Author Topic: Enigmatic 3.2JTS  (Read 12106 times)

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Ascari32

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Re: Enigmatic 3.2JTS
« Reply #15 on: August 03, 2020, 12:26:38 AM »
wow! you can wear out tires/tyres in less than 3k Miles or 4.8k kilometers
and you haven't been arrested you are very lucky.

Not really been hitting high speed, more checking on acceleration. Seems P Zeros are quite hard when new, but once you get beyond new, they seem to dump rubber very quickly. Well that's my experience with them on my GTV. In fairness, I think I can coax another couple of thou if I am not too silly. But this damned exhaust problem is really grating. I really think I screwed up on the back boxes.

But I do like the idea of that badge and the van connection. Farina badges used to be on Austins; A40? if I remember correctly.

Ascari32

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Re: Enigmatic 3.2JTS
« Reply #16 on: August 03, 2020, 05:17:18 PM »
From the various articles I have read, the Holden/Chrysler versions had a smaller advance retard angle, 35 deg. seems to ring a bell. Whereas the Alfa VVT system is a full 50 deg. And some variants of the Vauxhall and SAAB 2.8 only have VVT on the inlet camshaft. Something Alfa did with the Variator on the 156.

Authorities have said, 85% of the improvements made with quad cam systems can be achieved by just changing inlet camshafts. It is inlet valve timing that is more critical. It thus follows, similarly, fitting VVT to just inlet camshafts will have a similar beneficial effect.

Also, when one looks at the rotors, the Alfa timing plate is much more sophisticated, less crude. Well that is no surprise, because when researching the position sensors of the VVT system, it transpires that it is exactly the same as Bosch used when developing their "Hall effect" devices.

The signal detected by the sensor is very small and there is considerable noise surrounding it. To minimise noise, part of the VVT rotor - the collar, is alloy, in an effort to keep the actual rotor's noise footprint out of the signal. And because it is such a small signal, to help differentiate it from noise, as much metal is cut away from the sensor plate to isolate the signal, as much as possible from the rotating sensor plate superstructure - which is ferrous. Hence the slots!

The hall effect signal is pseudo - triangular shaped, with a fair bit of noise sitting on it naturally. So when processing it to a form which the ECU system can use, it is amplified, then filtered to remove this noise; then amplified again.

It then drives a very precise "Zero - Offset Schmitt Trigger". Because it is triangular wave, both the positive going leading edge and negative going trailing edge, of the signal, will cut the "Schmitt - Threshold" at exactly the same level. The net effect is to produce a square wave output waveform, which has both a very fast rise/fall time and is accurate wrt timing within the context of the timing of the ECU.

If the signal is low, then the Schmitt Trigger can ultimately fail to trigger or indeed simply trigger late and introduce a error which in the extreme can lead to a code failure for cam timing; rear bank exhaust sensor as a case in point. This also has a bearing on the front bank manifold cat and cylinder head overheating issues - but that is another story.

As pointed out earlier, unless the sensor is correctly fitted, the amplitude of the triangular wave quickly diminishes. And Bosch state, the field generated by the rotor plate should pass the sensor face at a right angle +/- 0.5 deg.


So the rear bank sensor is incorrectly fitted to the 3.2 JTS. This probably came about because the panels were cast when there was no VVT fitted to the exhaust camshaft.

However, with regard to Ferrari's involvement, it is my belief that the software control for the system and hence the ECU program is likely to be theirs. It is too good for Alfa to have come up with it - in my opinion.

