Downpipe>Exhaust

[Blitzeclips]

I've got a 20G turbo a downpipe outlet @ 2.5". The downpipe goes from 2.5 to 3.0" back. The problem here is, my cat back exhaust is 2.5" back. I'm on a budget and don't want to switch my exhaust system for the extra .5" unless it's worth it. What kind of performance would I be gaining if I did upgrade my exhaust to 3"? Would a 2.5" reducer in there disturb the flow of my exhaust if I connected the downpipe to my current system? It would be : Turbo>2.5">3">2.5" Hope that wasn't too confusing. TIA.

 

[VelocitàPaola]

The small amount of turbulence in the exhaust flow that that setup will create will be negligible; you won't notice any major power losses. Use a 2.5" reducer to connect the cat-back and downpipe and upgrade to a full three inch whenever you like.

I see that you have a built motor, so it's possible that you may be pushing larger amounts of exhaust. In that case, the full three inch isn't a bad idea, but it probably isn't direly necessary.

 

[XMasta19]

full 3" = boooost quicker

 

[clipsit]

full 3" = boooost quicker

What X said...3" For sure!!!

 

[Blitzeclips]

okay. So if I were to go 3" back, a GS-T exhaust would fit my car also, right? I can shop for n/t and turbo systems?

 

[clipsit]

YES...any GS-t exhaust will work on our cars, just not GS-x, but I assume that you knew that already. Just shop for GS-t exhausts.

 

[napkinthief]

If you are looking to save some money, get a muffler and a custom shop to make the exhaust. Or you can make it yourself.

 

[clipsit]

That works too, but it can sometimes be close to the same price depending on what you like and go with...

 

[Blitzeclips]

Im thinking of a custom shop making mine... This sucks! I love my Greddy Evo II... now i have to give er up for the whole 1/2 inch....

 

[VelocitàPaola]

GReddy? Eh... wret bought a Tsudo exhaust for $200 or so, and he loves it. I'm like him; I can't imagine paying $500 for an exhaust. Pipes are pipes to me, and Tsudo has found a way to effectively emulate the bigger name brands. Theirs are made from similar metal (SS), the bends are all mandrel bent and all of the welds are decent. I just don't see the advantage to buying an Apex'i or GReddy in this case.

I would recommend the same for anyone. If you need a new exhaust, look on eBay for the Tsudo 3" GS-T cat-back - it'll come about to around $300 with shipping. Here's one auction for it:
http://cgi.ebay.com/ebaymotors/TSUD...ewItemQQcategoryZ33630QQitemZ8042995000QQrdZ1

The only thing I don't like about some of these are the mufflers themselves (the tips are just ridiculously big). If anything, though, you can buy the exhaust and just have a shop weld a different muffler on.

Also, here's wret's review of the Tsudo N1:
http://www.dsmtuners.com/forums/showthread.php?t=213932

 

[XMasta19]

http://www.dsmtuners.com/forums/showthread.php?t=168484

...we all agreed on this exhaust over a year ago

I have the exact same exhaust, but what's that...the fedex guy is delivering my new tsudo 3"

 

[BigRand]

Im thinking of a custom shop making mine... This sucks! I love my Greddy Evo II... now i have to give er up for the whole 1/2 inch....

Keep the can, and have piping made for the eVO 2

 

[selmerguy]

Why don't more people go with a cut-out? I have a 2.5" dp and a cut-out right before the cat. I leave it open most of the time and I really flet a difference the first time I drove my car with it. I have stock exhaust with a tip welded on after the cat. When I close the cut-out I get better highway gas milage and it is not loud! Whole setup cost me way less then 200 and it sounds mean as anything open.

 

[BigRand]

Why don't more people go with a cut-out? I have a 2.5" dp and a cut-out right before the cat. I leave it open most of the time and I really flet a difference the first time I drove my car with it. I have stock exhaust with a tip welded on after the cat. When I close the cut-out I get better highway gas milage and it is not loud! Whole setup cost me way less then 200 and it sounds mean as anything open.

Open Downpipes aren't for everyone, I love my exhaust note.

 

[XMasta19]

meh...drove around all the time with my buddy in his srt with 3" cutout. sure it sounds cool and loud or what not, but you do know that you lose torque of course I just don't see it feasible really unless you're like trying to be complete sleeper or somethin. Pull up to the light all stock exhaust soundin, open it up and get on it, blah blah blah. Why not just run a side exit? I just think a full 3" all the way back is so sexy

 

[Blitzeclips]

Yea that side exit is something I am going to consider. Has anyone ever attempted/seen this done with our cars? Results? Might be a fun test to do..

 

[selmerguy]

meh...drove around all the time with my buddy in his srt with 3" cutout. sure it sounds cool and loud or what not, but you do know that you lose torque of course I just don't see it feasible really unless you're like trying to be complete sleeper or somethin. Pull up to the light all stock exhaust soundin, open it up and get on it, blah blah blah. Why not just run a side exit? I just think a full 3" all the way back is so sexy

You do lose a little torque but the turbo spools so much faster. Also I still spin the tires so the low end torque is still plenty strong. I feel in my butt dyno that the high end is much stronger. At 8 psi it really throws my head back when I hit boost. Can't wait for 15 psi

 

[napkinthief]

You do lose a little torque but the turbo spools so much faster. Also I still spin the tires so the low end torque is still plenty strong. I feel in my butt dyno that the high end is much stronger. At 8 psi it really throws my head back when I hit boost. Can't wait for 15 psi

Amen.

