Yes me too Santacruz. I don't think this is one thing that needs to be over analyzed, it's just stirring up crap no one really needs to concern themselves about. If you are concerned about it at all, well then stacks are not for you, plain and simple.

 

The graph is to illustrate the point I've been trying to make that larger diameter tailpipes slow the exhaust gas flow velocity, which allows the EGT to decrease, which causes the EGD to increase, and a higher EGD requires a higher EGP to push the heavier exhaust gas down and out, or in the case of stacks up and out the end of the tailpipe.

I recently posted the quote below on another thread.... If you take this water driven turbo analogy a step further, adding stacks to your truck is like making the water flow up hill after it spins the turbine, and this generates additional backpressure on the turbine and reduces it's efficiency. I'm suggesting that a proper diameter tailpipe will help to mitigate this increased back pressure by allowing the waste heat of the exhaust gas to aid the gas flow up and out of the vertical section of pipe.

For example, you can see from the graph that EGD increases from 0.05 to 0.057 lb/ft3 as the EGT cools from 400 to 300 F. That's a 14% increase in the weight of each ft3 of exhaust gas, and every 142 ft3 of gas that's pushed up the stack weighs 1 lb more at 300 F than it does at 400F. If you take the inverse of EGD, at 400 F it takes 20 ft3 of gas to weigh 1 lb, but at 300 F it only takes 17.5 ft3 to weigh 1 lb.

Now the trick is to find the correct diameter tailpipe that will preserve as much EGT as is possible without causing too much restriction to the flow. Smaller diameter maintains EGT but increases restriction, and larger diameter reduces restriction but decreases EGT.

 

i have a 4" dp that dumps into 5" right behind the front wheel goes back to the box goes up into dual stacks i don't see anything over 1100* 99% of the time thats measured at the exhaust manifold

 

exhaust at the ends of my 6" stacks is cool enough to hold your hand over. No wonder my in-dash exhaust restriction gauge with the sender stuck inside the stacks reads in the red zone... Maybe if i could find a way to defy gravity inside the stacks, to allow the COOL exhaust to rise up easier, or invent some sort of EXHAUST heater, no that wouldn't work. Or maybe i still don't give a F

 

what would the density of all the black smoke behind you regardless of the downpipe NOW THAT IS THE ONLY CONCERN TO HAVE. 4 inch downpipes rule...

 

The reason I'm irritated is because I just order a 4" downpipe and dual 5" stacks.... So YAY!

 

Sense I am the one that started this thread I am going to go with the duals mainly because it looks like I can do it cheaper and I am working on a limited budget and need to get my gauges to. I actually ordered a set of 5" grand rock straight cut (I like the straights the best) from Powerstroke Gogo. The 4 week lag time was kinda disappointing. Did not go for the downpipe yet do to the funds but I think sometime around spring I will be able to get rest. Of course I noticed they had the MBRP smokers stack system cheaper than anyone and the stacks in pairs cheaper than you could buy one for from anyone else after I ordered. I could have gotten that system for $85 more not bad and it comes with the downpipe so if anyone is looking there you go. Oh well I will look a little better next time huh.

 

Hey man. I just ordered the grand rock kit too. From a dealer on Ebay. He's got them in-stock.