2.5" or 3" for my true duals?
04-27-2013, 12:51 PM
#1
2.5" or 3" for my true duals? Hey guys, just looking for some help. Finally decided to go with duals. I have Kooks 1 7/8's and their 3" ORY. I plan to just modify the ORY into an X and dump it before the axle. I will be using 18" Sweet Thunders. Now, would I benefit from continuing the 3" all the way or should I reduce it to 2.5" at the X crossover? Mods are in sig however, the car will eventually be 400+ c.i. and will be procharged. I've seen both sides argues. Some say there is no need for dual 3" pipes and others say you are leaving some on the table going with 2.5". Just looking for some info and opinions before I order my parts. I plan to just use a Summit universal x pipe kit to modify my Kooks y to. Thanks for the help.
04-27-2013, 02:09 PM
#2
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with 3'' you lose some in the lower rpms but gain some in the higher rpms. So if you're gonna be racing the car I'd go with the 3'', but if you're DDing it then I'd go 2.5''. I got my exhaust guy to run my duals 3'' til right before the rear axle then he put a 2.5'' reducer on and welded my 2.5''in/out 18'' Sweet Thunders and ran 2.5'' the rest of the way. I figured doing that would create some backpressure and be the best of both worlds kind of thing.
04-27-2013, 02:28 PM
#4
with 3'' you lose some in the lower rpms but gain some in the higher rpms. So if you're gonna be racing the car I'd go with the 3'', but if you're DDing it then I'd go 2.5''. I got my exhaust guy to run my duals 3'' til right before the rear axle then he put a 2.5'' reducer on and welded my 2.5''in/out 18'' Sweet Thunders and ran 2.5'' the rest of the way. I figured doing that would create some backpressure and be the best of both worlds kind of thing.
I went from a 3" dumped ORY to a 4" dumped ORY and actually felt the car more lively down low, even cruising in 6th its easier to get moving. From my personal experience.
OP if it were me i would go with the 3", its a proven performer.
If your on a budget check these out i hear that summit x pipe kit fits like ****.
http://www.ebay.com/itm/1998-2002-Camaro-Trans-Am-NEW-STAINLESS-TRUE-DUALS-3-X-PIPE-DUMPED-LS1-SS-Z28-/150963065745?_trksid=p2047675.m1850&_trkparms=aid%3D222001%26algo%3DSIC.CURRENT%26ao%3D1%26asc%3D11%26meid%3D7264224559678868708%26pid%3D100011%26prg%3D1005%26rk%3D1%26sd%3D161004230686%26
https://ls1tech.com/forums/generatio...rue-duals.html
04-27-2013, 02:58 PM
#5
with 3'' you lose some in the lower rpms but gain some in the higher rpms. So if you're gonna be racing the car I'd go with the 3'', but if you're DDing it then I'd go 2.5''. I got my exhaust guy to run my duals 3'' til right before the rear axle then he put a 2.5'' reducer on and welded my 2.5''in/out 18'' Sweet Thunders and ran 2.5'' the rest of the way. I figured doing that would create some backpressure and be the best of both worlds kind of thing.
04-28-2013, 03:17 PM
#6
Are none of you guys going to explain to him about the backpressure thing?
Anyway, what you are wanting to do, ultimately, is create scavenging. I put down 430rwhp through a 244/248 cam with ported heads and 2.5" Lanes true duals with no problem. The car screamed up top through that setup as well. I had really good scavenging in that setup and it was well balanced, no rasp, nothing.
Anyway, what you are wanting to do, ultimately, is create scavenging. I put down 430rwhp through a 244/248 cam with ported heads and 2.5" Lanes true duals with no problem. The car screamed up top through that setup as well. I had really good scavenging in that setup and it was well balanced, no rasp, nothing.
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04-28-2013, 04:12 PM
#8
Okay. Well I went ahead and bought a 3" X pipe kit. I'm going to order my Sweet Thunders on Monday or Tuesday. I went ahead with the 3" because I plan to go with a much bigger engine in the hopefully near future. Although I've already made my purchase, I'm still interested in the info on back pressure and scavanging. As of now, my headers are Kooks 1 7/8's with 3" collectors.
04-28-2013, 10:24 PM
#10
Not to get too technical, but you need the proper balance of flow capacity and gas velocity.
Huge pipes will have great flow capacity, but exhaust gas velocity will suffer. On the other hand, smaller diameter pipes will have better velocity to a degree, but sacrafice capacity.
Finding the proper balance is the key. The faster the exhaust gas pulses flow, the greater the scavenging effect during valve overlap.
As you can see it isnt a simple thing, there is alot of factors to consider.
Huge pipes will have great flow capacity, but exhaust gas velocity will suffer. On the other hand, smaller diameter pipes will have better velocity to a degree, but sacrafice capacity.
Finding the proper balance is the key. The faster the exhaust gas pulses flow, the greater the scavenging effect during valve overlap.
As you can see it isnt a simple thing, there is alot of factors to consider.
04-29-2013, 01:46 AM
#14
Are none of you guys going to explain to him about the backpressure thing?
Anyway, what you are wanting to do, ultimately, is create scavenging. I put down 430rwhp through a 244/248 cam with ported heads and 2.5" Lanes true duals with no problem. The car screamed up top through that setup as well. I had really good scavenging in that setup and it was well balanced, no rasp, nothing.
Anyway, what you are wanting to do, ultimately, is create scavenging. I put down 430rwhp through a 244/248 cam with ported heads and 2.5" Lanes true duals with no problem. The car screamed up top through that setup as well. I had really good scavenging in that setup and it was well balanced, no rasp, nothing.
http://www.hondacivicforum.com/forum...ts-wrong-3064/
Its common sense. Look at all the all out race cars 99% of them run open headers and or some form of dumped x pipe etc... The facts are out there, just go to the track and tell me how many race cars you see running stock exhausts, ill be waiting.
Edit: another good link i think this is of the original document i was talking about
http://www.gencoupe.com/engine/10943...sure-myth.html
Last edited by adamantium; 04-29-2013 at 02:00 AM.
04-29-2013, 09:42 PM
#19
Yup, I'm supper excited about it. I ran a set of Pacesetter's with a 2.5" x pipe and a set of Classic Chambered Powesticks on my ol' LT1 with a Hotcam. I liked it but the powersticks didn't seem to have the aggressive sound the sweet thunders do. I'll be ordering the sweet thunders on Wednesday and my x pipe should be here that day as well.
04-30-2013, 04:03 PM
#20
I don't see how a 3" would change any driving characteristics or affect anything falsely over a 2.5" unless what you're getting at it being "too loud".
Simple thing i learned over the years with dumps is you want to angle the dump tips out towards the side of the car, not completely down to the ground.
It helps ALOT with drone and noise in the car.
I daily my car with a 4" dumped ORY and love it. Also i noticed if you don't have the little trunk divider flap thing its ALOT louder.