Regarding gas velocities and building 16v motors, the intake port and runner area needs to be increased quite a bit if the engine is to be taken higher than 6000rpm (the stock runner and port become limitations much earlier than this btw).
Here's a quick example with some rough numbers:
Let's say we want a somewhat worked 16v with a goal of 900hp@8800rpm on E85. I would build it as follows:
36mm intake valves with a bowl area of that's 87% of the valve's face area. I would gradually enlarge the port it until it has the equivalent area of a 44-45mm diameter circle (at the intake manifold gasket). This should give an intake flow of 310cfm@28", assuming it's been properly ported.
The intake runner would start (at the head) with an area equivalent to that of a 45mm (diameter) circle, then gradually widen to 52-55mm. The length of the runners would be about 14-18cm (plus the depth of the ports), followed by a large plenum and an 80mm throttle body.
I would keep the exhaust ports and valves stock. Cleaned up slightly they would give 250cfm@28".
The combustion chambers would remain largely stock, and the pistons would be inverted dome style with a negative deck height of about 2-3mm. The compression would land somewhere around 7.5-8.0:1.
Cam specs would be 245/0.05" on the intake side, and 250/0.05" on the exhaust side. Both would lift 13.5mm.
The header would have 47mm ID primaries approximately 50cm long with a divided inlet. A 50-60mm wastegate would control boost to approx. 37psi.
I would run something like a Holset HX60 or a Borg-Warner S400 with a 76mm compressor inlet and an 88mm turbine outlet with a turbine housing matched to make about 25psi of backpressure.
A large intercooler and a 4" exhaust would finish it up.
I would love a go at this in a mk1 343
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