Hi!

The old mythic with "long piping increases pressure buildup-times, wich again increases lag" ...

I cant see how much of an effect this will have as long as the pipe is flowing enough for the purpose it was ment for..

My theory is...

Take a 4 foot pipe, seal one end, and put your mouth to the open pipe-end, and blow. How many millisecs before you cant up the pressure in that pipe anymore with your lung-capacity? How many PSI are you increasing the pressure with?

Now take a 8 foot pipe and do the same, how many millisecs? its are barely measurable, the time difference.

Now try sucking X psi out of the pipe, and blow the pressure up to max of what your lungs can do again, how many millisec..?

My thought is, the amount of air you have to replace is not that big at all, and doesnt take a whole lot of millisecs to replace... Now imagine how much air a turbo pushes.... it takes you very little time to "cover this pressure gap" purely by lungpressure alone, how fast will a turbo replace the
air pressure difference from idle/closed TB vakuum---> open TB boost pressure?

Does really the difference between a short IC piping and a long IC piping make such a big difference, as long as the engine and turbo remains the same?


Is there any data on this at all?
I know that a shorter system is allways a win, but is that only a meassurable win scientificly, but it really has no effect you can feel or experience?

One thing i can see, is that shorter piping gives less surface for heatsoak from surroundings-->pipes-->intake air though...

 

Look at what the rally car guys are doing for a clue as to what's really going on.

Instant throttle response is mandatory, and they will run the inlet ducting about 4" diameter for the last two feet or so before the throttle body, with a taper at the throttle body end and a square-edge hole at the inlet.

Large diameter means low velocity for a given flow. Low peak velocity means it takes less effort to go from stopped to max flow.

They are deliberately making the ducting larger in volume, but it's the shape of that volume that is key.

 

in my experience the overall length isn't as important, as the bends, and diameter of the pipe. also the IC tank volume is important too.

i was just in bergen about a month ago, i didn't get much time to explore but it looks like a really cool town.

 

i thought up some examples, for my actual experience.

the first is the M2 medium IC kit. its a sparco 10-182 core, mounted in the same place as the stock iC, outlets are near the top, so the piping run is actually shorter than a stock FD. throttle response is fine, the difference from stock is hardly noticeable.

second M2 large. its basically the same kit, but the IC gets longer (from about 12" to 18"), piping is almost the same. throttle response is like a rubber band, big lag. the IC volume is HUGE and i think the stock primary turbo has a hard time filling it.

third. i had a Greddy core on my 3 rotor car, and in the first install, there was a 1.5" pipe that did a 270degree bend. throttle response was fine, however power was down, and pressure drop was in the 2psi area at like 5000rpm!

4th, is the same Greddy core, but with the end tank modified so that the 270 bend was 2 45's and in 2.5" inch pipe. this fixed the pressure drop and power problems, throttle response was the same as before, if not better.

 

OP Don't confuse flow with volume. Longer piping has more internal surface area. Anytime you pressurize something, it takes longer with a larger volume container/piping. It doesn't matter if the internal piping is silky smooth because that has nothing to do with volume.

Example: 6 cubic ft of pipe will pressure up faster than 10 of the same diameter. If it takes longer to pressurize the plumbing, the side effect is increased boost lag. It just takes a little bit longer to fill the piping. One way to test volume is to simply fill your piping and IC with water and measure the total amounts into a single container. The set-up that holds less water will have less lag because the smaller set-up has lesser volume to pressurize.

 

The more relevant question is how much volumetric flow are you creating? The answer is zero, so it should be obvious as to why your analogy is wrong.

The turbo isn't just building up pressure, it's also flowing air. That's why compressor maps are 3-dimensional.

Not only are you increasing the distance the air has to travel before entering the engine, but you're also adding heat to the air through head loss from the extra piping.