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Please define the "proper" statement.
Tubular manifold with reasonably equal lengths runners vs the square tubing and most def unequal length runners we see here.

Gut feeling would have suggested that this type of manifold would flow reasonably poor compared to a tubular one and that even in a forced induction engine that would be desirable, but I will happily accept that it doesn't matter too much, especially for lower levels of tuning, as Bob explained

I don't know too much about turbo charging beyond the basics and even though it's unlikely that I'll ever build such an engine the topic is interesting
 

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Here's one that I helped tune a few years back..I forget all the details..but it
made very nice power!




Text Line Slope Design Parallel

My bad I went back and forced scaled the chart to make it more readable. Torque and horse power curves cross at 5252 rpm.
Text Line Slope Design Pattern
 

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I would hazard a guess that equal length tubes of some rpm-optimal diameter (either exhaust or intake) are less relevant for forced induction engines. While less pressure drop might be desirable, losing a bit of a lot of boost (or conversely, reducing exhaust pipe-derived pressure drop and then sticking a VERY pressure-inducing turbo vane in the way) is outweighed by the total horsepower gain.

It also seems intuitive that the shorter the distance (and maybe more importantly, the smaller the volume) between the cylinder and the turbo, the less the turbo lag and the better the actual power delivery to the turbo.

Or am I just over-simplifying the process?
 

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I would hazard a guess that equal length tubes of some rpm-optimal diameter (either exhaust or intake) are less relevant for forced induction engines. While less pressure drop might be desirable, losing a bit of a lot of boost (or conversely, reducing exhaust pipe-derived pressure drop and then sticking a VERY pressure-inducing turbo vane in the way) is outweighed by the total horsepower gain.

It also seems intuitive that the shorter the distance (and maybe more importantly, the smaller the volume) between the cylinder and the turbo, the less the turbo lag and the better the actual power delivery to the turbo.

Or am I just over-simplifying the process?
You are correct that you don't want too much volume as it affects response but too little is actually much worse as it will induce a significant drop in pressure every cycle as air is drawn into the engine. This can cause problems tuning, uneven loading of the cylinders, etc etc. I'd much rather have too much than too little. Think of it as a big bank of air. Too big and it takes a while to fill but too small and you run out of the air pressure that is giving your engine the pick-me-up. I think it's a lot more important that you size the turbo correctly for the system. Even with all the piping on my turbo 2.5L datsun there is no real lag because the system was setup to make full boost around 3k.

Rallybob: all this turbo talk is making me want to throw a Haltech ECU in my opel and see what she could do.
 
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