Best after market exhaust for 3.2

[Ascari32]

Hi Stu,

Yes, it is really noticeable how much the throttle response improves. However, you confused me a little about what exactly it is you have swapped - out. So perhaps you could clarify for me please?

First off however, is my current set up.

1) Alfa manifold Cats - removed when engine was rebuilt and replaced with Autodelta's Headers - Stainless Steel. Principally I decided this was the right thing to do as the engine runs extremely hot and destroys oil at a hell of a rate.

2) Alfa's Centre Section has a small resonator/muffler in the propshaft tunnel, just after the twin cats under the car. It caused the exhaust system to drone at ~2500 rpm. This droning was there from the day I bought her and the exhaust system was standard. However, after the engine was modified and rebuilt with the Autodelta's and C.B. camshafts fitted, the drone became intolerably loud, again at 2500 rpm ~.

As the Alfa centre section resonator/muffler is integral to the pipe, the only option was to find a replacement which didn't have any fitted . So I found a Supersprint Stainless Steel section for a good price.

3) The S.S. section was fitted and the droning ceased. However, a lot of exhaust noise/harmonics ended up in the Back - Boxes. The Alfa ones were pretty good at low revs, but broke up badly at high revs - harmonics rattling them to bits. I then bought the boxes now fitted, thinking the problem with the alfa ones was about poor power handling. No! They made matters worse, pretty dreadful at low revs, but sublime above 3000 rpm ~ The gas flow comes alive, from the engine, all the way through to the tail pipes - delicious - reminded me of my Dellortos on my old twin cam Berlina. But, just impossible to live with below 3000 rpm as the slightest load/depression of the throttle and the car will waken the dead.

I had long suspected the Twin Centre Catalytic Converters but there is a long delivery time for a replacement Sports Cat - Supersprints are made in Italy and they are Made to order - mine is due the first week of October. So until then, I am refitting the Alfa Boxes and will have a few weeks to re - adjust myself before the new cat arrives and is fitted. I have bought a pair of new Lambdas for it as I don't want any distractions from whatever the results bring.

Assuming, this goes ok, I will again refit my new boxes, just to give them a fair hearing. I am hopeful they perform better with the new cat and the problems I currently have are genuinely due the the Alfa Twin Unit.

Now for your rig :- 1. Do you still have the Manifold Cats fitted?
                            2. Have you removed the small resonator/muffler, just after the twin "Under - car" cats?
                            3. Have you had a bespoke replacement for the Alfa Twin Cats made and fitted?
                            4. What rear boxes have you fitted - are they too, bespoke?

You are only the second person to my knowledge who has removed the central twin cats and reported the absence of droning. So I am hopeful that mine too will soon disappear. The modification and rebuild of the engine was really straight forward, albeit difficult to source parts and find an engineering shop to do it for me. Every Alfa Shop declined although Alfa would sell me a new one for mega - bucks. Eventually, it was a company that does Ford and Vauxhall competition/racing engines that undertook the work and a garage that had never dealt with Alfa's before that undertook to remove the old engine and refit the new - transfering all the ancillaries over from old to new. Both companies did brilliant jobs. I shan't comment about so called specialists! But I can understand why Alfa are in trouble over here. However, they only have themselves to blame given they give such little support to independants.

It would be helpful if you could clarify your set up for me. The process is ongoing but I am hopeful it is nearing completion. The power lift and performance is all I could hope for, even though I started this project just to get temperatures down. Well they certainly are now - even after a spirited one hour run, the inlet manifold is comfortable to touch. Previously, you could grill a steak on it!

Cheers.   
                         

[Stu159]

Hi Ascari,

The whole system is bespoke. I'm not going to name who did it (inner Sydney specialist), because while the end result is great, the process involved in getting to that point wasn't + the associated costs (20% more than the original quote, that I had to part with as a 2nd outlay to make necessary adjustments) + repeated visits. I will never return.......

