[AndyW]

I welded a 'nipple' cut of a fuel cheepo metal filter to a filler neck.....just a little bellow the venting nipple that is on the filler neck from the factory.

It works great

I was thinking about that. Maybe have the return further down the neck.
What is the state of your conversion .

 

[PSk]

Not sure why the flywheel would be better than the crank, otherwise engine manufacturers would do that? That said, they‘re effectively the same part assembled. Easier for DIY to access I guess.

Flywheels have been drilled (60-2) for pickup, novel way to lighten and (then) balance. Shed load of holes though (58).

I thought most engine manufacturers did use the flywheel to trigger sensors off, instead of the front of the crankshaft where the trigger wheel and sensor is exposed to damage
Pete

 

[Craig_m67]

I was talking about the current Alfa/FPT (etal) solution which is inside the crankcase/block.

Seems there are any number of hidden solutions

 

[fulcrum]

I was thinking about that. Maybe have the return further down the neck.
What is the state of your conversion .

I am keeping the carbs. I only made a return line, as where I live a lot of ethanol is added to the fuel.
When in stop and go traffic the dwelling fuel in the engine bay starts producing vapour boubles. After taking off at the traffic light the car stumbled.... Now I have a return line, so fresh fuel is always available and car is more pleasant to drive around town durng hot summer days

I am still using a tipical malpassi filter king as a pressure regulator. I have a orifice of 0,80mm in the return line to keep the pressure high enough. I took this idea from the 70s AMCs that used a 3 port fuel filter like WIX33040.

See T-connector on rear carb and the orifice in the return line

I do not have any pics of my filler neck mod. I just made it so, so the fuel is squirting down the filler neck, not across it

 

[gprocket]

Flywheel crank sensors were used with the early Bosch EFI on Spiders (two sensors actually). Later versions moved it to the common front pulley position. I would guess that relatively easy access would be the primary reason.

 

[gprocket]

Here is an example of a SPICA front cover machined back to accept a trigger wheel mounted to the rear of the crank pulley:

Here is the setup with the front mounted crank pulley and a CPS mount off the SPICA guard:

This set up does not require removing the front cover which means basically tearing down most of the engine. I suppose you could do this without even pulling the motor...

 

[PSk]

Flywheel crank sensors were used with the early Bosch EFI on Spiders (two sensors actually). Later versions moved it to the common front pulley position. I would guess that relatively easy access would be the primary reason.

I'd put the sensor near the bottom so you could get at it easily from underneath. You don't need easy access to the flywheel trigger wheel ... anyway, if I ever have to do this I will probably use the flywheel ... for some reason having the sensor and the trigger wheel at the front worries me
Pete

 

[Alfa69GTV1750]

Here is the setup with the front mounted crank pulley and a CPS mount off the SPICA guard:

This set up does not require removing the front cover which means basically tearing down most of the engine. I suppose you could do this without even pulling the motor...

Nice!

Did you weld a nut on the crank bolt to fast the trigger wheel bolt?

 

[goats]

does anyone know the resolution needed ? Obviously the larger the trigger wheel, the better the resolution of TDC. What's an acceptable error band around TDC with a wheel like this -- and how much dither is tolerable?

 

[gprocket]

I'd put the sensor near the bottom so you could get at it easily from underneath. You don't need easy access to the flywheel trigger wheel ... anyway, if I ever have to do this I will probably use the flywheel ... for some reason having the sensor and the trigger wheel at the front worries me
Pete

IIRC the Alfa CPS on the bellhousing are mounted near the top and they were accessed from the engine bay (again I think). There were two. I haven't taken the time to think through it but I trust that there was a valid reason that the flywheel CPS was abandoned for the front mounted CPS. From a retrofit perspective, I sure wouldn't want to fuss with the flywheel and the bellhousing ... I suppose you could find an S3 Spider assembly that had that arrangement. Not sure when the changeover occurred...

 

[gprocket]

Nice!

Did you weld a nut on the crank bolt to fast the trigger wheel bolt?

