EFI Reluctor "Engineering" advice sought

Dr.Jeff said:
Great, thanks for the clarification. Ya, Bosch likes to be vague about their terminology. As you say, their dizzys tend to be VR (except some older stuff), but over the years they used both VR and Hall for crank and/or cam sensors. However the fact yours is not a Hall sensor answers my question. From what I understand, a Hall sensor might be more prone to electrical and/or signal (trigger) interference, such as being in close proximity to ferrous objects. So that would go along with your experience of having no issues despite the trigger wheel being directly up against the pulley. This is encouraging for me (using a VR sensor) to shave more off the raised ridge of the pulley and get the trigger wheel closer to the face of it (makes things a bit more secure and compact). Thanks.

On the subject of Hall vs VR sensors. I've had mixed input from some experts about it. I've been told Hall offers a more linear signal, while VR increases its signal intensity with RPM. On the other hand Hall is very sensitive, requiring very tight tolerances and prone to interference (as described above), while VR is not. Funny but despite the dispute about which is 'better', the ECU makers say you can use either (without preference) and offer different settings according to which you have. I'm sure these 'settings' must allow for whatever differences exist between them. Also the car manufacturers have used either over the years with no apparent preference. So I'm not convinced there is any real advantage to either, other than for me a VR would be easier (matches the trigger wheel I'm using and is more forgiving with respect to making a custom mounting plate).
Click to expand...

I would say choice of sensor style comes down to EMS - if you have an EMS that allows for either ( like MS), then it makes sense to use VR where sensitivity to interference is an issue. Reading the Wiki link, VR requires the ECU to perform conditioning/conversion from a sine wave to the Hall style Square wave (assuming the article is accurate) which would mean some specific circuitry, so I would have to say the two are not interchangeable, except with aftermarket EMS.
 
Another reason I like the VR sensor over the Hall is simplicity, there is no semiconductor to fail, just a magnet and a coil of wire. Keep the semiconductor's inside the vehicle as much as possible.
 
Halfway there. I was able to put the stock pulley in my small lathe and turn the mating surfaces (for the reluctor wheel) to be true/square to the center bore. My setup isn't the greatest so everything is only within a few thousandths. But I'll try to make some final adjustments and get it a little truer once all the pieces are assembled.

Now I need to make the spacer, but I'll have to get a chunk of aluminum first. The general (rough) dimensions for the spacer ring are .5" thick, 4" OD, 2.5" ID.

Any suggested tricks for making it? The chuck in my lathe isn't large enough to hold the outside of a piece this size. So I guess I'll have to start by drilling a hole in the center and use the "inside" jaws on the chuck to secure the piece from the ID. That's how I was able to fit the pulley on the lathe and turn it with respect to the center line for trueness.
 
Dr.Jeff said:
.

Now I need to make the spacer, but I'll have to get a chunk of aluminum first. The general (rough) dimensions for the spacer ring are .5" thick, 4" OD, 2.5" ID.

Any suggested tricks for making it? The chuck in my lathe isn't large enough to hold the outside of a piece this size. So I guess I'll have to start by drilling a hole in the center and use the "inside" jaws on the chuck to secure the piece from the ID. That's how I was able to fit the pulley on the lathe and turn it with respect to the center line for trueness.
Click to expand...

Some ideas, knowing that I tend to find elaborate means of getting precise machining.

With your center hole cut, mount the piece from the center using a 4 jaw chuck and "last word" indicator to set it exactly centered and with no run out wobble.
Face the exposed side, and machine to the correct diameter.
Remove it from the chuck, flip it over, re center and true and face the other side, cutting to the correct width.

Does the center hole need to be precise? If so:

Drill the rough center hole.
Chuck it and face one side.
Machine a mandrel with a shaft that fits your lathe chuck and a face plate large enough to bolt on your aluminum spacer piece. Ideally use a parting tool on the back side so it is completely true. (Admittedly a slow process with a piece this diameter and a small lathe)
Drill and tap holes in the mandrel with matching countersunk flat head bolts on the spacer that fit below the face of the spacer.
Bolt onto mandrel.
Bore center hole to your precise size.
Face it.
Machine outside to precise diameter.

I am sure more experienced machinists than I will have better methods.

Paul Davock
 
Thanks Paul, I appreciate the input.

