[Gene 5.6]

Any backpressure isn't good for an engine. But remember that an exhaust setup is only as good as the other modifications before it. The intake, throttle body, intake manifold, heads and cams all dictate where the power will be made. I thought about doing a 3" true-dual setup on the Titan. But without any other options for an intake manifold/throttle-body the VK56DE is strictly a low-end/mid-range motor. It's not made for high-end performance where a true-dual or any extreme flow system would shine. I also have speculations that the VK56DEK (07+ up motor) might have more then just IVTC in comparison to the earlier VK. Why stick an entirely different cam control system and intake manifold on a VK without opening up the head up a bit? I'll be finding that out soon enough.

So for the VK56DE, I think a 2.25" true-dual (ie. NISMO) would be an ideal setup to retain most of the low-end/mid-range but also gains some ponies in the higher end.

 

[Gene 5.6]

If I had it my way I would just eliminate all catalytic converters, JBA shorties, sim off the rear o2s since all they're good for is catalyst efficiency and throw some magnaflow 14" 2.5" I/O round resonators on right after the headers and then dump them right then and there. So it's basically headers -> resonators -> dumps. It will be gnarly loud but I think eliminating the y-pipe would show some interesting gains in the high end. Then it's all up too getting a better intake manifold to really magnify those gains. Something with short runners, velocity stacks and a nice meaty plenum would be ideal.

The VK56DE has a ton of potential that has yet to be unlocked.

 

[Gene 5.6]

So a technical discussion has now turned into nothing more then a bunch of adults acting like children over the internet. Come on guys, get your ****ing heads on straight. I'm guessing that most if not all of you are grown men. Start acting like it instead of participating in these e-peen contests over the god-dang internet.

Now back on damn topic. I'm actually anxiously waiting on the 0-60 times, buuuuut... make sure to get some 60-100 times as well. I think those would improve a lot more in comparison to the 0-60 which in my Titan is most of first and a little bit of second. I think this modification is more of a top end modification.

 

[Gene 5.6]

O.K boys I couldn't wait here's the results using cipher and data logging all 4 0-60 runs. I did 2 runs with Y pipe and 2 runs with straight pipe off headers. Ran the y pipe setup then came home cut it off and went to town
REMEMBER ALL TESTS WERE DONE ON THE SAME ROAD, SAME EXACT SPOT
Run #
1. Y pipe 6.10 Afr's 12.3-13.1..........DA of 2200

2. Y pipe 6.12 Afr's 12.2-13.2..........Da of 2200

3. 2.25" straight pipe with borla pro xs 6.05 Afr's 12.3-13.3........DA of 2197

4. 2.25" straight pipe with borla pro xs 5.99 Afr's 12.4-13.3........DA of 2190


I can tell you this they sound F-IN amazing even w/out the dump pipe I'm going to put on. They pull hard as hell and the shift even feels firmer. The ECU hasn't even learned the new air yet and it still outperformed my old setup. I'll be posting track results hopefully this Friday weather pending.

Also one more thing, if I gained performance in the 0-60 I can promise you that it will only get better from 60-100 being opened up

Hot damn that's moving.

Yes! Get me some 60-100 results! I can't wait to see how those have improved with this setup.

 

[Gene 5.6]

Backpressure is ABSOLUTELY necessary for an engine unless your valves are set up properly to run without it. It's not about how large the ports on the head are, it's about how well the head flows. Look at ANY honda head. the ports are tiny, but they flow stupid amounts of air through them due to the way its channeled through the head. Basically backpressure is needed to help maintain pressure in the combustion chamber. Unbolting your exhaust still wouldn't give you zero backpressure. You'd have to let it come straight out of the ports for that, and I promise you it will run like 10lbs of **** in a 5lb bag. Additionally, saying that "the intake, throttle body, intake manifold, heads and cams all dictate where the power will be made" isn't really accurate. You basically named all the parts of an engine, without the crank and pistons, which are the base of power production. They determine the displacement, strength, and compression ratio of the engine. Internal combustion effeciency and power production revolves around air. Exhaust will shift your power curve, and MIGHT get you as much as 15 ponies, but your real gains will come from finding ways for more air to get in, rather than out.

The argument about an engine needing back pressure has already been answered so I'll skip that and dissect the remainder of your post.

I don't understand your statement "It's not about how large the ports on the head are, it's about how well the head flows." So a port that is smaller in size but more efficiently "shaped" can flow as much air as a larger port that is a little less efficient? You do realize that the size of the port is relative to it's efficiency, right? So a smaller port = less effective no matter how smooth it is. Try blowing into a straw and then a water hose. Tell me which is easier to push.

It's a simple equation: more air + more fuel = more power.

 

[Gene 5.6]

It's not about how large your port is. Try just grinding your ports out yourself, then have them professionally done, and see the difference in flow gains. Unless you're force feeding an engine, port shaping and smoothing to reduce turbulance is as important if not more important that overall port size.

And I totally agree with that. There's a big difference between "grinding" away at your heads on your own and having a shop with flow testing machinery doing it. Shops will almost always ask for the cam specs so they can match the heads as best to that flow as they can. But you can still do your own mild port and polish and see some good gains. We did a minor port-gasket match and polish on my Altima's intake manifold and heads when I noticed there was some overlap and saw some gains in the top-end. I think it was like 16-17WHP with the PnP and SSIM (secret sauce intake manifold) modification at redline. But if you oversize your ports you run the risk of slowing intake velocity especially on stock cams and throwing the whole shebang out of whack. So this is definitely a modification left for someone who knows what they're doing.