Exhaust system setups

[lcxu105]

Ok I'm starting this post to see what is working for everyone.

My new engine is a 3025 neo built engine and I want to maximize its performance. 

Old system is a 3inch turbo back 100 cel cat straight through muffler.

Was thinking about doing a 4inch dump pipe to 3 inch from dump back.

 

[lcxu105]

Old system was on a 25 Neo making 422 rear wheel horsepower

[zebra]

4" all the way

[sneakey pete]

Depends on your power goal, 4" dump and 3.5" cat back should be good for north of 450kw

[lcxu105]

7 minutes ago, sneakey pete said:

Depends on your power goal, 4" dump and 3.5" cat back should be good for north of 450kw

420rwkw on pump fuel 

[33GTRV]

3 5/8" step to 4" directly behind turbo down to the gate merge point then 4.5" from there back,  2 hookers and no cats. Cats shit in boxes and piss people off

 

535kw

[KiwiRS4T]

3in will be pushing it (not saying it won't work) but 3.5in would be better. There was a Stagea round here making 550AWKW with a 3.5 exhaust so that will definitely do it.

[iruvyouskyrine]

3" straight through on 2530 Neo 340kw easy as

[jet_r31]

You don't need anything crazy if you venting gate to atmo and run no cat..

If you not..good luck with that .., just take of exhaust on dyno before you piss fart around remaking stuff

400 should be a walk in the park for a 3 inch exhaust..

cheers

darren

Edited August 22, 2016 by jet_r31

[lcxu105]

So a 3 1/2"dump 700mm lone back to a straight through 3"with 100 cel cat with 50mm wastegate merged back in the 3" pipe should be able to handle 420 to 450rwkw?

[GTSBoy]

The smart* approach (fully fully custom) is to route the wastegate pipe back in behind the cat.  Face it, the gate is not open very much of the time on the street, therefore the vast majority of the time all the gas is going through the cat.  Then when you really need the gate to flow lots of gas, you're not also requiring the cat to flow lots of gas.  Win.  Was it dose pipe Johnny who's done basically this recently?

 

*Only smart until you actually do get some sort of EPA/police attention, in which case it's not actually legal.

[lcxu105]

Interesting. I found this on the net.

[zebra]

Thats rubbish.

 

There is 20+ hp on the cards going from a dual 2.5" system to a dual 3" system on a 500hp 6l v8.

 

Turbo cars will improve more again

[AngryRB]

1 hour ago, GTSBoy said:

The smart* approach (fully fully custom) is to route the wastegate pipe back in behind the cat.  Face it, the gate is not open very much of the time on the street, therefore the vast majority of the time all the gas is going through the cat.  Then when you really need the gate to flow lots of gas, you're not also requiring the cat to flow lots of gas.  Win.  Was it dose pipe Johnny who's done basically this recently?

 

*Only smart until you actually do get some sort of EPA/police attention, in which case it's not actually legal.

Yes Johnny did this and ive copied plus merged it later for good measure ?

[jet_r31]

3 hours ago, lcxu105 said:

So a 3 1/2"dump 700mm lone back to a straight through 3"with 100 cel cat with 50mm wastegate merged back in the 3" pipe should be able to handle 420 to 450rwkw?

i had a 3.5 inch dump, then a 3 inch with a slight offset lukey and a resonator on my r31. It ran 141mph through the mufflers on 25psi with a auto

it was quiet exhaust but with a vented gate 

My mate had same mufflers in his vl turbo( manual)  as he copied with a 3582 turbo on upper 27psi, but with a 3 inch dump..he ran 138mph (you work the power out out) on a 3582 1.06 turbo , he dropped the exhaust  at dump and it made 10rwkw difference...Had a vented gate

No meows..

 

It really really comes down to vented gate..if you don't vent it..good luck. You need a f**koff big exhaust. Just like a Gtr with the twins replaced with upgrades...

or perhaps merge it a long way back. But thats a p.i.t.a

honestly you just need to test it, as different mufflers and cats pose different restrictions..even in same sizing..

cheers

darren

 

[PSI086]

Interested to see what difference venting the gate to atmosphere would make with my set up. Currently running a 4" dump to the bellhousing and then 3" from there through a single round muffler after the diff. Single cam RB30 with a powerglide. Head is stock besides slightly oversize valves and a small 218 @ .050 wade cam. Making 396rwkw with a 1.06 gtx35 on 30psi. Basically stopped making decent gains in power with more boost and inlet temps rising quite fast. The gate plumbs back in maybe halfway down the dump pipe. Would it be much more efficient going to atmosphere as I presume a fair amount exhaust flow would be through the turbo at that boost level?

I didn't have a chance to dump the exhaust last time on the dyno to see if any gains were to be made but I guess the stock ports in the head would be holding things back a little also?

[sneakey pete]

More boost means less through the gate.

Would be expecting gains if you made it external , or got a bigger exhaust 

[lcxu105]

44 minutes ago, PSI086 said:

Interested to see what difference venting the gate to atmosphere would make with my set up. Currently running a 4" dump to the bellhousing and then 3" from there through a single round muffler after the diff. Single cam RB30 with a powerglide. Head is stock besides slightly oversize valves and a small 218 @ .050 wade cam. Making 396rwkw with a 1.06 gtx35 on 30psi. Basically stopped making decent gains in power with more boost and inlet temps rising quite fast. The gate plumbs back in maybe halfway down the dump pipe. Would it be much more efficient going to atmosphere as I presume a fair amount exhaust flow would be through the turbo at that boost level?

I didn't have a chance to dump the exhaust last time on the dyno to see if any gains were to be made but I guess the stock ports in the head would be holding things back a little also?

What fuel are you running? 30psi i would expect to see more hp than that 

[AngryRB]

Yeah, the motiveDVD gtr got 464rwkw on 27psi using 3.5in system and screamer using same turbo.

[jet_r31]

On 8/24/2016 at 7:10 PM, PSI086 said:

Interested to see what difference venting the gate to atmosphere would make with my set up. Currently running a 4" dump to the bellhousing and then 3" from there through a single round muffler after the diff. Single cam RB30 with a powerglide. Head is stock besides slightly oversize valves and a small 218 @ .050 wade cam. Making 396rwkw with a 1.06 gtx35 on 30psi. Basically stopped making decent gains in power with more boost and inlet temps rising quite fast. The gate plumbs back in maybe halfway down the dump pipe. Would it be much more efficient going to atmosphere as I presume a fair amount exhaust flow would be through the turbo at that boost level?

I didn't have a chance to dump the exhaust last time on the dyno to see if any gains were to be made but I guess the stock ports in the head would be holding things back a little also?

I wrote a big post and it didnt work. Cbf again

My mate morgz on ct ran 3 inch dump/exhaust plumbed back

With a 3582 with billet 67mm  comp 1.06

Went 10.20@140 -30psi-auto-450rwkw..made no more power

He unplumbed gate and it went straight to 40psi and maxed fuel system out in the midrange where peak torque is. Had to plumb it back..lol

So maybe worth a look

Cheers

Darren