Brera 3.2 JTS Q4 SV 48,000 miles Timing Chain - Page 7 - Alfa Romeo Forum
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There's a timing control sensor for each of the 4 camshafts that informs the ECU and the VVT solenoids so they should always be optimum irrespective of pressure and wear etc...
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^^ yes makes sense to me.

I see you've been busy on that keyboard again Brian, Interesting reading about the difference in oil supply in the banks.
So are both exhaust oil control solenoids on the same pwm feed, and are both inlet oil control solenoids on the same pwm feed? If not, and they are all on individual pwm feeds, it does suggest to me that oil pressure is not as important as each oil control valve is on a different pwm signal to achieve correct cam angle feedback and this was the thinking the Alfa engineers had too so the oil pressure difference was not a consideration?

I quite agree though, a constant oil pressure feed to the vvt system would take one variable out (that being oil pressure always on the move up/down while the oil control valves are trying to adjust cam timing and this adds delay to the system control and feedback (too many moving averages so -to -speak).

A fixed oil pressure vvt system would have far tighter and faster timing control.

I know to achieve this is alot of work with having a new pickup in the sump and electric pump and new oil line feeds to the heads, but it would show the biggest results I'm sure.
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There's a timing control sensor for each of the 4 camshafts that informs the ECU and the VVT solenoids so they should always be optimum irrespective of pressure and wear etc...
Where is the question? Can you give me component part numbers for these items? And why is another question? The None return valves in the cylinder head V.V.T oil ways are small, but identical. So oil pressure in each cam shaft void, a function of flow rates to those voids is irrelevant? When the intention of the designers is as plain to see!

1. Hypothetically, we shall say, it takes 10 psi for a cam shaft void to travel 50 degrees advance ( maximum as indicated by Alfa ). Bear in mind there is inertia involved here, insofar as the advance void has to overcome the fill in the retard void, now being vented to the drain. And vice versa.

2. Because of disparity in fill, we will assume only 7.5 psi on the left bank. The vanes in the cam shaft voids are uniform and from that one can state the pressure exerted across their faces is linear W.R.T each other.

3. Assuming the right bank has the prerequisite 10 psi. So it has achieved max advance, whilst the left is at 37.5 degrees. Slightly more complex, but not much so.

4. The timing is from the stator - the outer of the V.V.T sprocket. The rotor is connected to the cam shaft proper, which rotates within the void.

5. Why would any engineer want to complicate matters by sensing the internal rotational position of the cam shaft, when all that is required is a constant flow rate to all four camshaft advance/retard voids????

6. Advance can be arrested by the anti-knock device - common to all cylinders, so what more do you need? It does not mean the cam shafts are in their correct positions, but it is simpler, cheaper and just as effective as what is being suggested in the above. But it still does not mean the cam shafts are in the right position to maximize the power.

I repeat, give me the component numbers and location and take all the rabbits out of the hat at the same time please. Unless of course we simply want to go back to the grade of oil and just go on endlessly, in ever decreasing circles until we disappear up our own orifices.

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Each timing sensor acts on the VVT sprocket's flywheel and is located in the timing cover - left bank are here (right bank is similar). Unfortunately, I don't have access to a part No.s database:
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all modern vvt systems use position feedback. Usually the cam position sensor is used for that.

I think the size difference was intentional, maybe there are pressure issues with operating 2 camshaftsat the same time? being a V setup, they shouldn't operate at the same time anywayas you're not going to get to the advance you want in 1/50th of a second anyway.
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Alfa part is the same as many of Alfa/Fiat/GM 1.9 & 2.4 JTD(M) engines - part No. 55216243

These are some of the same OEN Part Numbers
* FIAT: 46798364
* FIAT: 55201874
* FIAT: 55201876
* FIAT: 55216243
* GENERAL MOTORS: 93 179 392
* GENERAL MOTORS: 93 190 702
* OPEL: 12 35 268
* OPEL: 12 47 060
* OPEL: 62 35 665
* SAAB: 93 179 392
* SAAB: 93 190 702
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Not sure even I believe those part No's now?? Google can lie shock..
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I think Part No. should be:

