Reading most of the above, makes me think you are trying to re-invent the wheel. The I.8T engine (not offered in the US market) is a tried and 'simple' solution for everyone wanting a turbo 4cyl old Alfa. We routinely make 250-300 crank hp. In std form, they had 155-165hp and with a simple chip change they went to 210hp (known as GpN spec). What this does is raise boost from std 0.65bar (9.5psi) to ~1.1bar (16psi) and 'desensitize' the knock sensor a bit. Of course, this is never enough, so we go even further. IF you know what you are doing, you can go to ~300hp reliably, without changing any internal parts, a definite tribute to the strength of this engine! For peace of mind and frequent trackday use, I do advise forged pistons, and that's about it, as std turbo rods are very strong -they may look exactly the same with 2liter rods but trust me, they are not. As for the turbo itself, the std Garrett T3 is Jurassic, so best solution now is a GTX2860 or G25-550. The first mandatory step for reliability is a good head gasket. We so far have an excellent record and zero failures with the Italian NAVA gaskets with separate O-rings. These have a square x-section and 3 shallow ridges topside which bite into the head. No worries up to ~2.5bar (36psi) where std 1.8T liners start to break. I've run up to 2bar in my engine (std pistons) no problem, although its set for a steady 1.7bar(25psi). With the old GT2871 turbo, I had 276hp @5150rpm and 400Nm (290ftlbs) @4380rpm. I have since upgraded to a GTX2860 and the car is a LOT faster -haven't gone to the rollers yet. Whatever you do, one of the first things to install is a good AFR gauge. The above was all about the 1.8T. A used 1.8T in Europe goes from 700-1200€ complete.
Now the 2liter... in few words its not suitable for turbo use unless you spend a LOT more, compared to the 1.8T. As proof, ask a simple question: in Europe where both engines are available (although the 1.8T is getting a bit rare) why do people prefer to play with the 1.8T instead of the 2liter?
In 1990, factory 1.8T racers had evolved to 430hp/490ftlbs (no mistake here) at 2.3bar(33psi), all under 6400rpm. Private owners have nowadays gone to 350-400hp, but my personal opinion is that up to 300hp you can have lots of fun with everyday reliability without having to fix ***** all the time. I will not go as far as to say such a car is as reliable as a na engine. Be prepared for increased preventive maintenance and checks, for example resurfacing the exhaust manifold 1-2 times yearly and replacing the fuel pump every 3-4 years or so, more frequent injector cleaning etc. For anyone interested, here's a list of what my engine cost to build (in €). Note that all this concerns the Alfa 75 and is not necessary if you don't push the car around a lot or. I have two such cars, both red and original 1987 1.8T models, one with the below mods and the other modified to 3.2liter 24v.
One last note regarding the IC (intercooler). Since I perfected the water/air system, performance is amazing, to the point that I reduced boost to 1.5bar(21psi). This all became possible by drastically reducing the intake manifold air temperature, after a lot of 'research' and under-hood measurements resulting in simple mods to the way air enters the engine.
In the 105 chassis.... you are very limited in space. Yes, I have a friend who shoehorned (proper word) a 1.8T inside his 105 2-door coupe after a lot of cutting and fitting. Actually, it wasn't a 1.8T engine per se, but a rare 2liter Turbodelta engine with all the 1.8T stuff around it. Lots of work to put it in there, especially around the exhaust manifold, alternator and steering box. With a stock ~175hp, he ended up breaking several rear ends and gearboxes in stoplight drags -torque breaks things, not power. Sure it was fast but every other month he had it on the hoist fixing/replacing something. When he finally ripped the motor out, he found peace...
Alfa 75 1.8T cost
Good Used 1.8T engine complete with wiring………1000€
105480320001 Intake cam............…………………………70
Aeromotive Adj. fuel pressure regulator..……………..200
Fuel pressure gauge………………………………………….……..20
MSD 6AL-2 Programmable ignition………………….…….400
3bar MAP sensor………………………………………………..…….90
4xChampion N2C plugs……………………………………..…….12
Large airflow meter (BMW535), std 1.8T pcb.………150
Bosch 5bar (75psi) fuel pump 0580464126….………130
0280150400 injectors………………………………...………..200
AEM failsafe gauge.…………………………………….………….300
GTX2860 turbo.…………………………………………….………1000
Nava O-ring head gasket..………………………………………250
Blow-off valve………………………………………………….………..80
63mm exhaust pipe, 2 mufflers……………………...…….600
Large water radiator, two fans……………………....…….300
78⁰C thermostat..……………………………………….…………….50
Large FMIC, relocated TB with suitable manifold/associated piping…….400*
Crank scraper/baffle…………………………………….………….250
Head rebuild………………………………………………….…………200
Alfa 75 Evo exhaust manifold………………………....…….400
Machine shop work…………………………………….…………..500
Silicone hoses, bearings, seals…………………….………..200
Turbine Ceramic coating…………………………....………….500
*OR:
W/A modified std I/C, front radiator for I/C and electric water pump……400
Options: std pistons/liners or CPS pistons + new liners…………..………~1000
TOTAL PARTS COST ~7900€ …WITHOUT LABOR!
~270-300hp @ 1.7bar boost
Jim K.
