Hi all,

Getting prepped for my downpipe install, looking for what type and size of flange gasket those of you running the 200 cell cat downpipes installed to the Manifold flange to Cat downpipe flange?

 

There is no gasket. The cat flange just tightens up over the manifold end.

 

I've had nothing but problems with these things since I put them on in 2016.

Originally they told me I wouldn't have to get a tune. Then I got a tune. There was still a code. Then someone on here told me they built the flange wrong so I wrote Velocity and they had me send them back (On my dime) to get new ends put on. $300 to take them on and off. Drove it around fine for a year. Coded again. Fixed it again. Now they're coding again. I love the sound but the car does not like them.

 

Well that would be why i cant find a part number lol.

Thats not great news Soviet, mine were made in 2019, i hope i dont have those issues, but thanks for the heads up. If the VAP gear gives me trouble, it will simply end up in the bin.

 

What codes do you get?
In some cases, typically P0420, fitting an extender/spacer on the post-cat oxygen sensors can solve it.
( if not forbidden by your country/state regulation of course...)

 

There are four downstream O2 sensors on that particular engine, and putting spacers on them is a terribly bad idea. The downstream sensors are also used for fuel trim adjustment, fool the sensors and you can have a momentary lean condition when getting on/off the throttle, it's not the 80's anymore, it needs to be done properly.

 

well, the sensors/ECM are already fooled by the unorthodox cat I’m afraid...

I’ve seen problems linked to cat modifications/removal solved on other modern engines, well after the 80s, by an extender, but then, indeed I never tested that on an engine with 4 downstream 02 sensors...

this means two on each cat exit... what is the purpose of that?

 

Hey Cambo, was hoping you would drop by, i have not fitted the VAP gear yet, but have nearly accumulated all the parts i feel are minimum necessary requirements in prep for the performace mods.
Was just researching parts on jaguarparts.com and going over the O2 sensors for the 5.0 S/C and can only find 2 upstream C2P16396 Denso part number DOX-0609 or 234-9094 and downstream C2P16397 Denso part number DOX-0402 or 234-4450.
Was thinking of replacing all 4 new sensors while fitting the cats (overkill maybe?)
Are there really 4 Downstream? Looks like i may have missed something somewhere.
Does this mean i have a total of 6 O2 sensors?

I dont really know if its a wise thing to replace all of these at the time of installing cats and tune, owing to fuel trims being re learnt on new sensors, i might be over complicating things and causing myself extra woes by replacing all overloading the ecu with too many changes at once.

I am not sure if the 2019 model cat downpipes are the ones that VAP have revised, i kind of hope so.
Any advice from those who have been there and done these mods is much appreciated, i am trying to get all my ducks in a row to make it as smooth a transfer as possible.

 

Ah I misread the post from SovietKitsch... I thought he fitted cats to a 2016 model.

The early 5.0L cars with Denso engine management have only one downstream O2 sensor per bank (total of four O2 sensors), the later cars with Bosch engine management have two downstream sensors (total of six O2 sensors).

In any case, don't put the O2 sensor extensions on the downstream sensors in a Denso car either, they are also used for fuel trim adjustment in addition to monitoring catalyst efficiency.