As many on here already know, I'm purely an Audi 077-series V8 fan. I know that engine as much as many know the 1.8T - that is, intimately.
I am building a V8 turbo, for B6 420-TS. From the 3.0-specific thread I started, considering boosting the ASN / AVK motor, the response and reception that thread generated was interesting. There are mentions of the aluminium block, not being suitable to hold decent boost.
Well, the issue is not the aluminium block being the issue. It's the very internal design. The limitations are deep within the guts. The C5 RS6 block is aluminium, and copes well with updated turbos. What it all boils down to is this:
An aluminium block, that was originally naturally-aspirated, but with forged pistons, and the correct rods will hold boost fine.
A cast-iron block, that was originally naturally-aspirated, retaining the stock cast pistons and inappropriate rods will not hold boost.
The above applies to the aluminium 3.0 V6 and 4.2 V8.
I was lucky enough to purchase a short C5 RS6 (BCY) block. It came from a front-ended car, the impact was enough to tear the aircon compressor and left-hand engine bracket clean off the block, so the threaded mounting bosses are shot. My plan was to transfer the pistons and rods into a regular 40V block, and that plan is still valid.
However...I was going to use a D2 4.2 V8 40V motor as the base. I have worked with sw\aps, involving both the C5/D2 V8, as well as the D3 V8. They are similar, though in the course of my last B5 V8 conversion, I discovered the D3 block is very different to that of the C5/D2 blocks. It is based heavily upon the C5 RS6 motor, larger rear end, designed for a larger flywheel, thicker webbing, making the block stiffer, and the coolant passages are significantly different, similar size to that of the C5/D2 blocks, but with more metal, meaning thicker walls.
And this is where I have decided to make a slight revision. I've located a complete D3 4.2 V8 40V, from a 2005 car. I will be building this, using the C5 RS6 pistons and rods, but not the RS6 crank. I don't want the 10-bolt flywheel mounting boss, as this severely limits the flywheel options open to me. I will be rebuilding the heads, using OEM C5 RS6 exhaust valves, and stock 40V intakes. Intake manifolds will be custom. I do have a C5 RS6 single-stage intake, but I doubt I'll be using it.
Building my 2000 B5 A4 Quattro, with a D3 (BFM) 4.2 V8 40V taught me a lot, the block similarities to the C5 RS6, the head similarities to the D2 S8, including the same dual-stage intake, and very similar camshaft profiles. And, the machining and drilling required to bolt a C5 RS6 motor to a stock 01E 6-speed, without the need for a length-increasing adapter plate (RS6 guys, take note).
My D3 4.2 V8 40V motor. I'll be making a 554-mile round trip to pick it up next weekend. I'm hiring a van, I definitely wouldn't put that in the back of my Avant.
I am building a V8 turbo, for B6 420-TS. From the 3.0-specific thread I started, considering boosting the ASN / AVK motor, the response and reception that thread generated was interesting. There are mentions of the aluminium block, not being suitable to hold decent boost.
Well, the issue is not the aluminium block being the issue. It's the very internal design. The limitations are deep within the guts. The C5 RS6 block is aluminium, and copes well with updated turbos. What it all boils down to is this:
An aluminium block, that was originally naturally-aspirated, but with forged pistons, and the correct rods will hold boost fine.
A cast-iron block, that was originally naturally-aspirated, retaining the stock cast pistons and inappropriate rods will not hold boost.
The above applies to the aluminium 3.0 V6 and 4.2 V8.
I was lucky enough to purchase a short C5 RS6 (BCY) block. It came from a front-ended car, the impact was enough to tear the aircon compressor and left-hand engine bracket clean off the block, so the threaded mounting bosses are shot. My plan was to transfer the pistons and rods into a regular 40V block, and that plan is still valid.
However...I was going to use a D2 4.2 V8 40V motor as the base. I have worked with sw\aps, involving both the C5/D2 V8, as well as the D3 V8. They are similar, though in the course of my last B5 V8 conversion, I discovered the D3 block is very different to that of the C5/D2 blocks. It is based heavily upon the C5 RS6 motor, larger rear end, designed for a larger flywheel, thicker webbing, making the block stiffer, and the coolant passages are significantly different, similar size to that of the C5/D2 blocks, but with more metal, meaning thicker walls.
And this is where I have decided to make a slight revision. I've located a complete D3 4.2 V8 40V, from a 2005 car. I will be building this, using the C5 RS6 pistons and rods, but not the RS6 crank. I don't want the 10-bolt flywheel mounting boss, as this severely limits the flywheel options open to me. I will be rebuilding the heads, using OEM C5 RS6 exhaust valves, and stock 40V intakes. Intake manifolds will be custom. I do have a C5 RS6 single-stage intake, but I doubt I'll be using it.
Building my 2000 B5 A4 Quattro, with a D3 (BFM) 4.2 V8 40V taught me a lot, the block similarities to the C5 RS6, the head similarities to the D2 S8, including the same dual-stage intake, and very similar camshaft profiles. And, the machining and drilling required to bolt a C5 RS6 motor to a stock 01E 6-speed, without the need for a length-increasing adapter plate (RS6 guys, take note).
My D3 4.2 V8 40V motor. I'll be making a 554-mile round trip to pick it up next weekend. I'm hiring a van, I definitely wouldn't put that in the back of my Avant.
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