Well, it isn't really a "Y" anymore, but here it is. What used to connect to the rear manifold is now a pre-cat (see my other post). So the "Y" pipe is really just a straight pipe. O2 sensors are still all in the same positions they were on the 99-2k1 cali-spec cars.

 

... after looking at both diagrams. Once the exhaust is past the manifolds, it is still flowing against itself in the pre-cat versus flowing in the same direction (same issue with the previous models). What I see for the 2K2 model is a smaller "y-pipe" about the length of the pre-cat, with the exhaust flowing in the same direction. It might be cheaper to production because of the size or expensive because of fitment (but there will definitely be some benefits)... My $.02

 

it looks like the install may go easier because you may not need any swivel joints and extensions to get at the bolts now

 

Not sure what you mean when you say the exhaust is "flowing against itself".

It goes straight back from the front manifold to the cat, and the rear manifold exhaust goes through the rear manifold pre-cat and joins the exhaust from the front at the collector in front of the main 3-way catalyst.

 

Well that just sucks. It's true, both front and rear precats are now part of the manifold. It appears the O2 sensor setup is one sensor above the precat where the precat and exhaust manifold are joined with a heated O2 sensor just ahead of the flex section. 3 O2 sensors total. There are no other O2 sensors shown. It looks like headers are the only way, but I have a hard time believing the ECU will operate efficently if the precats are removed seeing that the O2 sensors are now upstream of the precat. This isn't good. A less restrictive lower straight pipe will help, but we all know the true restriction is in the precats.

As it sits, it looks like the best "cost effective" mods for the 2k2 will be an intake, UDP, straight pipe (where the manifolds are joined) and a B-pipe. You could probably pick up about 15fwhp and 15 fwtq with these mods.


Dave

 

I see flow from the front manifold flowing against flow from the rear manifold where "both flows" meet (i.e. in the "pre-cat" before the flex section and the catalytic converter)

 

The precats was part of the restriction but not enough to make the big difference. The big part of the restriction is the 2nd downpipe which goes into the stock ypipe against the flow from the front down pipe. That was the main part of the restriction.

 

Russ,
I could not agree more. That what I meant by flow flowing against itself .

 

Kajeeno.

I understand now. What you DON'T see from that photo is that the exhaust from the rear manifold curves forward then back in a separate pipe from the pipe that carries exhaust from the front. It is not apparent in that diagram, but check out my photos at:

http://www.greghome.com under the "Random Musings" section. I have photos from a real 2k2 car from underneath.

Greg

 

That doesn't make sense. If what you say is true, why does the 2k1+ Y-pipe do very little?


Dave

 

We have torn apart a few stock ypipes, and me, ST, and Carlos91SE were the orginal beta testers of the 1st ypipes or should I say B pipes. That is how Nissan did it for the longest time and still does on the 2k1.

I am not sure where you got that info on the 2k1 ypipe does very little. It does alot, same for the 2000. Now, on a 5th gen, it does less than a 4th gen due to a slight change in the manifold itself. It is slightly better flowing than the 4th gen which gives it a better flowing exhaust to a point. That is why there is a bit of a difference between a 2k having less and a 95-98. 99 has the same ypipe as the 2k does.

 

I think I get it.

The problem with the 4th gen through 2001 ypipes wasn't so much that it had the pre-cats in it, but the convergence of the two downpipes, ie the actual "Y" part. On those cars, the rear downpipe literally angled INTO the front downpipe...the rear pipe didn't flow with the front pipe but rather against it. Seems ludicrous but that must have been the only way Nissan could fit the precat on the rear downpipe and get equal length downpipe sections. It was NASTY and that's why aftermarket ypipes made so much power on 4th gens and 2000-2001s also to a lesser degree.

HOWEVER, looking at this picture of the 2002, it looks like Nissan has finally solved that nasty "Y" section. Although the convergence "Y" pipes themselves are covered by that heat shield, it looks to me like the rear pipe curves towards the front of the car but then turns 180 degrees and convergences with the rear pipe in a far more flow-friendly way...if anybody remembers the first generation Stillen ypipe, that one did the same thing...and Stillen eventually dropped that design because they found there to be no power gains over the non-equal length (current Stillen) ypipe. Now that Nissan has located the pre-cats on the rear downpipe just like the front, which is right after the manifold, they must have found more space to work with and were able to add a good "Y".

Can anybody with a 2002 remove that heat shield under the "Y" section or otherwise verify this? Does the rear downpipe turn toward the front but then turn 180 degrees back towards the rear and converge with the front pipe?

If this is true, then you can forget even bothering with an aftermarket ypipe. If the "Y" is no longer nasty on the stock pipe, which was the main reason for the ypipe upgrade in the first place, expect very little gain with an aftermarket ypipe on 2002s.

http://www.greghome.com/images/Maxim...xSE-YPipe1.jpg