BLUE PRINT ADG07262
BOSCH 0 232 103 079
BUICK 12608424
CADILLAC 12608424
CHEVROLET 12608424
DAEWOO 12608424
ERA 550812
GENERAL MOTORS 12608424
GMC 12608424
LUCAS ELECTRICAL SEB2004
METZGER 0903166
OPEL 12 608 424
OPEL 4810352
PONTIAC 12608424
QUINTON HAZELL XREV486
SATURN 12608424
SCANIA 12608424
STANDARD 19160
STANDARD CS1715
STANDARD EPS350
STANDARD LCS396
SUZUKI 3322078J10000
VAUXHALL 12608424
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Originally Posted by no grip View Post
I think Part No. should be:

BLUE PRINT ADG07262
BOSCH 0 232 103 079
BUICK 12608424
CADILLAC 12608424
CHEVROLET 12608424
DAEWOO 12608424
ERA 550812
GENERAL MOTORS 12608424
GMC 12608424
LUCAS ELECTRICAL SEB2004
METZGER 0903166
OPEL 12 608 424
OPEL 4810352
PONTIAC 12608424
QUINTON HAZELL XREV486
SATURN 12608424
SCANIA 12608424
STANDARD 19160
STANDARD CS1715
STANDARD EPS350
STANDARD LCS396
SUZUKI 3322078J10000
VAUXHALL 12608424
Thanks guys,
Much appreciated, particularly No Grip's latest contribution. You all really need to stop "Hiding Your Light Under a Bush". There is nothing learned by being right. So it is in every respect, worth challenging convention. "Otherwise, life is irrelevant and no one will ever know you existed".

I need to analyze the latest contribution and respond J.B. I am still convinced the issue revolves around the V.V.T. and Oil flow rates. But in light of the latest info, I must rationalize it, in order to justify it. It won't be long before I have some kind of answer as the plumbing work is due to be done in the next couple of weeks.
The differences between the Busso 3.2 and the 159 3.2 are not sufficient to justify the engineering expense. Unless it was all emission related. I have never failed to get better than factory quoted consumption figures from all my Alfa's. And I don't see why this should be any different. The oil galleries are an abomination in an engineering sense. I have found some more information about the sensors No Grip refers to and it appears to me there is considerable latitude in what is an acceptable "window" of operation before errors appear. That doesn't surprise me as the design criteria and the production figures never usually correlate. "Precision Engineering occurs when predicted theoretical expectations, match production realities". It is my view, the disparity between the two is too great, although I believe this to be a good engine.
Many thanks and kind regards,
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^^ yes makes sense to me.

I see you've been busy on that keyboard again Brian, Interesting reading about the difference in oil supply in the banks.
So are both exhaust oil control solenoids on the same pwm feed, and are both inlet oil control solenoids on the same pwm feed? If not, and they are all on individual pwm feeds, it does suggest to me that oil pressure is not as important as each oil control valve is on a different pwm signal to achieve correct cam angle feedback and this was the thinking the Alfa engineers had too so the oil pressure difference was not a consideration?

I quite agree though, a constant oil pressure feed to the vvt system would take one variable out (that being oil pressure always on the move up/down while the oil control valves are trying to adjust cam timing and this adds delay to the system control and feedback (too many moving averages so -to -speak).

A fixed oil pressure vvt system would have far tighter and faster timing control.

I know to achieve this is alot of work with having a new pickup in the sump and electric pump and new oil line feeds to the heads, but it would show the biggest results I'm sure.
J.B. & all

This is my third attempt at getting something of in response to No-Grips info - Thanks. It's not the P.C., I'm just not used to anything faster than 50 bauds.

Yes I now see where those cam position sensors are. Does anyone know if they are inductive or Hall - Effect? Just curious. I think I understand how it all functions now. I have some experience on Power Generation Rotor Angle Systems, but they are real time and this system is Predictive. So from what little I have to go on, this is my take. If anyone can point out glaring misunderstandings on my part, please feel free to correct me. I remain convinced that Oil Pressures are the main problem and hopefully, if I can get the picture loaded, you will understand where I am coming from. If it is irrelevant, why be so specific about the profile of the cam shaft active region, insofar as to quote 250 degrees for the inlet and 254 degrees for the exhaust. Everything is related to the overall performance of this engine, including oil flow rates, in my opinion.

There are two sensors on the cam shafts, off-set and it is the changing rate of the pulses derived from these, which the E.C.U. responds to when setting the cam shaft advance. Also the timing of the ignition, I believe.

