efi A Cam Position Sensor design - please critique

[jimk]

I assume you are shooting to not have the intermediate spring loaded rod and reach with the sensor alone, fixed in position.

[AustrianVespaGuy]

Correct, makes everything MUCH simpler if it can be done that way.

[Dudeland]

4 hours ago, AustrianVespaGuy said:

. . . Yeah that's exactly what we're working on here, with the long pole in the tent being a sensor that can survive the environment. Once I validate that though. . .

 

Dude super cool!!!!!!!!!!!!!!.

 

[veronatii]

5 hours ago, AustrianVespaGuy said:

. . . Yeah that's exactly what we're working on here, with the long pole in the tent being a sensor that can survive the environment. Once I validate that though. . .

 

 

Looking forward to updates on this-- very very clean!

[AustrianVespaGuy]

So I've got about 80% confidence this will work so I went ahead and ordered the expensive DW-HD-621-m8-100 sensor:

https://www.automationdirect.com/adc/shopping/catalog/sensors_-z-_encoders/inductive_proximity_sensors/8mm_tubular/dw-hd-621-m8-100

It's got an IP67 rated 60mm SS body with 53mm of threads and rated up to 140C.  While I'd feel better if the prob end was also enclosed in the SS housing, it's at least a liquid crystal polymer (LCP) - like Kevlar, so about a good as plastic as you can get - so  I think this still *should* be good enough to survive tucked into the cylinder head.  I mean, they bolt lesser-plastic intakes to cylinder heads all the time, right?

Anyway, when the sensor gets here I'll be able to bench test it in short order however I won't be able to actually run it in the car for a while.  The head in the car currently is an E21 with no fuel pump hole, and the good one on my bench is an E12 which is waiting on the rebuilt bottom end to go in the car, which in turn is waiting on new Ross pistons I ordered via Ireland 4 months ago so. . . no clue how much longer that's all gonna take unfortunately.

Oh, and as for sealing the mounting, I just took a piece of the thick (I think 1/8") cork gasket sheet I had laying around and cut out a small section of it to mount the wire.  I think with a little RTV there to help seal the seams it should actually work great, with no extra machining of the block-off plate necessary!

 

So, all good news so far, but afraid it'll be a while yet before I can provide any 'trial-by-fire' results, sorry. . . 😕

[Son of Marty]

Pardon my ignorance, but why do you need a cam sensor on a fix cam engine, isn't the cam  tied to the crank?

[2002iii]

Just now, Son of Marty said:

Pardon my ignorance, but why do you need a cam sensor on a fix cam engine, isn't the cam  tied to the crank?

Fuel injection!

[Son of Marty]

15 minutes ago, 2002iii said:

Fuel injection!

Yes, but can't you take that off the crank also as the two are married?

[AustrianVespaGuy]

1 minute ago, Son of Marty said:

Yes, but can't you take that off the crank also as the two are married?

Consider this: Set engine to #1 TDC, and then take the head off.  Now, which piston, 1 or 4 is on the compression stroke and which is on the exhaust stroke?

 

 

While yes they're 'married,' cam turns at HALF crank speed, so for every crank position you have TWO possible cam positions, so we want a sensor to tell us which one of those two were at. Make sense?

[Son of Marty]

Yup, thanks.

[veronatii]

6 minutes ago, Son of Marty said:

Yes, but can't you take that off the crank also as the two are married?

They're married, but the crank does two rotations for every one rotation of the cam, so the fuel injection needs to know which half of the cycle we're on. 

[Henning]

16 minutes ago, Son of Marty said:

Yes, but can't you take that off the crank also as the two are married?

It's some weird kind of ménage à trois.

 

henn

[jimk]

The cam sensor is a simple "flag" signal that tells the ECU to begin counting the firing order at one (i.e. reset the count of crankwheel teeth) after the missing teeth section of the wheel

[veronatii]

On 7/19/2024 at 1:40 PM, AustrianVespaGuy said:

So I've got about 80% confidence this will work so I went ahead and ordered the expensive DW-HD-621-m8-100 sensor:

https://www.automationdirect.com/adc/shopping/catalog/sensors_-z-_encoders/inductive_proximity_sensors/8mm_tubular/dw-hd-621-m8-100

It's got an IP67 rated 60mm SS body with 53mm of threads and rated up to 140C.  While I'd feel better if the prob end was also enclosed in the SS housing, it's at least a liquid crystal polymer (LCP) - like Kevlar, so about a good as plastic as you can get - so  I think this still *should* be good enough to survive tucked into the cylinder head.  I mean, they bolt lesser-plastic intakes to cylinder heads all the time, right?

Anyway, when the sensor gets here I'll be able to bench test it in short order however I won't be able to actually run it in the car for a while.  The head in the car currently is an E21 with no fuel pump hole, and the good one on my bench is an E12 which is waiting on the rebuilt bottom end to go in the car, which in turn is waiting on new Ross pistons I ordered via Ireland 4 months ago so. . . no clue how much longer that's all gonna take unfortunately.

Oh, and as for sealing the mounting, I just took a piece of the thick (I think 1/8") cork gasket sheet I had laying around and cut out a small section of it to mount the wire.  I think with a little RTV there to help seal the seams it should actually work great, with no extra machining of the block-off plate necessary!

 

So, all good news so far, but afraid it'll be a while yet before I can provide any 'trial-by-fire' results, sorry. . . 😕

Any updates on your sensor? Also how are you holding the sensor in place within the head? 

 

My rod/spring setup works ok, but I'd like to remove the mechanical bits.

 

Thanks!

[AustrianVespaGuy]

Engine is back but still assembling it so I haven't gotten as far as putting the head on yet but I will be soon.  Keeping it in place in the head is going to be the challenge though; although the threads are *just barely* longer than the boss in the head, because of how the casting is not-at-all flat there still just isn't enough room to securely get a nut on the front and back.  So rather than risking having metal parts falling down inside my new engine, I'm honestly contemplating just 'sticking' it in there with black oil-safe RTV, as at least that won't do any damage other than to the sensor or an oil leak if it comes loose!