Trigger wheels

[OriginalCustoms]

That's good to know, thanks!

[klatin]

Actually,

Hall effect sensors (with or without magnets) are rarely used for crank trigger wheels. The reason is trigger precision. A hall effect sensor just senses the strength of the magnetic field. That field is strongest when the tooth is closest to the sensor. However, the electronic has to decide when the threshhold for "there's a tooth" is reached. Because the field strength varies strongly with the distance between tooth and sensor, even a small runout variation could cause a change in trigger angle of several crank degrees. For rotation sensors like wheel sensors, where the angle is irrelevant and only the pulse frequency is used, they work well. They work reasonably well if you have a low tooth count, like as electronic "points" in a distributor.

For crank trigger wheels VR sensors are used. A VR sensor is nothing but a coil wound around a magnet. You could easily build one yourself by winding transformer wire (a few hundred windings) around a magnet.
Different to a hall sensor, their output is NOT proportional to the field strength, but proportional to the rate of change of the magnetic field. If a tooth approaches, the output is positive, exactly zero when the tooth is closest to the sensor, and negative when the tooth moves away. A VR sensor detector just detects when the output of the VR sensor goes from positive to negative through zero. Runout does not have an effect.
You could also use a VR sensor to detect holes instead of teeth. Just reverse its polarity. For example you could mount it behind the flywheel and just drill 36 pocket holes into the back of the flywheel (36th hole drilled outside the circle of the other 35 so the sensor does not see it). Use the VR sensor "reversed" and it will fool the VR sensor detector in the ECU to behave as if each hole is a tooth and each space between holes is a tooth gap.

[Piledriver]

Great info as always, Klattin.

So... The Mk4 Golf sensor likely would work OK for the proposed 4/1 CAS setup (using the 2 teeth on the crank one-winged distributor for sync) but might not play so well at high RPM on a 36 or 60 tooth wheel, or at least would require perfect gap spacing and minimal runout for best results.

(I think VW used a 60-1 or 60-2, I'm now really curious and will have to dig in... It appears Bosch preferred Hall sensors at least at one point)

The Hall sensors have the advantage of not require the adjustable zero crossing detectors, but as I'll have 2 VR conditioners, I should probably use at least one

I apparently shipped the EDIS VR sensor off to Ray with the other goodies, anyone have dimensions for that?

Hmmm.. A T4 flywheel generally has 6 machined in oil "escape" holes in about the right place already...
(Will dig through my stash and see if that's universally true)

I just set final end play/installed seal etc and came in to cool down, before the PP goes on will take a quick peek if that's an easy option for using the generic wheel code (with cam sync)

[Piledriver]

OK... All T4 flywheels have 6 holes in the right place to line up with the AT flexplate bolt removal hole on the #3 side.
(T1 flywheels have them too, I guarantee it, but no hole in the trans flange there)

These holes vary somewhat depending on size of the flywheel (210/215/228) but all would be in range of a VR or hall sensor installed in a rotatable plug fit in the flexplate access hole. Easily secured w/setscrew or a number of other ways.

The holes are the backsides of the PP retaining bolt holes, and are relieved to ~12mm dia, at least on every FW I have.

So basically T4s already have a crank trigger wheel, with 6 evenly spaced "teeth"(holes), and an easy/safe engine compartment/topside mount location.
The only downside I can think of is they may not be referenced to TDC in any consistent way (different FW would have different positions) , not sure if that is a showstopper.

Won't work with EDIS, but might work fine with MS, used with a cam sync trigger, using the generic wheel option.

Now that I have thoroughly violated this thread, I'll start another thread when I get it going. (or not)
(my sincere apologies)

[MarioVelotta]

Now that I have thoroughly violated this thread, I'll start another thread when I get it going. (or not)
(my sincere apologies)

Gosh I feel so dirty... and used... Thanks Pile

I did some figureing tonight and came up with a total package price for the type 1 wheels.