Assuming a start position where the cam shafts are "locked". When the E.C.U. detects a changing rate of pulses from the crank sensors, it enable the inputs from the cam shaft position sensors. A fix period sampling timing is applied and it is compared with maps in the E.C.U. memory. The map which correlates to the rate of change of crank shaft derived timing pulses, which correlates to the rate of load change on the engine, is then "loaded into the E.C.U. timing routine. From this the E.C.U. knows when the pulse from the respective cam shaft rotational sensors are due; time elapsed. The cam shaft advance/retard do, as pointed out, function individually.

At the same time as when the cam shaft positional inputs to the E.C.U are enabled, the cam shaft Voids are "Unlocked", preparing the oil to fill the voids in the advance or retard direction, depending on the angle calculated by the E.C.U. from the maps within it's memory. When the timing sensor wheel, which I now
understand is connected to the cam shaft Rotor and thus the cam shaft proper, advances or retards across the rotational sensor face, for the respective cam shaft, a pulse is induced, which triggers the E.C.U. to "Lock" the cam shaft voids. The voids would have been filling between the period when they were "Unlocked" and the cam shaft Rotational sensor Pulse arriving at the E.C.U. This time will be proportional to the advance/retard determined by the E.C.U., from the changing rate of pulses from the crank shaft "Ring".

This process is continuous, perpetually locking and unlocking the voids with the continual change of load on the engine. Crucial to the correct operation of this process, is equal oil flow rates, from the galleries into the voids. That is why Ferrari use an accumulator as do BMW for their Vanos System and they don't run engine speeds of 20k. It is to sustain pressure to allow the timing to be accurately set during periods when there is oil pressure variation. I believe Ferrari and BMW have dedicated pumps just for their V.V.T. systems. And if it is good enough for these two prestige marques (finally got the spelling right), it ought to be good enough for Alfa Romeo. Nay - Mandatory.

Looking at the V.V.T. system, it seems to be generic. If so, is the Timing Sensor Wheel, "Keyed" onto the cam shaft rotor, or is it pre - adjusted in production? You will get the implication I am making! Either way, there has to be manufacturing tolerances. Over - tight and the development guys would never be away from the production line. In the early days of steam radio, Bit error rates were quoted so tight, that a few bits would cause a total loss of sync on P.C.M. systems. It should be no different with these type of devices; + or - errors in timing. However, The bias between oil pressures on both banks is so askew that, the system just can't optimize. Which is why I believe the economy figures are never met. And the restriction in oil flow for the left bank is so severe as to cause the timing chain tensioner system to allow slap.

I intend to banjo an 8 mm. pipe from the oil pressure pump, to the plug on the left hand bank gallery. Before and after pressures will be recorded and a shut off valve could be included to do continual A-B comparisons. Although it will not totally overcome the dependencies in flow rate for the advance galleries, it should improve it. And to balance the oil, left and right of the crack shaft bearings will be no bad thing. It will also get the oil pressure up at the lower timing chain tensioner more quickly; actually rising directly as the oil pump rotor starts to increase speed, a time when a few milli seconds can make all the difference to wear and chain stretch. It may also permit the use of a higher viscosity oil - food for thought?

My original idea is not abandoned, just circumstances are delaying it - Italy again. I think this simple mod will indicate the kind of improvements that should be achievable, with full modification. Or not, as the case may be. Who knows, it may flag something else up.

Included, I hope is a picture of the oil galleries. If this is to be believed then it is appalling. Unless of course the draftsman had to look after his five year old and gave him some crayons to keep him entertained. Also I include a picture of a high pressure oil pump, but have no information as to whether it is suitable. Anyone got any info?. It's from a Ferrari, or a Maserati Q.P. 226 inc. Also from a Selespeed. But not at that price from Alfa, The M.G.B's.

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that's a much higher pressure than needed oil pump, they deliver 50 bap pressure (750 psi) if it's from a selespeed system.

the cam wheels are usually keyed, but not always. the Twin Spark engine didn't have keyed cam wheels and VVT on the intake but required precisemeasuring of TDC and special cam locking tools (with cam profile cutout) for timing belt replacement.
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that's a much higher pressure than needed oil pump, they deliver 50 bap pressure (750 psi) if it's from a selespeed system.