   

kaleuclint

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Re: Enigmatic 3.2JTS
« Reply #17 on: August 03, 2020, 06:27:20 PM »
And to keep on topic at least the GM designed partially built? Holden V6 engine is of a 60 angle. not many V6's are 60 simply because most V6 cars over the decades were run down V8 production lines so a 90 V6 was just cheaper and easier to do. Even the Ferrari influenced V6 in the new Giulia is a 90 configuration.
Interestingly the "Ferrari-built" (using a U.S. cast block) Maserati Ghibli V6 is 60 degrees. 
2011 159ti 1750TBi


Colin Edwards

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Re: Enigmatic 3.2JTS
« Reply #19 on: August 04, 2020, 09:57:15 AM »
I guess the 3.2JTS is like anything else..........good enough for the present requirement and to be superseded as soon as the next iteration is released.  If continual development wasn't a requirement, we would all be still driving cars resembling the Model T Ford.
Like all engines, the 3.2JTS was just a stop gap design while the next engine is being developed.  The 12V Busso was a fair engine for its day, however very soon replaced by the 24V model.  That again was ok until superseded by the improved 3.2JTS.  None of these engines, in retrospect, was perfect.  They all had their design limitations.

No doubt the 3.2JTS had its limitations.  If it had none, it would still be manufactured.  Methinks Alfa Romeo / Fiat very soon acknowledged its shortcomings (as would be the role of engineers and accountants) and developed the Multiair system.  Certainly a more elegant and efficient way of controlling valve events.  The Multiair probably addresses most of the valve event and related hydraulic control issues identified in the 3.2JTS.  Makes sense to incorporate the recent advances in high speed mechatronics and general processing grunt.

With regard to the use of Hall Effect devices and signal processing, back in the early 1990's, a local lift manufacturer (who I used to work for!) used Hall Effect devices for velocity and distance measurement.  Tested and reliable well beyond 75,000 pulses per minute, the locally developed electronics and supporting software had no issues operating in a very hostile environment.  The application was unique however the technology was not.  High speed signal conditioning has been around for a very long time and high noise immunity Schmitt trigger technology for nearly as long.  Methinks any run of the mill electronic engineer and software engineer at Alfa would have had the expertise to develop the required systems. 
Then again, if an elegant solution exists within the group / company, why reinvent the wheel. 

 
« Last Edit: August 04, 2020, 10:19:21 AM by Colin Edwards »
Present
2020 Giulietta Veloce
2018 Abarth 124 Spider
1987 75 3.0

Past
2015 Giulietta QV
2009 159 3.2 Ti Q4
2012 Giulietta TCT Veloce
2006 147 Ti 2 door Selespeed
1979 Alfasud Ti 1.5

Ascari32

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Re: Enigmatic 3.2JTS
« Reply #20 on: August 04, 2020, 05:54:57 PM »
I can't agree with your analysis, it is a little too sympathetic towards Alfa Romeo and neglects the fact that they continually sit back and allow the field to get ahead of them. And the Multi - Air is no substitute for a 3.2 V6.

That Chrysler are keeping this engine; with some re - engineering work, in production until 2026 demonstrates Alfa failed to grasp the point about it's potential when it hurriedly dropped it, and the 159/Brera. Particularly after all the fanfare!

The GT only came to market because there was no replacement car available after the success of the 156 - again another car they dined out on, well beyond it's sell by date. The GTA stretched Busso's masterpiece to 3.2 litres in an attempt to keep the market interested. An illustrious title given to a dressed - up, "Buy One, Get One Free" front wheel drive car which should have been replaced long before it finally ceased production.

The company makes no mention of the fact that Busso' masterpiece was seen as a history, Busso having left the company two years, before Alfa thought to introduce it. Why? Because the new crop of management, and engineers simply carried on as before, sitting on their hands, not really having any idea how to move the Marque forward.

When the Busso adopted four valves per cylinder, it was for technical reasons surrounding emissions. They would just as soon have not bothered. But legislation left them no option. Yet again, they didn't think they needed too.

It was not for technical reasons the 3.2 JTS superseded the Busso, it was financial - pure and simple. Fiat were in financial difficulties, they wanted to close Arese and they were negotiating to climb into bed with another lame duck.

So the 3.2 was a Wedding Present. Albeit, a bit tacky! So they felt they needed to dress it up a bit. And failed miserably. The Platform of the 159 is superb, cost 2 billion in development and it too went the way of the Dodo.

