2.5" or 3" exhaust
07-14-2010, 01:21 AM
#3
07-14-2010, 04:17 AM
#4
From what I have been reading up on so far, you have to have 3" DP and exhaust or you can starve the turbo of boost. Im will be going back to stock headers (currently have Cattman headers) and swapping Cattman catback to 3" exhaust.
07-14-2010, 06:59 AM
#5
For the most part when dealing with turbos, bigger is better. Bigger exhaust means lower EGTs. That in itself should convince you to go atleast 3". Also, its been known that a restrictive exhaust can cause boost spikes and peak boost may not hold through out the power band. Which, as you probably know already, can cause a momentary lean situation that can lead to catastrophic failure.
Sure a 2.5" exhaust can work in a 400hp application, but you shouldnt dwell on just power. The safety/longevity benefits your motor gains outweigh the power.
Sure a 2.5" exhaust can work in a 400hp application, but you shouldnt dwell on just power. The safety/longevity benefits your motor gains outweigh the power.
07-14-2010, 08:41 AM
#6
no question, 3". the benefits go way beyond just the peak power number. spool time will be helped significantly, better wastegate functioning (assuming external gate) etc. you can never have too large of an exhaust on a turbo vehicle. larger is always better when it comes to post-turbine piping.
07-14-2010, 11:12 AM
#8
The only problem I have is I am might have to have a choke point on my downpipe. I might not have enough space to go 3 inch. So about a foot or so has to be 2.5" Ill have to deal with this soon. Ive been debating what to do here. My down pipe goes down between the motor and firewall.
07-14-2010, 02:12 PM
#10
Junior Member
Join Date: Jun 2006
Posts: 29
Go 3 inch.
In a turbocharged car the turbo itself is enough air restriction for the exhaust gases that anything else will just hender the turbos efficiency. In other words you want the most free flowing exhaust piping after the turbo as you can get, generally a 3 inch mandrel bent setup is sufficient for most setups.
In a turbocharged car the turbo itself is enough air restriction for the exhaust gases that anything else will just hender the turbos efficiency. In other words you want the most free flowing exhaust piping after the turbo as you can get, generally a 3 inch mandrel bent setup is sufficient for most setups.
07-14-2010, 06:20 PM
#11
You shouldn't even really be considering less than 3" in your application. I have 2.5" and it can spike pretty quick, in a way I wish I went with 3" from the get go and mine is just a dd hoping for a little over 300whp.
07-14-2010, 06:57 PM
#12
The only problem I have is I am might have to have a choke point on my downpipe. I might not have enough space to go 3 inch. So about a foot or so has to be 2.5" Ill have to deal with this soon. Ive been debating what to do here. My down pipe goes down between the motor and firewall.
07-14-2010, 07:09 PM
#13
um Im 3rd gen. Custom headers I made. There isn't much room between firewall and motor on a vg30e.
07-14-2010, 07:11 PM
#14
you can save money and go 3" electrical cutout? if its your daily driver.. All the 3" exhausts i've heard personally tend to be on the louder side..
My setups is soon to b 2.5" stillen catback and 3" qtp electrical cutout in place of the cat.. I have a 3" downpipe up until the cat by the way..
My setups is soon to b 2.5" stillen catback and 3" qtp electrical cutout in place of the cat.. I have a 3" downpipe up until the cat by the way..
07-14-2010, 07:22 PM
#15
07-14-2010, 11:57 PM
#18
3" probably would be cheaper than this, but this does have a "coolness" factor too it, ha ha.
Sound Performance Boost activated cutout.
This maybe more reliable than an electric unit.
Sound Performance Boost activated cutout.
This maybe more reliable than an electric unit.
07-15-2010, 03:41 AM
#19
3" probably would be cheaper than this, but this does have a "coolness" factor too it, ha ha.
Sound Performance Boost activated cutout.
This maybe more reliable than an electric unit.
Sound Performance Boost activated cutout.
This maybe more reliable than an electric unit.
edit, seen the price and since I already have a cut would rather get the electric part with a boost switch. I my just do that instead of a 3inch exhaust
Last edited by t6378tp; 07-15-2010 at 03:49 AM.
07-15-2010, 09:36 AM
#20
That don't look to hard to make. Might have to tackle this one. Just order me a manual cutout and modify it to accept a Internal waste gate. I have a few laying around. Set at 7psi. Once it 7psi should open up. Maybe even run a solenoid in the vac line to turn on and off as needed.
07-15-2010, 11:21 AM
#21
That don't look to hard to make. Might have to tackle this one. Just order me a manual cutout and modify it to accept a Internal waste gate. I have a few laying around. Set at 7psi. Once it 7psi should open up. Maybe even run a solenoid in the vac line to turn on and off as needed.
I think the way to do it would be to use a hobbs switch to control the opening of an electric cutout.
07-15-2010, 10:39 PM
#24
That don't look to hard to make. Might have to tackle this one. Just order me a manual cutout and modify it to accept a Internal waste gate. I have a few laying around. Set at 7psi. Once it 7psi should open up. Maybe even run a solenoid in the vac line to turn on and off as needed.
07-15-2010, 11:58 PM
#25
Looks like have to make one from scratch. They only make the pull type cutouts in cast iron y pipes. So Probably order me a 3 bolt flange and find a 3" throttle body. Rob the butterfly valve and you get the idea.
07-16-2010, 09:37 AM
#26
i wouldn't do a cutout again as I think they sound like ****, and definitely not a boost activated one. the last thing I want is my exhaust randomly going from decently quiet to loud and sh!tty sounding because i floored it for a second trying to get on the highway or whatever.
A 3" exhaust with a good large resonator and a good muffler will be nice and quiet and flow perfectly fine for 450whp.
Maxmaxima91 has 4" on his car and his car is really quiet. it's all about the resonator/muffler combination you choose.
A 3" exhaust with a good large resonator and a good muffler will be nice and quiet and flow perfectly fine for 450whp.
Maxmaxima91 has 4" on his car and his car is really quiet. it's all about the resonator/muffler combination you choose.
07-16-2010, 10:34 PM
#27
If you had thoroughly read what hotshot said you would get the answer from what he's saying.... he wasn't talking about other model cars... if guys that have the same car like you have runs a 3" piping and it made for better flow and increase in power in N/A form then wouldn't it be common sense that on a car that's probebly making almost twice as much power that this would be sufficient???.... (extended version I guess)
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