the cam wheels are usually keyed, but not always. the Twin Spark engine didn't have keyed cam wheels and VVT on the intake but required precisemeasuring of TDC and special cam locking tools (with cam profile cutout) for timing belt replacement.
Thank you for this. I did have response from a German company stating, the pump is not capable of a long duty cycle, so would not be suitable as a back up. Thanks also for the info on the TS. I was just curious about the 159 cams. But for the time being, I will accept this may an issue that comes out of what I propose to do. Have had further thoughts on the supplementary pump. I think I will initially try to utilize what pressure is available from the mechanical pump and look to re-distribute it in a more balanced way. In saying this, after my initial plumbing exercise, I will look to link both banks oil feeds for the V.V.T. mechanisms. That way the inertia is reduced and pressures are normalized (Left bank V.V.T. pressure + Right bank V.V.T. pressure)/2. If it transpires that each cam shaft V.V.T. has its own sub gallery, then (L.B.In. + L.B.Ex + R.B.in + R.B.ex)/4. That should balance everything out. But I don't think they do, if the diagram is to be believed. Although I will leave the cam shaft bearings feeds alone. These connections can be made inside the timing chain front cover without the need for bulk head feed through connections. But again that is a little way down the line. Hopefully the initial mod can be completed in the next week or two, but Paul is very busy at the moment.
kind regards,
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I fear you might end up just blowing lots of oil seals with that F1 pump.

The cam phasing is dictated by the difference in the oil pressure in the advance/retard chamber of the phaser as supplied by the solenoid, so increasing the maximum pressure is not really going to have much effect on VVT for normal running.

You're probably correct in thinking a quicker build up of oil pressure from a cold start is of benefit but would probably be more beneficial as a separate system, I even think kits are already available. I'd need to be convinced that the disadvantages of replacing oil seals and premature wear of relief valves etc. would offset any advantage in chain wear.

There's no direct relationship between cam position and phaser angle, it's determined by the ECU map based on lots of parameters provided by TPS, MAF, MAP, Lamda sensors, etc.. The ECU map governs the phaser angle, Injection duration, etc.. based on miles and miles of testing.

There's always room for refinement of the ECU maps and the engines are a mass produced commodity so Friday afternoon examples are out there. The engine's improved quality of production and tolerances using modern processes and materials probably explains why they are superior to the Busso in every department.

MPG is no real measure of engine efficiency since it is determined from very idealised testing of the whole car. If you put an Alfa'd Alloytec in a Busso'd GTV you'd get some impressive increase in performance out of the box.
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Hi, yes I see the gallery reduces on that diagram for just the oil control valves in the left hand bank, well spotted.
I would bet thats not a design fault, but an attempt to maintain a balanced pressure between the two sides (the left being further from the pump).

Flow is not as important...unless your trying to oil the chains with flow from the drains...
(I feer I may have opened another can of worms!)

Let us all know if you need any help finding a suitable electric oil pump.
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I fear you might end up just blowing lots of oil seals with that F1 pump.

The cam phasing is dictated by the difference in the oil pressure in the advance/retard chamber of the phaser as supplied by the solenoid, so increasing the maximum pressure is not really going to have much effect on VVT for normal running.

You're probably correct in thinking a quicker build up of oil pressure from a cold start is of benefit but would probably be more beneficial as a separate system, I even think kits are already available. I'd need to be convinced that the disadvantages of replacing oil seals and premature wear of relief valves etc. would offset any advantage in chain wear.

There's no direct relationship between cam position and phaser angle, it's determined by the ECU map based on lots of parameters provided by TPS, MAF, MAP, Lamda sensors, etc.. The ECU map governs the phaser angle, Injection duration, etc.. based on miles and miles of testing.

There's always room for refinement of the ECU maps and the engines are a mass produced commodity so Friday afternoon examples are out there. The engine's improved quality of production and tolerances using modern processes and materials probably explains why they are superior to the Busso in every department.

MPG is no real measure of engine efficiency since it is determined from very idealised testing of the whole car. If you put an Alfa'd Alloytec in a Busso'd GTV you'd get some impressive increase in performance out of the box.
Thanks again for this.
First point, absolutely right on that pump. Just looking at finding one which is up to the job for long term oil pressure supplementation. Or I could put adjustable outlet pressure switches, two in series as a precaution and use the pump to charge an accumulator to 6 bar. But then it is all getting too complicated. I think you said earlier, if the mechanical pump wasn't up to the job then GM would have just changed it. But it was Alfa that went for the V.V.T., adding extra load, but retaining the original pump - I believe. However, the situation is fluid. Not having direct access to workshop facilities, before I tackle the job, I need a degree of faith in what the results may be from any changes. And from that, I mean I want to try to make improvements without too many extras. So current thinking is to re- distribute the existing pumps oil pressure, more evenly. I think this covers your second point as well.