Not what one could call commercial sense for a Prestige Marque, to leave itself without a flagship model for so long.

The history of the Holden V6 is quite convoluted.

The design concept owes much to Ford's Duratec V6 with its primary engineering input coming from Porsche. The engine subsequently finding its way into Jaguars amongst others.

When the development team was broken up, fortuitously it found itself being substantially reformed under the Chrysler Banner. There are still elements of the Holden/Chrysler V6 covered by patents held by Porsche. So it is not without Pedigree!

The 3.2 JTS certainly has it's limitations. But none that Alfa Romeo Identified. However, they certainly added a few of their own! And still we are without a true Alfa Engine. The 2.9 belongs to Ferrari. After a litany of engineering disasters, spanning decades, it is inconceivable Alfa could have pulled this gem out of the hat like a rabbit.

With regard to Hall Effect, it was discovered by Edwin Hall in 1879 but little was done with it for many decades. For me, it is not new technology, but certainly not old. Stability was never very good in the years Valve Technology held sway, the era I hail from. With the advent of semiconductor technology; yet still discrete components, things got a lot better. And microprocessors now enable such technology to be employed in everyday devices.

Impedance Modulation was well understood as a method of increasing Broadcast efficiency, beyond what was thought to be theoretically possible. However, the man who invented it was long dead before component tolerances in manufacture made it possible to produce very efficient transmitters in the 1980's. And companies such as Bosch, can explore and develop technologies, the study of which lie in the vaults of many University Research Libraries.               
« Last Edit: August 04, 2020, 06:02:50 PM by Ascari32 »

Ascari32

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Re: Enigmatic 3.2JTS
« Reply #21 on: August 04, 2020, 07:03:35 PM »
I stand corrected - apologies for that. Senior moment kicking in!

However, I wondered why a block with such obvious strengths found its way into this engine? Even one Company Director, who gets considerably more from this engine phoned me to acknowledge its obvious virtues, having only just properly inspected it for the first time. Yet it is roundly condemned here in the UK, but no one seems able to give factual reasons for such an overtly negative view. 

Colin Edwards

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Re: Enigmatic 3.2JTS
« Reply #22 on: August 05, 2020, 11:18:53 AM »
From a personal perspective, I had no problem with the 3.2JTS in my 159.  Apart from needing to replace spark plugs not long after purchase as the car still had the originals after 70,000klms use, nothing of note to mention.  Then new plugs every 30,000klm.   Also always replaced engine oil and filter every 7500klm.  Always fed it 98RON.



Present
2020 Giulietta Veloce
2018 Abarth 124 Spider
1987 75 3.0

Past
2015 Giulietta QV
2009 159 3.2 Ti Q4
2012 Giulietta TCT Veloce
2006 147 Ti 2 door Selespeed
1979 Alfasud Ti 1.5

Ascari32

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Re: Enigmatic 3.2JTS
« Reply #23 on: August 05, 2020, 05:56:06 PM »
Sounds like a recipe for longevity. I doubt that too many in UK go to that length - regardless of Marque!

The Brera engine I rebuilt was run dry at about 40 - ish k. Many car owners do not change their oil and filter often enough, let alone have them properly maintained.

As a lot of cars are bought on Personal Finance Plans, I suspect their servicing schedules run along the lines dictated by the dealerships they bought them from, never thinking that the intervals are perhaps not best suited to every car. Meaning - some owners are thoughtful about the way they use their cars, others may not be.

So, buying on the secondhand market can be a bit of a minefield.     

Ascari32

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Re: Enigmatic 3.2JTS
« Reply #24 on: August 25, 2020, 07:22:42 PM »
The old AlfaSud plant were the last 159 was built is very close if not next door to the aviation division.
 I acknowledge and understand the history of the two plants and the radial engines alfa romeo built under the leader ship of Ugo Gobbarto were splendid examples of engineering.