 

[dsm-onster]

Bigger/no exhaust speeds spool up. Quicker spool up increases torque. If you felt less torque on your friends TURBOCHARGED srt-4, I think you just got used to being in the passenger seat . I have runn straight off of the o2 housing and, besides the fire from running too rich, I experienced INCREDIBLE off throttle response.

The only time a bigger exhaust can lower torque is with n/a applications where you're trying to tune scavenging. Here's what I've said in a previous post:

Scavenging is where one pulse leaves behind a vacuum pocket and sucks the next pulse out. The only way to get scavenging is to have a tube or pipe that is a certain diameter to match pulse frequency. Once the rpms move into the range that the exhaust pipe diameter/length is tuned to the back pressure goes away for the most part. And, at this point, the engine VE goes up and consequently more power is generated. A 3" exhaust pipe is tuned to 7-10,000 rpms (or exhaust pulse frequency). Unfortunately, a pipe with any diameter other than infinite has restrictive surface tension on the inside walls this adds to back pressure even when the exhuast is tuned to the rpm range you are driving in.

None of this applies to a turbo engine after the turbine blade. Before the blade (exhaust mani), scavenging has been proven to give a marginally benificial increase in high horsepower applications. But you won't get much or any gain going to a turbular tuned turbo header with an EVO3 [or anything meriting a smaller turbo]. Stock exhaust manis have gotten guys into the 9s.

After the turbine blade, the pulses are chopped up to almost a constant flow so there is no way to create a scavenging affect. Therefore, one would want to reduce the backpressure to 0. A turbo works on the premise of differing pressures. If you have 3 bar in the exhaust mani (before the turbine blade) and 1 bar in the exhaust pipe then there 2 bar difference is doing the work spinning the turbine wheel. Then if you remove the 1 bar in the exhaust pipe (0 backpressure), you now have 3 bar doing the work over the turbine wheel. 50% more work!!! This is why 3 inch exhaust on a little 4 cylinder turbo engine does so well. Spool up time is DRAMATICALLY enhanced. The negative sideeffect to having a turbo is the 30-50psi of back pressure it exerts on the exhaust gasses trying to exit cylinder. But that negative effect of the backpressure is worth it once the turbo has begun to spool.​

 

[selmerguy]

The only time a bigger exhaust can lower torque is with n/a applications where you're trying to tune scavenging. Here's what I've said in a previous post:

Scavenging is where one pulse leaves behind a vacuum pocket and sucks the next pulse out. The only way to get scavenging is to have a tube or pipe that is a certain diameter to match pulse frequency. Once the rpms move into the range that the exhaust pipe diameter/length is tuned to the back pressure goes away for the most part. And, at this point, the engine VE goes up and consequently more power is generated. A 3" exhaust pipe is tuned to 7-10,000 rpms (or exhaust pulse frequency). Unfortunately, a pipe with any diameter other than infinite has restrictive surface tension on the inside walls this adds to back pressure even when the exhuast is tuned to the rpm range you are driving in.

None of this applies to a turbo engine after the turbine blade. Before the blade (exhaust mani), scavenging has been proven to give a marginally benificial increase in high horsepower applications. But you won't get much or any gain going to a turbular tuned turbo header with an EVO3 [or anything meriting a smaller turbo]. Stock exhaust manis have gotten guys into the 9s.

After the turbine blade, the pulses are chopped up to almost a constant flow so there is no way to create a scavenging affect. Therefore, one would want to reduce the backpressure to 0. A turbo works on the premise of differing pressures. If you have 3 bar in the exhaust mani (before the turbine blade) and 1 bar in the exhaust pipe then there 2 bar difference is doing the work spinning the turbine wheel. Then if you remove the 1 bar in the exhaust pipe (0 backpressure), you now have 3 bar doing the work over the turbine wheel. 50% more work!!! This is why 3 inch exhaust on a little 4 cylinder turbo engine does so well. Spool up time is DRAMATICALLY enhanced. The negative sideeffect to having a turbo is the 30-50psi of back pressure it exerts on the exhaust gasses trying to exit cylinder. But that negative effect of the backpressure is worth it once the turbo has begun to spool.​

[/QUOTE]
Thats good stuff. Makes since too

 

[Blitzeclips]

That kind of makes me wonder about a 3.5" exhaust.... how do you think that would work out with the 20G?

 

[dsm-onster]

That kind of makes me wonder about a 3.5" exhaust.... how do you think that would work out with the 20G?

W/ a 20G

W/out a 20G (or any turbo)

EDIT: I meant to add a for "w/out a 20G (or any turbo)"

A scavenging effect would develop so high in the rev range that it is possible that it may only be effective over your revlimit. if you run a 2.0 w/ over 3" exhaust

 

[XMasta19]

wtfux0rz this thread just got crazy


put it on the dyno, cutout open / cutout closed...that will answer the question

I don't really care about pulse pockets right now

 

[clipsit]

put it on the dyno, cutout open / cutout closed...that will answer the question

I don't really care about pulse pockets right now

 

[XMasta19]

backpressure increases low-end torque to an extent (as in don't over do it) ...tell me I'm wrong

...therefore running a cutout, open downpipe, straight off j-pipe etc will subsequently sacrifice some of that low-end torque. @ got used to sitting in passenger seat too bad I've never run an open exhaust and can speak from experience welcome to the 2gnt side of the tracks


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