icicleboy

Hey all,

I'd like to inquire with anyone that has first hand experience with this, as I'm mainly just curious more than anything else. All of our turbo systems have always been a single turbo deal. Setup has always been E-cover (3" inlet x 2" outlet) compressor cover ---> 2" charge pipe ---->intercooler ---->2.5" charge pipe ------> maf/TB. We've never been worried about making the setup more powerful, or more efficient as they're always pushing the limits of stock reliability in the powertrain (mostly trans).

As an example, our 5.3L turbo LS4 makes 470whp (about 600 crank w/ 4t-65E losses). Based on calculations, the air through the 2" pipe is travelling quite fast, well over 650 fps. Should I assume a huge pressure drop through this one pipe? Has anyone gone from a 2" charge pipe to 2.5" and seen a hp difference on the dyno as a test? or upsize on any setup like that?

TIA

fenix999

iTrader: (17)

Many people use 2.5 right off the turbo and then 3" around the intercooler and all the way up to the MAF/TB for ease of transition since the MAF/TB are so dam big (3.5-4.0" in some areas) I dont think it will affect performance enough to keep a small 2" or 2.5" pipe.

icicleboy

thanks for the reply. I'm hoping some people can chime in with actual experience maybe, upsizing of any sort on charge pipes. I realize more lag is to be expected..... however check this out :

My calculations have shown me that a 2" OD pipe that is 4ft long will easily lose 4-5psi with a turbo oulet pressure of 12 psi!!!!! so 12psi out of turbo = 8psi at end of charge pipe where it enters intercooler. How does this affect hp if I wanted say 12psi at manifold? I'd then have to push 16+ at the turbo... this is based on 60lb/min flow.

That actually puts my Pressure Ratio right where we'd want it in the sweet spot for 60lb/min.... so what's better, getting into the sweet spot for efficiancy, or goign to a larger charge pipe and getting half the pressure drop through the pipe? Anyone?

Reject

iTrader: (24)

what calculations are you using? i always thought that three is the ideal size, or else we would all be using like 1 inch pipes

icicleboy

I'm using a java calculator which figures out pressure drop taking into account EVERYTHING. input pressure, length of tube, ID of tube, roughness of interior of tube, air temp, mass flow rate, etc etc... lots of variables. It's interesting to see how a rear mount 2.5" charge pipe (2.37" ID) is so inefficiant. 15ft of pipe will lose 4.3 PSI at 200f outlet temps.

I'm trying to figure out of the pressure loss is ok due to getting the compressor into the right range of the map, or better to be in a less efficient area, yet have less restriction in the piping.

RedHardSupra

iTrader: (1)

care to share this java calculator?

MonochromeSS

iTrader: (1)

To be fair, id say 9 feet of piping would be more realistic for the difference from a front mount vs rear mount comparison. At 1000 cfm its like 2.5 psi drop for that same 2.37 inch OD tube.

http://www.engineeringtoolbox.com/pr...pes-d_852.html

John_D.

iTrader: (2)

As a reference point, I'm seeing 4 psi at the manifold with a 5lb spring in the wastegate. This is a rear mount, with a mix of 2.5" and 3" piping and a big fmic. It's all 3" from just past the k-member up to the TB. Wastegate is referenced from the turbo outlet.

icicleboy

john, what kind of flow are you seeing through the pipe? what is your RWHP at 4psi? there would be a huge difference from 30lb/min to 70lb/min for pressure drop.

John_D.

iTrader: (2)

I haven't had it on a dyno yet, with the turbo.

With the same heads/cam/intake/exhaust combo before I got the turbo, I was making 380 at the wheels. No maf, so I don't know the flow rate.

Drew04GTO

iTrader: (1)

Wow, either there's something missing or the calculator you had for the fps through the pipe is a bit off. I have yet to see any application where any kind of air speed was higher than mach 1 through a tube or across a restriction point. Really really really bad things start happening to airflow way before then. I was in the import/turbocharging world for 5 years before going into the LS1 family and I can say I've never seen anyone run smaller than 2.5" intercooler tubing unless it was an OEM pipe meant for ~225hp. Quite a few people I know seem to think they're already getting restricted by 2.5" intercooler tubing at the 350hp level and I think Tony Paolo (local dude) just picked up well over 150whp by going from a gt4788 with with 2.5" tubing to a S380 with 3". Of course, it will lag slightly more, but the if you switch from 2" to 3" you're only increasing tubing volume by 2. The estimate of 9ft of intercooler tubing comes out to around 65ci of intercooler tubing, this will take no time at all with a fairly large turbo to fill.

icicleboy

Thanks for the response. What puzzles me, is that our little 3800 V6 kits have been making 450whp on lots of cars, on the same 2" charge pipe. Rather then sit in front of a calculator all day, I just went and did some testing on my 430whp car (DD). Boost at manifold was consistant 15psi at about 50lb/min of airflow. At the turbo outlet, I only saw 17psi, and thought I'd see so much more. This is with an IC, maf screen, and 5ft of 2" charge pipe to the IC. I repeated the test a number of times with the same results.

Are you saying that the speed of the air is much more important than the pressure drop through the pipes? if so, is 450fps the golden rule to stay under? We're generally working with fitment contraints...

DeltaT

iTrader: (5)

We've always used the output of the turbo or blower +-1/8th" to size our systems all the way through, which usually ends up being 3" tubing with as large radius bends as possible to fit it up.

Corky Bell does cite some equations in his book "Maximum Boost' which might be helpful and is well-written.

Jim