The travails of this Enigmatic car continue! To be fair, it is not of Alfa's making - damn. It has more to do with the way I chose to modify my car. The manifold cats have gone. They are the metal type and clearly can withstand much higher temperatures. Although I knew the twin cats below the car are Ceramic and thus lower temperature, I felt as they are some distance away from the engine, they would probably cope ok. It was the output of the twin cats that appeared to be the problem as they  form a "Clarinet Reed" for the gases exhausting into the central section where the resonator is. After my modifications, the higher power level was causing extreme droning @ ~ 2500 rpm.

I fitted a Supersprint central section which has no resonator and sure enough, the drone disappeared. But this resulted in a cacophony of noise emanating from the rear boxes. Cue new rear boxes - a lot worse, although both the sound and acceleration from 3000 rpm is brilliant. But impossible to live with at below.

My worst fears seemed to be confirmed - a new cat would be needed. And Supersprints is not cheap. So having bitten the bullet, contacted Supersprint Technical Department. By this time, the Cat had been ordered, but I had the daunting prospect of having to buy yet another pair of rear boxes as the new ones seemed incapable of handling the power. I wanted Supersprints assurance theirs, which would complete my system once the cat is installed, would handle the extra power. I quoted a figure of 350hp as a target figure. I even picked up a brand new Alfa Nearside Box cheaply, fearing I would end up going back to theirs. It confused me, the Alfa boxes handle the lower revs well, but break up at higher revs, the new ones handle higher revs, but break up at lower ones.

I needed Help.

That's where S.S. tech dept. came in. I laid it out as baldly as I could and within the space of the weekend I had a comprehensive reply.

"It's not your rear silencers that are your problem, it's your cat". Brilliant, so at least I had a second opinion supporting my view about the Alfa Twin Cat".

But not for the reason I believed. Quote:- "I would be very surprised if there are any cells left in them". They are 500 CPI (Cells per inch) and very restrictive.

So to shorten a long story, having a spare twin cat in the garage - which I was intending to take to the dump - I got a garden chair to sit on, a 10mm. piece of stainless pipe, an eight pound club hammer and drove the pipe through the cat. Initially it was very reluctant but eventually smashed my way through. A quick check below and sure enough, there were pieces of the Ceramic Cat on the garage floor.

I picked up, what clearly had been part of the outer matrix, which was very hard. The initial strength must have been this outer screen/matrix. However, along with it on the floor was part of the inner honeycombe. Inspecting that revealed it was almost of a dust consistency - extremely crumbly. One could rub a small lump between two fingers and it quickly fell to dust/coarse powder.

So, full marks to the Supersprint tech guy for pointing me in this direction. I don't think the "Reed" helps, but if my twin cat has collapsed cells, it certainly would contribute to my problem.

Funnily enough, after a quick blast to get out into mainstream traffic flow, from a junction yesterday, the exhaust system appears to have got a little less "Rackety". It's not the way it should be. But it seems a bit quieter. And although my doubts about my new rear boxes remain, the throttle response is such that, blipping the throttle a little on down shifts brings an exhaust note that reminds me of my old twin cam Berlina and her Dellorto carburettors.

Funny - the tricks the mind can play on perceptions!!!!!!!     

Ascari32

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Re: Enigmatic 3.2JTS
« Reply #25 on: August 25, 2020, 08:42:59 PM »
The old AlfaSud plant were the last 159 was built is very close if not next door to the aviation division.
 I acknowledge and understand the history of the two plants and the radial engines alfa romeo built under the leader ship of Ugo Gobbarto were splendid examples of engineering.

The travails of this Enigmatic car continue! To be fair, it is not of Alfa's making - damn. It has more to do with the way I chose to modify my car. The manifold cats have gone. They are the metal type and clearly can withstand much higher temperatures. Although I knew the twin cats below the car are Ceramic and thus lower temperature, I felt as they are some distance away from the engine, they would probably cope ok. It was the output of the twin cats that appeared to be the problem as they  form a "Clarinet Reed" for the gases exhausting into the central section where the resonator is. After my modifications, the higher power level was causing extreme droning @ ~ 2500 rpm.

