Tiger Super Six
|
| posted on 18/2/11 at 09:25 AM |
|
|
Duratec Crank Sensor - Why?
Chaps,
I don't know much about engines so this might be a stupid question, but it got me wondering.
When I got my Duratec engine the crank position sensor got broken taken the engine out of the donor car and I therefore needed to replace it. When I
replaced it I looked into how to do this and was told to line the hole up on the bottom of the crank pully and put in a bolt. The missing tooth on the
trigger wheel would then be at 11'o clock and the crank sensor fitting tool would then fit over the 9th tooth back, which it did, so I assume
all is OK.
My question though is why does the engine need to be in this exact position when fitting the crank sensor as if you ever turned the engine over by
hand, surely this would then change all these positions as the crank sensor wouldn't be working at that time, so would this then cause problems
starting the engine.
My view was that the sensor picks up on the trigger wheel and effectively calibrates itself each time you start the engine by picking up the missing
tooth, is this right, and also a point to remember is that this is just simply replacing the sensor not rebuilding the engine when the cams, timing
etc would all need to be set.
Thoughts?
Mark.
Mark
Tiger Avon
|
|
|
|
|
bigrich
|
| posted on 18/2/11 at 09:38 AM |
|
|
in my experience, it makes no difference what position the engine is in when changing just a crank sensor.
If the bracket is also changed then there may be need to adjust and align to a reference mark or tooth.
.JPG)
A pint for the gent and a white wine/fruit based drink for the lady. Those are the rules
|
|
|
r1_pete
|
| posted on 18/2/11 at 09:44 AM |
|
|
Are you reading the guide to Cam timing by any chance? this would require the crank loking at a specific position, probs TDC.
Replacing the sensor should not require any specific crank position.
|
|
|
nib1980
|
| posted on 18/2/11 at 09:46 AM |
|
|
as far as i'm aware crank position sensor can be removed an replaced with the CRANK in any position
at least i hope so..........
|
|
|
BenB
|
| posted on 18/2/11 at 09:47 AM |
|
|
Really?
If the crank sensor was at any old position how would the ECU know when to deliver the sparks. Although the timing is adjusted for a single cylinder
relative to TDC, the only way the ECU knows when each cylinder is a TDC is relative to a known constant. So surely it's therefore vital that the
crank sensor is at the right position otherwise the timing will be off.
Of am I confused? 
|
|
|
nz_climber
|
| posted on 18/2/11 at 09:53 AM |
|
|
That is correct
For everything thing to work, the ecu needs the sensor to be in the exact position, and also the toothed wheel needs to be the exact position on the
crank (usually by a key) so it can work out where TDC each rotation and supply fuel and spark to suit..
Replacing the sensor should be a easy remove and replace deal though, not sure about the duratec, but all other engines (mainly toyota) I have dealt
with have dowels to ensure the sensor goes in the correct position every time.
http://aarons7.wordpress.com
|
|
|
mcerd1
|
| posted on 18/2/11 at 09:53 AM |
|
|
quote:
Originally posted by BenB
Really?
If the crank sensor was at any old position how would the ECU know when to deliver the sparks. Although the timing is adjusted for a single cylinder
relative to TDC, the only way the ECU knows when each cylinder is a TDC is relative to a known constant. So surely it's therefore vital that the
crank sensor is at the right position otherwise the timing will be off.
Of am I confused?
the missing tooth tells the ECU where TDC is
the sensor needs to be placed correctly for this to work (e.g. 90deg before TDC for EDIS4 based setups like megajolt)
but unless the duratec sensor mounting is adjustable then I can't see how it would make any odds...
 
Description
[Edited on 18/2/2011 by mcerd1]
-
|
|
|
Tiger Super Six
|
| posted on 18/2/11 at 09:53 AM |
|
|
quote:
Originally posted by BenB
Really?
If the crank sensor was at any old position how would the ECU know when to deliver the sparks. Although the timing is adjusted for a single cylinder
relative to TDC, the only way the ECU knows when each cylinder is a TDC is relative to a known constant. So surely it's therefore vital that the
crank sensor is at the right position otherwise the timing will be off.
Of am I confused?
That seems to be logical in one sense and I guess what I was told, BUT, the ECU would know by picking up the missing tooth, that's why the
position of the trigger wheel would be very important, but I am not so sure about the crank sensor.
If it was that important it would mean that if you put the car in gear to test something, clutch biting point etc, then if the engine turned over
slightly doing this, the crank sensor would be out of alignment, surely something this simple couldn't affect the timing of the engine?
Mark
Tiger Avon
|
|
|
Tiger Super Six
|
| posted on 18/2/11 at 09:58 AM |
|
|
There are two mounting posts that it bolts onto and then the holes in the sensor are elongated (not sure how you spell that!). When you get the sensor
there is a plastic cover that fits over it which then has a slot in it that fits over a tooth on the trigger wheel. So when you push that over you
then tighten the bolts and it should be in the right place.
