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Old 17-05-2019   #1
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Question MES - timing values

Hi guys,

GP 1.4 8V VVT - in MES I saw 2 values for camshaft timing on idle:

Desired cam position = -2 degrees
Real cam position = 0 degrees

Is this normal or bad? I expected zero for both parameters...No errors in MES, so I think that it's still in some "tolerance". Do you know your values? Is there some tolerance before ECU's reaction on it? Because by these parameters it looks that mine timing is little bit incorrect - camshaft is turned a little bit forward and should be set anti-clock-wise 2 degrees... What do you think guys?
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Old 17-05-2019   #2
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Re: MES - timing values

Ok, well I suppose it's not absolutely spot on but I doubt if it'll make a rats difference to how she runs at idle. Have you tried taking readings at higher revs? If it consistently shows an advance, compared to any "desired" figure, my guess would be that the cam pulley has not been tightened up in exactly the correct position - if the cam belt was a tooth out it would be more than 2 degrees. To do anything about that you'll need a set of timing tools (probably around £40 on ebay. (that's what I paid anyway)

On the other hand, although I'm a perfectionist and would like to see it spot on if it were my car, a consistent couple of degrees out over the extended rev range is probably not going to make a difference you'll notice either in terms of performance or fuel consumption.

So try taking some results further up the rev range, say every 500 rpm up to say 4,000 rpm? and get back to us.
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Old 17-05-2019   #3
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Re: MES - timing values

Hi Jock, thanks for info. I didnt measure it in higher rpms...my fault...I'll try. Car is running well. I know that its not big issue because ECU is still happy when it compares crankshaft position against camshaft position on any rpms...so no engine light or errors in ECU.
I'm still solving that high ticking sound from cylinder head and getting all information. And one of my unclear things was this "-2 degrees" issue. But every day I'm closer to solving this tricky puzzle. Now I know that exhaust valve on 3rd cylinder is shiny oposite other ex valves, so someone chaged it recently. And because that ticking is related to temperature, I think that changed shiny valve has thicker bottom than original valves, and once engine is getting hot and reaching operational temperature, lenght of this valve is growing and its hitting piston a little bit. And thats that ticking noise. Because valve clearances were measured and are ok, so at the top of this valve its ok. (One of my thoughts was, if this -2 degrees correction can prevent this hitting piston...)
Sorry for my English...
This sunday I'll meet Aurick - he has camera, so I believe that we will see some cracks on 3rd piston's surface by this ex valve - this will proove my theory
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Last edited by Rado77; 17-05-2019 at 21:39.
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Old 18-05-2019   #4
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Re: MES - timing values

Considering a cam opening angle of 114° (opening before TDC + 180°stroke + closing after BDC)/2 and a lifting value of 6mm, a deviation of 2 degrees would translate in an offset of 0,21 ish mm at the valve (for a linear lifting ramp of 1/2 opening angle).
I doubt mass production engines have so tight construction tolerances to not allow this 0,2mm offset, but if not, that could explain the annoying tick noise ...Null-off this 2° discrepancy and hear what happens.

BRs, Bernie

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Old 18-05-2019   #5
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Re: MES - timing values

Quote Originally Posted by Bernievarian View Post
Considering a cam opening angle of 114° (opening before TDC + 180°stroke + closing after BDC)/2 and a lifting value of 6mm, a deviation of 2 degrees would translate in an offset of 0,21 ish mm at the valve (for a linear lifting ramp of 1/2 opening angle).
I doubt mass production engines have so tight construction tolerances to not allow this 0,2mm offset, but if not, that could explain the annoying tick noise ...Null-off this 2° discrepancy and hear what happens.

BRs, Bernie

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Wow Bernie! I haven't done calculations like that since my City and Guilds Technicians Certificate days! Wonder how I've managed? My respect to you sir!
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Old 18-05-2019   #6
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Re: MES - timing values

Hi Bernie. Can you please translate your calculations? :-) What does it mean? Offset 0.2mm is calculated valve lenght? Does it mean joining valve with piston because of longer valve, or because of that incorrect timing -2 degrees? I think....if -2 degrees is real problem, then all 4 valves will meet their pistons...? But in that case ticking will be very quick. But my ticking is "slow"...like only 1 valve has issue.
Tomorrow we will make compression test and camera test with Aurick...I'll report results...
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Last edited by Rado77; 18-05-2019 at 15:26.
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Old 19-05-2019   #7
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Re: MES - timing values

So thanks to Aurick ;-) we measured compressions - all good and also checked valves and parts of cylinder walls with camera. All looks good, so result - to ignore high ticking and if it don't get worse after next 1 year, then it will be ok forever.
And regarding timing -2 , its big intervention for me, I have to buy tools, to have time to do that on street and so on...so I'll keep it as it is and only check from time to time (wife's car) if everything is ok
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Last edited by Rado77; 19-05-2019 at 17:00.
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Old 20-05-2019   #8
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Re: MES - timing values

Quote Originally Posted by Rado77 View Post
Hi Bernie. Can you please translate your calculations?
By "offset" I meant the difference between expected and actual position (travel) of any valve. So at valve opening and as it occurs earlier, the valve will be more open" for a same piston position (close to TDC), with potential collision possible for the valve(s) that was already closest to piston (new valve, new seat, machining tolerance).

