Choosing a crank trigger/wheel

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SleepyKeys
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Choosing a crank trigger/wheel

Post by SleepyKeys »

A buddy of mine is retrofitting an efi system onto an old V8. I recommended to him that he get a Hall type pickup and a 36-1 crank wheel. The guy he ordered his M$ kit from said they sell VR type sensors and wheels to go with them. From what I have read VR type setups can be problematic and I have always preferred Hall type setups. What do you guys think?
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BenFenner
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Re: Choosing a crank trigger/wheel

Post by BenFenner »

Only reason to go VR is because that's what you already have, the EMS doesn't do HALL, or you can't get the power for a HALL sensor. If you're starting from step 1, and the EMS supports it, you want HALL every time because of the signal clarity.
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SleepyKeys
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Re: Choosing a crank trigger/wheel

Post by SleepyKeys »

BenFenner wrote:............ want HALL every time because of the signal clarity.
My thoughts exactly! Thats why I was disappointed when I didnt see any hall kits for sale.

I noticed that most OEM wheels with Hall sensors have "square" type teeth. Does anyone know if VR type wheels with "pointed" teeth will work ok?

-sean
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jbelanger
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Re: Choosing a crank trigger/wheel

Post by jbelanger »

I don't know the answer to that but you should consider this. The VR conditioner circuits are zero-crossing detector which means that the output signal will change level when the VR sensor is in the middle of the tooth (and, possibly, the middle of the gap). The Hall sensors will change level on the edges of the tooth.

I would assume you'd want the teeth to be as square as possible to have the most consistent timing over the whole rpm range. With ramps instead of sharp edges, I would think that the timing could vary.

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SleepyKeys
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Re: Choosing a crank trigger/wheel

Post by SleepyKeys »

All very logical. So what you're saying Jean is that I should draw up my own wheels with square teeth in CAD so everything is most accurate? :)
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BenFenner
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Re: Choosing a crank trigger/wheel

Post by BenFenner »

There's got to be HALL friendly wheels already out there for this application. Yah?
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SleepyKeys
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Re: Choosing a crank trigger/wheel

Post by SleepyKeys »

You would think so, but I checked the more popular DIY store fronts and didn't see anything. Maybe I need to look again.
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Re: Choosing a crank trigger/wheel

Post by Fred »

I have zero issues with my VR setup!

I know the MS setup is a pain, but if setup right and the wiring is done right it does work.

Basically, if you wire it right and shield it and ground it right it will be as quiet as any other system and the reverse is also true. IE if you wire the hall setup badly it WILL give you trouble.

Jean raises a good point there too! Good to see you posting btw! :-)

Don't you need magnets on each tooth for hall to work reliably and strongly anyway? I understand you can do it without, but they work best like that AFAIK.

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davebmw
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Re: Choosing a crank trigger/wheel

Post by davebmw »

My Stock BMW VR sensor and 60-2 wheel combo works very well.
The only issue i had was connecting it round the wrong way so that a tooth = negative going half of a sine wave so the whole timing was out by 6 degrees.
I found that using a signal generator and a scope I was able to set the zero crossing to give me a perfect 50/50 duty cycle square wave coming out of the VR IC. although with it in the car you have to turn both pots quite a bit to get it to upset the smooth running at idle.

So in all honesty why worry?

some pro's for the VR:
They have to be more reliable than hall as they have no active components internally just a coil of wire around an iron core.
Their relatively low impedance prevents stray signals from becoming a problem.
I haven't checked this but they are probably cheaper and more than likely fitted to the engine as OEM.
With a VR sensor and ECU based VR chip you have some degree of tweak-ability should the sender ring have some irregularity about it.

the cons:
You are required to have a few more components on the ECU PCB,
If you get them round the wrong way you have 10 minutes of head scratching before you realise.

Hall sensor pro's:
simple logic 1 or 0 almost straight to the CPU assuming you have a 5V sensor and not a 12V.
Lower component count on the PCB,
Suitable for a half moon type cam phase sensor.(BMW VANOS)
Less ambiguity regarding polarity as the wires are more than likely colour coded.

Cons:
Electronics in potentially harsh conditions,
connect it wrong and you may kill it,

hmmm decisions decisions :)
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WTDeuce
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Re: Choosing a crank trigger/wheel

Post by WTDeuce »

VR sensors are noise prone... Dont have to use shielded wire with Hall sensors.

This place has 36-1 wheels that arent spiky.

http://trigger-wheels.com/store/index1.html
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