Author Topic: 3.2 JTS Unanswered Questions!  (Read 1281 times)

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Ascari32

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3.2 JTS Unanswered Questions!
« on: August 15, 2021, 05:19:36 PM »
Many will not understand the endless fascination this engine/project has; and continues to generate, for me.

There are so many technical innovations, encapsulated within this engine, it isn’t difficult to see why it took Alfa so long to bring it to market.

I think I understand why the Vauxhall and SAAB, 2.8T versions are probably more reliable, not least because they have VVT on the inlet valve timing, whilst the exhaust timing remains fixed. Their Turbos provide an external EGR function, which is much more predictable and their twin rotors whilst utilising spent exhaust gas energy, also simplify the exhaust system.

But, it is what it is! An Alfa; and much more sophisticated than all my previous Alfa’s.

I have just spent many hours researching “Engine Braking” and the effect NVO has on drag. It is clear to me it has a tremendous influence on braking efficiency and it leads me to believe I need to update my brakes.

For engine braking to be effective, the engine, when the throttle is closed, must exert a counter force upon the drive system. In doing so, this must transfer energy to the rear faces of the timing chain system and thus place considerable force on the timing chain tensioners - trying to drive them back into their housings.

Under normal circumstances, these tensioners are simply taking up slack! However, whenever there is “Reverse drive” - force coming back from the gearbox - the pressure is enormous and on inspection the internal “ratchet” of the tensioners, which adjust as the chains stretch, do not seem man enough. Indeed, I have seen pictures where the “Pin/Peg” inside the tensioner has sheared off.

This scenario is exacerbated by virtue of Alfa’s choice of valve timing, ie. NVO.

Beyond knowing what the static valve timing angles are when the engine is switched off, I cannot hazard to guess what they may be dynamically. All I can say is, with conviction, it creates a great deal of drag when lifting off the throttle.

But, according to a lot of research material, NVO can play a great role in reducing pumping losses, increase engine efficiency by 7% - according to one eminent study - and improve performance on light load, whilst reducing emissions.

PVO however, is not so good at dealing with emissions. But that can be effectively dealt with by Catalytic converters and constant Lambda monitoring of exhaust manifolds. It seems also, Alfa got it wrong wrt pumping losses as the valve timing creates substantially more than when NVO is replaced by PVO. Throttle response is dramatically improved.

I have watched so many YouTube videos of 159/Brera, where the sounds of various exhaust systems have been compared. Whilst many have been “Aurally Impressive”, everyone that I have viewed have demonstrated varying delays in engine “Pick -up”: where the driver, stabs the throttle, the engine responds meekly, pausing, then finally getting going, picking up.

To what do I attribute this too? So many things are interrelated, all having a knock on effect and all, in this instance; imho, having a detrimental effect on performance.

1.) Poor VVT response time - unless valve timing changes rapidly, the engine will not respond quickly to throttle inputs. This is categorically due to poor oil flow/pressure within the engine.

2.) Manifold Cats - the restriction they present to exhaust gas flow, guarantees any potential for scavenging is greatly reduced.

3.) Twin Cat - neglecting the appalling fabrication work, conjoining the two paths after the catalysts, where the exhaust diameter increases, ensures no negative pressure can exist to assist in scavenging. Furthermore, the restrictions, the canisters present to the forward flow of exhaust gases,  is applicable also to reverse flow, further attenuating whatever scavenging Alfa’s choice of valve timing could create.

4.) A performance engine, such as the 3.2 JTS; particularly given its 11.2:1 compression ratio, should have a healthy VVT range, to generate good torque characteristics across its range. Valve timing of the order of - inlet 6deg. to 10deg. BTDC: exhaust the same, ATDC. However, the 3.2 JTS Exhaust static is 9deg. ATDC, their Inlet is 11.5deg. ATDC.

The VVT range of the 3.2 JTS inlet is 50deg., from -11.5deg. ATDC to 38.5deg. BTDC. Thus as far as performance is concerned, 11.5degs. do not come into the equation. And if one accepted a static timing advance  of 6deg. for the inlet valves, the effective range of the inlet VVT is 32.5deg. compared to a fixed valve timing engine, not very impressive at all!

However, the Exhaust VVT angles by comparison seem almost normal, from 9deg. ATDC to 41deg. BTDC. Also, it is undestood, the exhaust camshaft is disproportionately advanced on start - up, to assist in Cat warm up, via the NTC sensor in the water jacket of cylinder 2 exhaust port.