Not saying that's what happens! Nor that fixing this -2° timing error would cure the ticking noise, it's just a possibility...

BRs, Bernie

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Old 20-05-2019   #9
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Re: MES - timing values

Thanks for explanation. I talked to service who changed timing belt, tensioner and water pump and they said that they used fix tools for crank/cam. So I don't know why expected timing by ECU is -2 degrees. By my understanding - setting proper timing should be like this:

-> remove old belt, add new tensioner
-> insert both fixators up and down (TDC for 1st piston, both valves closed)
-> dismount center cap of camshaft VVT puley (torx)
-> release a little bit center bolt fixing VVT puley and camshaft
-> add new belt, set tensioner properly, tighten center bolt fixing VVT puley
-> remove fixators, turn engine 2 times by crankshaft bolt
-> inster fixators again to make sure that timing is still ok
-> tighten tensioner's bolt, remove fixators -> done

I think there's no other chance to add there belt properly. Because if they didin't release center bolt holding VVT puley with cmashaft (it's tighten more than 200Nm), new belt will have some loose (or too big tension) between water pump and VVT puley (I hope that you understand what I mean....) . I'll check belt tension by removing upper belt cover...
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Last edited by Rado77; 20-05-2019 at 10:33.
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Old 20-05-2019   #10
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Re: MES - timing values

Quote Originally Posted by Rado77 View Post
Thanks for explanation. I talked to service who changed timing belt, tensioner and water pump and they said that they used fix tools for crank/cam. So I don't know why expected timing by ECU is -2 degrees.

-2° is what the ECU request as an offset to the basic timing, 0° is the actual timing the ECU computes with the true angular position of camshaft vs crankshaft sensors

By my understanding - setting proper timing should be like this:

-> remove old belt, add new tensioner
-> insert both fixators up and down (TDC for 1st piston, both valves closed)

Not sure about TDC, most probably @ midstroke (90°) where all 4 pistons are away from valves and can't therefore collide with ANY of them, the camshaft being rotated for any reason...

-> dismount center cap of camshaft VVT puley (torx)
-> release a little bit center bolt fixing VVT puley and camshaft
-> add new belt, set tensioner properly, tighten center bolt fixing VVT puley
-> remove fixators, turn engine 2 times by crankshaft bolt
-> inster fixators again to make sure that timing is still ok
-> tighten tensioner's bolt, remove fixators -> done

I think there's no other chance to add there belt properly. Because if they didin't release center bolt holding VVT puley with cmashaft (it's tighten more than 200Nm), new belt will have some loose (or too big tension) between water pump and VVT puley (I hope that you understand what I mean....) . I'll check belt tension by removing upper belt cover...
BRs, Bernie

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Last edited by Bernievarian; 20-05-2019 at 11:59.
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Old 20-05-2019   #11
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Re: MES - timing values

You are right, fixing position couldn't be TDC for 1st valve... And I remember one thing - service called me that they had to wait few days for new bolt which holds VVT puley on camshaft, becuase it should be replaced everytime after it's removal. So they did it correctly.
Anyway I'll check tension of timing belt. If this will be ok, I can investigate if "expected angle value" is calculated only by data from crankshaft/camshaft sensors, or if there is also some other data which can affect that "expected value". I'll also check MES on higher rpms. I also wrote e-mail to authorised service regarding this angle and tolerances...there must be some tolerance between these 2 values, otherwise ECU will light on engine icon
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Last edited by Rado77; 20-05-2019 at 12:35.
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Old 20-05-2019   #12
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Re: MES - timing values

Quote Originally Posted by Rado77 View Post
... I can investigate if "expected angle value" is calculated only by data from crankshaft/camshaft sensors, or if there is also some other data which can affect that "expected value".
The ECU calculates the correction to initial timing by computing several data sets such as Revs, engine load, delivered torque, coolant temp, driver's request (pedal) etc.
It will then instruct the actuator to deliver oil to the VVT, which will result in an angular Outer (pulley) / Inner (camshaft) coupling variation...

BRs, Bernie

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Old 20-05-2019   #13
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Re: MES - timing values

OK, I'll check it again through MES on cold idle, hot idle and in rpms. Maybe I find something interesting...
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Old 20-05-2019   #14
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Re: MES - timing values

So I checked it - there are 3 parameters:
- Cam position
- Desired cam position
- VVT (phase variator)

The first is always zero, even I rev up engine. That probably means that timing belt is set correctly. Desired cam position is -2 degrees and stays -2 even I rev up engine. And VVT is of course percentage of cam angle when I rev up engine.
I still dont know why is desired -2, but as you said, it depends on many other engine parameters. But I think that 1st parameter Cam position = 0 is mandatory and it says that timing is made correctly
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Last edited by Rado77; 20-05-2019 at 21:11.
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Old 21-05-2019   #15
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Re: MES - timing values

Quote Originally Posted by Rado77 View Post
... And VVT is of course percentage of cam angle when I rev up engine...
Hhmm, I wouldn't be so sure... that actuator is PWM driven so the %age you see is probably the duty cycle that's sent to the solenoid...

Could you monitor the curves in road conditions? They HAVE to change somehow otherwise VVT would simply be useless!

BRs, Bernie

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