

Scott - how much variation are you seeing in fuel temperatures?

I don't have any data anymore as I sold the race car and the laptop with the data on it.

Also, I changed the fuel cell setup in the race car and did not have enough data to come to any real conclusions.

I went with a Fuel Safe fuel cell with a Radium FCST-X in cell surge tank setup. The return line returned fuel to the surge tank. So, in theory, the heated fuel returning from the fuel rails to the the surge tank might have less time to cool down in the fuel cell than it would it the fuel was returned to the bladder area. The Radium Radium FCST-X setup operated perfectly though and it may have had little actual impact of fuel temps compared to my previous setup.

But, fuel does get warm over the course of a long race so it is a very good idea to have an ECU than can compensate for fuel temperature changes.

[dannichols1474]

Originally Posted by montauk

For my TPS, I sourced the Variohm sensor from Digikey—it features a standard D connector.

https://www.variohm.com/products/motorsports-sensors/rotary-position-sensors-for-motorsport/euro-xpd-d-shaft

https://www.digikey.com/en/products/detail/variohm/EURO-XPD-2832-812-214-911-00/22286984

I used the same Variohm sensor from Digikey as Montauk used, see his link in the quote above. This unit is made for mounting holes spaced 32 mm or 38 mm apart. For the RHD ITB's, I used the 32 mm version.

The Hall effect TPS arrived today and I got busy and installed it in the same location as the existing BMW TPS on the cylinder #3 ITB. The throttle valve shaft protrudes 3/4 inch from the end the throttle body, so I fabricated a 1/2 inch spacer out of aluminum bar stock (1 1/2 inch wide x 2 inch long x 1/8 inch thick, sandwiched 4 pieces) with a 1/2 inch hole in the center and 2 x 1/4 inch holes centered about the 1/2 inch hole and spaced 32 mm apart.

I removed the 1,2,3 ITB's to get better access to the TPS.



The existing TPS set up.



The existing TPS removed showing the throttle shaft with D protruding 3/4 inch out of the throttle body.



Test fitting the 1/2 inch spacer block.



The Variohm TPS installed on the 1,2,3 ITB's.



A page from the Variohm Datasheet showing the wiring diagram - for my application I used the CW sensor connections.



The 1,2,3 bank ITB's re-installed with the Variohm TPS and the IAT sensor.



Re-calibrated the TPS on TunerStudio for the new Variohm TPS.



The TunerStudio dashboard while running the engine with the Variohm TPS and the IAT sensor.



Engine running with the Variohm TPS and IAT sensor installed.