MicroSquit Conversion, Giving this a try Options

[Mblizzard]

I am pretty happy with my stock FI. But after seeing some of the setups at Okteenerfest, I thought this might be worth trying.

The stock system is not easy to modify and get things running correctly. I spent a lot of time making minor adjustments by trial and error. While I am not looking for huge HP gains or anything, it is pretty clear that the mods I have could potentially benefit from a bit more precise control.

Going to start with fuel only at this point to get things going and see where it leads me. Any help or suggestions for set up would be appreciated.

[Dtjaden]

Some comments on my 2 year journey with Megasquirt:

1. Install a crank trigger while you have the engine out of the car. Mario at the DubShop sells the one I used at a very reasonable price. I believe McMark also sells one.

While injection control could possibly work with less than a 36-1 trigger, ignition control would never be accurate enough. I am also concerned that a distributor based control would have too much trigger float because of the backlash in the distributor gears.

2. You can definitely use the existing injectors (2 liter), but have them rebuilt and flow tested. I used WitchHunter for this. You can also drive the injectors without resistor packs (which slow their response) by using a peak and hold driver board form JBPerf or DIYAutotune. You will need the flow rate of the injectors at the fuel pressure you decide on and the injector dead-time. I can give you those for my setup but yours may differ. They are not hard to calculate.

3. Once you decide to add ignition control it is almost trivial to get started with this. I used individual GM LS3 ignition coils which can be directly driven by the Megasquirt system. For a start at timing you can duplicate the the timing of the 914 advance curve and then go from there.

4. I tried using the stock CHT sensor - I went through 2 - and finally settled on the one sold by the DubShop. Its based of a GM sensor and is much more consistent. I had a lot of drift with the stock sensors. By the way, once the engine reaches normal operating temperature the CHT has little effect.

5. My throttle position sensor is a lightly used Bosch TPS that I adapted to the stock throttle body using a low tech aluminum plate. You can find this on numerous BMWs at your local junk yard or on ebay for around $30.

6. If you want reliable startup under varying temperatures you will need an idle control valve. I am again using a used Bosch ICV and as with the TPS this can be found on BMWs and others or ebay for $30 - 40. This is a PWM valve, not a stepper based valve.

7. To start tuning you can use the map that TunerStudio generates. You need to set the baseline tune with all TunerStudio Startup/Idle settings off and the engine fully warmed up. Set the idle using the idle adjustment screw on the throttle body. After that you can use the Startup/Idle settings to get a reliable cold start. If you don't do it this way you will chase your tale for weeks (ask me how I know).

8. If you want to do accurate tuning you will need a wide-band AFR meter. I use the Innovate Motorsports MTX-L for this.

9. I mounted the Megasquirt (not Microsquirt) in the rear trunk and have used WeatherPack connectors for all of the wiring. This includes two 22 pin bulkhead connectors into the engine compartment. I built my own mounting plate for the Megasquirt which includes a fuse panel, relays and breakout terminals for much of the wiring. I can build a 914 engine bay wiring harness for you using the Megasquirt standard wiring colors if you make a definite decision on the location of the Microsquirt/Megasquirt and the rest of the components that you will use.

That's a quick summary. If you have questions let me know.

By the way, on the drive to Medford and back I got near 40 MPG driving at 75 plus MPH.

Darryl

[Mblizzard]

Some comments on my 2 year journey with Megasquirt:

1. Install a crank trigger while you have the engine out of the car. Mario at the DubShop sells the one I used at a very reasonable price. I believe McMark also sells one.

While injection control could possibly work with less than a 36-1 trigger, ignition control would never be accurate enough. I am also concerned that a distributor based control would have too much trigger float because of the backlash in the distributor gears.

2. You can definitely use the existing injectors (2 liter), but have them rebuilt and flow tested. I used WitchHunter for this. You can also drive the injectors without resistor packs (which slow their response) by using a peak and hold driver board form JBPerf or DIYAutotune. You will need the flow rate of the injectors at the fuel pressure you decide on and the injector dead-time. I can give you those for my setup but yours may differ. They are not hard to calculate.

3. Once you decide to add ignition control it is almost trivial to get started with this. I used individual GM LS3 ignition coils which can be directly driven by the Megasquirt system. For a start at timing you can duplicate the the timing of the 914 advance curve and then go from there.

4. I tried using the stock CHT sensor - I went through 2 - and finally settled on the one sold by the DubShop. Its based of a GM sensor and is much more consistent. I had a lot of drift with the stock sensors. By the way, once the engine reaches normal operating temperature the CHT has little effect.

