Buddy of mine pushed 1,125HP through a Mufflex 4" catback. Took it off to save 50# weight, put collector mufflers and turndown on the LT's, and saw no increase in HP. Was a blower motor, so that might affect the results.

 

I run 3" off my Hooker LT's, no crossover, dumps at axle, w/ Dynomax race bullets. Excluding the headers, the rest cost less in parts and having an exhaust guy weld it up than a cheap catback alone would cost.

That said, the car is freaking LOUD, which I don't mind, since it is a weekend toy / racer for the most part now. I may go over the axle this summer once the motor/tuning is all done.

 

hmm wonder if I should go true duals then... I don't want too loud lol

 

How much did you guys pay to have a system welded up?

 

you cant just look at pipe size when it comes to exhaust flow. I think everyone here will agree that (2) 2.5 pipes have more internal surface area compared to a single 3". this increased surface area negates the difference in total area since the (2) 2.5" pipes now cool the exhaust quicker than a single 3" , and cool exhaust flows slower. so just because you have more total area doesnt mean it will flow more. so a (2) 2.5" system and a single 3" system will perform about the same with the 2 pipe system taking a slight advantage at higher RPM's.

 

lt's -> h-pipe -> two 18" chambered mufflers -> over the axle -> exits out the back

i love it! it really cut back on the interior resonance from having a cutout right underneath the cab.

 

hey trudual, thats exactly the system im doing right now. do you have pics?

 

i sure dont. i had a few but i had to lay on the ground so they didnt come out very well. im wanting to get it up on a lift (i should have taken pics when it was all done)

ive had a lot of compliments on it. people look for the 1in/2out muffler in the back and are surprised when they see its not there.

 

well when you get some pics let me know!

 

yes, and if anyone says it sounds like crap they are stupid. i did it and am very very pleased with it. plus it is less than a cat-back exhaust. you only need duel 2 1/2 pipes. duel 3 inch is overkill and will hurt ground clearance.

 

You've lost me with this analysis (and it may be my misunderstanding of what you said). Its obvioulsy true that the dual 2.5" pipes will have more wetted perimeter, compared to a single 3.5" pipe. Not sure how the increase in wetted perimeter "negates the difference in area". You're headed in the right direction.... because of the issue of wetted perimeter, you can not simply compare the cross-section the dual pipes to the single pipe, and assume if the area is equal, the pressure loss at any given volumetric flow would be equal. I think you'll find that the pressure loss for any given volumetric flow would be better approximated by using an exponent of 2.2 to 2.5 to compare the flow equivalence, rather than simply squaring the diameter.

Then there's the issue of heat loss. Again, seems headed in the right direction... more surface area in the dual pipes, more heat loss, cooler exhaust gas. Gas cools down, density increases, velocity drops. But that's not a bad thing. As velocity drops, pressure loss (aka "backpressure" in this case) drops. Reducing velocity in the exhaust, once you are past the primaries and the collectors is not a bad idea.

The questionable part of your analysis would appear to be that because the exhaust gasses cool and slow down, the sytem is not flowing as much exhaust. In fact its flowing less "volume", but its flowing the same "mass", at a lower pressure drop.

Or did I miss the point of your post?

 

Nope you pretty much got the point I was trying to get across, A dual 2.5" flows exhaust gas about as well as a single 3" but if I understand your last paragraph right your saying cooled gas flows as well as hot gas? just because it has less volume? maybe im not understanding you. Ive always thought you wanted your exhaust to be as free flowing as possible. and hotter gas flows more easily and quickly than cooler gas.

 

I know that I am probly going with the X pipe duals with bullet mufflers, comming off of some pacesetter long tubes. Hopefully durring spring break. Not sure about the power gains and loses compaired to having the cat-back. But man o man do I love the sound. Quite worth it I think.

 

I'm putting a set of Kooks LT with true dual over the axle next month, also using twin Pypes 450cfm cats and a set of DynaTech oval 14" mufflers at the rear. The headers have 3" collector and will have 3" cats, then necking down to 2.5" where need be for clearence. This is on a '95 TA that dyno'd at 236rwhp completely bone stock original everything. I will be dynoing it again after the header/true dual install just before the heads/cam swap. I'll have some good pics on my lift and the numbers posted when I get there next month sometime I hope.

 

u have too much money