1. Do you still have the Manifold Cats fitted? yes
2. Have you removed the small resonator/muffler, just after the twin "Under - car" cats? replaced with an after market sports muffler
3. Have you had a bespoke replacement for the Alfa Twin Cats made and fitted? no, removed altogether
4. What rear boxes have you fitted - are they too, bespoke? yes, bespoke high flow
All the new gear is theirs and it's custom. Hopefully of a much higher standard than their ability to communicate.......

As I noted, the big difference in sound is when starting up cold, but it has a nice purr at idle once it settles and that sweet sound it always had up around peak revs, is more of a deep growl now. Noticeably louder overall, but no droning and unless you put your foot down, no louder than an old school V8 with a twin system. Next time I go to see my mechanic I'm going to get him to drive it up the road so I can have a listen 

P.S. I love your passion for the 159. I've always found the purists comments about the GM block amusing. It's a great car to drive and after 116,000 k's of ownership (I bought it as a dealership demo), I have no regrets

Cheers
Stu

[Ascari32]

Thanks Stu,

Glad it all worked out in the end - but it seems a familiar story. Exhaust people here also want to lump "Development Costs" onto the customer. It is like they are doing an exhaust system for the very first time. Surely there is a degree in commonality between cars of the same class. A company here wants to sell me yet another set which they "developed", but as I point out, the gas flow is somewhat different now the man - cats have gone. What you have done seems to be similar to what this company has done although they said they were going to do cat - free manifolds some years ago.

However, whilst your engine purrs on tick - over, this thing does not. It growls! It has a meaty sound, despite ticking over at 750 rpm. I can only assume, the removal of the cats and the valve timing change the camshafts have brought, has resulted in a better AFR at tick - over.

When this engine idles, the phasor pins are in and the camshafts "Locked". And the ECU is setting the AFR according to the MAF, I think. So the mixture may well be more appropriate for slightly higher revs, but the ECU detects the throttle position and will not release the Rotors.

But there is no doubt the engine is drinking more air and exhaust gas velocities are much higher. So mufflers designed on a standard 3.2 JTS have less demand on them, because of a) the restriction of the manifold cats, b) the restriction of the central cats, and c) the standard valve timing. My engine is devoid of all three of these issues.

So I can't go down that route because when this company realises the truth of what I say, they will be lumping more money onto the boxes and pushing the price to silly levels - similar to what you experienced.

At least I have assurances from Supersprint engineering dept., that their boxes will cope and they will bear the cost of resolving the issue if they don't.

I can see genuine benefit of removing the central cat, as you have done, whilst leaving the man - cats. You will most definitely have better flow through them now and by joining the two paths directly - no central cat - the velocity of the gases, away from idle, will directly aid the flow characteristics of both banks - a real plus. And I think your engine/cylinder heads will be a bit cooler too!

However, it is clear the central cats are a problem not least because of the way they co - join. The two outlets, being squeezed into one form a "Reed" across which the gases alternately blow and generate harmonics. And because the join tangentially cause vortices/turbulent flow from there - on back.

Your throttle response has increased fundamentally because your pumping losses have reduced. Have you noticed an improvement in economy?

It is encouraging to know what you have achieved and although I have removed the manifold cats, the new Supersprint Cat is designed to unify the flow at the input and create laminar flow at the output. The union of your two banks effectively do the same. the difference being there are only the tail boxes on my car, no central resonator or muffler in place of the twin cats. So it is going to be louder regardless. I can see your system will sound sweeter and less loud than mine. But it is the thoroughly unpleasant edge to mine that is really grating on me.

So I am going back to basics - refitting the Alfa Back boxes - and allowing myself time to re-adjust, so when the sports cat is fitted, I can make some sense of what has changed. Up till now it has all been getting a little confusing. Clarity is what I need now.

Cheers

Stay Safe!

       

[Stu159]

I love all the info Ascari! Thanks again

In answer to our question re fuel economy, you'll have to give me a while longer for that to be fully realised. I need more time to get past the enjoyment of the new acceleration & sound, before I'll be able to gauge economy. I do less than 5000 k's annually, so I don't drive that much and the conversion we've been discussing was only done a few weeks ago. I never take that much notice of fuel economy as I only fill up once every 5-6 weeks anyway, so it's not an issue. I'm going to add a remap soon also, to further enhance the exhaust.

