ALFAGTV6.COM

[Duk]

Got a friend with a 420hp turbo TS powered 75 street sedan. His words : "Mostly undrivable./unusable power".

Without knowing a lot more about it, I'd guess he's got a pretty sizeable turbo on there. Probably of the GT30 variety?
Fairly sizeable turbo on a fairly small capacity engine does tend to be a bit abrupt in its power delivery/torque curve. Overly big intercoolers and plumbing exacerbate the problem.
Lots of people often build turbo engines with turbos that are bigger than they need. Similar with intercoolers.
But when you look at how car manufacturers do it, you see they use much smaller turbos and make them work hard(!). The Giulia Quadrifoglio swallows over 20psi to make its power and the turbos are far from big.

Personally, as hinted at before, I'd rather a smaller (modern turbo), make it work hard for the power I want. I'd sacrifice 20-50hp of outright power for a broader tprque curve and a more predictable engine.
Much like cylinder head ports, bigger aint necessarily better.

[Jim K]

'How do Greeks do it?' Haha, I like this one! Well, just like everyone else but not often enough, that's why population is declining!
Now on cars, I will agree with MD -as much as I hate to. First you gotta know what the hell you're going to use the piece of junk for. A 747 can't be a fighter and vice-versa. We have a few guys here with powerful 1.8T's who have busted their share of 'boxes and guibos but they are street-dragsters, something I despise for several reasons. True, if you beat the crap often enough out of anything, it will break, transaxles included. You want everyday torque and low-rpm grunt? Get a V6. But if you have to pay ridiculous cube-based taxes, you build a turbo. You know it'll suck until ~3500rpm, but you're planning on ~300+ up top? Tough shit, live with it! Some of these idiots have nothing under ~4500rpm and are not bothered at all, driving on the street! Or, as Duk says, size the snail right and be happy with the best possible driveability it can give you, forgetting about breaking the sound barrier up top. It does take some intelligence to build a fun, properly usable turbo engine and 99% of owners/mechanics do it wrong. AFAIC, even my industry-hyped GTX2860 is too big for the 1.8T, I had best low-down performance with the GT2854, but 'only' 240hp. Maybe I'm a bit paranoid about the low range and I believe it has a lot to do with also owning a 75 with a 3.2liter. Drive the V6 for awhile, park it and take out the 1.8T.... boy, you'd be pissed, too!

Jim K.

[75evo]

Who is this man? He claims to be JK but he said good things about the V6.....

[Jim K]

Bull! This is slander! I like the V6 (24v) but I'd like it a lot more if it had, say, longer stroke, a bit bigger valves and double Vanos.... Any objections?

Jim K.

[maxiboy]

Cant increase the stoke ... can increase the bore and fit bigger valves though ..

[75evo]

If the rods were slim enough could we squeeze like 10mm of stroke or so? I think in the US you can get a crank for around $5K.

AHM has special cranks for the V6, still the stock stroke though, but if you total up the pure race V6 parts, you could buy an E46 M3 CSL. Kinda of a no brainer at that point....

[Duk]

Going by what Jim has said, you might aswell start with the Holden (GM) 3.6 litre engine. All aluminium with continuously variable valve timing for all 4 camshafts.
Jammed into the now dead local Commodores, they move those barges OK. Modified for more power and in a much lighter car, they'd make decent power plant without going for forced induction. Hardly an Alfa engine, even if a 3.2 litre variant powered some of the later FWD cars.

[75evo]

I think the days of these cars being a daily driver ended a while ago. So for me VVT is no longer necessary and adds to unwanted complexity. These cars, IMHO are more of a semi-daily or weekend car. So I wouldn't mind putting up with some less drive able characteristics like a bit more turbo-lag or a peaky power curve.

Most of l my cars are laggy. The Golf 1.8T, despite being a 2016 model is laggy (standard engine, no real power until 2500-3000 rpm), Accord Euro Type-S (no power until "VTEC just kicked in you" at 5500 rpm).

In fact like Jim K said, the V6 offers the best usable output. The 164 3.0 12V was fantastically torquey, the 2-valve engine and long runners definitely made it feel alive in traffic.

The two top choices for me for Jim Steck's poll would either be a laggy 2.0T with 300 bhp or a 8000 rpm V6. Both would add some excitement to the mundane everyday cars. I don't want a V6 that dies at 6000 rpm. I have other newer boring cars that do that, and do so more comfortably too.

[4SFED4]

Sorry for any confusion... Jim goes by "4SFED" and I go by "4SFED4"... my name is Brian and I am the owner of the 78 GTV with a Steck built turbo motor.

Working with Jim we first built the car in 1995. The first iteration has an on center turbine housing and a log manifold and while it made a little over 300BHP it was laggy. Once on song and on a track the lag was non-existent since engine rpms remained at or above 4000rpm most of the time. The car was going to be a track car but then I got in to racing purpose built race cars and realized I did not want to drive a track car on the street so this car has remained a street car, ac, stereo, power windows full interior etc. It is driven 12 months a year, when it is dry. It is not an everyday, take me to work car.

