just little question

is there clearance for 3" y pipe

for exhaust im thinking either
2.5 y pipe with 3 or 4in I pipe

or use a 3in ypipe too 4in i pipe

3.5 exhuast would be more expensive to make then a 4in locally around here

power goals is being above 400ish

only issue with 2.5 is that if i get headers with 3in collecter i think i would loose flow going down to 2.5 y pipe

and running a 3 y pipe and 3 i pipe seems like a restriction also with 3in collectors

any input let me know if im just overthinking it then slap me lol

trans is a 4l60e

400 whp?

You can do that thru a single 3" but its a restriction. Can make alittle more with 3.5-4" single over 400 whp. Higher you go the more 4" helps.

Ypipe can be 2.5 into 3.5-4" or you can fit 3" off collectors into 3.5-4" single. Just takes some custom exhaust work to get best fit and finish

It seems the wisdom of the internets (hah) has determined that the 3" into 4" Flowmaster merge is the hot ticket. There seems to be plenty of Flowmaster stickers in this pic so you don't get confused.



There is room under our cars for this type of setup, but you'll need a good double hump crossmember and a competent exhaust man to get it all together with good clearance.

If you run that cutout, followed buy a 3" or 4" cutout you won't have any restrictions and can make as much power N/A as you wish. It took some fabrication work to make it happen with my car.

I made this crossmember so I could keep the TQ Arm mounted and still have room for 2 3" pipes.
https://www.thirdgen.org/forums/post...53-post28.html


Ended up with this Y-pipe using the Flowmaster merge:


Followed by this 3" cutout. FWIW, I have a new 4" QTP cutout and in my "quest for 10's" I plan on redoing this part so its a true 4" all the way.


Good ground clearance, I just have the Eibach Pro-kit but I rarely drag on anything. Obviously though you still have keep an eye out when driving.

i relized that too there are other options out there i think flowmaster is the cheapest tho

i plan on using a douple hump trans mount

it just didnt make since why would people go down 2.5 then back up to 3 in all the way back

im no scientist but my gut doesnt like it

i was woundering about a cut also i have electric 3in exhuast butterfly
and run a 4in cutout but with the 3in butterfly

I didnt see your post till now Yes 400 whp if i dont get it this time around it is a goal this year

im pretty set on a 4" cat back i rather do it right now then spend more and upgrade later

im more concern with the 3" collector dropping down to 2.5" then to a 4" merge
vs
3" y pipe to 4" merge

i would go 3.5 but its more expensive to build then a 4 in system

i had bought a 3.5 cat back but that fell thru and lost my money so looking for better stuff now

Reason i suggest 2.5 in the y is for better clearance as thats a pinch point. 3" around an autoxmember is harder to do on lowered cars. Even stock height can have issues. Dual 2.5" is plenty for 400 whp. Can squeeze more out of it but backpressure may start to rise. Single 4" is good to 550-600whp and maybe more. Dual 3" is good to more than that. I saw a noticeable improvement with dual 3" over single 4" on 700-800 hp boosted motor

But just the ypipe section is 2.5", and thats not alot of pipe length. Shouldnt pose too much an issue with 4" downstream

yea i know 4" is more than enough but i do plan on some more upgrades in future

t56 guys have alittle more room to play with than the auto guys and im running sportlines so clearance is a concern also but dont like the idea of having restriction but sometimes you have to sacrafice something

On sportlines, with what you have in mind, and an auto, you might run into some problems...as you already suspect. Its tight even with a double hump and 2.5" collectors/y-pipe. But if you are patient and take your time figuring out your piping, its not TOO bad.

As for flow for 400 hp, you should be ok. That flowmaster merge is great. And once you are there, the exhaust is pretty much a nice straight shot out back. Save for the hump over the axle...unless you dump it. A cut out before the axle will pretty much mean backpressure isnt an issue. Unless you have some nasty kinks in your y-pipe.

Here's my y-pipe. As you can see, one side is almost straight through. You can see through it. And the other only has a slight bed and I kept it as smooth as possible. Obviously with an Auto yours will look different. My car is lowered on a ProKit also and I take speed bumps with no problem.













I too am shooting for 400ish with my new build. Might be a pipe dream...but Im fairly certain if I dont hit it, my exhaust wont be the issue.

J.

yea i should be fairly close
LS6 Intake, Ported TB
243 Heads Bowl Blended ,Mild Porting
Spec Cam by EPS seen cam break 400 on stock exhuast manifolds
Getting it tuned also
Flow Match Inj. now Flow 42lbs
thinking of splurging for long tubes right now lol
im prob missing other stuff but thats the main stuff

We All Can Dream Can We sigh

400 is very doable. 394 at tire on a WORN OUT ls1, unported 243s that were milled, ls6 intake, stock TB and longtubes, good exhaust.

Its all a dream untill i get tuned lol
ive freshen up the engine put so it wont be a worn out block no longer
arp rod bolts had them resized
new piston rings
new camshaft
polish journals

im looking at some mandral bends

i was think getting a couple 18 degree bends and maybe some 45s

don't worry about running 2.5" pipe to your y. there is a reason a lot of headers get reduced from 3" to 2.5". 3" dual exhaust is overkill on just about any "street" car. you are wasting the scavenging effects by going too big in most cases. don't let the hype scare you.

you got a point

i was just looking at hawks y pipe it looks horrible didnt relize they used crush bend tubing and 50 buck y pipe

I got stainless magnaflow bends. Pretty sure I used Summit Racing, but ebay has some good deals on them too sometimes.

Get yourself a 180* bend. Because you can cut angles all the way around that. And then get a couple 45's. The 45's are good for having some straight before a transition. Shouldnt take much more than a 180 and a couple 45's to get you where you want.

Did you want to do stainless, or carbon steel? Carbon steel will not only be cheaper but easier to work with. Stainless really needs to be TIG welded. Yes you can do it with a MIG, but its 10x nicer with TIG. Carbon steel can be welded up no problem at any average exhaust shop. If you have a welder, but dont want to weld the whole thing yourself, just tack it together and take it to someone, slip them a few bucks and they'll do it in no time.

Oh...and I bought the original Hawks Y-pipe. It donated a lot of its stainless mandrel bends to my custom y-pipe

J.

i have been looking around for the best deal havent look at ebay yet ill do that later today