I know the 5.2 is designed to benefit from some back pressure, and will loose some torque if it is opened up all the way. Turbulance is the real enemy here. Getting some headers would give you positive gains, even if it all stays at the stock size all the way out. For my money, I would do headers, then high flow all the way back. I deleted my cat & have a flowmaster with a single outlet so I am not even running dual exhaust. I noticed a great bit of pep after those simple upgrades. I will also try to explain something an engineer did to me many years ago about the sound of exhaust. This is a bit of a rant btw. The sound of the exhaust note creates a sine wave that causes some of the exhaust to get pushed back into the combustion chamber, which creates more compression & helps the performance. This is mostly true for 2 stroke engines, but it does apply to 4 stroke engines also. It was proven also that those fart pipes kids put on rice burners actually hurt their performance because the sound is not what the engine needs to create full compression with the proper amount of back pressure. I wish those goofy emo kids with fart pipes on honda's would stop cutting themselves & start cutting out those crappy mufflers that make more of a cartoon sound. I also wish my yard was emo so it would cut itself.

 

Having 3" midpipes buys you nothing other than the headache you get trying to round up all the odds and ends it will take to piece it together like that. Just leave them at 2.25" down to the Y-pipe and do the step up to 3" there. Magnaflow makes a 2.25" X 2 in and 3" X 1 out y pipe that would work perfectly without anything else other than some straight pipe to attach all the pieces together with.

I'm betting, if anything, converting to the 3" midpipes will just be an extra place for turbulence to occur at the transition between the manifold and midpipe and would probably slightly hurt performance rather than help it.

 

Too bad Big Daddy"Don Garlits" didnt know about back pressure! All those championships he won with open pipes kind of makes you think.
I tune 2 stroke engines where back pressure is needed!
A 4 stroke engine hates back pressure!
Please someone in here with tech knowlage back me up and finally put this f****g
back pressure issue to rest.

 

Just wanted to add for those who can understand to benifit from back pressure 2 or 4 stroke you need a finely tuned expansion chamber independant for each cylinder to get any gain in power you ever seen a 4 in 1 -2 stroke exhaust?
any gains from backpressure come from a timed pulse wave bounced "back" into "a" cylinder not by chokeing off an entire bank of cylinders.

 

http://www.thumpertalk.com/forum/sho...d.php?t=659727

 

Three inch pipes off the manifolds will hurt you. Exhaust gases have too much room to expand/cool, and will slow down, reducing the scavenging effect that you really want. Doing headers (shorties, or long tubes...) a 2.25 or 2.5 inch y-pipes, to a single three inch exhaust will give you the most bang for the buck. You aren't building a blown, 500+ cubic inch drag motor here, bigger is NOT always better.

 

expansion chambers on a 4 stroke??? Never heard anyone calling it that before...Is that what the idea behind a megaphone is? I have a megaphone exhaust n my thuimper and it's sweet.

not exactly...I have seen several 3 into ones on two strokes. Though as far as I know, everyone generally agreed that 3 individual tuned pipes would have been better. All the most serious racers I'm aware of use fully independent expansion chambers for each cylinder.

 

what if i just did them 2.5" instead?

 

For one it costs more and two you only stand to hurt performance. Why not just leave the midpipes as is and do a 3" from the y back?

 

or should i just focus on some headers and scratch that?