Ok so pretty much all the kits I find are just the stack kit and using what exhaust you have from the turbo back so my question is is there that much gain with the 4" turbo back over the stock 3.5". should I just go with what I got or spend the extra cash and get a 4" down pipe and some 4" pipe. The single stack kit I am looking at goes from 4" to 5" with a 7" stack. And the dual kit is pretty much the same but with 5" stacks. Thanks in advance for any help.

 

Why do you want to install a vertical tailpipe? Do you think that will increase your HP or reduce the exhaust back pressure at your turbine?

 

Nope as far as the stacks go it is mainly personal preference I think. It will be the open ended exhaust that will help with the rest.

 

I'll give you a bump. I'm curious to hear about going to a 4" downpipe and results/differences if any.

 

4" down pipe! i have dual 6" stacks with stock down pipes and im still reaching 15000 easily, im upgrading to the 4" down pipe this weekend, its in the mail...why a single stack?

 

Yah If I had a 350 I would get dual stack IMHO,
Nick

 

Go for the downpipe, while you are at it. Why not, the stock one is 3", not 3.5". It then necks out to 3.5'' after the trans cross member.

 

Would you mind posting your results if you see any temp drops with a 4" downpipe? Or even do a small writeup to make future searches easy to come across.

Thanks!

 

I think you might be better off with the smaller diameter pipe running from the turbo to the stacks! The reason is that a larger diameter pipe slows the flow velocity which allows the exhaust gas to cool to a lower temp and become denser by the time it reaches the vertical portion of the tailpipe, and it will then take even more backpressure to push this denser heaver mass of gas against the force of gravity up the 6' vertical rise of pipe.

You might even consider insulating the horizontal run of tailpipe under the truck. This will keep the heat in and increase the flow velocity so the exhaust won't cool as much by the time it reaches the stacks so it will be less dense and easier to push up the stacks.

The configuration for the least amount of back pressure is to run the pipe horizontal, and use a smooth large radius bend to exit in front of the passenger side wheel. The shortest horizontal length with the fewest bends is the best for minimizing back pressure.

 

With a 5 to 7" pipe i don't think he has that much to worry about. Go start analyzing that thread about old trucks and mileage.

 

Something different and I kinda like the look I believe there is someone on here that has a single on a dually and it looks kinda cool the sad thing is that I am finding dual kits cheaper than the single kits so I am still undecided.


Kris thanks I thought the 99.5 and up had the 3.5" from the turbo back. I thought it was the early 99 and down that had the 3" down pipe the great thing is you get to learn something new every day around here.

 

By this statement I assume you "think" that a 7" diameter vertical run of tailpipe will produce less backpressure than a 5" diameter size? Have you ever heard of a "thermal inversion" where a layer of "cold heavy air" traps "hot lighter air" beneath it? When I post information on FTE it's based on proven engineering principles, and usually has some calculations as well as data from independent sources to back it up!

I'm not trying to talk anyone out of getting stacks, but rather provide some useful information as to how you can minimize their adverse impact on performance by properly exploiting the waste heat in the exhaust gas so that you get a smaller adverse increase in back pressure due to the stacks.

Now the question that was asked is what's the best diameter pipe to run from the turbo back to the stacks. If this pipe has too small a diameter the flow resistance increases EBP at the turbo, and if the diameter is too large the gas cools too much and the need to push this heavy gas up and out of the stacks increases EBP.

So what do you think is the optimum diameter for this horizontal run of pipe to minimize EBP?

 

This reference is a good place to start for anyone who wants to understand their exhaust system a little better before they start spending a lot of money to mod it, and possibly wind up with worse performance than they had to begin with.

It also explains why you can vent the CC to a bung properly located in the collector pipe that joins the header pipes, but if you place a bung in the tailpipe region following a turbo you'll just pressurize the CC with backed up exhaust gas.

http://www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.htm

Exhaust Theory... We've seen too much misinformation regarding exhaust theory. What kind of misinformation? For starters, there are a lot of people in the "Bigger is Better" camp. We're talking about exhaust pipe diameters. Even the big magazine editors are boldly smattering statements like, "For a turbo car, you can't get an exhaust pipe that's too big." Also, terms like "back pressure" and the statement, "An engine needs back pressure to run properly!" really rub us the wrong way.

Pipe Sizing... We've seen quite a few "experienced" racers tell people that a bigger exhaust is a better exhaust. Hahaha… NOT. As discussed earlier, exhaust gas is hot. And we'd like to keep it hot throughout the exhaust system. Why? The answer is simple. Cold air is dense air, and dense air is heavy air. We don't want our engine to be pushing a heavy mass of exhaust gas out of the tailpipe. An extremely large exhaust pipe will cause a slow exhaust flow, which will in turn give the gas plenty of time to cool off en route.

The Exhaust Pulse... Keep in mind that for a "pulse" to move, the leading edge must be of a higher pressure than the surrounding atmosphere. The "body" of a pulse is very close to ambient pressure, and the tail end of the pulse is lower than ambient. It is so low, in fact, that it is almost a complete vacuum! The pressure differential is what keeps a pulse moving.

 

go with a 4 inch down pipe I went from a 3.5 to a 4 inch down pipe and WOW!!! way better that was the only thing I change was the down pipe big diffrence.

www.mkopower.com

 

I'm kinda irritated by at this technical bumbo jumbo.