It will include the new style CB santana pulley, machined for the trigger wheels and it will have 3 set screw locations around the perimeter for 3 forms of securing it. Epoxy/interference/set screws. And the VR sensor and bracket. Total will be $245 until I can get some price breaks. At this point my machinist will do one wheel at a time although he would prefer to do a more.

Type 1 hidden trigger package $245 + shipping.

[Boneloader]

How do you attach the wheel for the type 1 setup? Would it work with a steel Gene Berg pulley?

--Tim

Hey Tim, the pulley need to be machined to accept the trigger wheel. It may not be as sensitive as with a aluminum pulley. But the advantage of the steel wheel is the trigger can be tig welded in place. In the Aluminum pulley it needs to be epoxied in.

Tim, this is just what I've been looking for! How do I get one?

~T

[didget69]

A few little birds sent myself and Ray a pair of lonely 1.01 boards.

Mine was still in kit form, so I basically hacked it into a v2.2 with early injector drivers, which are actually better in some ways.
(not using them as such anyway)

Ray has a working/assembled board, a stim, a case, and a few additional bits that might help things along.

With a little luck we'll both be able to help more with MS specific questions sooner or later

let me get this straight..............pile working on sequential, and ray working on a modern ECU? hell freezes over

Pile & Ray have obviously been dragged into the 21st Century against their wills...

bnc

[TIMMA]

How do you attach the wheel for the type 1 setup? Would it work with a steel Gene Berg pulley?

--Tim

Hey Tim, the pulley need to be machined to accept the trigger wheel. It may not be as sensitive as with a aluminum pulley. But the advantage of the steel wheel is the trigger can be tig welded in place. In the Aluminum pulley it needs to be epoxied in.

Tim, this is just what I've been looking for! How do I get one?

~T

Um, you'd have to talk to Mario about getting a wheel tig'ed to a Gene Berg steel pulley. The pulley is available from Gene Berg: http://www.geneberg.com/product_info.ph ... cts_id=809 or the heavier one http://www.geneberg.com/product_info.ph ... cts_id=810


--Tim

[MarioVelotta]

That is definitely an option. If you guys want to provide the pulley's I can make it happen. Or pay upfront and I will get everything taken care of no problems. I can get them machined and then tig the wheel in, it's perfect

[SUbuggy]

Actually,

Hall effect sensors (with or without magnets) are rarely used for crank trigger wheels. The reason is trigger precision. A hall effect sensor just senses the strength of the magnetic field. That field is strongest when the tooth is closest to the sensor. However, the electronic has to decide when the threshhold for "there's a tooth" is reached. Because the field strength varies strongly with the distance between tooth and sensor, even a small runout variation could cause a change in trigger angle of several crank degrees. For rotation sensors like wheel sensors, where the angle is irrelevant and only the pulse frequency is used, they work well. They work reasonably well if you have a low tooth count, like as electronic "points" in a distributor.

sorry, but not buying description AT ALL. there are tons of OEM's using high tooth count, hall effect, crank sensors out there. very common example would be GM LSx 24x and 58x trigger uses a hall sensors, for example.

The advantage of a hall effect sensor is much greater resistance to EMI/noise interference. This is especially important when using high power CDI type ignitions.

The issues you mention with "detection" of when a tooth passes the sensor is resolved by proper trigger wheel design. trigger disc material, tooth height, tooth shape, diameter, and yes, tooth count in relationship to RPM are all factors.

I almost exclusively use hall effect, whenever possible.

[Piledriver]

.............
The advantage of a hall effect sensor is much greater resistance to EMI/noise interference. This is especially important when using high power CDI type ignitions.

Great point, I didn't even think about the high Z/noise issues VR sensors have, thanks!
This is likely the reason Bosch still uses hall sensors almost exclusively.
(This means most cars on the road today, as most OEMs use licensed Bosch based systems)

[MarioVelotta]

Hi guys, how about another thread on Hall vs. Vr

[Piledriver]

Hi guys, how about another thread on Hall vs. Vr

I must have missed those

Have a link?

