I've been reading up a lot on ypipe exhaust for these cars and whether or not a 3" catback is enough. Here is my situation: I have Pacesetter LTs and a TSP catted y. The previous owner had installed some custom [badly welded] catback with a flowmaster 80 into a weird center exit setup. I want to ditch the setup and buy/make a new better flowing one that is hidden tip. The questions is not whether I need to replace that, the question is about the sizing of pipe needed to help me out.

Here is my thought/idea:
cut off the neck-down section of the TSP y and mate it to a 3.5 or 4" ipipe, reduce it to a 3" over axle and do a single in/out muffler [still unsure on muffler] with hidden tip. Would this benefit me in any way? The motor is a stock 04 crate LS6 [CTSV] from Scoggin Dickey. I seem to recall a thread from Pat G where he added a 4" section to his ipipe and benefited. I mean logically it makes sense that having 2 3" pipes converge into the same diameter would not be optimal for flow. Converging into a 3.5 or 4" section should help out I think.

I could have a shop modify the ypipe with a 3.5 or 4" section, connected it to one of those Dynomax 3" over axle pieces [pre-bent and cheap!], and finally into a hidden tip single out muffler. Does this sound like a pretty legit idea? From what I've read a whole 4" would be overkill for me since I'm not doing big cubes.

Yes, I am new to LS engines and muscle cars in general. I've been reading a lot of threads on exhausts lately but am looking for input from people more knowledgeable than myself. But I'm trying to learn here hahah

I welcome all input/feedback/explanations/reasoning! [so if it is a bad idea, please explain why so I can get that knowledge!!] Thanks

 

A 3.5 or 4" I pipe will give you a deeper exhaust note. A more efficient merge will give you a little more power. It's been done by many.

 

Adding a 4" pipe to 3" exhaust will not increase the flow because you are still limited to the 3" pipe that is surrounding the 4". It would be a waste of time and money to attempt such a thing unless your doing it strickly for the sound..

 

3" inlet/4" outlet y> 4 i-pipe > 3"reducer > 3" catback is a proven combo. The further back the reducer the less of an effect it will have, if any at all. Don't let anyone tell you different.

 

Proven how? If you have a reduction in the pipe at any space it will not increase the flow!! It's physics. The 4" pipe will only change the sound and harmonics of the exhaust not the CFM..

 

The further back the reducer in the exhaust system, the less of an effect it will have on flow. That is proven.

Tons of ppl are running this combo with proven results.


Sure i can see if your running big monster cubes and a radical cam, it might be more of an issue, but in this guys case it won't.

 

i say just put a cutout at the end of the 4" section and then you can use whatever you want behind that. at that point, nothing would flow better than your open cutout and you'd still have the option of a "quiet" exhaust by closing it.

get an ecutout and flip the switch when you want to go fast.

 

Exactly, i failed to mention that in my initial post.

 

wrong. 2 3" pipes will merge together into 3" I pipe < 2 3" pipes merge into a 4" i pipe. as you said it is physics. the bottle neck will be your 3" i pipe not the 2 3" pipes off the headers. increasing your I pipe diameter WILL increase flow, deepens the sound and not to forget lowers the rasp ..i my self going with FM merge and a 3.5" I pipe all the way to the back.

 

I was basing my idea/logic off the this post from Pat G:
https://ls1tech.com/forums/7248595-post9.html

And another thread that stated:
A 2.75” (stock) single system is good for a 310hp engine with zero loss…
A 3” Single system is good for a 370hp engine with zero loss…
A 3.5” Single system is good for a 503hp engine with zero loss…
A 4” Single system is good for a 657hp engine with zero loss…
A 2.25” dual system is good for a 457hp engine with zero loss…
A 2.5” dual system is good for a 513hp engine with zero loss…
A 3” dual system is good for a 812hp engine with zero loss…

I know the cutout would help with restriction and have definitely considered adding one in.

I've read that reducing back down after the ipipe wouldn't hurt too much since the gases have cooled a fair amount by that point. And if you look at Pat G's post, he stated he only lost ~9hp through that setup vs the cutout. I mean if that setupt supports 500, it should be more than enough for my use.

I cannot seem to find exact info on where the reducer would induce restriction. I was drawn toward the Dynomax 3" over axle piece since it is already bent to our config and pretty cheap. If 3.5 would be better and not much more than that might be the route I take I just couldn't seem to find a seller of a prebent 3.5.

 

honestly, if i was going with a bullet muffler id get a 3.5 bullet in the I pipe and route it all the way to the back. the main reason id go with regular muffler and a reducer would be the tail pipes and the queitness but thats just me. you wont regret a 4" or a 3.5" merge and I pipe.

 

oh i missread the OP first post. my apology to odarabla . he is correct if your going with a reducer it will only benefit in sound . my bad

 

The dynomax part I'm referencing is

Not a bullet muffler. Like Jay-P stated it would be
dual 3" y > 3.5" or 4" ipipe > 3" over axle with single in/out muffler

If the 3.5 from ipipe back would be a better option I may do that I was just unaware of where you can get the over axle piece and think the Mufflex is a little much since I am not too fond of the muffler choices they have

 

yes i get it. you get a better sound. deeper and less raspy in fact WAY less raspy . but have you looked into customs? it would be better to get a custom 3.5-4" all the way to the back with a 3.5-4" in/out muffler. but if your staying with no h\c then a 3" would be sufficient.

 

Stu at your power level a 3" reducer placed before the axle will not result in a huge power loss, if a power loss at all... Like you stated, at that point the exhaust gases have cooled and slowed down.

Having the 4" at the y-pipe outlet helps minimize the restriction on the 2 3" as they transition in to 1 pipe.


If you feel that is a concern for you, toss in a cut-out before the reducer. Lots of ppl run this style so there are numerous examples to reference from.

Having the 3" gives you more options for muffler "rear" sections. If i wasn't running a cme i would just consider a 3.5" or 4" single.

This has been argued over and over, with ppl taking either side of the fence.

 

Just the sound difference alone makes this a worthwhile mod.

 

Have a link to this piece? I couldn't find it...

TIA