Your fourth point has always been a bone of contention for me. Production techniques are invariably not for the customers benefit, although obviously we do in most cases. But to get production costs down and thus profit margins up. One can make the unworkable, work, with software. But that can simply hide poor engineering practices. And on too many occasions, production tolerances have simply been an excuse to align equipment such that it is "in Spec". But they don't stay in spec for very long. If mechanical alignment is optimized, then applying software techniques to change operating parameters, such as across the range torque figures, emissions etc, will result in greater consistency of performance, for longer. But if one has ruddy great holes in your software program, namely, a limited amount of data to cover a wide spectrum of performance parameters, one doubly needs to ensure the devices one is trying to control are "Optimized" properly. This is where I think this engine comes unstuck. Which brings me to your second point. Yes it is the pressure in the advance/retard voids and increasing it makes no difference; pressure limits accepted. It is not that which concerns me. It is the disparity in pressures between left and right bank that is the issue. Which a poor software program cannot disguise. Although it would probably be "adequate" if the mechanical alignment: in this I include pressure distribution, were optimized.

If we consider that peak torque occurs between, let us say 100/120 degrees after top dead center. the power distribution in a 60 degree V is 120 degrees apart. Let us suppose it is the right bank which has just executed a power stroke. If the power stroke of the left bank is delayed, because, the advance/retard mechanism is not responding at the same rate as the right bank, i.e. slower to fill, then the "overlap has been been reduced as the torque is falling off from the right bank, before the left bank power stroke occurs to support it optimally. Thus lower mean power/torque output from the engine. So it is imperative that mechanical timing for the engine is as accurate as possible, before the application of software control, such that the E.C.U. applies. Because of what I see as the engine performing of the "Cusp", even when new, failure codes are more likely to occur earlier in the engines life than they should, if pressures were optimized. The figure 120/120 is hypothetical as I don't really know exactly where it is with this engine.

I omitted all the other functions the E.C.U. has to address for brevity's sake. But all they will do is modify the setting/timing, the E.C.U. applies to the appropriate advance/retard characteristic. Paul has confirmed to me, the positional sensors are "Hall-Effect", solid state proximity switches, operated when the "Timing Sensor Wheel" passes across it's face. This, T.S.W., as I understand it is attached to the Rotor and is able to rotate by 50 degrees, the full extent of the advance/retard mechanism. It's movement is proportion to oil pressure and oil pressure duration - before the valve closes. If they are not identical on both banks, the lower pressure on the device (left bank) has to be applied longer, to assume the same position/angle, dictated by the E.C.U. as the higher pressure driven one (right bank). The increased time is directly related to the rotation of the crank shaft and thus when detonation occurs, although the advance/retard characteristic is correct with respect to the E.C.U. setting, it is beyond the appropriate detonation time required to support the previous cylinder which fired on the right bank. So the overlap is reduced and specific power/torque is less than optimum. If one was able to get a storage oscilloscope or data analyzer on the outputs of the T.W.S.'s it would confirm what I believe to be the truth. No change in advance and the pulses should be 120 degrees apart. change the throttle position and they should move proportionally to the change in engine advance/retard. But then they should re-assume the 120 degree position, if the new position is held. But they should do this quickly. I do not believe they do, because of the pressure differences between left and right bank V.V.T.'s.

It is true, this will occur in any case as one changes throttle position. But it should not be on a whim, because oil feeds are not balanced.

The relationship to the cam position is linked to phaser (Rotor) because they are physically connected, to which is also connected the T.W.S. Yes, the setting they adopt is dictated by the E.C.U. **The Phaser is the Rotor of the V.V.T. The Stator is simply the timing chain sprocket within which the phaser, thus the cam shaft and the T.W.S. can rotate, up to 50 degrees**

Your observation about always room for improvement in E.C.U. maps is true. But real improvements will always be encumbered by lack of mechanical optimization.
Thank you for your input, it stimulates the old gray matter. I love my Q4 and just want to understand as much about it as possible. The work on the rear arms and differential has transformed the car, it's really superb. But I just feel, the engine is not at it's best. And I don't think it ought to be too difficult to get right. I have no access to software. However, with regards to the mechanicals, software performs better, when the mechanicals are correctly aligned.
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The vvt 3.6 versions of the same gm v6 seem to suffer the same odd timing chain issues, sometimes very early in their lives. There was a newer chain and sprocket set released with more smaller links and teeth which is supposed to be quiter but doesn't seem to have cured chain issues, especially in engines serviced at standard intervals.