Iteration 2 used an equal length manifold and a T04 divided turbine inlet. The manifold runners were each about 30" in length. It was very large and took up a lot of engine bay. This made a little more power and was much more responsive. It used an external wastegate vented to atmo but retained the 2 1/4, 57mm exhaust so top end power was limited. The car was still a blast to drive.

Iteration 3 was to go to a new tubular EL manifold and a modern Garrett GT3071R, the smaller of the 2 GT30 framed dual ball bearing turbos. I also went to a full 3" exhaust front to back with the external wastegate plumbed in to make it a little quieter. This is a very nice combination. positive boost under 2500rpm, max TQ at 4000RPM and a power band to 7500RPM. This upped the power to a little over 350BHP at about 1 bar on pump gas. Just for fun, about 3 years or so ago Jim helped me adapt a VVT intake cam. One of the best mods I have done. Picked up 60TQ at the wheels under 4000RPM and gained 20WHP over 5800RPM. The engine is managed by an Electromotive TEC 3R so the VVT is controlled by the ECU and switches from advance to retard at 5800. I also added an IAC for better cold idle control.

Fast forward to a month or so ago when Jim tells me of a very inexpensive 8v TS head that is available. While the car does not "need" any more power I figure it will be a fun project to go with a TS head, new Garrett G25 550 turbo and shoot for 450BHP. Also going to go with DBW for power management and cruise control!

FWIW, I do drive this car. I do NOT do standing start burnouts or donuts but I do give it some stick EVERYTIME I drive it and... other than replacing a worn second gear syncro, clutch disk and a front guibo I have not had transaxle issues since 1995! But no doubt 30 minutes of spirited street fun is nothing compared to a 30 minute track session. I am using a Milano Platinum (read 75 turbo) transaxle with limited slip and the V6 prop shaft. Jim modified the front Alfetta bell housing to fit the front V6 guibo. I do not use guibo cages, might in the future and I do not have a gearbox oil cooler.

Someday I will have another Busso but I love the front end turn in the lighter Nord affords the chassis.

-Brian

[Duk]

How far could the capacity of the 2 litre motor be taken?
With 2.2 or more litres of engine and a well sized (as small as you could get away with) turbo, you'd broaden the torque curve of the engine noticably.
Really speeking, if you were able to add 10% more engine capacity, then you should be able to get 10% more torque and off boost, that would be quite helpful.

[4SFED4]

How far could the capacity of the 2 litre motor be taken?
With 2.2 or more litres of engine and a well sized (as small as you could get away with) turbo, you'd broaden the torque curve of the engine noticably.
Really speeking, if you were able to add 10% more engine capacity, then you should be able to get 10% more torque and off boost, that would be quite helpful.

You can get to 2.1 liter via stroke and Alfaholics increases bore to get to 2.2. Bore and stroke increased from the stock 84.0x88.5 mm to 87.0x94.0 mm, netting a 2,235cc or 2.2L displacement.

Not sure I would boost liners that thin.

[Duk]

Does anyone know of a suitable liner material other than grade of cast iron that usually gets used?
If a stronger, stiffer steel type of material could work as a cylinder liner, then it might be more suitable for a high stress application even with a thin wall thickness.

[105gta.]

I'm pretty sure we're stuck with cast iron for liners, although steel is stronger/tougher per mass, it is more elastic and certainly doesn't have the porosity needed to hold oil within the surface grain structure. With the harmonics and surface temps reached at the ring face im sure you'd loose ring seal and also have limited lubrication so would wear quite badly/quickly.
If you really want to pick the limits of wall thickness have a chat with the likes of Darton in the US. I'm sure they will be better able to advise on what the options are for a wet liner.

[Jim K]

You can order special liners from Darton (US), Westwood Liners (UK) or Gozzoli Autotrasformazioni (Italy). State your requirement and they will use the proper material. In Italy they use 'spheroidal cast iron' as they call it. Alternatively -for a 4cyl engine- you can pay a lot more and buy a monosleeve, or even a matching pair dry-deck block/monosleeve like the one offered by Alfaholics -but at a much lower price. There are some specialized machine shops making these to order.

Jim K.

[KevinR]

Definitely busso twin turbo followed by Nord turbo
I learnt once you break your first crown and pinion you learn to drive it more smoothly on the road and can still be very reliable . I know in nanny state ( MD country ) you can't speed around but in SA in UK there are loads of places in the country to stretch the legs without public around ... But yes it could be expensive when caught .
The joy with the twin turbo my small pea brain found was to play on the throttle in third and fourth as the boost was coming in and listen to both the turbos chattering between each other .... Yeah MD ... I know very mature ... But hey I won't grow up .
This GTV still had standard brakes and suspension just to keep things more exciting and was probably the reason it was not driven in extreme anger ...in the bends