ryan1

does ic piping size and lenght really affect spool up time,in my searching i have seen mixed reviews,so whats the truth.

i ask this cause i have build a low buck turbo set-up on a nother mazda bp 1.8 dohc car using a
small vj-11 with no ic right now, it spools up super fast and i really like it and what to keep it that way,

im use to running bigger t3/t4's and other garret t3 turbos on all of my other boost cars (i have 4 of them,stupid i know).

xternal

Generally 2" piping + small turbo will result in quicker spool

clwtwizted

i used a vj11 on my civic with 1 1/2 pvc and when i changed it over to 2" it spooled up quicker and spiked like a bitch

ryan1

anyone else?

marcj

umm.. common sense would be less volume to fill results in quick positive pressure. there is a good medium for boosted small displacement semi-built motors, which is between 2" and 2.5". the less distance needed to travel helps.

also RUN A ------- INTERCOOLER DIP ----

bitchM0VE

Use 2" or 2.5". It won't affect spool measurably. You're thinking too hard. And put an intercooller. BP 1.8's love boost. Got a GT3271 going on my BP05 1.8L. Shooting for 350whp on a stock motor.

HiProfile

Think about how the system works - turbo moves air while the motor sucks it down. To *increase* your pressure by 2x, you double the flow of the motor plus the pipes.

Example: A 1.6L motor at 3k rpm is taking ~85cfm to run at 0psi. 6' of 2" charge piping holds ~19 cubic feet, 2.5" holds 29 cubic feet. That means to get 14.5psi of boost, you need to increase turbo flow by 268% for 2.5" and 244% for 2". With all the math done, that's only a ~10% difference overall. So if you hit 14.5psi in 1 second with 2" piping, you'll hit 14.5psi in 1.1 seconds with 2.5" piping. Thats 0.1 second longer - useless IMO! For 3" it ends up being 1.22 seconds (~22% more). The 'shocker' is pipe displacement: 2.5" has 56% more area to flow intake air vs 2". IMO that fraction of a second is useless, even with a smaller turbo & motor.

After you hit target PSI, your requirements drop to that of the displacement-per-revolution (85cfm at 3k), rather than ['d-p-r' + chargepipes], which is why increasing 2x pressure is difference than maintaining 2x pressure.

darkhorizon

I run 3inch charge pipe and exhaust on my setup, works well and doesnt pretend to lag.