We tapped the crank nut, faced it, machined a spacer to take up the gap between the nut and the trigger wheel. The crank nut is installed and torqued, then the trigger wheel is mounted with the thru bolt using thread locker.

 

[gprocket]

does anyone know the resolution needed ? Obviously the larger the trigger wheel, the better the resolution of TDC. What's an acceptable error band around TDC with a wheel like this -- and how much dither is tolerable?

I honestly don't have answers except to say that 36 and 60 tooth trigger wheels seem to be the standards as well as 140mm diameter. We use 36 for the stock-ish 1750 and 2L and 60 teeth for the high performance Twinspark motors but I suspect that 36 would work for all in a pinch.

 

[sepehr]

If I recall correctly there are either 130 or 131 teeth on the 105/115 flywheel starter ring. If you're considering this setup, I suggest making sure the ECU that you've chosen supports these weird tooth counts.

The S3 Bosch Spider has two crank sensors. One reads off of a nub on the flywheel (crank position) and another reads the off the teeth (crank speed).

 

[PSk]

IIRC the Alfa CPS on the bellhousing are mounted near the top and they were accessed from the engine bay (again I think). There were two. I haven't taken the time to think through it but I trust that there was a valid reason that the flywheel CPS was abandoned for the front mounted CPS. From a retrofit perspective, I sure wouldn't want to fuss with the flywheel and the bellhousing ... I suppose you could find an S3 Spider assembly that had that arrangement. Not sure when the changeover occurred...

I know why I would want to use the flywheel. It is because I would want to hide this modern technology. And no I would not use an existing flywheel CPS, I would lazer cut a plate that bolts in between the pressure plate and flywheel (the flywheel would have the thickness of this plate machined off it)

Just ignore me
Pete

 

[gprocket]

Just ignore me
Pete

I can do a lot, ignoring you is NOT one 🤣🤣

 

[Alfa69GTV1750]

does anyone know the resolution needed ? Obviously the larger the trigger wheel, the better the resolution of TDC. What's an acceptable error band around TDC with a wheel like this -- and how much dither is tolerable?

This article gives some information on that. Crank position sensor

 

[Craig_m67]

Hiding it all would be the direction I would take also, hence the (current Alfa) solution I proffered which mounts the reluctor wheel directly to the crank (the source) inside the block. Away from eyes, fingers and bits of crap from the starter/teeth remaining undisturbed/factory accurate unless a significant rebuild is underway that requires machining the crank.

Is it that much harder to retrofit machine/balance the crank to accept a thin lightweight wheel, than the flywheel - genuine question?


Edit. Tried to answer/quote Pete’s post (failed). And that’s the same article I posted earlier, obviously talking to myself. As you were. Apologies to the OP for the tangent, just use the aforementioned crank pulleys.

re resolution, I imagine that would be determined by how fast the sensor and also ECU can reliably measure the changes in teeth/holes (pulse width). Trade off between what you actually need to fire injectors/plugs and what you can design, reliably manufacture and implement simply (repeatability). Bound to be a Six Sigma study on it somewhere.

Sensor types
Resolution- Knock yourself out

 

[Lifer]

The sensor that I used is a Hall sensor, with a pull up resistor to get down to the right voltage for the ecm.

Hall Effect Threaded Body Crank/Cam Position Sensor

Crankshaft position sensor - Hall Effect with threaded body for easy adjustment - tested to over 19,000 RPM using our trigger wheels.

www.diyautotune.com

I machined up a bracket that utilizes the spica cover bolts to mount the hall sensor. I bought a 36-1 wheel, but I never liked the size or weight. I've started in on 2.0, smaller wheel, thinner material less rotating mass. Might try and tie the mount into the spica plate somehow.

 

[PSk]

It amazes me that these sensors work in such dirty environments, whether front or rear of crank AND somewhere in between. Clever
Pete

 

[Alfa69GTV1750]

I'm getting a quote on having the flywheel drilled like @Craig_m67 showed in the attached picture. The machine shop wanted to know if the flywheel is "mild steel". I'm not sure. Anyone know for sure?