I was also gooling for brushless oil pumps, i found this one which seems good:
Engineered Machined Products : Press Releases : EMP Launches Advanced Brushless DC Electric Oil Pump (Model OP40i)

And this little one which might be too small? Maybe if a pressure switch could be fitted to the accumlator to trigger it via a solid state relay: Brushless Electric Start/Stop Oil Pump | SLPT Global Pump Group
If the oil pressure collected via the pump bypass was also routed to the accumulator, with one way valves on both accumulator inputs, then maybe this little pump would be enough?
I'm looking forward to your test results sizewell
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what's the hole size in the VVT actuator? the ones I've seen ahve about a 2mm hole on the intake side, so gallery size is irrelevant
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Originally Posted by alfafanboy View Post
The vvt 3.6 versions of the same gm v6 seem to suffer the same odd timing chain issues, sometimes very early in their lives. There was a newer chain and sprocket set released with more smaller links and teeth which is supposed to be quiter but doesn't seem to have cured chain issues, especially in engines serviced at standard intervals.

I was also gooling for brushless oil pumps, i found this one which seems good:
Engineered Machined Products : Press Releases : EMP Launches Advanced Brushless DC Electric Oil Pump (Model OP40i)

And this little one which might be too small? Maybe if a pressure switch could be fitted to the accumlator to trigger it via a solid state relay: Brushless Electric Start/Stop Oil Pump | SLPT Global Pump Group
If the oil pressure collected via the pump bypass was also routed to the accumulator, with one way valves on both accumulator inputs, then maybe this little pump would be enough?
I'm looking forward to your test results sizewell
Thank you for this. I shall give the people in Cramlington, Northumberland a ring later, theirs looks really good.

You relate to problems related to chains being redesigned and still suffering failures regardless of regular servicing. From that I take it oil changes and recommended grades were adhered to. And yet there are still those who doggedly cling to the notion that gallery sizes are irrelevant? I wonder if Mclaren designers fret over this issue, being as so little credence is given to this issue with Alfa.

If I fill my empty water Butt with my finger over partially over the end of it, it will take considerably longer to fill, Pressure in the hose will have gone up, but flow rate will have gone down. 1/2 the diameter of a pipe and the cross sectional are is 1/4. True pressure has increased, but one is not just supplying a single outlet at half the diameter. On the right, one is supplying three. If there were four outlets, there would be no pressure change, but the flow rate is one quarter the original in each outlet. Then divide this by three again for the left bank and throw in a chain tensioner for good measure. But one is now introducing a pressure reduction as the tributary galleries are the same diameter as the primary left hand bank main arterial gallery. So pressure has reduced, to a degree proportional to the bleed of oil through the tensioner lubrication valve and the cam shaft bearings. But the water Butts, which are the cam shaft voids are still the same and they are going to take more time to fill. certainly much more than those on the right bank.
I said some time ago, I got what I described as a "Ferrari like Kick", when I held the throttle in second or third gear. It was a rate of acceleration that was more noticeable than the norm. That I now believe to be a symptom of the inaccuracy which exists in the V.V.T. system, principally because of imbalances in the oil pressures/flow rates which are a consequence of the poor gallery design.
Kind regards and many thanks
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The chains were changed in the GM versions around 2008 - not sure about Alfa. The Primary 11 pieces Morse chain and roller Secondary chains were changed for 5 piece Morse chains for both Primary and Secondary. Presumably for cost reasons rather than anything else. Manufacturers see these as service items (although don't advertise it) since anything over 100k miles is likely to be out of warranty so not their problem. It saves on servicing time/costs not having to replace the cam belts, tensioners and idlers etc. every 36k.

I doubt oil pressure will have much affect on the chain life since it takes very little oil to separate the chain from the slider surface. It's contaminants in the oil that cause the deterioration of the chains and slider surfaces so if the oil is changed more frequently than the manufacturers recommended (cheapest) interval there's a good chance that chain life will be extended.

Apologies for rubbish picture..
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The chains were changed in the GM versions around 2008 - not sure about Alfa. The Primary 11 pieces Morse chain and roller Secondary chains were changed for 5 piece Morse chains for both Primary and Secondary. Presumably for cost reasons rather than anything else. Manufacturers see these as service items (although don't advertise it) since anything over 100k miles is likely to be out of warranty so not their problem. It saves on servicing time/costs not having to replace the cam belts, tensioners and idlers etc. every 36k.

