FormulaNHRA

iTrader: (1)

I'm getting ready to do a header and y pipe/mod install in early june and i've finally purchased all the parts, and wondered where the best place for my cats would be....Here's the scenario: I have a slp loudmouth catback, with the slp ory, i just bought pacesetter lt's, two pype highflow cats, two reducers (headers 3 to 2.5 y), and some clamps. I was planning on welding on the reducers after the headers and clamping that onto the y/cat. Where should I put the cats so that i get the most power and flow outta my system??? I can pretty much put them anywhere after the reducers cause ill be cuttin and weldin. Will the reducers cause me flow problems?? Any comments or expertise is greatly appreciated, i wanna make sure i'm milkin the most out of my system (even if its not the best setup)

s346k

iTrader: (4)

on the garage floor next to the air/egr systems.

NHRAMAN

iTrader: (1)

YESSIREE...

FormulaNHRA

iTrader: (1)

lol, good suggestion but i need em, sound, smell, and emissions purposes

TheBlurLS1

iTrader: (8)

Passenger side can go right after the collector, driverside can go right afte the 1st bend, right before the y-merge. Look at the pics in the link in my sig, you'll get the idea.

1 question, why don't you just buy a catted y-pipe?

300bhp/ton

Well when you get under the car you'll see you are limited for fitment of the CATS due to the space available. Take a look at TSP's website at there catted Y and see where they locate them.

However if you want my honest opinion I would sell the bits you have. The LT's and the LM are good so keep them just get a new catted Y pipe.

Personally for the price I'd go for TSP's one, it's not that expensive and it's also very good.

A 2.5" Y pipe is IMO restrictive, I would run a 3" as a minimum. Also I'm not too keen on the CATS you have (if they are the ones I've looked at in the past). On a stock 4.6 Mustang (260bhp) they would be fine. But a stock LS1 is getting dangerously close to exceeding their efficent flow rate, a modified one certainly is.

The TSP Y uses Magnaflow Carsound CATS, these are not the greatest but they are pretty good, a whole level above the ones you've got. And should be fine on a full bolt on LS1 and only minimal affect on a cammed car.

FormulaNHRA

iTrader: (1)

so are you saying that i might be close to having to much flow for a stock engine?? Is the flow rate of the pype cats to great then? I didn't buy the catted y cause i saw too many pics with little clearance and i didn't want to deal with the y pipe jackhammering the floorboard and having to put in motor mounts and possibly hangers, etc.

300bhp/ton

Essentially you can never have enough flow. Backpressure is only bad although there is a beleif you need it. This is totally wrong. On a stock tune (EFI or Carb cars) by reducing backpressure will alter the a/f ratio and thus alter performance, usually for the good but not always. And as many people are lazy and don't tune the beleif has grown up that you need backpressure.

As long as you tune to the current setup (not really needed on a bolt on LS1 but a cam would definaelty require a tune) the least restrictive setup is wanted.

The 2.5" and the CATS you have chosen are IMO restrictive on a bolt on LS1. So again IMO you would be better off with better CATS and a 3" as they will flow more.

As for banging on the floorboards, well this could happen with ANY setup although it's more common with the larger diameter Y pipes. But there's easy fixes.

If you're doing headers you might as well swap in some poly motor and tranny mounts. They are well worth regardless of what exhaust you run and should be on everyones mod list. Thunder Racing sells them.

If the Y pipe does still hit Mufflex make a small simple bracket that helps support it. It's easy to fit and is certainly worthwhile espcially considering the cost. This is also available from Thunder Racing.

If you think you'll never do more than bolt ons then the setup you have listed will be fine but if you cam it you will be costing your self HP and it really isn't a big effort to rectify from the get go.

Still it's your choice so run with what YOU consider to be the best setup for you.

FormulaNHRA

iTrader: (1)

thanks for the info, i'll try to piece everything together now

FormulaNHRA

iTrader: (1)

one more question, in theory where is the best place to put cats on the exhaust system, if they are needed. Is there any science behind it and the flow rate leaving pipe size negligible?

Phoenix 5.7

iTrader: (7)

its not a matter of the best place for flow, its a matter of where the floorboard will allow. look under your can and u will clearly see where the cats have to go

300bhp/ton

Well aside from the floorpan dictating where they will fit there's two answers here.

The CATS will work best the closer they are to the engine. However from a performance standpoint you don't want them right on the end of the collectors as you need to let the exhaust flow striaghten out.

You best bet is just look at other catted Y pipes (TSP, QTP, Kooks, etc.) and see where they put them.