^ You are correct that the worst is on the passenger side. There's a spot where it gets to approx 2 sq inches -a 2.5" pipe is 4.91 sq inches. The DVs dump just aft of the MAF.

Updates from my stuff, I saw a peak of approx 41" on the magnahelic gauge. Now in the process of fabbing hard piping -I've got the driver's side done and have the part that goes over top of the motor in as well, just need to bring it down to the passenger turbo. I'm into it $300 with the aluminum piping vice the questionable dryer/vac ducts, but it is much more difficult to fab with the motor down only a few inches.

 

I am SO looking forward to the after results Were you able to drive it with just the driver's side done? I'm rooting for you!

Oh, and IMO proper flexible hosing ought to be okay although obviously not dryer duct The piping shouldn't see too much vac if it's sized right so something flexible that's got some rigidity and some support ought to be fine - you just have to watch out for rubbing. That said, I think short intake lengths into the fenderwells will still be the best but require many more changes, none of which appear to be cheap

 

Thanks! Couldn't drive it because I had already pulled the passenger side mess down.

 

updates?

 

Update: It's a b*tch to fab hard intake pipes with the motor in the car but everything clears now. I'm prepping and high temp coating the pipes now and should have it all back together this weekend.

 

Bumping an old thread for further discussion

 

I'm no engineer and higher math is Greek to me, but I saw a vid recently about the Venturi effect. Could Porsche have designed the stock pipes with the venturi effect in mind, and would that be better than a larger pipe that is a consistant size from start to finish?

 

I see this old thread is still hanging on, well, by a thread.

To answer the question of; could Porsche intend to design a venturi at this section of pipe? I doubt it.

A simple way to look at the issue of air flow in the intake system is the desire to reduce flow restrictions. Less restriction more air flow to the cylinders. More airflow, more mass in the cylinder, more mass more energy released during combustion.

A venturi introduces some restriction or pressure drop. So unless there would be a another purpose for a venturi it would not be beneficial to put one at this location.

Very probably the reason this short section of intake piping is the small diameter it is, is because the compressor inlet is small and there is not enough length of pipe to make increasing the pipe diameter worth while.

Pressure drop in piping (flow restriction) is increased with expansion (increasing pipe dia.) contraction (decreased pipe dia.) bends, discontinuities, roughness of interior pipe surface, etc.

This section of pipe is very very short, to increase the pipe dia. then decrease dia to the compressor inlet would likely add more pressure drop than simply keeping the pipe at the compressor inlet dia.

Again, a venturi would provide no usefull function here and only add pressure drop.

As an aside, a venturi is a way to measure fluid velocity with minimal pressure drop. Maybe you can recall the antique engine component called a carburetor, which included a venturi to measure airflow, and the resultant reduced pressure at the throat, to suck in fuel.