keysflier

I've just started a campaign to modify my 97 GT 4.6L engine and related components. Immediate changes will include non-cat exhausts and aftermarket mufflers. I'm eyeballing a set of PI heads and will end up with long tube headers and possible cam swap when I'm done. How crucial is it to hook up an aftermarket performance tuner once you've accomplished these mods? Another way to ask is, how "smart" is the onboard engine control computer at detecting these changes and making internal adjustments as required? Thanks for any input.

jrp1588

If you do head and cams I'd certainly get a tune. With the others it's optional, but you'll get more out of them with a tune. Plus, a tune adds power itself, why not get one?

cliffyk

A non-catted (off road) X or H-pipe will only add stink and NOISE as compared to a so-called "high-flow"¹ catted pipe. Noise and lower cost may be your goals however there is no performance advantage versus any aftermarket catted pipe.

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¹ - There isn't really any such thing as a "high-flow" cat, they are just converters that are physically smaller (have less "stuffing") than would normally be used on any given sized engine.

keysflier

I'm all about noise snd stink. You'll never convince me that a straight exhaust doesnt flow better than one with cats. Those things are like breathing through a cocktail straw (well, thousands of tiny cocktail straws anyway).

cliffyk

I have done back-to-back dyno runs--not with a Mustang but with a 235 rwHP supercharged '92 Miata at 15 psi--with 4-2-1 header and a "cheater pipe", and the cheapest "universal" catalytic converter we could find ($65 at Advance Auto).

There was NO discernible or even remotely noticeable difference in engine output.

If you have dyno runs to prove otherwise let's see 'em. In fact, if you wish to meet at RAABE Racing in Daytona, and provide the o/r and "catted" pipes and labor to change 'em out, I will pay for the dyno time--and if there is more than a 5 rwHP difference I'll cover your costs...

stevednmc

Ooooooh....keysflier youve been called out!

sn95_331_GT_ yellow

the ONLY difference is the amount of noise thats it...

certain mufflers sound great some ways, others the other way

they ALL sound better with longtubes

example: SLP LM1's with LT's and catted X sound AWESOME, OR X sounds like crap

Magnaflows and Bassani sound GREAT with an OR X, just a little quieter with the catted

keysflier

Seems I've stirred up quite a stink and now others are wanting to make a lot of noise about nothing... But just for the record, I stand by my statement that a straight pipe will BREATHE EASIER than one with a CAT. Will it show up on a dyno? Cliffy says no (and since it’s been posted on the Internet, it must be true).

I don't care. My goal is twofold. I want to: a) create enough decibels to frighten small children [NOISE] and b) generate the largest carbon footprint I possibly can [STINK].

cliffyk

So I guess we're not going to Daytona?

scrapman

If this is REALLY what you want, then you need to yank off that fuel injection, through a carb and intake on it, and set it so rich that you have flames coming out the back.