I fitted a Supersprint central section which has no resonator and sure enough, the drone disappeared. But this resulted in a cacophony of noise emanating from the rear boxes. Cue new rear boxes - a lot worse, although both the sound and acceleration from 3000 rpm is brilliant. But impossible to live with at below.

My worst fears seemed to be confirmed - a new cat would be needed. And Supersprints is not cheap. So having bitten the bullet, I contacted Supersprint Technical Department. By this time, the Cat had been ordered, but I had the daunting prospect of having to buy yet another pair of rear boxes as the new ones seemed incapable of handling the power. I wanted Supersprints assurance theirs, which would complete my system once the cat is installed, would handle the extra power. I quoted a figure of 350hp as a target figure. I even picked up a brand new Alfa Nearside Box cheaply, fearing I would end up going back to theirs. It confused me, the Alfa boxes handle the lower revs well, but break up at higher revs, the new ones handle higher revs, but break up at lower ones.

I needed Help.

That's where S.S. tech dept. came in. I laid it out as baldly as I could and within the space of the weekend I had a comprehensive reply.

"It's not your rear silencers that are your problem, it's your cat". Brilliant, so at least I had a second opinion supporting my view about the Alfa Twin Cat".

But not for the reason I believed. Quote:- "I would be very surprised if there are any cells left in them". They are 500 CPI (Cells per inch) and very restrictive.

So to shorten a long story, having a spare twin cat in the garage - which I was intending to take to the dump - I got a garden chair to sit on, a 10mm. piece of stainless pipe, an eight pound club hammer and drove the pipe through the cat. Initially it was very reluctant but eventually smashed my way through. A quick check below and sure enough, there were pieces of the Ceramic Cat on the garage floor.

I picked up, what clearly had been part of the outer matrix, which was very hard. The initial strength must have been this outer screen/matrix. However, along with it on the floor was part of the inner honeycombe. Inspecting that revealed it was almost of a dust consistency - extremely crumbly. One could rub a small lump between two fingers and it quickly fell to dust/coarse powder.

So, full marks to the Supersprint tech guy for pointing me in this direction. I don't think the "Reed" helps, but if my twin cat has collapsed cells, it certainly would contribute to my problem.

Funnily enough, after a quick blast to get out into mainstream traffic flow, from a junction yesterday, the exhaust system appears to have got a little less "Rackety". It's not the way it should be. But it seems a bit quieter. And although my doubts about my new rear boxes remain, the throttle response is such that, blipping the throttle a little on down shifts brings an exhaust note that reminds me of my old twin cam Berlina and her Dellorto carburettors.

Funny - the tricks the mind can play on perceptions!!!!!!!     

Ascari32

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Re: Enigmatic 3.2JTS
« Reply #26 on: August 30, 2020, 06:20:05 PM »
For me, "Enigmatic"remains the term most applicable to this car, but more specifically the engine. It is difficult, without access to full workshop facilities to move anything along quickly - automotively - a local exhaust fabricator is fully booked up until November and I await my Sports Cat with baited breath.

In the mean time, I have been ploughing through E.U. Research Documents on Emissions, Manifolds, Catalytic Converters, Diffusers, Resonators and Silencers/mufflers.

One document is 317 pages long. It covers these areas scientifically but seems to be directed at guidance for car manufacturers in a manner, which allows scope to develop their own unique way of resolving emissions issues. Compliance being the critical point. How it is achieved is up to individual car makers.

Catalysts however, remain mandatory!

But there are many ways of skinning a cat! And it appears to me, it gets to a point when ultimately car manufacturers apply economics to solutions in a manner which cannot be sustained from one generation of cars to the next. I wonder if the drive towards electric would have been so fast, had not motor manufacturers applied more of the known science to getting emissions under control, than they have hitherto.