I've read your other posts also, which are a great. Each time I replace something, I upgrade. I've gone for B16 suspension and a complete replacement of poly bushes all round, in recent years. Next is fitting my Ti seats that I recently bought & I'm planning some tweaks to the interior to compliment those. I found the improved cornering ability with the new suspension was magic, but I couldn't stay in my seat to completely enjoy it, hence going with the Ti option. Also with the seats replacement and I intend to look into the option of making the adjustments to the rear shocks accessible. It's great to have adjustable shocks, but when you need to remove the rear seat to access them, well, not so good 

Catch you next time and look forward to reading your updates with your exhaust set up

Stu

[Ascari32]

At eight this morning I watched as the original Alfa Boxes were fitted. 30 - 40 minutes later and the car was driven out of the servicing bay - and peace returned to the world!

I thought I would have to concentrate hard to detect the difference, but it was glaringly obvious. I had expected to attribute subtle changes to the sound, confirming my view, it is the Cat which is fundamentally the problem. Well, if only that were true - the world would be a simpler place. No! whatever noise the cats generate, is dwarfed by the racket these new back boxes were making.

So now I must tune my hearing again, such that when the S.S. Cat arrives and is fitted, the differences are obvious. Oh, if only it were that simple. But it is increasingly clear, the new back boxes cannot withstand the exhaust gas pressure and are nowhere near as good as the Alfa originals. I fitted the new nearside rear box (LHS) but I doubt that is responsible for the dramatic reduction in noise. I still need to check at higher revs where the Alfa boxes appeared to break up, but all in all, I think I made a serious mistake with the new boxes. I should have taken a little more time over deciding which to go for - S.S. or these. The S.S.'s are expensive, but in the long run I think they would have been the wise choice.

Four weeks, or there about and the new cat will be fitted. Then we shall see what we shall see. In the mean time, I have booked a fitting for two new rear tyres. I am on the legal limit now. Not many miles out of them at all, but I have been testing my mods/playing enthusiastically.

God, I just love this car. The engine, with its Mods, Cams and Manifolds is extra special. Should any engine be this flexible? At 3.2 litres, I don't know any naturally aspirated V6 engines that are. It feels a bit undergeared now.

Still looking for a Holden Badge though!

[Ascari32]

At eight this morning I watched as the original Alfa Boxes were fitted. 30 - 40 minutes later and the car was driven out of the servicing bay - and peace returned to the world!

I thought I would have to concentrate hard to detect the difference, but it was glaringly obvious. I had expected to attribute subtle changes to the sound, confirming my view, it is the Cat which is fundamentally the problem. Well, if only that were true - the world would be a simpler place. No! whatever noise the cats generate, is dwarfed by the racket these new back boxes were making.

So now I must tune my hearing again, such that when the S.S. Cat arrives and is fitted, the differences are obvious. Oh, if only it were that simple. But it is increasingly clear, the new back boxes cannot withstand the exhaust gas pressure and are nowhere near as good as the Alfa originals. I fitted the new nearside rear box (LHS) but I doubt that is responsible for the dramatic reduction in noise. I still need to check at higher revs where the Alfa boxes appeared to break up, but all in all, I think I made a serious mistake with the new boxes. I should have taken a little more time over deciding which to go for - S.S. or these. The S.S.'s are expensive, but in the long run I think they would have been the wise choice.

Four weeks, or thereabouts and the new cat will be fitted. Then we shall see what we shall see. In the mean time, I have booked a fitting for two new rear tyres. I am on the legal limit now. Not many miles out of them at all, but I have been testing my mods/playing enthusiastically.

God, I just love this car. The engine, with its Mods, Cams and Manifolds is extra special. Should any engine be this flexible? At 3.2 litres, I don't know any naturally aspirated V6 engines that are. It feels a bit undergeared now.

Still looking for a Holden Badge though!

The Alfa Boxes have been back on the car now for a few days and yet again I am re - adjusting to how they change the cars behaviour.

Clearly the Supersprint centre section works as the droning shifted from the resonator which is just after the under - car Cat, to the rear boxes.