Pretty sure I have done it OK, I am just not sure that I really needed to line the engine to TDC and count back to make sure it was the right number
of teeth to the one I aligned on as the trigger wheel is already in the correct place and the sensor will calibrate when I turn the engine over by
seeing the missing tooth.
Mark
Tiger Avon
|
|
|
BenB
|
| posted on 18/2/11 at 10:09 AM |
|
|
quote:
Originally posted by Tiger Super Six
quote:
Originally posted by BenB
Really?
If the crank sensor was at any old position how would the ECU know when to deliver the sparks. Although the timing is adjusted for a single cylinder
relative to TDC, the only way the ECU knows when each cylinder is a TDC is relative to a known constant. So surely it's therefore vital that the
crank sensor is at the right position otherwise the timing will be off.
Of am I confused?
That seems to be logical in one sense and I guess what I was told, BUT, the ECU would know by picking up the missing tooth, that's why the
position of the trigger wheel would be very important, but I am not so sure about the crank sensor.
crank sensor = trigger wheel ??? Isn't it?
|
|
|
Tiger Super Six
|
| posted on 18/2/11 at 10:12 AM |
|
|
The crank sensor and trigger wheel are two seperate things. The trigger wheel is mounted behind the crank pulley and the crank sensor bolts to the
front of the engine case to pick up the movement of the trigger wheel.
Mark
Tiger Avon
|
|
|
vinny1275
|
| posted on 18/2/11 at 10:29 AM |
|
|
You can turn the engine without it in the car and the sensor will use the first turn of the engine to determine the cycle of the engine, by
calibrating against the missing tooth - it won't put in any fuel until it's found the engine position, and as long as the cam is timed
properly, nothing can get damaged. If you were to move the sensor around the rotational edge of the wheel, you'd need to either adjust the wheel
by the same number of degrees, or adjust the ECU to a different number of degrees before / after TDC.
The position of the sensor is important as there is a fine clearance required between the sensor face and the edge of the trigger wheel - normally
about a mm or so...
|
|
|
mcerd1
|
| posted on 18/2/11 at 11:07 AM |
|
|
quote:
Originally posted by Tiger Super Six
There are two mounting posts that it bolts onto and then the holes in the sensor are elongated (not sure how you spell that!). When you get the sensor
there is a plastic cover that fits over it which then has a slot in it that fits over a tooth on the trigger wheel. So when you push that over you
then tighten the bolts and it should be in the right place.
Pretty sure I have done it OK, I am just not sure that I really needed to line the engine to TDC and count back to make sure it was the right number
of teeth to the one I aligned on as the trigger wheel is already in the correct place and the sensor will calibrate when I turn the engine over by
seeing the missing tooth.
that explains it then
the likes of the zetecs just have a hole to stick the sensor through and the trigger wheel is actually just machined into the back of the flywheel so
there is nothing to adjust - I'm guessing mazda didn't think that was good enough for the MZR (aka: duratec)
-
|
|
|
nz_climber
|
| posted on 18/2/11 at 08:39 PM |
|
|
Gives the instructions in the link below
http://www.turbosp
ort.co.uk/showthread.php?127406-Grahamb-s-Mk1-Fiesta-XR2-Duratec-HE-Hillclimber&p=1690225&viewfull=1
I think this method is better than the zetec method on the fly wheel, especially for our uses as it means you don't need that same pattern on
any new flywheels (when doing to light weight alloy flywheels etc)
But agree most manufactures don't alloy for adjustment (so can be something else to get wrong..)
http://aarons7.wordpress.com
|
|
|
prawnabie
|
| posted on 18/2/11 at 08:52 PM |
|
|
Am I missing something or is he just replacing the sensor? It doesn't matter how many times you turn the engine over with no sensor, if you put
the new one back where the old one came from bobs your uncle.
|
|
|
mcerd1
|
| posted on 18/2/11 at 09:26 PM |
|
|
quote:
Originally posted by nz_climber
Gives the instructions in the link below
http://www.turbosp
ort.co.uk/showthread.php?127406-Grahamb-s-Mk1-Fiesta-XR2-Duratec-HE-Hillclimber&p=1690225&viewfull=1
I think this method is better than the zetec method on the fly wheel, especially for our uses as it means you don't need that same pattern on
any new flywheels (when doing to light weight alloy flywheels etc)
But agree most manufactures don't alloy for adjustment (so can be something else to get wrong..)
I wish you hadn't posted that link - It makes me wish I hadn't sold my old mk1 (even if it was just a 1.1l)
I'm very jealous now 
-
|
|
|
MikeRJ
|
| posted on 19/2/11 at 11:04 AM |
|
|
quote:
Originally posted by prawnabie
Am I missing something or is he just replacing the sensor? It doesn't matter how many times you turn the engine over with no sensor, if you put
the new one back where the old one came from bobs your uncle.
That's the whole point, on the Duratec the crank position sensor isn't positively located like it is on the Zetec etc; it has to be
properly aligned when installed before the mounting bolts are tightened.
|
|
|
