Secondary cat delete pipe

porsche girl

Junior Member
Messages
35
Hiya.

What's the best option for the secondary cat delete pipe.

Benny is going to do me an Xpipe but I want a larini styley secondary cat delete pipe which has a better attempt at the squish section...

Answers?
 

Aredes

Junior Member
Messages
159
The car has to be remapped if both cats are removed, am I correct? Otherwise there will be a CEL, or am I wrong?
Has anyone ever done that, removing all cats and remapping the car? Does it work well afterwards?
 

porsche girl

Junior Member
Messages
35
I'm just looking at ditching the secondary cats. If you have no cats at all then:

1. you will light the MIL
2. you will have insufficient back pressure for the design of the cylinder head
3. The engine calibration will be messed up and so will need to be reworked.
 

drewf

Member
Messages
7,159
Couple of points - why do you think the OEM 'squish' section is a problem? It actually flows very well indeed - just because it might intuitively look wrong doesn't mean it is wrong.

And back pressure for the design of the cylinder head? Not really - there's a great deal more to the reflected pressure pulses seen at the exhaust ports than just changing static system pressures due to removing the cats. What do you think the back pressure is doing to assist the power production? Pushing fuel/air mixture back into the cylinder during the inlet/outlet valve overlap? Handy on a 2-stroke, but not really going to happen in any useful sense on a highly tuned V8.

Velocity of the exhaust gases being scavenged is what these engines need. You'll notice nobody is putting bigger pipes on - there's a reason for that. Going overbore will reduce the velocity, actually increase the back pressure and reduce power. Plenty loud though :)
 

maverick

Member
Messages
1,982
I don't know if it's all in the mind but the car feels noticeble quicker esp in 1st and 2nd with the 200cell cats
 

drewf

Member
Messages
7,159
Not surprised - you've reduced some static pressure restriction in the system, and the gases are flowing much more readily through the cats Mav. You should have an engine which can spin up faster, so it will feel faster, but I bet there's only a few bhp difference measurable. I'd guess at 3..5.
 

maverick

Member
Messages
1,982
Not surprised - you've reduced some static pressure restriction in the system, and the gases are flowing much more readily through the cats Mav. You should have an engine which can spin up faster, so it will feel faster, but I bet there's only a few bhp difference measurable. I'd guess at 3..5.

Yes you probably right but would be interested to do a dyno test just to see but I suppose unless you do a before and after on the same rig in the same conditions it would be difficult to get a accurate result
 

rockits

Member
Messages
9,167
I got Marios @ Autoshield to make a custom dual round secondary decat section for me. No CEL's, no emissions issues & flew through MOT no problem. With a rear boxes delete as well. Lambda sensors are pre & post primary CATS so no issues all round.
 

boomerang

Member
Messages
412
Supersprint decat was flawless; no cell, no problems fitting, sound got a little extra "Bass", the engine feels a little bit more alive.
SDC11011.jpg

SDC11012.jpg

SDC11015.jpg
 

boomerang

Member
Messages
412
Not in Holland, don't know about emission regulations in the UK, but presume its the same overthere.
Only thing was, that the engine really needed to be hot, to get the right values.
But after a short blast, everything was well within specs, no problems.
 

Gp79

Member
Messages
1,393
Is there still one set of CATS in the manifold? with lambda senders either side?
 

CatmanV2

Member
Messages
48,549
Is there still one set of CATS in the manifold? with lambda senders either side?

'It depends'

US spec manifolds have cats in them. Euro spec ones don't. Which you have appears to depend on how Luigi was feeling....

C
 

CraigWaterman11

Sponsor
Messages
762
I don't know how euro cars are set up with the lamba/O2 sensors. Here we have the wide band sensor and the monitoring sensor. I gutted the primary cats on my previous Spyder, which I knew would set off the CEL. Basically it's the monitoring sensor picking up that basically the cat isn't doing it's job. I had the ecu flashed so it no longer pick up the monitoring sensor. Afterwards I never had a light again about it. The car was quite throaty as well.
 

boomerang

Member
Messages
412
Is there still one set of CATS in the manifold? with lambda senders either side?

Yes, the primairy cats including sensors before/after cat are there.
The system looks different though, compared to the system of Maverics car.

SDC11014.jpg



There seem to be two systems, the later cars have the US exhaust if i am well informed.
 

D Walker

Member
Messages
9,827
Supersprint decat was flawless; no cell, no problems fitting, sound got a little extra "Bass", the engine feels a little bit more alive.
SDC11011.jpg

SDC11012.jpg

SDC11015.jpg
How much do they cost, pm me if you would prefer, just trying to remember if the bottom of my manifolds are 2 or 4 bolt, sure mine are us type!!!!!!
 

D Walker

Member
Messages
9,827
Just found them on a U.S. site, $735, cheaper to go on holiday,bring em back than get Larini's.