However, with the new boxes fitted, below 3000 rpm is just intolerably loud with a cacophony of rasps all over the place. But what I had not appreciated was, these boxes were throwing this noise back through the system towards the undercar cat, so at some points, it sounded like the whole of the system, from the tail pipes, forward to the under - car cats were resonating. Resonance is not perhaps the right word as it implies a single tone when in fact it is a wide band racket.

It was only when I refitted the Alfa boxes that I realised this was what was going on because, on reinstating, everything sounds so "Muted".

Taking the car for a drive, aircon and fan off, windows down, clearly the only distinct sounds are from the tail pipes. So much so, I wondered whether I have been incredibly lucky as it sounded so much sweeter than I remember, prior to fitting the new boxes. Is one: the one that remains in the garage - nearside, faulty after all? Or does the one which I just bought; and is now fitted, have differing characteristics?

It comes as a bit of a shock - particularly given the expense and the grief I have endured. Apart from wanting to avoid further grief by purchasing yet another pair of boxes, on the assumption they would solve my problem, my inclination now is to live with the Alfa boxes for the foreseeable future.

True, I have not wound the engine up with the Alfa ones reinstalled. But, apart from cold start - up, it all sounds very civilized. And it seems to emphasize just how quiet this engine is. The exhaust note seems throaty and progresses up the scale without any obvious holes in the audio foot print - which marries up with the brilliant progression one gets from the throttle.

So I seem to have come full circle. I could persuade myself that the nearside box was faulty throughout and fitting the new one has highlighted just how good the Alfa boxes appear to be - well certainly that is true when compared to my new ones. But I have yet to fit the Sports Cat, which may well find the Alfa boxes wanting - again.

I think there is a problem with the old box, but not sufficient to justify the cost of this exercise to date. I will however, continue to look for another new Alfa Box to replace the existing old one - rear offside 51813723. If the car continues to behave as it does now, and given more and more Urban driving is being done by me, then I won't be unhappy. I would like to have kept the performance as was above 3000 rpm, but the price is too high - the dead can't sleep.

Besides, with the few intervening weeks remaining before the sports cat arrives, it will give me time to familiarize myself with the sound and performance so that I should be able to detect the changes the Sports Cat makes. And with increased scavenging, who knows, it might restore a little of what I think I may have lost above 3000 rpm, when I removed the faulty new boxes.

Cheers!
           

[Stu159]

Hi Ascari,

What sort of power output are you getting with all the engine mods? I know you've changed cams but what else did you have done?

Have you thought about not worrying about sorting the exhaust note issue any further and just opting for the Holden badge option you mentioned? 

Stu

[Ascari32]

Hi Stu,

I will fit Holden badges to my car, if I can find a couple of those suggested in an earlier post "Designed by Holden". Particularly if I can prize out the Lions Head and insert the Alfa Badge. It is no less than Alfa deserve for the way customers have been, firstly fleeced and then abandoned, wrt the 939 series.

However, in the meantime, my son and I have been debating what the car should now be called. He bought me a couple of Alfetta badges and suggests "Alfetta Competizione". And I favour "158 Competizione". The 158 logo should arrive today. But I see no reason why the Holden flashes can't go on the front wings.

Although I bought a failed ~ 40,000 miler Brera engine just to try to understand why this engine suffered so much criticism, very soon after my 159 engine gave up the ghost and it became necessary to either, scrap the car or rebuild one of the two engines. Alfa would have prefered I scrap the car and the Brera engine, if their attitude was anything to go by.

Parts were very difficult to source and their prices exorbitant. Alfa would graciously sell me a new one for £16,500 or a reconditioned one for £12,500. A new crank for circa £3,500.

The Brera crank was bent and wherever I went it was the same story - can't be pulled back; it will break. So provision had to be made for a new crank, from somewhere.

Step forward  "RevHigh" - take a bow! Great Aussie outfit. New crankshaft from them + shells at a fraction of the cost. Shipped Au$ 900. By this time I had inspected the Brera engine and come to appreciate what a good block it was. It was not without its problems but nothing that I though could not be resolved.