In this case the center hole is not relevant, so your first method would be appropriate. One drawback for me is the fact I only have a 3-jaw chuck for this little lathe. So getting it correctly centered and square will be very close but not perfect. That is why the pulley was only within a couple thousandths. But I think it will be close enough considering I'm using a VR sensor. As I mentioned in a prior post, they are much more forgiving and allow greater tolerances. Which is why I decided to do the machine work myself rather than pay a shop to do it.

The spacer is mostly to help keep the reluctor wheel from traveling around. So it needs to be firmly within the outer lip on the pulley and fill the gap between the wheel and pulley. Really the important aspect (tolerance wise) is the mounting holes for the 4 bolts that go through the wheel, spacer, and pulley. If those are located correctly then the wheel will be centered despite the other items being slightly off. I'm also hoping to be able to assemble it all together and do a final trueing of the OD of the wheel (if it ends up being slightly off).

Worst case I take it to a machine shop to fix my mistakes if it comes out poor. ;)
 
I finally had time to get back on this project.

Turned the related surfaces on the stock pulley, made an aluminum spacer to help locate the reluctor wheel onto the pulley, drilled/tapped mounting holes, and made a mount for the sensor. It appears everything worked out. With a mock-up of the components on a old engine/crank, they seem to fit the way they should (or at least as I intended). I set the sensor at a little under 1mm gap (specs are 1mm), and turning the crank by hand I measured around 2 to 3 thousandths maximum variance in concentric tolerance (between the reluctor teeth and the sensor head). I think that is good enough for a VR sensor?

Here are some pics:

001.JPG


The trued and squared area on the pulley to accept the spacer:
002.JPG


Aluminum spacer to locate the trigger reluctor against the pulley:
003.JPG


Ford reluctor ring on the spacer:
004.JPG


Spacer sitting on the pulley. It is not seated here. Being a interference fit, it is a chore to get it in and out. Once fully seated the major surface of the spacer is flush with the raised ridge on the pulley:
005.JPG


With the reluctor on the spacer and pulley (still not fully seated):
006.JPG


The Ford crank sensor mount for the X1/9 block. It does not show here, but the holes are slotted for fore-aft adjustment (sensor gap), similar to the arced ones for sensor timing that can be seen:
007.JPG


Finally a general idea of how it all fits together:
008.JPG


I generally do not photograph my stuff like this. But I wanted to show how all of your inputs served to make this happen. As things developed I realized the necessity for some of the engineering aspects you guys explained and I tried to integrate everything. Big thanks to everyone for helping with this. And to Brian P for offering to do it if I wasn't successful (I guess the final test won't be until I finish everything else and try to start the engine though)...so you still might be hearing from me one day.

A couple of questions regarding what you see here.
1) Any reason why the tolerances I mentioned (2-3 th roundness) won't be good enough?
2) I painted the reluctor ring to keep it from rusting. That includes over the "teeth". I assume the magnet on the sensor will be able to read through the paint? Or should I sand off the paint on the ends of the teeth?

Thanks
 
Dr.Jeff said:
I finally had time to get back on this project.

Turned the related surfaces on the stock pulley, made an aluminum spacer to help locate the reluctor wheel onto the pulley, drilled/tapped mounting holes, and made a mount for the sensor. It appears everything worked out. With a mock-up of the components on a old engine/crank, they seem to fit the way they should (or at least as I intended). I set the sensor at a little under 1mm gap (specs are 1mm), and turning the crank by hand I measured around 2 to 3 thousandths maximum variance in concentric tolerance (between the reluctor teeth and the sensor head). I think that is good enough for a VR sensor?

A couple of questions regarding what you see here.
1) Any reason why the tolerances I mentioned (2-3 th roundness) won't be good enough?
2) I painted the reluctor ring to keep it from rusting. That includes over the "teeth". I assume the magnet on the sensor will be able to read through the paint? Or should I sand off the paint on the ends of the teeth?

Thanks
Click to expand...

Looks great. I think the .002-.003" will be fine. and paint shouldn't effect it.

Great job.
 
Great work. You should photograph the work you do like this more often, you do good work and showing it enables and inspires others.
 
Looks really good. Based on the wobble I had whilst setting up my trigger wheel centering on the hub, they work with up to about .5mm deviation, so you should have zero worries there.
 
Great to see the end result - I think you nailed it! Really nice work, especially considering the equipment limits you were working with.
 
Thanks for the kind comments everyone. As I said, it was the input from this forum that helped me to accomplish it. Now you need to motivate me to get more work done on the car. :p
 
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