5. My throttle position sensor is a lightly used Bosch TPS that I adapted to the stock throttle body using a low tech aluminum plate. You can find this on numerous BMWs at your local junk yard or on ebay for around $30.

6. If you want reliable startup under varying temperatures you will need an idle control valve. I am again using a used Bosch ICV and as with the TPS this can be found on BMWs and others or ebay for $30 - 40. This is a PWM valve, not a stepper based valve.

7. To start tuning you can use the map that TunerStudio generates. You need to set the baseline tune with all TunerStudio Startup/Idle settings off and the engine fully warmed up. Set the idle using the idle adjustment screw on the throttle body. After that you can use the Startup/Idle settings to get a reliable cold start. If you don't do it this way you will chase your tale for weeks (ask me how I know).

8. If you want to do accurate tuning you will need a wide-band AFR meter. I use the Innovate Motorsports MTX-L for this.

9. I mounted the Megasquirt (not Microsquirt) in the rear trunk and have used WeatherPack connectors for all of the wiring. This includes two 22 pin bulkhead connectors into the engine compartment. I built my own mounting plate for the Megasquirt which includes a fuse panel, relays and breakout terminals for much of the wiring. I can build a 914 engine bay wiring harness for you using the Megasquirt standard wiring colors if you make a definite decision on the location of the Microsquirt/Megasquirt and the rest of the components that you will use.

That's a quick summary. If you have questions let me know.

By the way, on the drive to Medford and back I got near 40 MPG driving at 75 plus MPH.

Darryl

Got TPS coming from McMark.

Hoping to not go the crank trigger rout because I have AV. Looking at the Min Can Sync as an option.

I have heard good and bad about use of the Stock CHT. Checking with Mario on the options. The GM NPT threading is not the same as the 10mm x1 stock threading so would you not need an adaptor for that?

Like the idea of the peak and hold but I don't have the abilities to build the electronics and the prebuilt ones seem expensive.

Had not considered idle control valve. I hoped that the warm up programing in the MicroSquirt would address those issues Seem like that was a wrong guess?

Have wideband O2 already installed.

As this will be a build in stages I am not sure I cam plan out the locations of everything in advance. But I would love to see some photos of your install for some ideas.

Lots more questions to follow! Should be receiving my first batch of parts today.

[Dtjaden]

The DubShop CHT sensor is installed under one of the engine tin screws. It uses the GM sensor element in deferent housing.

If you are going to continue to use the 914 ignition you can't use the DubShop mini cam sync since it replaces the distributor. If you don't want to use a crank trigger wheel (which I strongly reccommend) your only option is using coil/points triggering.

Without using an ICV it will be difficult if not impossible to get hands off (really foot off) start up. You will need to use the accelerator for the first few minutes to keep the engine running until it reaches operating temperature.

Some comments on my 2 year journey with Megasquirt:

1. Install a crank trigger while you have the engine out of the car. Mario at the DubShop sells the one I used at a very reasonable price. I believe McMark also sells one.

While injection control could possibly work with less than a 36-1 trigger, ignition control would never be accurate enough. I am also concerned that a distributor based control would have too much trigger float because of the backlash in the distributor gears.

2. You can definitely use the existing injectors (2 liter), but have them rebuilt and flow tested. I used WitchHunter for this. You can also drive the injectors without resistor packs (which slow their response) by using a peak and hold driver board form JBPerf or DIYAutotune. You will need the flow rate of the injectors at the fuel pressure you decide on and the injector dead-time. I can give you those for my setup but yours may differ. They are not hard to calculate.

3. Once you decide to add ignition control it is almost trivial to get started with this. I used individual GM LS3 ignition coils which can be directly driven by the Megasquirt system. For a start at timing you can duplicate the the timing of the 914 advance curve and then go from there.

4. I tried using the stock CHT sensor - I went through 2 - and finally settled on the one sold by the DubShop. Its based of a GM sensor and is much more consistent. I had a lot of drift with the stock sensors. By the way, once the engine reaches normal operating temperature the CHT has little effect.

5. My throttle position sensor is a lightly used Bosch TPS that I adapted to the stock throttle body using a low tech aluminum plate. You can find this on numerous BMWs at your local junk yard or on ebay for around $30.

6. If you want reliable startup under varying temperatures you will need an idle control valve. I am again using a used Bosch ICV and as with the TPS this can be found on BMWs and others or ebay for $30 - 40. This is a PWM valve, not a stepper based valve.