So it appears to be the inlet camshaft that is the main culprit with respect to NVO and its lack-lustre range.

5.) Poor VVT alignment of rear bank exhaust camshaft position sensor.

"Fact" - Bosche Specify their Position Sensors, which are "Hall Effect Devices", should be within +/- 0.5deg. of cutting the sensor field at 90deg. The rear bank is somewhere in excess of 10deg. out of limit. This has come about because the front cover to which it is mounted was not recast with the provision for vvt on the exhaust camshaft and thus the "Boss" is obstructed by another fixing which restricts correct alignment. The two front bank sensors and the rear bank inlet camshaft sensor are correctly aligned!

If they are not aligned to within this tolerance, the output levels quickly fall, resulting in timing errors and potentially the ECU failing to detect the "Trigger Pulse". Combine this with timing chain stretch and poor rear bank oil pressure and it is hardly suprising it is always the rear bank exhaust camshaft that signals failure first!

6.) Flats" cut across the dividing walls of the VVT Solenoid Supply, Advance and Retard Ports. The consequence of this is, the inability of the ECU to "Lock the Angle" chosen, such that the correct valve timing angle can never be maintained.

This causes the exhaust camshaft to be driven away by the internal spring pressure forcing oil from the advance port and into the drain, ably assisted by the rotating face of the cam lobe exerting pressure on the camshaft phasor sprocket.

This is equally true of the inlet camshaft which, although having a weaker internal spring - because cam rotation normally drives it in the retard direction, but in this instance is more readily "Shifted" from its position by vitue of the cam face/valve inertia forcing the oil out of the rotor, across the flats and into the VVT drain.

"So the valve timing angles, if they are ever set by the ECU locking the ports, are never held in position because these flats allow the oil to be forced out and their angles change from the optimum."


Compounding this - and a hint of the consequences of it can be detected in video clips; whereby there seems to be a delay before the engine revs up is: whenever the ECU is operating the solenoid valves, the flow rate into the vvt rotors is reduced as hydraulic oil from the inlet port, bridges these flats and goes straight to the drain and back to the sump, via the head. This occurs, regardless of whether the ECU wants to advance or retard either the inlet or exhaust camshafts!

I shall not advance the case for fitting Colombo Bariani camshafts other than to say, I believe they recognised the issue of Valve/Piston interference is no different from that of any fixed valve timing engine, ie, there is sufficient clearance to enable a greater range of valve timing without interference, thus they increased the duration from 254/250 to 278/278, whilst maintaining the lift as standard. This has eliminated the NVO and created an inlet valve timing advance of 50.5deg. Maximum.

At the same time the range of the exhaust timing is now 23deg. ATDC to 27deg. BTDC. By the same token, increasing the static angle from 9deg.ATDC to 23deg.ATDC has meant that, on start - up, the NTC sensor needs to use a greater proportion of its temperature range, before the ECU finally rotates the exhaust camshafts back to a normal angle, and thus the "Noisy Period" of pre - heating the Catalytic converters is somewhat longer. Componding this is of course, the fact that there are no longer  any Manifold cats to preheat and thus it is more noisy than hitherto, where the cats would tend to muffle the sound during pre-heating. 
« Last Edit: August 15, 2021, 07:15:18 PM by Ascari32 »

Alfatango

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Re: 3.2 JTS Unanswered Questions!
« Reply #1 on: August 15, 2021, 10:12:12 PM »
Ascari you are a born engineer. Some people are narurally wired like this.

So the engine has an engine braking system when you let go of the accelerator? That would explain the noise it sometimes makes when it's decelerating ta bit more vigorously rather than letting go of the accelerator on the freeway.  I thought it was my just my engine but that would make a lot of sense.
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Ascari32

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Re: 3.2 JTS Unanswered Questions!
« Reply #2 on: August 16, 2021, 02:13:41 AM »
Yes, it can definitely be heard and fitting “Super - dooper” exhaust systems can’t hide it - in fact it makes it more obvious. Being more obvious, it is touted as being a virtue, aftermarket manufacturers “Big - up”, which I don’t understand!

But again, returning to unanswered questions - “Why has Engine Braking reduced when valve timing changed?”

The old Twin cams had two twin choke Weber’s, Solex or Delortos  fitted, which meant each cylinder was presented with a massive restriction, when on overrun as each butterfly closed off every inlet tract. Another reason why they sound so glorious.

