Marathon
Wow, what a paragraph!
OK, my opinions...
I've heard of amazing rwhp gains from midpipes on stock 99-04 Mustang GTs - but never seen them, nor seen them proved in any shootout. 32rwhp would be nearly a 40HP gain at the flywhell... Sorry, I just don't believe it. I don't have ANYTHING against the MAC ProChamber, but no way will you net 32 hp at the rear wheels from it - more like 8, MAYBE 10 on a perfect day and a kind dyno.
Top quality after cats WITH a full exhaust might contribute another 2, maybe 3.
LT's add 10 or 12, pretty reliably. 20-25 (and I think 20 in real life) is the more likely result.
Just some background: Manufacturers of these kinds of bolt on parts ALWAYS test them on the strongest supercharged Cobra they can find (and we all know its not hard to get one of them to put out 500 rwhp), and then advertise: "Our stuff gained 32 rwhp in a Mustang".
Cars with highly modified motors CAN see big increases from these exhaust changes, mainly because they are resricted by the stock exhausts. Our more mundane stock or mildly modified cars are NOT restricted nearly so much, so the gains are modest.
Earlier Mustangs (particularly the 5.0's, but also the early 4.6's with 6 cats) see bigger gains because their stock exhaust is garbage.
The 99-04 stock exhausts are decent and made of stainless steel. (I know, they look orangish and aren't pretty, so it's not show quality SS, but it IS stainless steel). The cats are more modern, low restriction types and work pretty darn well. Going to an xpipe with just 2 cats DOES gain some power, and that's where the 8 hp comes from. Eliminating cats altogether actually hurts the tone (imo - and "good sound" is one of those subjective things that means it all depends on what the OWNER likes to hear), makes the car illegal in all 50 states (although you're more likely to get caught in a state that does emission testing, of course), and gains about 1 - 2 rwhp (though cars with built motors and blowers gain MORE, every time, count on it).
If these cars could gain 50rwhp just from an exhaust, believe me, we'd know about it.
This is NOT directed just at MAC products - NONE of the expensive SS systems really does any better. They might live longer, that's all, or have some fractional hp advantage that hardly offsets their high price.
Oh, and the MAC ProChambers are sort of unique. They are similar to an X-pipe (look at their shape), and function essentially the same, with a small chamber (hence the name) located at the center of the X. They are NOT H pipes. I think of them as modified X-pipes.
I have read/heard that the Pro chamber adds the most HP than any midpipe by a ton, nothing even close, 32whp with the mufflers and headers of ourse. Does this sound right? Considering headers are good for 10whp and a catback 3-5whp the Pro chamber must be the best with the potential for adding 15+ whp, can anyone confirm this? I am looking at changing my SHM #2730's for a set of Hitech stage 2's with the pro chamber but may stay wit the stock catback that I just had replced the PYPES catback I had with the optional Race Pro mufflers(a $40. option for quieter sound than the Violators, yeah right!) THe drone at 2k was enough to rattle fillings and became untolerable. I still hae the PYPES catted X-pipe, 2.5" and just have the stock mufflers and tail pipes at 2.25" but the way I see it the gasses have cooled by the time they are through the mufflers and 2.25" is enough and actually likely keeps the gas velocity up as the smaller pipe would even if and especially since the volume of the exhaust gasses has condensed. Thoughts?