7. To start tuning you can use the map that TunerStudio generates. You need to set the baseline tune with all TunerStudio Startup/Idle settings off and the engine fully warmed up. Set the idle using the idle adjustment screw on the throttle body. After that you can use the Startup/Idle settings to get a reliable cold start. If you don't do it this way you will chase your tale for weeks (ask me how I know).

8. If you want to do accurate tuning you will need a wide-band AFR meter. I use the Innovate Motorsports MTX-L for this.

9. I mounted the Megasquirt (not Microsquirt) in the rear trunk and have used WeatherPack connectors for all of the wiring. This includes two 22 pin bulkhead connectors into the engine compartment. I built my own mounting plate for the Megasquirt which includes a fuse panel, relays and breakout terminals for much of the wiring. I can build a 914 engine bay wiring harness for you using the Megasquirt standard wiring colors if you make a definite decision on the location of the Microsquirt/Megasquirt and the rest of the components that you will use.

That's a quick summary. If you have questions let me know.

By the way, on the drive to Medford and back I got near 40 MPG driving at 75 plus MPH.

Darryl

Got TPS coming from McMark.

Hoping to not go the crank trigger rout because I have AV. Looking at the Min Can Sync as an option.

I have heard good and bad about use of the Stock CHT. Checking with Mario on the options. The GM NPT threading is not the same as the 10mm x1 stock threading so would you not need an adaptor for that?

Like the idea of the peak and hold but I don't have the abilities to build the electronics and the prebuilt ones seem expensive.

Had not considered idle control valve. I hoped that the warm up programing in the MicroSquirt would address those issues Seem like that was a wrong guess?

Have wideband O2 already installed.

As this will be a build in stages I am not sure I cam plan out the locations of everything in advance. But I would love to see some photos of your install for some ideas.

Lots more questions to follow! Should be receiving my first batch of parts today.

[Mblizzard]

The DubShop CHT sensor is installed under one of the engine tin screws. It uses the GM sensor element in deferent housing.

If you are going to continue to use the 914 ignition you can't use the DubShop mini cam sync since it replaces the distributor. If you don't want to use a crank trigger wheel (which I strongly reccommend) your only option is using coil/points triggering.

Without using an ICV it will be difficult if not impossible to get hands off (really foot off) start up. You will need to use the accelerator for the first few minutes to keep the engine running until it reaches operating temperature.

The mini cam is the next stage. Starting with the coil for the tac signal for the fuel only stage.

I understand that there might be some variance in the use of the dizzy timing approach but I guess I just don't know enough about the crank trigger to determine why it would be better.

My goals are a low cost, dependable, and drivable system. Not trying to see great HP gains just a reliable system.

Can you point me to an ICV?

[JamesM]

The DubShop CHT sensor is installed under one of the engine tin screws. It uses the GM sensor element in deferent housing.

If you are going to continue to use the 914 ignition you can't use the DubShop mini cam sync since it replaces the distributor. If you don't want to use a crank trigger wheel (which I strongly reccommend) your only option is using coil/points triggering.

Without using an ICV it will be difficult if not impossible to get hands off (really foot off) start up. You will need to use the accelerator for the first few minutes to keep the engine running until it reaches operating temperature.

The mini cam is the next stage. Starting with the coil for the tac signal for the fuel only stage.

I understand that there might be some variance in the use of the dizzy timing approach but I guess I just don't know enough about the crank trigger to determine why it would be better.

My goals are a low cost, dependable, and drivable system. Not trying to see great HP gains just a reliable system.

Can you point me to an ICV?

I trigger using a Pertronix unit inside a distributor with a locked out advance mechanism. a 36 tooth wheel would be more accurate but I have had no problem triggering timing from the dizzy. Output is to a Mallory highfire 6-al.

I also run a stock CHT. The biggest downside is that the stock CHT grounds through the engine rather than back through the ECU common ground. It adds an extra step in that you need to set the curve in the MS tune to match the sensor. Two wire sensor should in theory have less chance of interference.

ICVs are not mandatory, especially if you only drive in warm climates. I am using a stock 1.8 CSV which is not tuneable via the MS but provides the same function of allowing more air in when cold. If you want to go with a full stepper motor ICV I believe (dont quote me on this one) the ICV from a water-cooled vanagon will work.

It runs pretty good https://youtu.be/kk9_5ewkIOU