cam and crankshaft; VR or hall sensor ? can't decide...

[bigboss59400]

Hi,

(future owner of a fury x)

After doing some research I finally can't decided which type of sensor to go...

VR is more robust (especially for temp) and has a better reponse time since it's a passive

Hall is more easy to work with (square wave), less sensible to noise and there is no adjustment needed for the airgap (just need to respect the datasheet and that's it)

the famous gt101 from honneywell is operating up to 150°C, has a reponse time of 15us which give me an imprecision of 1 degree at crankshaft (24-1 at 8k rpms)

So I guess for new setup hall is prefered ?

Best regards

[Adamw]

I generally prefer VR on crank, since it it is more precise, more reliable, and has a better signal to noise ratio as engine speed increases.  

And if I have the choice I go for hall on the cam. They output a signal at lower speeds so sync can be determined sooner (cam is 1/2 speed of crank and VR output is relative to tooth speed) and since you are only using it for phase identification the precision or slow rise/fall time doesn’t matter.  

The important thing is to consider target design - VR needs teeth short & sharp, about the same size as the sensor pole and a special design in the missing tooth area.  Hall typically wants wide/long teeth with deeper cutouts between teeth.

 

[bigboss59400]

Thanks for such valuable informations !

The aftermarket trigger wheel that I firstly choose is for a hall sensor and the teeth are not sharp; it's more like a gear ("triangle" shape). Not good enough so I will need to make my own.

I FINALLY found an interesting sensor and rather cheap !! 0261 210 136 bosch motorsport

https://cdn.shopify.com/s/files/1/0057/7712/9587/files/Inductive_Speed_Sensor_IA-C_Datasheet_51_en_2782136331.pdf?100626007659879745

So I will just follow the datasheet

 

A few remaining questions :

- since my wheel diameter will be different that the one on the datasheet, should I just adjust the width of the gap ? or should I adjust the other parameters too (width teeth, depth of regular teeth, depth of missing teeth) ? if so in what proportion ? pro ratio ?

- (dumb one sorry) I guess I can't damaged the input of the ECU if I put too close the VR sensor ? (meaning higher voltage)

- for the cam trigger, all the aftermarket disc has only a teeth on it, I suppose you adjust (mechanically) the rising edge of the pin to the start of one phase ?

I was hoping something more like half of the disc "1" and the other half "0" ?

[Adamw]

4 hours ago, bigboss59400 said:

- since my wheel diameter will be different that the one on the datasheet, should I just adjust the width of the gap ? or should I adjust the other parameters too (width teeth, depth of regular teeth, depth of missing teeth) ? if so in what proportion ? pro ratio ?

The tooth should ideally be about the same length as the pole diameter - up to about 1.5X the dia is generally ok.  The pole diameter is shown in the pic below.  The length of the gaps do not matter.  

A more detailed explanation is here:  

 

4 hours ago, bigboss59400 said:

- for the cam trigger, all the aftermarket disc has only a teeth on it, I suppose you adjust (mechanically) the rising edge of the pin to the start of one phase ?

I was hoping something more like half of the disc "1" and the other half "0" ?

With a missing tooth crank wheel and sync mode set to Cam Pulse 1X, all the ecu does is checks if it saw a cam edge in the last crank rotation or not.  Whether it saw a tooth or not it can determine which phase it is on from that.   

 

[bigboss59400]

Thank you for your support !

I think you misunderstood my point :

What if my target wheel (ie crank trigger wheel) is not 160mm :

- if it's bigger then should I just have b2 bigger than 4.3mm ?

- if it's lower then should I remove teeth or lower b2 ? I'm afraid in 2 scenario that VR might not be quick enough

 

OK so it's not better to have a cam level in this case, just need to respect the trigger event 2 following your help guide

 

Where should I put the missing crank toothany guideline ? (RB26 with 60-2)

In case the trigger 1 and/or 2 event occurs at a wrong time, can I shift it by SW ?

 

I'm planning to use intake VVT (hks vcam), does it add any constraints ?

[Adamw]

1 hour ago, bigboss59400 said:

- if it's bigger then should I just have b2 bigger than 4.3mm ?

Correct.

 

1 hour ago, bigboss59400 said:

if it's lower then should I remove teeth or lower b2 ? I'm afraid in 2 scenario that VR might not be quick enough

You can shorten the tooth (b1) down to the pole diameter (3.5mm on the drawing), so you can pick up a little space there.  I wouldnt want the gaps (b2) to be shorter than the teeth (b1), so if you cant achieve the diameter you want with the teeth and gaps no less than 3.5mm long then you would be best to reduce tooth count or find a sensor with a smaller pole.   

 

1 hour ago, bigboss59400 said:

Where should I put the missing crank toothany guideline ? (RB26 with 60-2)

Not too critical, I like to place it outside of the normal range of ign timing so 60BTDC or 60ATDC is a good option on a 6cyl.

 

2 hours ago, bigboss59400 said:

In case the trigger 1 and/or 2 event occurs at a wrong time, can I shift it by SW ?

It is not critical, the trigger offset is set in the software when the engine is running. 

 

2 hours ago, bigboss59400 said:

I'm planning to use intake VVT (hks vcam), does it add any constraints ?

You can just use the 3 teeth on the HKS cam as both your sync (phase) and VVT position, you dont need a separate sync sensor.  This would use the "Cam window" sync option.  

[bigboss59400]

Thanks a lot Adam !!

For my understanding, am I correct if using cam pulse window, in fact 2 over the 3 teeth are "useless" ?

[Adamw]

There are two different functions going on - 1) triggering to determine crank position and phase.  2) measurement and control of the VVT cam position relative to crank.

The cam pulse window is part of the triggering strategy - it means the ECU will only look for one tooth on the cam within a specific crank angular range so it can determine what phase the engine is in (Exhaust or compression stroke).  Effectively ignores the other two teeth so it only sees one unique event every 720  deg.

The cam pulse window is only used for the triggering, all 3 teeth on the cam are used to measure the cam position for the VVT control.  

[bigboss59400]

Indeed 

I somehow forgot the second point ! 

Thanks a LOT Adam !