exhaust size

Is there anything wrong with running 3" back from the headers? I have my stainless cat-back that I made for the turbo setup, was thinking about just keeping it for now to save some time since I would only have to add in a y-pipe to get it running.

Where is that open can of worms emoticon? There have been lots of different opinions about this topic. A single three inch is good for 370 engine HP without any loss. If you are planning more HP than that you will neeed a bigger exhaust.

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 for a 513hp engine with zero loss…
A 3” dual system is good for a 812hp engine with zero loss…

I got that from [You must be registered and logged in to see this link.]
Not sure where he got it from.

Thanks for the info.. I guess I will just keep what I have for now.

I'm gonna do the same thing, y into my existing 3" exhaust. I'm even gonna stick a high flow cat in it. I figure it'll cost me some power but it'll get the car running and it won't stink or make cop attracting balls of flame.

Rich

Thats pretty much what I had with my LT engine. 2.5" off the headers into a 3". With the LS3 engine, I have 3" collectors into dual 2.5".

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There's where I'm at. Ignore the black square tubing, that's the lift. The engine is installed without crossmember spacers so I have some body interference to deal with. The 3" exhaust has a resonator in the center and a Magnaflow muffler in the back. It was ridiculously loud with the 4 cylinder so the cat idea is also to quiet things down a bit. But maybe I'll just try it with the v8 and see.

Rich

Nice headers. I am planning to go without cats to a 2.5 into a 3 inch merge and out with a 4inch round body 14 inch long magnaflow in the I-section and either a 14 or 18 inch body offset in/center out magnaflow muffler out back. With both mufflers being 3in in and out. I think it will be a comfortable sound level, I hope so.

Rich, that's not a bad idea with the cat. I did the same thing with mine, have a 5" bullet muffler where the cat used to be but the back of my car is always filthy from the soot.