Dave B

These new 3.5 VQs are some real torque monsters and I can only assume a Y-pipe could reap some good gains for these cars. Unfortunately, after looking at the exhaust manifolds, it appears that there is a sensor (possibly O2) that is located directly in the flange where the exhaust manifold meets the Y-pipe. I have a hunch that if the a new Y-pipe was installed without precats, this sensor will possibly "freak out", throw a CEL, and put the motor into a "limp home mode". What I mean by "limp home" is that the ECU may run an overly rich fuel program because it thinks the emissions system (ie precats) have failed. I've never seen these sensors on any of the 3.0 VQs. Has anyone else?


Dave

BriGuyMax

iTrader: (1)

Why would it matter if the precats were removed since they are "downstream" of that sensor?? That sensor shouldn't be affected at all by removal of an emmissions controller. The o2 sensors on the 3.0 VQs are all "up-stream" on the precats too...same situation, it's just that the 2k2 is just a little closer to the engine...probably to get better readings.

UMD_MaxSE

iTrader: (1)

in the 2k and 2k1 cali spec maxima, the front exhaust manifold contains the front pre cat and the rear pre-cat is in the y-pipe. If you install a y-pipe, you keep the front exhaust manifold and bolt the pipe up to the end of that after the pre-cat. The rear cat is removed and the sensor that was for that is placed behind the sensor for the front pre-cat so it doesn't trigger any CEL.

I don't know about the 2k2, but is it different from that setup?

2K2DEMAX

iTrader: (1)

UMD, you got it right. It's the same as the 2K & 2k1 Cali spec so any Y-pipe for the 2k2 will only replace the rear precat. The front one stays in place.

BriGuyMax

iTrader: (1)

ok...sorry I was thinking FED spec.

then there should be no problem with a y-pipe on a 2k2...right?

2K2DEMAX

iTrader: (1)

Correct.

Burton069

iTrader: (2)

On WSP site, they say they are workin for a 2002 pipe

dmbmaxima2k2

iTrader: (1)

good thiung, i was getting worried reading this thread. i need my Y

UMD_MaxSE

iTrader: (1)

if you want to go all out, you can even replace the front manifold that has the pre-cat in it with a fed spec manifold from a 4th gen or 5th gen. All you will have to do is move the O2 sensors that were supposed to go behind the front pre-cat to behind the main cat so they don't trigger a CEL. Now, I don't know if this will work for the 2k2 since the manifold may bolt up differently, but a few have done this on their 2k and 2k1 maxima

gLok

Or you can get an 02 simulator that fools your ECU into thinking a properly functioning 02 sensor is in place.

http://www.mvpmotorsports.com/Templa...CatalogID=2215

GregP

I agree with Dave B's assesments.

The 2K2 exhaust manifold is slightly different from the 99/2k/2k1. First off - ALL 2k2 Maximas seem to follow the "CA-SPEC" type exhaust design now, with no differentiation between Federal and Cali-Spec with regard to the exhaust.

Secondly - the only difference in the 2K2 exhuast since 2K1 seems to be the moving of the rear precat to right beneath the rear manifold (just like the front precat). It is no longer in the "y-pipe" or front exhsut tube assembly. I agree with Dave B that adding a y-pipe to this car might prove to be fruitless as there does not seem to be a way to bypass either precat now without freaking out the ECU.

But... who cares? The car makes monster torque and hp as it is!

sleepermax

iTrader: (5)

As long as you can unbolt both pre-cats from the manifolds (as you can the front pre-cat on 2K1's) then a Y-pipe will be very do-able. You could unbolt the rear pre-cat, and leave the front precat in place, bolt up a y-pipe and put both rear O2 sensors behind the front pre-cat in the y-pipe, exactly like you do on 2K1's. It would just need to have a different flange design to bolt up to the rear manifold. As long as you can unbolt the rear pre-cat from the manifold, this is really the only thing that would have to be changed for 2K2 Y-pipes.

And, better yet, as UMD said, you could swap the front manifold with a FED spec manifold (assuming the manifold bolt pattern was the same as for 2K1's) and get rid of the front pre-cat too. You would just need to relocate the two rear O2 sensors behind the main cat in the B-pipe. I've done this on my 2K1 auto and have been very happy with the results. Just don't forget to get a FED spec heatshield also.

PhatGuy

Rumour has it that Stillen is making headers for the 2K2 Max. That is just a rumour as of now.

2k2se6spd

As I stated in another thread I started, I think the breathing system on the 2K2 3.5VQ is very limited and could really benefit from airflow solutions. I would love to see some headers for the 2K2.

PhatGuy

Get yourself and intake in the meantime. A stillen intake should give you at least 6HP/6tq to the wheels based on the 2K2 6spd dynos done today. That would put you around 263HP at the crank.

PS It sounds a lot better too!

ToYLeT902

iTrader: (12)

not me.

UMD_MaxSE

iTrader: (1)

dmbmaxima2k2

iTrader: (1)

headers will be more of a pain in the *** then they are worth to install. just ask emax

gLok

Did anyone even read my post? All you gotta do is make the y-pipe without the cats and sell the 02 simulator with it. Of course your other 02 sensors would still work just fine so the engine would run the same. If i was making y-pipes for these cars i would sell it as a kit.

Dave B

I guess people are misunderstanding what I'm saying. The sensor in the exhaust manifold above the precats "talks" to the downstream sensors and determines A/F ratios. With a aftermarket Y-pipe, the precats are gone and now exhaust manifold senosr becomes confused because the downstream sensors are getting in correct reading. These late model emissions systems became far more complicated in 1999/2000 in all US-Spec cars to meet the stricter emmissions standards for 2000+.

Haven't we already seen that the 2k1 Maxima doesn't gain much power with the "1/2" Y-pipe (the one that leaves the front precat)? I hope the 3.5 VQ can use the full Y-pipe setup because I wouldn't mind getting a 3.5 SE Altima. But, if it doesn't take to Y-pipes, it's no faster than the earlier modded models Fingers are crossed.


Dave

UMD_MaxSE

iTrader: (1)

dyno results between removing the front pre-cat and bolting up a two-piece y-pipe were not much different than using a cali spec y-pipe on the 5th gen

GregP

As a prior owner of a Y-Pipe for my '99, I can say that I definitely will not be getting one on the 2k2 when mine comes in. Not needed, and I don't need the excess aggravation when it comes to inspection time. The car has ***** on top of ***** as it is. If I do any power mods at all it will be a UDP and that's it.