The Busso 2.5 V6, when fitted with six down - draught Delorto’s; if anyone managed to balance them, made sounds from another world.

But with modern engines, came common manifolds, where inlet tracts share a common plenum, and thus “All was Lost”.

Beemers, I believe, have individual butterflies, but BMW choke the hell out of their engines and still do not compare with the sound of the old Alfa’s.

A Quad 3.2 Bussos, with Throttle Bodies, is as close as one can get now, although they sound lovely. The same would apply to the 2.5 or 3.0 variants.

However, I digress - back to the 3.2 JTS!

If one “Scopes” the cam position sensors, one would see the camshafts rotating back to wards their preset angles at a rate which cannot be arrested by the ECU. This is due to their internal springs, the thrust faces of the cams, the lack of oil pressure to control their movement and the flats which are cut across the solenoid supply/advance/retard ports.

Consequently, the NVO, plays an important part in the engine braking the 3.2 JTS suffers from. I am not saying engine braking is entirely a bad thing. However, in this instance it is excessive and has a negative impact on the longevity of the timing chain system.

Alfa’s valve timing creates an excessive “Vacuum Load”, which the reverse drive from the transmission system has to overcome on lift - off. The force this generates has to be borne by the timing chain system and without adequate oil pressure, forces the tensioners back into their housings, driving oil out of the port which is behind the lower timing chain nylon guide/chain follower. If engine braking is excessive, depending upon the drivers style of driving, no oil remains to buffer the impact against the mechanical internals of the lower timing chain tensioner.

This exacerbates timing chain guide wear, chain stretch and failure of the timing chain tensioner. It cannot be avoided as the oil supply for the lower timing chain tensioner is at the most distant point of the oil supply system, so it is pretty low.

Importantly, the valve/orifice supplying oil from the gallery, is much smaller than the orifice which faces the chain guide. This is an orifice to lubricate the chain, and not a valve! So there is little to prevent the tensioners oil cylinder from being evacuated, until the piston comes up against the “Mechanical Stop/Auto adjust Mechanism”.

In the worst case scenario, I have seen the “Pin/Peg” sheared off as the force exerted was so powerful!

PVO, negates the degree of vacuum that can exist to produce excessive drag/engine braking. And because, a considerable amount of PVO exists operationally with performance engines, arresting the uncontrolled release of valve timing angle, such that the ECU can still control it makes a tremendous difference.

In this instance, the C.B. cams provide for the PVO and modifications to the VVT solenoid valves, inhibit the uncontrolled drain of the VVT Phasor Rotors.

« Last Edit: August 17, 2021, 07:02:08 PM by Ascari32 »

Ascari32

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Re: 3.2 JTS Unanswered Questions!
« Reply #3 on: August 18, 2021, 06:36:57 PM »
"The old Twin cams had two twin choke Weber’s, Solex or Delortos  fitted, which meant each cylinder was presented with a massive restriction, when on overrun as each butterfly closed off every inlet tract. Another reason why they sound so glorious."

I feel I must clarify the context of this statement. The old twin cams have twin duplex chains which from time to time need to be adjusted. Slack would acrue over a period of thousands of miles. So the timing chain tensioner "Nut" would be loosened, after the cam cover was removed and in my case, the long shank of a hammer would be used to "Lever" the slack out - pushing forward the tensioner sprocket. It seems so long ago noe - actually it was. Whilst holding the force, the "Nut" would be retightened. The flex of the shank ensured one didn't apply too much force and cause uneccesary strain on the chain system.

The point being of course, there was no question of the timing chain "Giving - up", when on overrun, despite the indivdual butterflys of each inlet port. And to my knowledge, Negative Valve Overlap was never a feature of these twin cams. Oh that the JTS had a system as strong as those engines! 

Alfatango

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Re: 3.2 JTS Unanswered Questions!
« Reply #4 on: August 18, 2021, 07:28:42 PM »
I don't see a point of fitting brembo brakes and than putting in an engine braking system. It seems like Alfa like trying a lot of things that get implemented with not much testing ie the selespeed technology. Its pretty good when everything is in peak condition but it seems like there is little redundancy systems in place so any issues cripple the car. Hence why you see so many old alfa being wrecked for spare parts after only 2 decades on the road. Its high technology but very sensitive. If it lead to a massive increase in performance or reliability than that would be great but it doesnt seem to add up.
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Ascari32

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Re: 3.2 JTS Unanswered Questions!
« Reply #5 on: August 18, 2021, 09:17:54 PM »
A.T., the "Engine Braking" is not a system, it is a consequence of the attention Alfa were paying to having the lowest emissions vehicle and achieving the highest award for their car.