Although the 159 had new chains and tensioners fitted at 110,000 miles, I didn't want to reuse them. Step forward "Mace" - take a bow! They supplied their uprated kit and Oil Pump + Rocker Arms.

I contacted a company in the States about fabricating a windage plate and soon the Director and I established a friendly rapport. So much so, he sourced many of the research papers on the evolution of this engine and found parts which were unavailable to me in UK. For instance, the latest Spray Jet Nozzles which are much more accurate and operate at a higher pressure.

The first modifications were to the oil filter/cooler which I determined could supply the rear bank lower timing chain tensioner - direct. It was a fundamental mistake to place the principal tensioner at the end of the oil way supply. The residual pressure there, after all other services had taken their quota was far too low to maintain tension.

There was also "Three Serious Restrictions" within the block, almost immediately the oil leaves the filter/cooler. So they too were bypassed, taking the oil directly from the filter/cooler, into the front bank main oil gallery.

These first modifications were however, tested while my 159 was still running. They gained me 10 BHP as indicated on my dynamometer run. But I had still to modify my VVT's which I considered to be worth a few more horses. I estimated at the time of failure, the engine was good for ~285 HP.

At this point restoring the Brera began in earnest. Despite a new crankshaft being on its way, a local engineering company - Ivor Searle - take a bow, pulled the original crank back to within 3 thou, peigned it and inspected it for telltale fractures. None were detected and a regrind and 1st oversize crank and conrod shells were sources - Lithuania.

The Oil way mods had worked well but the sump needed modifications. Drainage from the heads appears from ducts in the sump, directly in line with the rotating crankshaft journals, whipping oil immediately into windage. Aluminium plates were welded over these openings to carry the oil directly below the windage plate and into the sump. At the same time the windage plate was extended to cover the full length of the sump, completely shrouding the oil pan from the rotating crankshaft.

The Oil pick - up for the pump sits too high above the surface of the sump floor. So a new one was acquired from the States and was modified, lowered to help eliminate oil starvation in corners. It is worth about an extra litre of oil in the sump before the pick-up is exposed. At the same time baffle (Swage) plates were welded to the sump floor to channel oil via the face of the pick - up, no matter what direction the car is travelling.

The VVT solenoids were modified to block off oil leakage, back to the drains when the camshafts were either advancing or retarding, greatly reducing the time it takes for the camshafts to re-adjust as dictated by the ECU. The rear bank exhaust camshaft positional sensor was modified and realigned to eliminate the error inherent in its location.

Every one of my Alfa's were maintained by me, until the GT and the 156. I was quite happy about that, although the 156 was the most expensive car I have ever run. I could have bought a Roller, the money that car consumed. And the 1.9 GT the cheapest - a brilliant little motor.

My 3.0 GTV is also garage maintained - a local guy I have known for over 20 years and that will continue.

But the 159 is different territory altogether. The prices are eye watering and there was no way I would allow anything done that was not under my direct control.

However, whilst having committed to restoring the Brera engine into my 159, there seemed little point if all I got from it was much the same as before.

I have used Colombo Bariani camshafts on four of my previous Alfas and they were brilliant. And, I knew of the existence of a set of C.B. Special camshafts, which have gone unsold for years. I decided I would give them a go! It was clear to me, if I was going to get engine temperatures down, different valve timing would be required.

I had already decided the Alfa Cats were going in the bin. And one would not be effective without the other. So, C.B. cams and Auto Delta headers it was then!

I thought very little about the exhaust system up until recently. I was sick to the eye teeth of the ridiculous claims made about cat - backs and all. But the drone I had a 2500 rpm, whilst livable before, when the engine was reinstalled became intolerable. And I allowed myself to be sucked in.

I have refitted the Alfa Boxes, the nearside being new and she is driving beautifully. Quiet at low revs now, in conjunction with the Supersprint centre section, no drone at 2500 rpm and loads of torque at very low rpm. 1200 rpm in 5th on rural roads is so sedate - it feels very special.

