i have 2.25 inch full exaust and wonder if 3 inch exaust whit 2.5 inch downpipe would make my mitsu 18 g spool faster or more laggy?.
do we need back pressure to make turbo spool early?

 

It'll spool faster and be less laggy.

Tom

 

How much of a HP gain could be expected from a full 3" DP and exhaust after running a 2.5" DP and 2.25" exhaust? Also how much quicker will the turbo spool up with the 3" setup?

 

A turbomagazine article said they pulled a 2.25" Thermal and put on a 3" Thermal and at ~8psi they made 7hp. The real benefits of a 3" wont be seen untill higher boost pressures.

 

Ask art about his gains after he went 3" dp...he made some good #'s. Or search for it...

Tom

 

would a 3in. exhaust cause any lose in hp or tq before the turbo starts to spool or does the earlier spooling make up for it?

 

No. The turbo it self is a restriction in the exhaust, so a bigger exhaust will not cause a torque or HP lose. Also you wouldn't because the bigger volume allows for a faster spool thus Increasing power.

If you put a 5" exhaust on a turbo system, I don't think You would lose any power. It's just because the turbo is such a restriction in the system.


[Modified by Bryson, 11:48 PM 2/25/2002]

 

3" Exhaust + Turbo = Good

 

old setup: 2.25" dp closed loop, stock cat, apexi RS catback (2.36") -- 181 whp, 169 torque

new setup: 2.75" dp open wg, 3" cat, 3" custom catback -- 202 whp, 179 ft/lb

a lil quicker spool up too

 

nice reply voodoo
thx for your spec

 

wow thats a nice gain

 

vudoo why didnt you go w/ a 3" downpipe?

 

How much power do you loose funning a closed loop setup?

 

Vudoo, how much boost are you running?

 

what about....if your only gonna boost 8psi?? i mean i have in my sig. 3 in...cause thats what im planning on doing...but i was thinking 2.5 i mean my d/p is like 1.75 then mate that to a full 3 in exhuaast? i dont wanna spend the money on the 3in d/p now....will the 3 in give me less hp then the 2.5?? or more

 

I'll be running a 2" with no cat, and straight through to a free flowing dual tip stanless muffler. Think this will be ok for 5-6psi?

Oh yeah on my D16Z6/Y8.

 

its in my bio, 7-7.5 psi

i didnt go 3" cuz jeff (importbuilders) told me that 2.75" and 3" wont make much/if any difference w/ the boost levels i'm running, 3" would be a tight fit on the 5-bolt flange. i dont plan on boosting more anyways cuz my engine is stock.

 

ok heres my newbie question... what is the difference between closed loop and open ?

 

Closed loop routes the wastegate dump tube back into the exhaust. Open loop dumps into the atmosphere.

 

Do you loose HP running closed loop?