I doubt oil pressure will have much affect on the chain life since it takes very little oil to separate the chain from the slider surface. It's contaminants in the oil that cause the deterioration of the chains and slider surfaces so if the oil is changed more frequently than the manufacturers recommended (cheapest) interval there's a good chance that chain life will be extended.

Apologies for rubbish picture..
Thanks N-G,
I'm not implying the chains are failing due to lack of lubrication. It is the chain stretch issue which, I believe is exacerbated by lack of sufficient oil pressure, to keep the lower one taut. This was the original basis for the thread. But, the more I looked at the issue of it and engine performance, the more I became suspicious of the oil pressure distribution, critically whilst maintaining flow rates. If the system did not bleed through the bearings and the V.V.T., the the whole of the block would assume a working pressure that may sustain sufficient tension on the chains.

But sticking with the V.V.T. for the moment, it looks like they are Siamese-ed on each bank. I can only judge this from the pictures I have. If this is correct and indeed as I now understand all four operate independently, it is not four voids to be filled at any one time, but eight. ** For each cylinder, both the inlet cam shaft and the exhaust camshaft are adjusted simultaneously to optimize the timing to that which the E.C.U. dictates. As has been commented recently, the cylinder head orifices are about 2 mm. in diameter. The only thing that can sustain the correct fill rate for the voids, to maximize the engine response time is Oil Pressure ""AND"" Flow Rate**.

It is like charging a battery or a capacitor. The charge (Flow) rate is dependent upon capacity. A large battery; higher Ampere/hour capacity takes much longer than a small one. The batteries/capacitors have not changed is size, but by reducing the flow rate, the time it takes to fill them is extended. The charge rate of a battery or a capacitor is exponential. With the V.V.T. system, one wants to avoid that. But, I contend Alfa Romeo have introduced an exponential to the fill rate by neglecting to maintain pressure and flow rates. Ideally, Both banks V.V.T. should be fed directly from the oil pump. That way the fill rate (exponential element) is minimized and they would be "Identical for both Banks". One must remember, the voids are continually adjusting and by definition their "Set Volume"; greater the advance/retard change, the greater the amount of oil required to fill them; dV/dT. Therefore causing a gallery pressure to drop, which I would argue does not have time to recover to avoid introducing an exponential. The right bank has a much better chance, being as its V.V.T.'s are directly off the main gallery at the input of the block.

I don't suppose you have a picture of the front of the engine, from which the picture of the front cover you sent me came? Also, does anyone know the size of the thread for the oil pressure switch on the block? It is becoming increasingly clear that all four V.V.T.'s must be fed from a common point, nearest to the block pump or via a supplementary pump. Also, feeding the block left and right, should have a marked improvement on the lower timing chain tensioner. A supplementary pump would be ideal as the pressure could be set to optimize response time of the V.V.T.
Thanks for the pictures.
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Don't forget that tensioner pressure is exerted by the spring, the oil is just a damper so doesn't really need any pressure.
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Don't forget that tensioner pressure is exerted by the spring, the oil is just a damper so doesn't really need any pressure.
Sorry N-G, don't buy that one. The spring is their to provide some tension on the chain, when the engine is switched off and at low pressure when at tick-over. Just as the Busso spring provided tension. But the oil pressure backed it off on the Busso when the engine started. Two totally differing philosophies. Also lubrication of the front face of the lower chain tensioner is by a valve, which discharges under pressure. The e-disc states, there is a valve to maintain oil pressure on the tensioner; it's in the text.
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Interested to know what the benefit would be of varying chain tension with oil pressure. A spring seems like a much more reliable device for this sort of application.
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The valve is simply a hole in the tensioner & sliding surface. The spring is very stiff and more than capable of maintaining the pressure on it's own. The valve primarily ensures that the oil system pressure is maintained rather than the tensioner pressure, although there will be some contribution. The primary function of the oil is to provide damping resistance to the tensioner to prevent too much chain lash.
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The valve is simply a hole in the tensioner & sliding surface. The spring is very stiff and more than capable of maintaining the pressure on it's own. The valve primarily ensures that the oil system pressure is maintained rather than the tensioner pressure, although there will be some contribution. The primary function of the oil is to provide damping resistance to the tensioner to prevent too much chain lash.
Sorry N-G, still not buying it. Below are quotes from the "Descriptions" and "Procedures" sections of e-disc.