But, I just checked a few times and the rear boxes do break up a little at higher revs. I can't confirm anything yet, but again I am drawn to the Alfa Central Catalytic Converter. It just has a particular edge to it. So I must be patient - only another two - three weeks. Then all being well, if and when I can find one - a second new Alfa box will go on and that will be me finished.

After all that, It will be down to getting the bodywork polished and some cosmetic touches.

Now what is she likely to be - powerwise? I forgot to mention the crankshaft, conrods and pistons were fully balanced and am ignoring gains from more accurate VVT settings - camshaft angles are now very much more precise.

Autodelta have indicated about 8 bhp of recovered losses. The headers don't increase power, they reduce losses. So ~ 8 bhp is quite a conservative figure when one considers the reduction in pumping losses after the man - cats have gone.

Colombo Bariani state the gains made with their camshafts depend wholly upon the state of tune of the engine as a whole. So again, conservatively an increase of 10% in torque is not unreasonable. But they say, not less than 10%, so given all the work I have done - here's hoping!

Calculations based upon my Dynamometer plots indicate ~293 bhp @ 6670 rpm - neglecting the headers. However, cams and headers are mutually beneficial to each other. But ignoring this aspect 8 bhp recovered losses from the headers would take the engine to 301 bhp.

But I anticipate further gains, which cannot be confirmed until I have the car dynamometer tested. The manifolds in conjunction with the valve overlap definitely introduce a degree of scavenging that hitherto was absent. So volumetric efficiency will have improved as a function of PVO and reduced pumping losses. In combination with this is the benefit of the Supersprint Centre section and the absence of the post cat resonator/muffler.

In conjunction with these will be the new 100 CPI Sports Catalytic Converter, which in itself will not only reduce exhaust gas flow resistance, but also add considerably to scavenging, given the two flexis now combine at the input to the Cat, whereby there is transparency between gas flow from both banks - ie. they are physically connected.

I have not included the benefits of the revised VVT performance which noticeably increased torque at the bottom end and clearly this will have a marked effect at higher revs too. I originally predicted 315 to 325 bhp. I remain confident that it will be at least 315 bhp, but increasingly I suspect it is going to be nearer the upper figure.

Whatever it is, the sewing machine sweetness of the engine - reminiscent of my Alfetta GTV6 is absolutely beguiling. Whilst not wanting to tempt fate, all the ancillary components fitted to the Brera engine remain unchanged.

I have yet to suffer burnt coil packs or miss - fires. In fact, if what is reported on forums about this engines systemic failure are to be believed, clearly this is not an Alfa Engine. The car in itself is very un - Alfa like. In fact, aside from the finer details, which perhaps could have been done better, it's as good as any 3/5 series BMW, ignoring the "M's". I wouldn't swap it for any Audi or Jaguar. And, given it at least has six cylinders, it remains the second best Alfa of late - behind the Giulia 2.9 - which isn't and Alfa in any case - it's a Ferrari.                                   

[Duk]

Some rather interesting reading, Ascari32.

The 159 is built on the FIAT/GM 'Premium platform' https://en.wikipedia.org/wiki/Alfa_Romeo_159
The chassis have exceptional torsional rigidity.

And the engine is a GM creation that was manufactured here in Australia by Holden. The same family of engines were used in our local Commodores and also the last of the Saabs.
Tho the really powerful, twin turbo versions of the engine were only used, as far as I can tell, in the U.S. in the Cadillac CTS. A car I think was built on the same chassis as the VE/VF Commodore.
The best of the twin turbo engines used all of the very best modern methods of making lots of power, with a hugely broad torque curve. If mechanically tough enough, it would/should be able to rival the twin turbo BMW M3 and 2.9L Alfa engines. But GM seam to put all of their emphasis on their V8 powered machines.

[Ascari32]

Thanks for that Duk.