Unquestionably, they would have recognised the impact of negative Valve Overlap as it was specifically designed to "Contain the unburnt HC's from around the piston ring/piston/bore interface and promote the swirl characteristics, in aid of stratified charge techniques". But, the weakness of the timing chain system was an unkown factor. And thus, NVO has a great influence the engines overall performance, and not in a positive way!

In essence, the VVT system should always been under the control of the ECU. But restrictions reduce sufficient flow capacity to maintain oil pressure,  beyond them! In particular the lower timing chain tensioner and more generally, the rear bank.

The front bank can "Live with" its restrictions because it is supplied first from the output of the Cooler/Filter assembly. Also, the gallery of the front bank is huge, therefore flow rate can be sustained, without suffering pressure reduction.

However, the VVT system fails to hold the camshaft angles, after the ECU has chosen them. It is this factor which increases the impact of NVO.  Consequently, the resultant performance is less than it should be.

But you are right, there was too much going on and not sufficient control and supervision of the project.

If they want to succeed, they need to stop being the "Industry Test Facility",for inovation, as other manufacturers benefit by learning from their mistakes and avoid making the same "Cock - ups".

 

Alfatango

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Re: 3.2 JTS Unanswered Questions!
« Reply #6 on: August 19, 2021, 01:47:16 PM »

If they want to succeed, they need to stop being the "Industry Test Facility",for inovation, as other manufacturers benefit by learning from their mistakes and avoid making the same "Cock - ups".


I think its an Italian mindset thing. Its the same reason Ferrari in f1 almost always get the pit stop calls wrong nowadays. Mercedes nails them. Same with the engineering.

A good example of this is the collaboration of bmw and toyota on the supra. The japanese were suprised at how much the germans cared about chassis dynamics. The germans were suprised at how much the japanese were focused on ensuring the reliability of each bolt.

Alfa know that they need to stir the emotion so the owners stir their wallets. So focusing on the reliability of each area/system is a secondary concern. The 159 seems like an attempt at that by outsourcing the engine and gearbox. Not sure where the awd system came from. It seems like a car that took alfa away from the cheap 156 platform and was an in between for the new giulia platform being rwd and ferrari engined.
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Ascari32

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Re: 3.2 JTS Unanswered Questions!
« Reply #7 on: August 19, 2021, 04:05:11 PM »
There is much in what you say. But it appears to me, outsourcing; Alfa's interpretation, means engineers can put their feet up and sit on their hands.

To put it bluntly, I think they are a bloody disgrace and have been for decades.

I have been involved in development work for decades, where boxes in engineering departments were full of prototypes, each one "cast" into the box when it was found not to work and completely different design would take it's place; it too cast into the same box if it did not work.

It seems, Alfa engineers, took their first prototyle and put it into production, regardless of whether it worked or not!

It was Alfa who introduced the Quad Phasors to the 3.2 JTS because the engine had to disguise the fact that it was a Holden.

But, whilst Alfa claimed they designed their own heads for the 3.2 JTS, that just is not true! They modified the Holden cast to accomodate the quad VVT system and the JTS pump.

But SAAB and Vauxhall used this engine for their 2.8 Turbos. However, they retained the variable valve timing on only the inlet camshaft - the exhaust cam had fixed timing. This is significant as the vvt system demands substantial oil and constant pressure. The fixed valve timing on the SAAB and Insignia exhaust camshafts, only required sufficient oil for camshaft bearings and hydraulic tappets.

The consequences of this is, given the front and rear banks are "Off - set" by the position of the con - rods on the crankshaft, the "Cast - in", rear bank oil gallery is smaller in diameter, its union with the front bank main oil gallery, at the centre of the Vee does not align, and the "Step - back of the rear bank results in the feed from the block, up to the rear head being mis-aligned, causing a massive restriction - certainly when it comes to maintaining oil flow and pressure.

Alfa tried every which way to resolve it; small orifices through the cylinder head gaskets, non return valves in the oil feeds to the vvts, etc, etc. But all they had to do was "Scallop" some metal from the top of the block, the rear bank feed - way to the cylinder head, to eliminate the mis-alignment !

Instead, they buggered about with the head gasket and ended up with a double right - angle crank in the oil flow path. Brilliant!

