1990 Alfa Romeo 75 3 Litre V6 Potenziata
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Join Date: Aug 2007
Location: South Australia
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Garage
Vehicle Name
Year 1990
Make Alfa Romeo
Model 75 3 Litre V6 Potenziata
Color Metalic Grey
1990 Alfa Romeo 75 3 Litre V6 Potenziata
1990 Alfa Romeo 75 3 Litre V6 Potenziata 1990 Alfa Romeo 75 3 Litre V6 Potenziata 1990 Alfa Romeo 75 3 Litre V6 Potenziata
History 1990 Alfa 75 V6. For some reason they get called 'Potenziata'. I don't know why and I've never seen anything official that says that's what it really is.
The real differences between the '90 3 litre and the '89 and earlier 3 litre are the (over rated) Motronic engine management system (they must have been the most entry level version that Alfa could buy), 9.5:1 CR, apparently different cams, the interior trim is apparently different, the instrument letters/numbers/icons are white instead of (friggin) orange.
But I think the most worthwhile difference is the 3.73:1 diff ratio. Not too low like a TS diff ratio (it is a road car, after all), but better suited than the 3.55 diff ratio.
Everything (or near enough) is the same as the 'Pre-Potenziata' cars. And with the exception of the diff ratio and the white instrument numbers, can be made as good as (but why would you bother?) or better than.

This thing has been a VERY long term modification project for me........
Exterior
1990 Alfa Romeo 75 3 Litre V6 Potenziata Exterior 1990 Alfa Romeo 75 3 Litre V6 Potenziata Exterior 1990 Alfa Romeo 75 3 Litre V6 Potenziata Exterior
Initial thoughts were to simply use the 'non impact absorbing' bars (mine came from a 2.5 litre with the fender flares), but these don't really cover the leading edge of the front tyres very well (much wider track width).
I also think that the bar itself is a bit fussy looking. So I (like to think that one day I will.........) make a new bar that is better suited, while staying neat and tidy.

Interior
Standard except for an Isotta steering wheel.

I'd like to do a nice, well integrated instrument upgrades or just simply modify the factory ones to be driven by stepper motors that are controlled by Arduino micro controllers.
We'll see.

In-Car Entertainment
Who cares????

Under the Hood
1990 Alfa Romeo 75 3 Litre V6 Potenziata Under the Hood 1990 Alfa Romeo 75 3 Litre V6 Potenziata Under the Hood 1990 Alfa Romeo 75 3 Litre V6 Potenziata Under the Hood
Here's an ongoing saga, from someone who can't make up his mind................
Initially the idea was to just midly tweak the engine and use a retuned, early Nissan engine management system.
This then became 'Hmmmmmmm a centrifugal supercharger and WTA intercooler would be a nice idea'.
But I wasn't convinced the the Nissan ECU would work well with that set up and I wanted to get rid of all of the HT leads and go coil on plug.
So a second hand Adaptronic E420c was purchased and all new wiring looms were made.
I couldn't get the Adaptronic to run the engine (angry face!) and attempts to do so revealed compression leaking back past the inlet valves (valves not sealing, even tho valve weren't riding).............
So the engine came out and the heads came off.
This (obviously) led to ports being given a nice tidy up and valve seats being modified RJ style. New valve guides, valves and heavy duty valve springs are also in the mix.
Lightened flywheels are in there, too.
There's heaps of other stuff, but then a new idea took root in my noodle....................
How about leaving the car NA, removing as much weight as is realistic (still a road car and will have A/C) possible from the front of the car, move the engine back as much as I can, etc..............

The extra idler gives much needed belt wrap to the driver's side (RHD, remember) cam sprocket. Unfortunately I broke an Ezi-out in the reducing bush that was screwed into the head, so the bracket looks the way it does due to that...............
The heads are (STILL!!!) in pieces, so I'll be able to sort that out one day and make a better mounting bracket.
Anyways, the extra belt wrap seems to have all but eliminated the potential for the belt to skip teeth while still using the dynamic belt tensioner and is really up there with the "Why didn't the factory do this?".