[SUbuggy]

the biggest trouble i see around here is everyone goes for used/junkyard sensors and guesses on how to set it up. unstable timing, ECU resets, and poor running (If at all) are the reults. how many threads are there that you can think of for these type of issues?

Not all crank angle sensors are created equal. It is very important to know the specifics so you can build a trigger wheel ( and ECU software parameter settings) that will work best. I have used many oem sensors, but you dont just slap them on and forget about it.

Different to a hall sensor, their output is NOT proportional to the field strength, but proportional to the rate of change of the magnetic field. If a tooth approaches, the output is positive, exactly zero when the tooth is closest to the sensor, and negative when the tooth moves away. A VR sensor detector just detects when the output of the VR sensor goes from positive to negative through zero. Runout does not have an effect.

sorry but this too is complete hogwash. the output of a hall sensor IS ABSOLUTELY linerar, and NOT afected by speed. Hence the term "square wave" sensor. the output of every trigger event is always of the same amplitude, you can make the duty larger by making the teeth wider/narrower. there are also many other types, including "flying magnet" that output a hall signal.

sorry but runout does have an effect, on both hall and VR (inductive). and the signal amplitutde does VARY GREATLY with VR type sensors, in fact, that faster you turn the wheel, the higher the volatge output (amplitude) of the sensor.

not saying you cant use a VR sensor, but to blanket say hands down VR is simply better is flat out wrong.

[klatin]

Different to a hall sensor, their output is NOT proportional to the field strength, but proportional to the rate of change of the magnetic field. If a tooth approaches, the output is positive, exactly zero when the tooth is closest to the sensor, and negative when the tooth moves away. A VR sensor detector just detects when the output of the VR sensor goes from positive to negative through zero. Runout does not have an effect.

sorry but this too is complete hogwash. the output of a hall sensor IS ABSOLUTELY linerar, and NOT afected by speed. Hence the term "square wave" sensor. the output of every trigger event is always of the same amplitude, you can make the duty larger by making the teeth wider/narrower. there are also many other types, including "flying magnet" that output a hall signal.

sorry but runout does have an effect, on both hall and VR (inductive). and the signal amplitutde does VARY GREATLY with VR type sensors, in fact, that faster you turn the wheel, the higher the volatge output (amplitude) of the sensor.

not saying you cant use a VR sensor, but to blanket say hands down VR is simply better is flat out wrong.

I said "Different to a hall sensor, their output is NOT proportional to the field strength". Field strength does NOT change with speed. Therefore HALL sensors are linear with field strength, and NOT speed. Field strength changes with the square of the distance from the magnet. Hence their output amplitude is depends on the distance. You can make the duty cycle of the output larger and smaller not only with the tooth shape, which changes the shape of the field, but also with the distance between sensor and teeth. That's why runout affects them. The center of the output pulse happens when the center of a tooth passes under the center.
But here's the rub:
The duty cycle is irrelevant. What counts for an ignition application is where the rising (or falling) edge of the signal is with respect to the tooth. And that changes with that duty cycle. A change in duty cycle means that both, the rising and falling edge of the signal, move closer or farther from the center of the pulse (when the center of the tooth passes under the sensor) with changing sensor distance. Which means a changing angle from tooth center with changing duty cycle.

A VR sensor signal amplitude of course changes with RPM. It has to. As I said, it's dependant on the RATE OF CHANGE of the field, which changes with RPM. It's maximum value is of course ALSO dependant on the overall field strength, just like a hall sensor, and therefore changes with magnet strength, distance, and so on.

But a VR sensor detector DOES NOT use the maximum value for angle detection. It detects when the output of the VR sensor goes through zero. It ALWAYS goes through zero when the center of of a symmetric tooth passes under the sensor, irrespective wether the maximum was 0.1V or 100V.