Which brings me back to the engine which I term "Enigmatic". So little is given away by manufacturers, with regard to their motives for adopting x,y or z approach to problems which are common to virtually all cars. OK, specific perhaps in the sense they are diesel or petrol driven, but common wrt either type.

And so I return to the issue of valve timing in respect of the 3.2 JTS. If anyone has further expert knowledge or insight into this issue, I would appreciate their views. It certainly would be a lot easier than having to pull together all the specific research contained in 317 pages into one concise document. Trying to determine the interrelationship between such complex areas is hard work. However, I think I have; courtesy of such documents, stumbled upon another reason for Alfa's choice of valve timing, in particular the exhaust valve timing.

Not only would it appear to be their method of generating "Internal EGR", it may also be intended to reduce "Reverse Flow" through the Catalytic Converter Element. By closing the exhaust valves at such an angle, it probably reduces any depression pulling gases back into the cylinders, thus slowing gases through the cat or indeed causing reverse flow. I am still working my way through this one.

However, one thing I am absolutely certain of is the second feature of closing the exhaust before the inlet opens. There is little point in fitting manifold cats in an attempt to maintain "Light - off", which enables Catalization, if valve timing allows cross-flow between inlet to exhaust - PVO - which would in effect cool the Catalytic Converter down!

Somehow, it all seems to have got lost in the mix for Alfa. It is Paradoxical for a company whose History is founded upon a "Racing Heritage" to apply such contradictory principles to cars such as the Brera and 159 and claim they continue this into the modern era.

As flawed as they are, the 147/156 GTA's are more in keeping with that ethos than these two models. Even the base model 147/156 can be tweaked by enthusiasts, in much the same manner as Berties, Berlina's and Spiders were. And it wouldn't cost a Kings Ransom.

It's a shame, given the 159 and Brera are both fine cars. If only Alfa had not gone so far in strangling the life out of the engines for the sake of fickle legislation, which so often changes due to "Woolly Headed Bureaucrats". The 3.2 JTS would comfortably made 280 BHP and could still have met emissions regulations had they really wanted to maintain their sporting image. I calculated, the Q4 would need to be 286 BHP to match the 156 GTA. Front wheel drive versions would have bested it!

Wasted opportunities. And now we all need deeper pockets to afford Alfa's.       
« Last Edit: August 30, 2020, 06:24:05 PM by Ascari32 »

Ascari32

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Re: Enigmatic 3.2JTS
« Reply #27 on: October 10, 2020, 09:42:10 PM »
The Supersprint catalytic Converter has now been fitted to my 159 for about two - ish weeks. The Alfa boxes cope very well and it generally sounds very sweet, with no popping or farting on overrun. Just a good solid "Blat". But it still did not feel entirely right.

At the same time as the cat going on, a failed rheostat was found and a replacement ordered. I thought I was faced with a very big bill for the climate control system; but no, the guys picked it up very quickly and temporarily the A/C is working.

Although not quite feeling right, I believe when the rheostat is replaced, i will refit my new boxes again. I think that is only fair, before I consign them to the scrap heap/ebay. Prior to the S.S. cat going on, I was experimenting with different fuel grades, provoking management codes at will when swapping from RON 95 to 97. However, I had not cleared the codes when the cat was fitted.

Subsequent to this, I disconnected the MAF, wondering if the slight lack may be due to the MAF, but no change. So I went and saw the guys and asked if they could just give the history file a once over and reset the alarms for me. There was a fairly substantial log to be cleared, all relating to Lambdas and MAF with a couple of cylinder misfires in the mix.

Since the log has been reset however, that slight niggle about performance has evaporated. The engine is running beautifully. Silky smooth at low rpm and what is particularly noticeable is how smooth it is when pulling away and changing up. First and second have always been "Notchy" and not getting it right, the the revs would die off very quickly. Getting my timing right between first and second was crucial. But, because there is now so little drag on the engine - the engine gently dies - off the revs; as I dip the clutch, move from first to second and the re - engage. It really seems like a different car. Progressively it gets better 2nd to 3rd, 3rd to 4th. And fifth and sixth have never been a problem.