A prototype Alfa was designed around twin turbos and that was north of 400BHP:-

https://r.search.yahoo.com/_ylt=AwrJQ6DAxGlfjygAKHUM34lQ;_ylu=Y29sbwNpcjIEcG9zAzEEdnRpZANDMDQ1NF8xBHNlYwNzcg--/RV=2/RE=1600795968/RO=10/RU=https%3a%2f%2fen.wikipedia.org%2fwiki%2fAlfa_Romeo_Visconti/RK=2/RS=gerhpCGVI2zrATHTW5kzUbegy.I-

Of course the SAAB and Insignias had twin turbo versions at 2.8ltrs. I was at one point contemplating a new SAAB engine complete with all ancillaries and just over £2000 as an alternative to rebuilding the Brera engine.

The standard JTS engine performance is not enough to test the wonderful chassis the 159 Q4 sports. It really is very rigid. Happily, I am starting to see its true virtues. Strut braces are available although in standard guise it hardly seems necessary. Pushing on now, uphill on a local sweeping righthander, the car is now starting to talk to me: the Q4 system is brilliant.

However, instead of just replacing the rear P - Zeros: 235/40/18, I decided to get back to what they should have been - not least because the 40's were very noisy. So I went for 235/45/18 UniRoyal RainSport 5's. Took them on recommendation and road noise has dropped tremendously. And they were a fair price.

Just received prior notice my S.S. Cat is in transit from Denmark and should be here in the next day or two. However, another issue has just popped up - no A/C - Climate control completely dead. So just ploughing through the e-disc to see what may be going on. There is a pressure sensor on the condenser which may be the culprit, but I am really stabbing in the dark. Perhaps the garage can check it out when the cat goes on.

However, as an indication of just how well this engine is regarded, in revised form it will remain in production until 2026. And I can understand why. As good as the Busso is, casting technology has moved on and its block cannot compete with the likes of the 3.2JTS. The 3.2 JTS crankshaft is literally buried/encapsulated within the main superstructure.

Stepped bearing caps with six bolts two each side, of differing sizes, torque settings and on two levels, either side of the mains give incredible rigidity, complimented by two bolts either side from the outer walls through to the sides of the caps adding further bracing and strength making it vastly superior to anything I have come across.

The bores, cast into the block add further strength and the way the underside of the block is sculpted - almost cathedral - like - creating a continuous architectural casting must add tremendously to the overall strength. Wetting of this void, by oil, thrown by the rotating crank creates an even distribution of temperature across the whole of the blocks internal surface. It is a brilliant piece of engineering and for a mass produced engine is outstanding. Alfa completely missed that!

The Heads however -Alfa's, are a different matter altogether. If there is a limiting factor to this engine, this is where it lies.


Vauxhall Insignia and SAAB 2.8 - Twin - scroll turbo I believe.           

[Colin Edwards]

When I had my 159ti Q4 I felt the "best" exhaust was the factory one the car came with!  A fairly docile growl from the pipes that allowed you to hear and feel the engine.
I enjoyed the song from the engine more than the exhaust "note".  I believed I could hear and feel every cylinder ignition and resultant mixture burn.  A crispness I have never heard in anything else other than a 16 valve Sud motor or a Rotax kart engine!

Considered installing improved flow manifold cats but didn't get around to it.  Might have lost the ability though to hear and feel that lusty V6!

I don't mind loud exhausts.  Problem is they continually remind me how much energy is lost out of the exhaust by a non-turbo engine!

[Ascari32]

I arrived home to find the Supersprint Cat, sitting on the drive at the front door.

Continuing for the moment with the rear Alfa boxes, they are very civilised up to 2000 rpm. Loading the engine does not provoke break - up. But stab the throttle and there is a raspiness reminiscent of the old 1300 Sud. Lovable, but not right for the car.

Up to this point, the system is very quiet from the engine, to the tail pipes, with a nice throatiness, coming out the back. Just as it should be with no untoward noises. But from 2000; a multitude of low level sounds, combining to sound louder; if that makes sense, start emanate  along the full length from the Twin cat below, all the way back to the tail pipes.

I am making the broad assumption, these harmonics are a function of the Twin - cat: if this were not the case, they would extend to the exhaust ports of the engine. But no; the engine remains incredibly smooth although flow - through starts to sound more melodic.

