The Project Pad

As long as you have one silicone one in there, you'll be good.

I don't plan on having any silicone in my piping system, but the couplers I'm using allow for flex. Definitely always gotta have flex.

2 silicone 90s with that AL 90 is no big deal, you have 2' total of plumbing, big whoop. look at a subaru setup with 6-8' of piping and 10 bends still making 500+. you have a big turbo with a high psi sweet spot, i wouldn't worry about a pressure drop from a bend in a street driven car

I agree that it isn't going to be the end of the world, but subaru STI's are extremely laggy for the displacement and VVT once they ditch the top mount. We make more power at the same pressure with .3L less displacement for the most part. 1 psi of pressure drop on my setup equates to almost 35whp!!

I don't see why pressure drop matters if your turbo is capable of making up for that drop. Also, 10 feet of pipe will result in about 0.06 psi of pressure drop for air in a rough, three-inch pipe. Not a big deal. Now pressure propagation through time within that pipe as a function of pipe size may be what we are really after in terms of lag. I haven't given that any thought yet, but it should be simple enough to figure out.

If your wastegate is clamped shut(as mine often is) you are decreasing the amount of air that can get into the engine. Even if it isn't clamped shut, the efficiency is compromised. The compressor is still seeing the pressure drop.

www.Boostcontroller.com has a huge selection for silicone products if you end up needing anything. Located in western NY so fast shipping for us too.

Hank, how is the turbo seeing a pressure drop? It is seeing a head rise (pressure increase at the outlet). I agree that this could take the compressor out of its efficiency range in extraordinary circumstances, but we are talking fractions of a psi for pressure drop purely from head losses, even in a ten foot section of pipe. There effect of head losses (pressure drop) in this kind of application are entirely negligible. However, as I said before, the volume of pipe and how long it takes to fill that volume up may not be negligible.

WARNING

**here comes some more seriously nerdy stuff**

Again, assume the turbo is capable of flowing 1000 CFM. Assume we are neglecting differences in flow rate of the turbo vs pressure or time (this may not be a good assumption, but it will do for now).

The calculation I did is based on the ideal gas law and the only bad assumption I think it makes is that the turbo is flowing 1000 CFM instantaneously. I can do a more in-depth analysis with flow rate changing as a function of time, but this will have to do for now.

Basically under this assumption, if you change the length of pipe by a factor of ten, you increase (or decrease) the time it takes to fill the pipe by a factor of ten. At 1000 CFM or ~0.47 kg/s, it should take about 0.07 seconds to fill a ten foot section of 3" pipe with air at 300 K. If anyone is interested in the more hardcore analysis, let me know and I'll try it. Otherwise, I'll quit mucking up Casey's thread with maths

Oh look at that. I think my brain just melted.

One more thing I just realized that I should note about this analysis. It assumes that there is no net flux of fluid through the pipe other than the fluid which is filling it up. In other words, it is as if we are assuming the throttle plate is shut (turbo wouldn't likely spool in that event, but it makes the analysis simpler to think about).

So I did it with a changing flow rate. I assumed that a 35r-sized turbo might go from 10 lb/min to 60 lb/min within two seconds. I then fit a polynomial curve to that such that the flow rate would ramp up within those two seconds rather than being a linear relationship. This made for about a half-second difference in pressurization between a one foot (3 in diameter) pipe and a ten foot pipe. It also turns out that the flow rate was nearly constant within that half a second because of the way I defined to polynomial curve shape. Anyway, I hope someone seriously geeks out to this and either agrees or disagrees with my thoughts on the matter.

CLIFFS NOTES!!!

My conclusion is that you might indeed notice about a half second more lag than normal with this difference in pipe length which is kinda cool.

Easy there Mechanical Engineer. Less theory and more application . I have not measured my current intake path, but before on my crappy ebay IC, I would see 42psi at the turbo outlet, 41psi by the IC ( basically a 6" radius 180 degree into the intercooler), 36psi by the time it got through the crappy core, and finally a 33psi into the intake where my ECU Map sensor is. The pressure sensor was in the IC exit cap, thus the sharp 90 coming out the side of the core, the sharp 90 going into the throttle body and some rough edges on the BOV were causing another 3 psi of drop! Upgrading to a Garrett core took away the 5 psi drop across the core, and making my inlet into the intercooler like Casey has it now instead of the the 180degree. I have not taken the time to put bungs on the intake yet, but I now see a solid 38psi peak on the dyno. Even though the overall distance only changed by less than 12" total, I was able to get a *free* 4 psi, or about 80whp more on the dyno! Yum!

My stock intercooler is still stock.

Carry on.

good thing we're not really talking pipe length then since even if he flipped the end tank (not recommended cuz it sucks to reweld and pressure test and weld and pressure test....) he'd only add 8"

::insert thats what she said joke::

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