The SES light ownz me.

 

Just relocate the REAR O2-sensors from both banks behind the main cat.

The ECU is looking for a difference and without the precats it's not seeing it. I've been told you can also make a sort of "shield" around/over the O2 sensor tip to change the readings and maybe trick it.

 

So if the pre-cat is a seperate piece from the manifold, why couldn't we just manufacture a a piece of pipe that doesn't have the pre-cats in it?

As for the SES light, welcome to the club. My light shows up with my Y pipe when I drive at a high speed in 6th gear for a long duration at a constant speed. I've narrowed it down to the fact that the car uses the O2 sensors to adjust the air/fuel ratio. With that being said, I'm not sure if relocating the O2 sensors behind the main cat would affect the calculations or not. I'm still working on getting a properly measured Y pipe created exactly to the computer's specs, just larger.

 

Thats exactly what I had to do with the turbo. Now I cant remove the cat to put in a straight pipe otherwise I would not have any cats. Im going to still do this, but I will get O2 simulators for the cat-sensing o2s.

Dixit

 

My main cat is hollow too.

There is a fix for this and I will post it after I can prove it works.

 

Tell me you didn't gut a $700+ cat vs. buying a $35 straight pipe...

Just shield the rear O2-sensors(somehow) and it will work.

I wonder if swapping a different part O2-sensor(350Z, Pathfinder, etc.) might satisfy the ECU...hmmmmmn.

 

Front is that way, rear isn't. The front can be replaced with a FED spec. 95+ manifold and using a Stillen Y-pipe. Look at DesertPearl's Cali-to-Fed spec conversion. However, if you don't want to swap manifolds, the opening is HUGE. You'd have to come up with some type of "cone" shaped reducer, which might hurt flow even more.

Front O2-sensors are used in closed loop A/F adjustments. Rear O2-sensors aren't. They indicate cat failure, which is why you are getting the MIL code.

 

Well they probably cost more than that brand new and I did not gut the one that came with the car. I bought one from Kloogy for $75 and gutted it. Now I have a straight pipe that looks like a OEM cat and the dealer won't know.


Thought about it. But there is a better way.

I don't think so. The voltage standards are supposed to be all the same.

 

If you do a search on o2 spoof you will find stuff. Thhe GTP guys put a resistor in and that seems to work for them.

 

Flow [Q]=VELOCITY X AREA. now we assume the flow rate is constant...that is Qin=Qout. this assumption is based on the fact that we igore minor head losses like....friction, orifice, and weirs and bends and such. (which would be created from the fragments of left over cat).

So that means if you make the area smaller then the velocity must go up proportionally. so that is the basic idea..so NO you would not hurt your flow, you would actually speed it up a little which is good. All of this has it's limite of course so don't get any crazy ideas like a 1 inch pipe with a really high velocity, because then you can't ignore minor losses. Too big of a pipe and your air doesn't flow.

This is my basic Fluid mechanics lesson of the day, i will accept payment via paypal....you are welcome.....

 

How about adding a resistor to the O2s. Or would that just make the SES light go on sooner??

 

That's what I was thinking but could you tap the front o2 sensors with a line, put it in a resister and connect that to the rear sensor connectors. Eliminating the need for the rear sensors all together.

My 2000 engine will have no cats.

 

So the 3.5L and the 3.0 L have the same manifolds? Any one verify that for me? Thanks

 

It's going to cause turbulance and thus decrease flow.

UNLESS you have a properly designed reducer, which you'll never get without modeling.

So, I still say it *MIGHT* hurt flow.

 

No, but they are interchangeable supposedly, ie ehaust ports/bolts line up.

 

Yes, this is a fact.