Acceleration is strong, with no flat spots, revs rising very quickly, the car belying its weight. Exhaust, very throaty at low revs but I do miss the sound it makes with my new boxes over 3000 rpm. Not bad though and the Alfa boxes coping well. Noise levels are very acceptable - nothing like the original but acceptable. Tick - over solid but meaty. I cannot see that when the new boxes are refitted, it will be any quieter. So that mat be the sticking point. But it is worth a try.

I shall have the front drivers side wheel bearing changed at the same time as the rheostat is done as that is the only untoward noise coming from the car. All in all, I love it. Next stop - heart in mouth - Dynamometer. But I will wait a couple of weeks, just building up the courage. That aside, what a fabulous car the 3.2JTS Q4 is - now!!     
« Last Edit: October 10, 2020, 09:45:55 PM by Ascari32 »

Ascari32

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Re: Enigmatic 3.2JTS
« Reply #28 on: October 10, 2020, 09:50:27 PM »
The Supersprint catalytic Converter has now been fitted to my 159 for about two - ish weeks. The Alfa boxes cope very well and it generally sounds very sweet, with no popping or farting on overrun. Just a good solid "Blat". But it still did not feel entirely right.

At the same time as the cat going on, a failed rheostat was found and a replacement ordered. I thought I was faced with a very big bill for the climate control system; but no, the guys picked it up very quickly and temporarily the A/C is working.

Although not quite feeling right, I believe when the rheostat is replaced, i will refit my new boxes again. I think that is only fair, before I consign them to the scrap heap/ebay. Prior to the S.S. cat going on, I was experimenting with different fuel grades, provoking management codes at will when swapping from RON 95 to 97. However, I had not cleared the codes when the cat was fitted.

Subsequent to this, I disconnected the MAF, wondering if the slight lack may be due to the MAF, but no change. So I went and saw the guys and asked if they could just give the history file a once over and reset the alarms for me. There was a fairly substantial log to be cleared, all relating to Lambdas and MAF with a couple of cylinder misfires in the mix.

Since the log has been reset however, that slight niggle about performance has evaporated. The engine is running beautifully. Silky smooth at low rpm and what is particularly noticeable is how smooth it is when pulling away and changing up. First and second have always been "Notchy" and not getting it right, the the revs would die off very quickly. Getting my timing right between first and second was crucial. But, because there is now so little drag on the engine - the engine gently dies - off the revs; as I dip the clutch, move from first to second and the re - engage. It really seems like a different car. Progressively it gets better 2nd to 3rd, 3rd to 4th. And fifth and sixth have never been a problem.

Acceleration is strong, with no flat spots, revs rising very quickly, the car belying its weight. Exhaust, very throaty at low revs but I do miss the sound it makes with my new boxes over 3000 rpm. Not bad though and the Alfa boxes coping well. Noise levels are very acceptable - nothing like the original but acceptable. Tick - over solid but meaty. I cannot see that when the new boxes are refitted, it will be any quieter. So that mat be the sticking point. But it is worth a try.

I shall have the front drivers side wheel bearing changed at the same time as the rheostat is done as that is the only untoward noise coming from the car. All in all, I love it. Next stop - heart in mouth - Dynamometer. But I will wait a couple of weeks, just building up the courage. That aside, what a fabulous car the 3.2JTS Q4 is - now!!

P.s. The feeling of having lost a little at the bottom end has now gone, with good solid torque coming in, low down Always better than standard, it just seemed in the process of trying to resolve my exhaust/cat problems, a little was lost in the mix. Now, back to what it was - absolutely fine. Hope that feeling wasn't down to my new boxes. However, I will find that out when I refit them!!! 

Ascari32

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Re: Enigmatic 3.2JTS
« Reply #29 on: November 07, 2020, 09:52:50 PM »
The Saga goes on - and on - and on!

