Is this VR signal useable?

[Jawa2112]

Hello all this is my first Megajolt install, hoping for some advice.

the VR signal in these pics comes right from the VR sensor while the engine is idling at 800RPM "using the distributor"

I have included a picture of the trigger wheel its mounted to the back of a pulley and its an inside tooth design.

im worried the amplitude is too uneven probably caused by pulley runout of the cheaply machined pulley i mounted it to "sensor getting nearer and farther from sensor during rotation" Im also worried my missing tooth part of the signal is too small. The VR is aimed at the back of the pulley, at the center of the teeth.

Ive seen other scope pics of a really nice even signal is that normal? or do i have a garbage signal?

Thanks for any input.

[Dicky Blighter]

Is that pulley aluminium or steel and is there a gap between the pulley and trigger wheel?
I noticed you have a screw next to the missing tooth and a bit of a pulse in the gap on the scope - I think your sensor is seeing the screw heads.

[Jawa2112]

The pulley is aluminum, the wheel and the screws are both steel

I had considered the idea the sensor is picking up the screw heads but i don't believe thats the problem because there dosen't seem to be 6 evenly spaced places of higher or lower amplitude. I had also thought that the steel screws would fade into the magnetic background per say... when countersunk into the larger surrounding material.

there is a gap between the sensor and pully i can increase the overall amplitude by moving it closer, but the uneveness remains. Initially i had the sensor touching a section of the wheel during part of the rotation "which is why i am confident the pully isn't true, the sensor is not currently touching the wheel.

[Dicky Blighter]

how true does the edge of the trigger wheel run and can you mount the sensor so it looks at the edge ? it will give you a much cleaner signal, also convinced your gap blip is the screw.
Main thing is to get clearly defined pulses and gaps, if you cant mount sensor on edge try current set up but take that one screw out and see if the gap pulse is completely gone then.

[Jawa2112]

The sensor is right up against the block and there is no space behind the pulley, i have included pictures "that were shamelessly borrowed from another site"

My setup is identical to these pics, the sensor cannot be moved to look at the tips of the teeth, The engine is a High performance Type 1 aircooled VW I mounted this wheel and sensor because these engines occasionally throw belts, and this setup would avoid damage to the sensor if that should occur.

[NITROPIXIE]

Can you not get the trigger wheel lathed true?? Then move you sensor a little closer. This will help with the varying peaks, but the edis unit wont switch at the peaks. It will switch on and off at a threshold voltage less than this. What is important, obviously, is the time of each wavelength is the same (or distance each and every tooth is apart from oe another), but then it wont be a great problem as there are alot of teeth and error will be minimal and it shouldn't cause an enormous issue. The peaks of each cycle looks pretty much the same distance apart so i think you are pretty safe.

Also the variation in peaks aren't on a whole rotation (as if the whole wheel was on a skew) so it looks like some teeth are proud and some aren't. From the first low on the oscilloscope reading to the next there are 6 teeth (which is equivalent to 10 x 6 = 60 degrees, as every tooth is 10 degrees) then it rises a little bit then reduces again just before the missing tooth.

Could you get me a closer pic of the missing tooth as well please as i can't quite make it out easily in that picture because of the light??

[BRUCEROE]

There are a couple problems with putting the VR beside the wheel, instead of outside it. Any side to side wobble & engine end play will directly influence the waveform, as opposed to no effect outside. It appears to me that the gaps from the side aren't as well defined magnetically, because the continuous metal nearby is pretty close to the VR. Maybe this is hurting the missing tooth waveform; I might try moving a hair closer to center here to get farther from the tooth supporting metal. Bruce Roe

[Jawa2112]

I hope to get the pulley cut true, but i think to do that i would need to have it mounted to a crankshaft and spinning the entire assembly to have it proper wouldent I?

When I took these pictures of the missing tooth area i more critically analyzed the mark left on the teeth from when the sensor contacted them previously. It is obvious to me that some of the teeth are proud to others as Nitropixie mentioned and ironically the tooth before and after the missing tooth are not. the sensor contact occured right across the missing tooth area and the tooth on the right has no contact at all, the one on the left only slight contact, the teeth to either side of these had heavy contact. this does make me wonder since thats where the pully is making the wheel be physically closer to the sensor why is the signal smaller on the scope in that region?

In the short term I plan on shimming the wheel with small washers on the low side to see if that gains me any improvement.

the wheel is laser cut, there is some roughness and some slight variation in the shape and squareness of the teeth, i think knowing now the sensor is so sensitive i will need to clean that up some also.

[cng1]

Based on all the testbench work that we've done over the years I would say that signal looks OK. Best thing to do though is give it a go and see if it works as you never know till you get it on the car.