I can only speculate it is the poor design of the Alfa unit - in particular the way the outputs combine. I also think, it is the central resonator/muffler that is used, principally to suppress these harmonics, which they did with my car. But progressively, the level of these products and their harmonic content, provoked the resonator/muffler into resonating, peaking at ~2500 rpm.

With the S.S. centre section fitted, the pipe has a more pronounced metallic ring/tinkle to it than the mild steel section it replaced. But this, I am convinced is only because of the harmonics generated by the twin cat.

The car is booked in for the S.S. cat to be fitted on Tuesday, so all will be revealed.  Not wanting to make it to easy for me, not only did the C/C pack up, having windows open to get a little air flow, on parking up, the drivers window failed to close! Then on the way home, it rained! Still, at least the S.S. Cat was there to greet us, package sitting in the rain with the rest of us.

The new boxes I bought may be retried at a latter date. The sound they made above 3000 rpm was to die for. And it seemed the engine was even free - er reving. But impossible to live with below. To what extent the Twin Cat was exacerbating this, needs to be established. And it may give me an opportunity to modify them a little to make them more tolerable. That is more in hope than belief.

[Ascari32]

29/9/2020 - Supersprint Catalyst fitted this morning. After what seems like a lifetime, at last - all the theory in the world becomes irrelevant. Is the Alfa cat the problem or not?

Answer - YES. The rear boxes; Alfa, hitherto breaking up badly at higher revs, no longer doing so. I cannot believe how quiet the exhaust system now. It will take some time to sink in but in essence, my new boxes will need to be refitted at the very least to determine just how much their appalling low - rev performance can be attributed to Alfa's Twin Cat.

Sound level is about a dB or so greater, but because all the spurious noises emanating from the Alfa Cat have now vanished, the perception is that the car is now actually quieter.

It will take some time to digest exactly how different the car, engine and exhaust system is, but at least the case against is proven. Quite an exercise, an expensive one at that. It would be nice to think I could refit my new tail-boxes, so that it wasn't the absolute disaster of a mistake, it appeared to be up until today. That would be a real cherry on the cake. But for the moment, I am over the moon about the improvement the S.S. Cat has made to my car.

And the engineer at SuperSprint predicted exactly what to expect. Nice to know at least he shared my belief in where the problem lay. But until that Cat was fitted, it was pure hypothesis.

Now however, it's fact!

Well done SuperSprint!

[afelice001]

What a comprehensive thread. Serious work has gone into research, development and testing here!

I've just started researching 3.2 exhaust options and it sounds as if there are no *easy* or cheap power gains to be had, or even sound improvements.

A somewhat silly question - is the stock system 2.5"?

[Colin Edwards]

Hi Afelice001,

I found the best bang for your buck with regard to improving the performance of the 3.2 equipped 159 was to make the whole car more mechanically efficient.  I had a Q4Ti. 
The 159 had a bit of a reputation for eating front tyres - especially the FWD Ti model.  The AWD Ti not so bad.  Cause of the tyre consumption was excessive front negative camber.  Cause of the excessive negative camber is the 159Ti is a "lowered" standard 159.  The reduced ride height caused an increase in negative camber.  Unfortunately the 159 suspension is not adjustable for camber.

I replaced every possible rubber bush on the front end with polyurethane.  My replacement upper control arm bushes featured cam eccentrics allowing camber and caster adjustment.  This work AND careful front end alignment setup by a club sponsor allowed significant reduction (but not elimination) of negative camber.  An increase in caster is also worth pursuing.

Negative or positive camber causes "camber thrust".  This camber thrust caused by excessive negative camber can be managed by increasing toe out.  However tyre wear is excessive AND excessive toe eats up engine power by increasing the rolling resistance of the car.

A further means of improving the mechanical efficiency of the car is using low rolling resistance tyres.  In the past, this meant using very hard tyres with little grip.  Todays tyres can be significantly more efficient with regard to generating grip for a given rolling resistance.  The latest Michelin PS4s tyres, while relatively expensive, do realise measurable fuel consumption reductions. 

If the "whole car" is more efficient, for a given engine performance, it MUST accelerate quicker and achieve a higher top speed.


Colin