I've left A LOT(!!) out, but like I said, an ongoing saga...............

Suspension
1990 Alfa Romeo 75 3 Litre V6 Potenziata Suspension 1990 Alfa Romeo 75 3 Litre V6 Potenziata Suspension 1990 Alfa Romeo 75 3 Litre V6 Potenziata Suspension
Ahhhhhhh, the suspension!
The area of the car that I believe is most underdone, in standard form.
Front suspension starts with some Pace Engineering extended top ball joints to get the front roll centre higher and to give a better camber curve.
Bump steer correction comes in the form of a modified bump steer correction kit for an R32 Skyline GTS-T.
Additional coil springs (375lb/in) are there to give a combined spring rate incredibly close to that of 28.7mm TBs.
105 caster arm ball joints are there, too.
Standard Konis are in the picture, but these will be replaced with small bodied, suitable valved Bilstein Digressive valve dampers.
The inner box sections were seam welded, a brace is added in the engine bay (see engine bay pic). And inner guard bracing is also added. Tho new and more sturdy bracing is partly made as they give better wheel clearance.
The front anti-roll bar will be made from a piece of 1.25", 0.125" wall thickness 4130 Chromoly tube (pipe) with, with fabricated arms. This weighs less than the original AR bar, important because it's mounted at the front of the car, but should be aproximately 40-60% stiffer.

The rear is simpler.
Adjustable spring seats are welded to the original spring seats (tho I might do a better/neater job of this), 175lb/in springs (Eibach) are used and they have nylon spacers/locators top and bottom (made from a 3/4" nylon chopping board).
I made my own spherical bearing arrangement for the DeDion pivot point and polyurethane bushes are used in the Watt's linkage.
The Koni's that came with the car are still there, but again, suitably valved Bilstien Digressive valve dampers are planned.
I'd also like to make the rear AR bar adjustable.

Unfortunately the Doctor Frankenstein that lives inside my head wants to do a bunch of stuff to the suspension that would be more inline with a dedicated track car.
Well actually it would be just nice thorough suspension engineering, spring rates and damping would determine track or road usage, but I'll need to talk to a cooperative engineer first.............

Wheel and Tire
1990 Alfa Romeo 75 3 Litre V6 Potenziata Wheel and Tire 1990 Alfa Romeo 75 3 Litre V6 Potenziata Wheel and Tire 1990 Alfa Romeo 75 3 Litre V6 Potenziata Wheel and Tire
Light and strong series 6 Mazda RX7 wheels.
16 x 8 rims, I got these off of eBay with 225/50/16 tyres. Even tho the this wheel tyre combination was substantially bigger that my factory spare, it was noticeably lighter.
The plus 50mm offset allows the use of 20mm thick front hub adapters and 25mm thick rear adapters. This gives a considerable track width increase and JUUUUUUST fits inside the guards.
Tho this idea maybe on the chopping block as a better solution becomes available............... ;-)

Front brakes are the fairly typical Volvo 240 4 piston caliper, 164 rotor and 6mm spacer. Heavy, but very effective. And so are the Race Brakes brake pads.
I'd like to replace these with Series 4/5 RX7 Turbo 4 piston calipers. This may or may not happen and is tied to the 'big maybes' that are part of front suspension changes.

Never tried, the rear brakes are vented Wilwood rotors on custom made hubs, with Series 4/5 RX7 Turbo rear calipers. Again with some nice Race Brakes pads.
I think this will be a good upgrade, but I would really prefer a different set up.
The preferred set up would be based around R32 Skyline GTS-T rear brakes (2 piston caliper on a vented, 305mm rotor) that use an integrated hand brake drum. The rotors/calipers would be mounted outboard and the hand brake mechanism and a custom made drum, would be mounted inboard, next to the diff.

The factory brake pressure regulator is in the bin and an adjustable Wilwood brake pressure regulator is part of the plan.
The 4 point brace that lives in the engine bay also incorporates a support for the master cylinder to massively reduce firewall flex when the anchors are stood on.
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