This post is intended for Kierenc. However, anyone who has a particular interest in the Holden Derived 3.2 JTS Alfa engine may find it worth reading - or not, as the case may be!
Hi Kierenc,
Good to see your interest has been sparked in the 3.2 JTS. The 2.2 JTS probably has problems common to the 3.2 - in particular oil pressure and timing chains. I envy you your spider, a car I have grown to like a lot. I saw a couple advertised a few months ago, one £9k and the other £11k; one being blue with special leather and the other in stunning red. They have been snapped up as they were quite low mileage. But I feared, I would end up taking on another rebuild and knowing myself would probably - yet again go "The Whole Hog".
So I passed on them as my 159 needs finishing first. and that is proving a little time consuming, not to mention costly. And time is at a premium.
I have done very little cosmetically to my Q4 as I viewed that as being the final part of the project. I have already done all wheel bearings, discs and rear differential mounting bushes, plus the trailing arms now have Polys, courteousy of Powerflex who used my trailing arms for development and graciously gave me the first production set. They work brilliantly and given there is relatively little movement under normal circumstances, do not squeak. The C.C. has a new compressor and condenser, new radiator, in fact most of the peripherals have been replaced.
The engine, from the off, was never going to be easy as there was and remains little understanding of its niceties, and its failings. But everything I have done is documented in my thread on its rebuild, on the UK Forum under Sizwell. It has been a monumental challenge to find parts, some of which were far too expensive. However, I had some considerable help from the likes of American guys, Aussie Companies and various European suppliers. For instance - a new front subframe from Germany at less than 1/4 the price Alfa wanted.
It was always my intention to get cylinder head temperatures down and from the very start I was determined the manifold cats would have to be binned. It was not primarily the fault of the Manifold Cats that was the cause of the elevated cylinder head temperatures, but the valve timing and software techniques Alfa chose to use. Most of what Alfa chose to adopt can be found in an EU funded research document, which unfortunately they overzealously incorporated. The manifold cats need to be kept at "Light - Off Temperature" to destroy the emissions, mostly the HC's, which they do very well being metal. The secondary cats, under the car being ceramic with a lower working temperature, which suits the destruction of NOx's to the extent the residual emissions were some of the lowest seen in any car of that Era.
The camshafts are key to maintaining light - off temperatures so once the manifold cats were removed, there was little point in maintaining the valve timing as was, and the timing angles do nothing for out and out performance. This is an important point as the static valve timing creates a 2.5deg. Negative Valve Overlap, where there can be "No Scavenging" - crossflow, whereby the exhaust gases draw air from the inlet manifold, across the cylinder head and out into the exhaust manifold. So changing the manifolds for free flowing Autodelta's in themselves would do very little to lift the performance of the engine. I am not interested in the odd ten bhp - my oil way mods gained me that by simply maintaining oil pressure on the timing chains and speeding up the VVT and its accuracy. The valve timing would have to be changed to generate Positive Valve Overlap, which promotes effective scavenging.
So, I am afraid equal length headers would have very little effect, without radically changing valve timing. I chose to buy a set of C.B.'s as I was aware of an unsold set in the UK and I have had several sets on previous Alfa's. However, were I to undertake another 3.2 JTS rebuild, I would not change the exhaust camshaft. The standard valve timing has the exhaust valve closing at 9deg. ATDC and the inlet valve opening at 11.5deg ATDC - hence no scavenging. My C.B.'s have the inlet opening at 0.5deg. BTDC and the exhaust closing at 23deg. ATDC, creating a PVO of 23.5deg. and generating massive scavenging.
I had hoped to avoid any software modifications as I do not have the budget for professional services and I do not trust those that see software more as a hobby from which they can make a living. But, I fear, the consequences of such a massive POV is metering errors due to the increased flow through the MAF. I believe I have identified the problem and have gone some way into resolving it. but it is not going to produce the ideal which the engine now deserves. So to reduce the error, at the price of some performance, I may have to refit the Alfa exhaust camshafts which would then reduce the valve overlap: PVO, to 9.5deg. ie, inlet C.B. opening at 0.5deg. BTDC and exhaust closing at 9.0deg. ATDC.
I am coming to think this may also help the exhaust system as it seems I cannot find a way to manage the velocity of gases, the new Supersprint Sports Cat generate. The Alfa boxes seem unable to contain them and my Ascaris, although stunning above 3000 rpm are dreadful below. I am fast forming the opinion, removing back boxes altogether and just fitting straight through pipe sections may be the only solution.
I am currently going through an exercise of changing MAF inserts. But, I don't see there being any real solution to the problem, beyond refitting the Alfa Exhaust camshafts. The car is stunningly quick - even with the 3.0 GTV MAF element and the 280 - 218 - 008 elements fitted. The Porsche 911 insert is too insensitive, although the Transfer Characteristic looks good. My last hope is probably a Bosch 281 - 002 - 421. Or to simply go back to the original MAF insert and provide my neighbours with ear plugs. Hell, she is fast with that fitted. but the police would be alerted at Martlesham, 30 miles away, as soon as I start her up.
However, until I crack this particular nut, I won't be able to get her on the Dynamometer, apart from being in lock - down again. I would however suggest, if you are that keen, you read my posts, with attached pictures of my 3.2 JTS rebuild. My understanding of this engine started at Zero, so naturally as it progressed and I learned more, I have come to appreciate the interrelationship of so many factors, hitherto not understood or indeed known of. That aside, my regard for this engine has steadily grown. That some elements of it's design are covered by patents held by Porsche, who were instrumental in the design of the Ford/Jag V6 which they had a major influence in research and development thereof - not to mention a massive budget. And when the project ended, key players took up new posts within the GM team which developed the engine which Alfa adopted for the 3.2 JTS.
One aspect I was puzzled about was how upper cylinder lubrication was performed. This too is in part a function of the Negative Valve Overlap as the negative pressure generated before the inlet valve opens, draws both HC's out of the piston - ring/cylinder - bore interface region; and oil, past the rings to lubricate the bores above the piston. The spray jets direct oil to the underside of the piston which has ports through to the oil ring groove. This explains the astonishment the Engineering (Racing) shop displayed when they pulled my 113,000 mile 3.2 JTS engine apart and inspected the bores. Their condition was as if the block had just come off the production line. Absolutely flawless. The piston rings however are seen as "Sacrificial" and considerably cheaper and easier to replace than having to re-bore the block.
I enjoy the Australian Forum for several reasons, not least the clear enthusiasm some of the guys have for their cars and the opportunity they get to drive great distances gives them a better insight into how their cars perform than one gets on congested British roads. I have picked up some interesting tips from that site along the way so I shall continue to look in to find out what is going on, despite being thousands of miles away.
Regards,