So here's my situation:

I have had the OBX headers on for some time now and I am convinced that the old design(which is what I have) is robbing me of some power. Rather than getting rid of them, I want to remove the y-pipe and convert my exhaust to a true dual exhaust system with an x pipe right at the point where the the y-pipe is at.
I really would like to avoid using the same design as the original exhaust.... these are my plans:


I know, I know, I will be getting a lot of criticism for running the exhausts to the side, but I think it might give me a better air flow eliminating that huge almost 90 degree turn Maximas have towards the back.

I plan on using a 1 7/8 piping, but I'm not sure if thats too big, too small!?

I'm thinking that a 2 inch would be too big for individual exhaust...

What does everybody think!?

 

http://forums.maxima.org/showthread....hlight=meximax

Theres an idea of what a true dual exhaust setup requires

 

It is useless to put the rear O2 sensor in the X pipe, especially without a cat.

Meximax did it, but he did it all the way back instead of before the rear wheels.

How big are the primaries (pipes that come off the header)?

 

I believe it is 2 1/16.
I'm going to be using an O2 simulator to trick the back O2 sensor.
The O2 sensor would be for a WB O2 system.

Would you guys recommend me just staying with a single exhaust system and having a y-pipe fabricated?? And if so, would a 3 inch exhaust be too much for the car!? I know a 2.25 was okay for the 3.0 but I now have the 3.5 and it feels like theres a struggle in the exhaust, especially when its cold. After a couple of minutes, I guess when the exhaust really heats up, the car feels smoother in air flow.... I dont know how to explain it really.
I just think it would be more expensive to have a y-pipe made than to convert it to a dual exhaust system.

 

There shouldn't be a struggle @ 2.5" NA. I have a Cattman B pipe(2.5") that goes into the stock muffler(<2.5"), and I'm breathing just fine.

Get a good set of headers instead of having the y-pipe made to accommodate the true duals/old OBX design.

That's what I would do.

 

I think that the header design on the OBX are good. (i think) I dont see a problem with them... thats why I wouldnt want to invest another 500.00+ for a set of headers when I can have my exhaust re-done for 150.00.

A local shop was actually commenting that I should go with a 3 inch catback exhaust rather than a dual exhaust set-up. I think it might be a good idea since it might give it a good air flow... but is it too big of a diameter??

 

3" is overkill for NA. You'll loose alot of exhaust velocity, which will in turn decrease scaveging effect- not good for NA.

Check your PMs

 

Do it that would be sweet. is your exhaust going out the rear or out the sides before your rear tire.

 

Dyno first, then do it, then dyno again... Let us know if it's worth it. Be the first penguin pushed off the cliff.

 

Thast a great idea!! LOL.. why didnt I think of that! They have a local shop that hosts a day for dyno specials! I might have to do that. Either way, i'm just doing research right now.. no funds, just ideas...

 

True dual 1 7/8" will be very loud without serious muffling; I speak from experience. I agree that the the rear O2 is pointless. No need for a sim either if you get a 95 ECU.

 

Explain further. . . .

 

95 ECUs, although being OBD2, seem to be quite negligent about the rear o2 sensor being gone, where as 96+ will almost certainly set off the CEL. Either way for trimming the a/f maps, the ECU uses the upstream o2 sensors. The rear- from what I recall from the FSM (im at work so I cant verify), is only used for diagnostics and incase the upstreams dont work.

I've had my rear (downstream) o2 sensor removed for a while now. I cut the harness and zip tied it to the bottom of the car, as it would NOT turn off from the cat when I put on the test pipe. That was 6-7 months ago and still no code for that o2 sensor

 

No one believes me that I drove around for years w/ a test pipe and no CEL. I was not aware of it being negligent. Now i know why I got away w/it. Thanks,

 

same here my rear O2 is zip tied to my EVAP line, not one cel from it

 

My cat's gutted, and at one point i had left the O2 out of the cat, never a CEL. What else is the '95 so lenient about?

 

EGR and EVAP. 95 ECU could care less about it. MAYBE IACV

 

it doesnt know about the stupid boost sensor later maximas have also but i know for a fact IACV it "cares" about

 

- It defiantly notices IACV being missing
- EGR... I get the code. I know others with 95s dont ever get them. Either way this is easily fixed with a resistor
- EVAP... mine is just electronically hooked up to the harness, and its just zip tied in my engine bay. No vaccum lines are hooked up to it at the moment. That was enough to take care of that CEL code

Thats all I can think of that may differ from later ECUs

 

I have gotten an EGR code before, the insufficient/excessive flow code. I have all of my EGR in place except the guide tube, though, everything is just blocked off. The temp sensor is dangling in the engine bay and I've never gotten a code for that

 

so 3" single exhaust is no bueno? vQr'inWla has one on his i30 and he tells me it feels more torquier and feels good gains on it...i drove in it too, so yeah...i noticed difference...

 

This thread is dated. And it has been seen in the Z33 world as well as our world, even A34 modders say towards single 3" for best performance.

 

True, I remember the days when people said 2.5 would be too big