It is such a pity. I will never forget the expression on Gareth's face as he came through from the engineering shop to get me too look at my wrecked 159 engine - 112,000 miles and black tar lacquer all over the heads, and bearing caps. It must have been 2 - 3mm thick. But he was astonished - and this guy builds racing engines - that the bores were unmarked, looked like the block had just come from production. Although the crank had failed, the block tolerances for bearing were as good as new and the cross - hatching on the bores was clear as day, dispite the high mileage and clear abuse it had suffered.

 

Ascari32

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Re: 3.2 JTS Unanswered Questions!
« Reply #8 on: August 19, 2021, 04:18:18 PM »

If they want to succeed, they need to stop being the "Industry Test Facility",for inovation, as other manufacturers benefit by learning from their mistakes and avoid making the same "Cock - ups".


I think its an Italian mindset thing. Its the same reason Ferrari in f1 almost always get the pit stop calls wrong nowadays. Mercedes nails them. Same with the engineering.

A good example of this is the collaboration of bmw and toyota on the supra. The japanese were suprised at how much the germans cared about chassis dynamics. The germans were suprised at how much the japanese were focused on ensuring the reliability of each bolt.

Alfa know that they need to stir the emotion so the owners stir their wallets. So focusing on the reliability of each area/system is a secondary concern. The 159 seems like an attempt at that by outsourcing the engine and gearbox. Not sure where the awd system came from. It seems like a car that took alfa away from the cheap 156 platform and was an in between for the new giulia platform being rwd and ferrari engined.

"Alfa know that they need to stir the emotion so the owners stir their wallets."

You would think after so long, plummeting sales, poor press and designing cars which are in production less time than it takes to wear out a good set of Brogues, they might have got the message.

Do any of them care? As I have said before, permanently out to lunch. Too much Pasta and dossing in the afternoon. Their mornings are spent sipping black coffee and swigging Cynar, after over - indulging the night before. Or so it seems to me!

Alfatango

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Re: 3.2 JTS Unanswered Questions!
« Reply #9 on: August 19, 2021, 06:56:21 PM »

If they want to succeed, they need to stop being the "Industry Test Facility",for inovation, as other manufacturers benefit by learning from their mistakes and avoid making the same "Cock - ups".


I think its an Italian mindset thing. Its the same reason Ferrari in f1 almost always get the pit stop calls wrong nowadays. Mercedes nails them. Same with the engineering.

A good example of this is the collaboration of bmw and toyota on the supra. The japanese were suprised at how much the germans cared about chassis dynamics. The germans were suprised at how much the japanese were focused on ensuring the reliability of each bolt.

Alfa know that they need to stir the emotion so the owners stir their wallets. So focusing on the reliability of each area/system is a secondary concern. The 159 seems like an attempt at that by outsourcing the engine and gearbox. Not sure where the awd system came from. It seems like a car that took alfa away from the cheap 156 platform and was an in between for the new giulia platform being rwd and ferrari engined.

"Alfa know that they need to stir the emotion so the owners stir their wallets."

You would think after so long, plummeting sales, poor press and designing cars which are in production less time than it takes to wear out a good set of Brogues, they might have got the message.

Do any of them care? As I have said before, permanently out to lunch. Too much Pasta and dossing in the afternoon. Their mornings are spent sipping black coffee and swigging Cynar, after over - indulging the night before. Or so it seems to me!

And yet for all their flaws we love the cars. So are the cars to blame or are we ;D?
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Ascari32

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Re: 3.2 JTS Unanswered Questions!
« Reply #10 on: August 19, 2021, 07:51:58 PM »
Yes, they are like magnets!

I perhaps would be more forgiving, had I not a history which goes back to the 1970's, having owned Alfa's exclusively. The last car that was not an Alfa Romeo was a Rover 2000 TC and Alfa's have been the only form of transport in the family since.

But in recent years, unscrupulous main dealers have ripped off many owners, not just me. I shall not buy another modern Alfa. I love my 159, despite the issues. But it would be a different matter altogether had I bought it new. Although only paying £3000 for her, I have spent a small fortune since. But it has and continues to give me a great deal of pleasure. I hope it sees me out!

I would; I think, do it all again. But only if the purchase prices was the same. I would not touch it with a barge pole when new, now that I know the issues. I now understand why the motoring press quickly fell out of love with it; with these engines.

The F40 gearbox was funded by Fiat for their luxury platform cars. And I believe the fourwheel drive system is derived from Lancia's.