We have been here before, with the Oil Pump Pressure release Valve and Spring, where observations were made to the effect, the spring may have weakened, further exacerbated perhaps by temperature. If anyone seriously believes this engine functions on springs, then the conundrum about 48,000 miles timing chain stretch should never have attracted such intense consideration, for so long. And Alfa, and G.M. could have saved themselves the trouble of creating oil ways for the tensioners. Just fit a bigger spring.
Work is going ahead, despite yet another "Rabbit from the Hat". I am starting to suspect there are those who are trying to defend the indefensible. The oil pressures and flow rates of this engine are not worthy of a first year engineering student. However, I am still searching for any reference to "Timing Chain Spring Tensioner's"

Quote "Hydraulic tensioners
All the hydraulic tensioners are fitted on the crankcase or the head with a gasket in between that has the task of keeping an oil reserve inside the tensioner to ensure correct operation during starting.

Primary chain hydraulic tensioner" Un-Quote, e - disc.



Component

Fastening

dia

Value (daNm)

Validity


Primary chain hydraulic tensioner

Bolt

-

2.3

3.2 JTS


- Release the hydraulic tensioner so that the piston pushes the pad.

- Place the oil pump bolt removed previously in position.

- Prepare the hydraulic tensioner for the primary timing chain following the instructions given below.

- Insert the piston in the hydraulic tensioner body.

- Compress the piston in the hydraulic tensioner body rotating it and locking it in the end of travel position.

- Slowly release the pressure on the hydraulic tensioner piston.


The hydraulic tensioner piston should remain in the compressed position.



1. The crankshaft should be positioned so that the ball (1a) stamped on the primary timing chain drive gear is aligned with the ball (1b) stamped on the oil pump.

2. Fit the primary timing chain.


Position the chain so that the following conditions are adhered to:

- the grey mesh (2a) should be aligned with the ball (2b) stamped on the drive gear;

- the yellow mesh (2c) should be aligned with the ball (2d) stamped on the idler pulley for the left cylinder head;

- the yellow mesh (2e) should be aligned with the triangle (2f) stamped on the idler pulley for the right cylinder head.



3. Place the fixed pad (3a) in its housing and secure it using the bolts (3b).


Component

Fastening

dia

Value (daNm)

Validity


Main timing chain fixed pad

Bolt

-

5.8

3.2 JTS


4. Place the hydraulic tensioner (4a) pre-loaded previously in its housing complete with a new gasket and secure it without tightening the bolts (4b).

- Check that the gasket is correctly positioned.

- Tighten the hydraulic tensioner retaining bolts.


Component

Fastening

dia

Value (daNm)

Validity


Primary chain hydraulic tensioner

Bolt

-

2.3

3.2 JTS


- Release the hydraulic tensioner so that the piston pushes the pad.

- Prepare the hydraulic tensioner for the secondary timing chain for the right cylinder head following the instructions given below.

- Insert the piston in the hydraulic tensioner body.

- Compress the piston in the hydraulic tensioner body rotating it and locking it in the end of travel position.

- Slowly release the pressure on the hydraulic tensioner piston.


The hydraulic tensioner piston should remain in the compressed position.



1. Rotate the crankshaft until the ball (1a) stamped on the primary timing chain drive gear is aligned with the ball (1b) stamped on the oil pump.

1. Fit the right cylinder head secondary timing chain.


Position the chain so that the following conditions are adhered to:

- the black mesh (1a) should be aligned with the ball (1b) on the idler gear;

- the back mesh (1c) should be aligned with the triangles (1d) and the letters "R" stamped on the phase transformers.



2. Place the fixed pad (2a) in its housing and secure it using the bolts (2b).


Component

Fastening

dia

Value (daNm)

Validity


Secondary chain fixed pad

Bolt

-

2.3

3.2 JTS


3. Place the moving pad (3a) in its housing and secure it using the bolt (3b).


Component

Fastening

dia

Value (daNm)

Validity


Secondary chain moving pad

Bolt

-

2.3

3.2 JTS


4. Place the hydraulic tensioner (4a) pre-loaded previously in its housing complete with a new gasket and secure it without tightening the bolts (4b).

- Check that the gasket is correctly positioned.

- Tighten the hydraulic tensioner retaining bolts.


Component

Fastening

dia

Value (daNm)

Validity


Primary chain hydraulic tensioner

Bolt

-

2.3

3.2 JTS


- Release the hydraulic tensioner so that the piston pushes the pad.

1. Place the oil seal (1a) in its housing
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