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Excellent analogy.
 

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Since I'm tracking OregonFront's progress to modify his exhaust and saw this linked in his thread, i figured I would comment here.



This statement makes little sense and its one of the oft-repeated, always mistaken myths of exhaust tubing. BACK PRESSURE IS BAD. You do not want back pressure. What you want is a balance between tubing that is not too large to slow down exhaust velocity yet not too small that it creates back pressure. It is very hard to have too large of an exhaust system on a forced induction motor as these motors create a larger exhaust volume than your standard N/A motor. If your motor performs well out of boost with the new headers, then it should perform better in boost as well, unless you have a bottleneck somewhere else - the Nismo exhaust, but I'll get to that.

Think of a garden hose. Ya'll remember playing with one of these when you were kids? Well I do, and its been a long time, but bear with me. We were too poor to afford a nozzle for our hose so we had to get creative during our water fights. When you turn on the spigot, the water came out with a little bit of force, but not enough to soak the kid standing out of blast range. However, when you put your thumb partly over the end of the hose, what happened? That water came out a helluva lot faster and shot farther, right? You were then able to direct a pinpoint stream of water into that little bugger's eye. Put your thumb too far over the hole and the water either stopped or still came out but you noticed water coming out of hose joint right there on the spigot - this is back pressure. You needed to balance flow and velocity to make this work and reign supreme in neighborhood water fights. Some scientist also calls this the Venturi effect and since it's a law of science, it applies to exhaust tubing as well.

At the OP, try something for me before you go and waste money on a Flowmaster. Pull your exhaust off from the Y-pipe back (that over-priced Nismo can and piping) and go do a couple pulls with the truck and come back and tell us how it behaved. My guess is your in-boost power will be greatly increased without that Nismo piping on there. How big are your cats (diameter-wise)? How big is the diameter of that single Nismo pipe? My guess is too small.

I have worked at a performance shop for motorcycles for the last 4 years. (at a Yamaha dealer for 8 years) We deal with this stuff all the time. And he is accurate. This is a good "dumb down" way of explaning it. This threory works everywhere on a motor. You must have a balance, or it will not work properly. And let me spoil the end of the story....

Some where he has a kink "resrtiction" and when he removes it he comes back and says..."OH HELLS YEAH!!!!" thats way better!!!!....The End.
 

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so what exactly is the draw back of the nismo exhaust?
 

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so what exactly is the draw back of the nismo exhaust?
Not really a drawback just to the NISMO but to any exhaust that one side dumps into the other.

I think dual pipes would be the best route off the larger headers.
 

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instead of making a new thread i gotta ask...if you get these headers or the 4x4parts headers and you run high flow secondary cats do you think it will pass emissions test? maryland does a stupid friggin emissions test every 2 years, and if i were to get these headers no way am i intalling, taking off, then reinstalling the headers every 2 years. thanks, oh and there aint no suck thing as good backpressure, look at diesels they really wake up with larger exhaust, dragsters use open headers sometime zoomies. i plan to get more from my 3.3, people always talk down on them.
 

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People talk down on the N/A 3.3 because it's a low compression, gutless pig. That said, if you put in the headers and run a CARB-compliant Magnaflow cat, you will have zero problems passing an emissions sniffer. You might fail a visual if the tech knows that Nissan has four cats and you only have two, but I'd risk that.
 

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People talk down on the N/A 3.3 because it's a low compression, gutless pig. That said, if you put in the headers and run a CARB-compliant Magnaflow cat, you will have zero problems passing an emissions sniffer. You might fail a visual if the tech knows that Nissan has four cats and you only have two, but I'd risk that.
low compression indeed! maryland don't do a sniffer they just plug a machine into the OBDII port and see if you pass or not, see if i get these headers i'd be afraid it would detect 2 missing cats and that would just F everything up for me. i still plan to delete my 2nd cats, no big deal if i needed to put the stock peices in (if i had everything custom built). i could do a stroker vg33 build but no way in hell do i have money for that, then it wouldn't be a low compression gutless pig :).
 

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It won't detect it. Your o2 sensors are located before and after the primary cats. The ECU would have no idea if you deleted the secondaries and replaced them with duck calls.

I would not run clamps though simply because of the pipe angle right before the secondary cat. There simply isn't enough straight run for a clamp to make a decent seal.

 

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It won't detect it. Your o2 sensors are located before and after the primary cats. The ECU would have no idea if you deleted the secondaries and replaced them with duck calls.

I would not run clamps though simply because of the pipe angle right before the secondary cat. There simply isn't enough straight run for a clamp to make a decent seal.

Are those stainless test pipes in the pic? Curious this would be a good upgrade if I could get someone to do these test pipes.
 

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It won't detect it. Your o2 sensors are located before and after the primary cats. The ECU would have no idea if you deleted the secondaries and replaced them with duck calls.

I would not run clamps though simply because of the pipe angle right before the secondary cat. There simply isn't enough straight run for a clamp to make a decent seal.

ewww look at that stock pipe, new one you made is MUCH better. i need to find some place that can do this job for me for cheap, if you don't mind me asking how much did all that cost you to do? i plan to get my y pipe redone as well, them pipes are too small!
 

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so they still dont fit?
 

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ewww look at that stock pipe, new one you made is MUCH better. i need to find some place that can do this job for me for cheap, if you don't mind me asking how much did all that cost you to do? i plan to get my y pipe redone as well, them pipes are too small!
The only thing it cost me was a bunch of time. I had some extra pipe laying around the garage, a few flanges, and I used my acetylene torch to burn out some old sensor bungs and weld them to the new pipes. That said, materials shouldn't more than about $50 to do this with mild steel from scratch.

Are those stainless test pipes in the pic? Curious this would be a good upgrade if I could get someone to do these test pipes.
I think it is, but I just grabbed what was laying in my scrap bin to make this work. It is a good upgrade, but I still need to finish out the rest of the exhaust as the stock single exit exhaust is too small. I'll get to it eventually.
 

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ah ok thanks, don't have experience with a welder...don't even have a welder lol. so i guess some speed shop will have to do this for me, probably cost me an arm and a leg though :(.
 

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Dunno. Not a lot, but butt dyno says a little bit. It doesn't fall on its face as hard when I try to pass someone when I going 65 now.
Well you 2004 engine is rated at 180HP. What did your butt dyno say?
 
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