typhoon43

Finally got out to my fab guy during lunch and we started talking about my new setup. When he finally got under the hood he told me there was a lot more space than he thought there would be (he's done a few 5.0 stangs). He saw my 4" Intercooler ends and my 4.25" Throttle body and told me he thought it would look great with a 4" cold side all the way. I have to agree it would look mean. I was wondering though, will that hurt me in any way? I can imagine my spool time would increase due to the increased volume, but would you think it would be night and day compared to the 3" I was considering? Just looking for some opinions, as I need to start ordering pipe soon.

Specs:
5.4 4 Valve bored .020 over
Turbonetics T-76, 76mm, Ceramic Ball-bearing, Q-Trim Wheel, .96 A/R
Belle 4" in/out Air/Air Intercooler.


Any opinions are welcome! Thanks!

lightningDan

i always thought bigger was better, until steve stock told me about how, if you are running 4" tubing, remember now that the boost needs to now build psi threw 4" tubing, might take alittle bit longer to build up psi because now it needs to fill up the 4" tubing

i guess it depends on the TB as well, since your already 4" why not, i was going to use 4" piping but had a 75mm throttle body

kinda backwards lol

danny

Frank5L

8ft of 4" piping would be about 100 cubic inches

8ft of 3.5 piping would be 77 cubic inches

8ft of 3 piping would be about 57 cubic inches....

Now it might take a little bit longer but I doubt you'll be able to measure it if you are in the efficiency range of the turbo.

typhoon43

Thank you Frank. I just figure with the MAF, IC, and TB all being very close to 4", it would keep my transitions to a minimum (just off the compressor outlet).
My machinist is VERY anal though (suppose that's a good thing). He was telling me that 16 Gauge (.065") pipe would eventually get stress cracks, and he'd prefer if I went with something thicker. The catch is that in 4-inch tube, I can only get 16 or 11 gauge, which is fricking .120" wall. I assume it will be twice as heavy, and racepartsolutions.com said I can figure on a 20% increase in cost per pipe.

If you guys were in my shoes, would you go for 4", or get 3" and work with the transitions. Will 16 Gauge hold up? I'm only planning on 20lbs MAX with this thing. 15-16 on the street. I can get 4" 16-Gauge everywhere. 11-Gauge is hard to find, which limits my saving.

Thanks!

brainbypass mod

why not use aluminum then?

__________________
03 black lightning - VT powered, tuned by dynojoe.com
"And another thing.....when I gun the motor, I want the whole world to think it's coming to an end"
-Homer Simpson

Frank5L

I'm running 14gauge aluminum exhaust.... All my discharge tubing has been 16 gauge.

typhoon43

brain, I am talking aluminum

Frank, how much DD usage did your turbo setup get. My machinist said for a race vehicle 16 Gauge is fine, but for something going down the road every day he prefers at least 14 gauge. I'll have to talk to him some more. THANK YOU for the help so far.

oiN8io

16 gauge is fine. I had it on all my stuff on my old setup for over a year and it is showing no signs of wear at all.. You will be fine as long as the welder is good and you have your tubing braced along the way so its not flopping in the wind..

__________________
1040RWHP/991RWTQ 25psi q16
TWIN TURBOS... enough said!!

Frank5L

I've probably only put about 2k miles on my truck since December of '04.

5point8LiterImportEater

My guess is that the intercooler is generally a much bigger mass of air than what is in the pipes. I have wondered this too though. Like in most mustang 302 kits the piping is only 3 inches, and yet they claim that over 800 hp is possible. With a SC most of the guys have huge inlet pipes, and pressure pipes compared to a lot of turbo systems. On top of the whole 3 vs 4 thing, it seems to me that someone important once wrote that it isn't pressure that makes power, it is flow. That is why lots of people use bars instead of psi. I don't know, I would love to see some testing on this. maybe some day when I am a millionaire I will do this....
Chris

brainbypass mod

bar is just a metric unit of pressure

Gen1SVE

16 gauge or .065" wall tubing will not crack on the cold side, massive amounts of weight/stress aside. I have not even had any cracks on my hotside after 6 years on a turbo lightning and 2 years on a turbo mustang.

rcain02

I can tell you from experience that changing to 4 in downpipe from 3 inch will kill your launch.....makes more power up top at higher rpm.
Thanks,
Ronnie

typhoon43

How big of a snail were you running? What kind of flow was your engine making? I'm hoping this 4-valve will kick enough through the hot side to get that wheel spinning with a 4" downpipe.