has anyone got a "spare" set of exhaust manifolds that I could use to create a header jig ?

Not being a high speed metal fabricator - removing mine is NOT a workable solution - but once I have a jig........

Any other suggestions ( be nice ) are welcome.

I am most after a boost in bottom end torque, which of course means long runners if possible. None of the existing commercial headers that keep the CATS are long - probably as room is tight.

 

Sorry Red, Ive got nuthin!

As always

H

 

Nuthin here also!

Would a Nissan dealer help out there, loan you the parts or pay for them and return for credit, just a though.

David

 

Tried that - it only works for parts in stock and exhaust manifolds are not stock items - therefore NO refund. Still trying......

 

Lambros from Hi Tech already has them done. Try calling him...

 

Yes, i know there are commercial systems around - but I want to have a bit of a "play" with some different designs/lengths to see whats possible in boosting the bottom end. The commercial systems runners are far too short for serious low RPM gains.

But thanks for the info - if all else fails........

 

They'd have to be short to fit the cats. The cats can't really be relocated either due to the Y pipe and if you're thinking of removing them consider the size of the fine carefully.

 

Yes thats seems to be the problem, I am not going to remove the CATS ( i can't figure out how those that do don't get an OBDII emission systems fault ) but its not out of the question to move them back and replace the standard "Y" piece with something that flows better. would be keen to keep some flexibility however as a previous turbo vehicle was forever breaking the exhaust at the first muffler.

Perhaps I just need a spare Z to get this all under way ( and about six other Z related schemes ( oil cooler/remote filter ) etc. )

 

Are you thinking of replacing the 4 cats with 2? I had a look at some compact hi flow cats a few months back but couldn't justify the cost for such a small gain.

 

Must look a bit harder but I would swear minehas only two CATS, only plan to move them if

1/ I get really motivated !
2/ To fit longer header primaries

Really just testing the water right now..........

 

I haven't looked myself but my understanding is there's a cat before and after the 02 sensor on each side.

 

Theres two lambda sensors per CAT - a pre and post cat sensor, perhaps thats whats confusing things. The use of two lambda sensors is to monitor CAT performance and CAT oxygen storage capacity for emission control. ( Thats why I cannot understand why the CAT bypass pipes don't produce an ECU fault light !) the Lambda test system is very complex so there's no easy "just disconnect it" fix. Will connect to the OBD2 diag. port and see what the ECU really thinks...

All this electronics is making it hard, can't even play with the exhaust system without worrying about the #$%^# ECU.

 

That's probably it.

I'll be interested to see what you come up with.

 

Sounds like the Cats aren't working hard if the sensors don't go off with test pipes.

Either that or they aren't being polled by the ECM! huh?

 

it could be that the Lambdas sensor bring up an OBD2 error that's only availalbe from the diagnostic connector. Perhaps its not considered a critical ( warning lamp ) failure ? Also the CAT/LAMBDA sensor monitor program only executes after a particular series of driving events - so perhaps that hasn't happened for the CAT bypass boys yet.When I ran that idea around some of the emission engineers - they didn't think it likely, but ?

Thats why your vehicle very inferquently "cuts out" for a few hundred milliseconds - its actually the OBD system introducing a mixture fault and checking for resultant CAT/Lambda emission system response.

 

Thought I'd post an update of sorts. I've been looking at the hi flow cats they're selling in the US a lot this past week and via that I've been able to confirm there are 4 cats, it's just that they're packaged so there appears to be just 2 long ones but if you remove the outer shield there are 4 seperate ones in there.

 

Thanks Apsilon - the mystery is no more.....

Am saving the exhaust issue up for the christmas break, assuming the oil cooler doesn't turn into a MAJOR issue ( everything under the bonnet on a Z is a major issue !).

Looked at the OBDII diag output on the weekend and the CAT tests don't run very often around town ( they have to have met a predifined set of drive cycle parameters - so I couldn't easily fake a no CAT situation. I am still no wiser as to how the no CAT systems don't generate MIL warnings......

Perhaps when the dyno is free I can squueze in some tests. ( need to smile at the right people ).