Ascaris now History although they have been useful in trying to resolve the exhaust issues, which I believed were at an end.

The Standard 3.2 JTS has valve timing such that the engine is 11.5deg. into its induction stroke before the inlet valve opens, the exhaust valve having closed 3.5deg. earlier. Thus there is no crossflow - air passing from inlet to exhaust. So the velocity of air in the inlet tract is interrupted, if not completely halted.

As a result, it is difficult to see how good volumetric efficiency can be achieved. Also, this means the ECU has a less time to calculate the Air flow upon which it can meter the fuel injection. So; by my reasoning, Alfa needed to fit a MAF with a very fast rise-time; dr/df transfer characteristic - a steep slope, to enable the ECU to read Peak Airflow very quickly.

Unfortunately, when fitting the Colombo Bariani camshafts, which have a 23.5deg. valve overlap, the increased air flow, - crossflow element+cylinder fill results in the ECU setting AFR which is too rich. The obvious consequence of this is the powerful/meaty exhaust sound, even though the engine is at 750 rpm - solid: and rich operating conditions overall.

So logic suggested, a MAF with a different Transfer Characteristic is needed. I tried a new 916 GTV 2.0 version - (2) on the attached data sheet - and there was a good improvement at the lower end with a more subdued tickover. But it's range is too low and it topped - out at 4500 rpm, which tied up with Bosch's data sheet.

I then tried the new MAF from my 3.0 GTV - (3) on the attached data sheet - which clearly has a higher flow rate and things really did improve dramatically.  So much so, that I was able to "Trim" the output signal with resistance values the original 3.2 JTS MAF would not tolerate.

This was where the Ascaris became invaluable. Small changes in the "R" - values were immediately reflected in a change in the character of the exhaust sound emanating from the Ascaris. Indeed, the character of the exhaust became that much more harmonious, acceleration seemed sharper to the extent that it seemed like major changes had been made and not just changes to (R) values. I eventually settled for 600 ohms, nearly three times that of the test values used when trying to understand the problem with the original JTS MAF.

At this point, I decided to stop as I had already booked the car in for the Alfa Boxes to be refitted. During this period, I was searching for a MAF which would give me a less acute transfer characteristic and the only one I could find, which was a HFM 5 was the 911 Porsche 2.8L. My logic being such that, a turbo car would require a lower/less acute transfer characteristic. But needless to say, that is expensive. An alternative; I thought, could well be (5) on the attached data sheet, but that is very difficult to find - I have seen it, but at Mega Bucks.

Happily, I found version (4) on the data sheet which is used on some Volvo models. It's transfer characteristic follows a similar profile as (3), but with a higher airflow limit. I am hopeful that I can also trim the dr/df transfer characteristic to give an optimum AFR characteristic.

Although not as precise as the Bosch method - which is why the covers on these sensors are sealed with a gasket enabling the makers to calibrate the response to any car makers requirements - it would require test facilities which are beyond me. But, it isn't entirely crude and should enable me to adjust fuel metering to a greater degree of accuracy than with the JTS's standard MAF. Indeed, were I to fit a vernier resistive network and quality AFR gauge, it would be possible to trim fuel continuously on long journeys.

Alas, whilst standing in the workshop as Adam drove the 159 into the bay, with the Ascaris, it finally sounded absolutely glorious. Nothing like it sounded from the driver's seat. So I suppose it must be down to acoustic coupling. Either way, they will go on eBay or to the dump. The Alfa Boxes are back on now, but they have benefited from the ability to set the current loop of the MAF when the Ascaris were fitted. 

The Bosch 0280218008 MAF should be here in a week or two and the exercise of trimming the loop again will be done with the Alfa boxes insitu - I hope they are as responsive enough to find the sweet spot as it was with the Ascaris.

Torque seems a little stronger below 1500 rpm and beyond she just comes on strongly, but with less audible drama which I got with the Ascaris. If only I could have made them work! Above 3000 rpm, they are in a league of their own!