Manifolds & Sensors

[TVR Thunder]

I have bought off flea bay a set of manifolds and y-piece for my chim 500.
Only to realise that they are from a 4.3 pre-cat Griff!!!

Does anyone know the thread type/size of the O2 sensor's so I can get my local
mahine shop to cut / weld in place a suitable thread etc.

many thanks!

Ian.

[Roberto Rica]

Surely you'll need precats and main cat fitted too - best sell on what you bought in error and get the correct manifolds and Y-piece.

Rob

[The AJP Griff]

Roberto Rica said:

Surely you'll need precats and main cat fitted too - best sell on what you bought in error and get the correct manifolds and Y-piece.

Rob

To make it run correctly you will not need any cats,just the lambda sensors fitted.To pass the mot you will not need pre cats,but you will need either the main cat or a freindly mot tester.Sounds like an ideal time to get a green tune resistor and discover the benefits of running fully de-catted.
Just as an aside,i was once told that the downpipe on a pre-cat will not quite line up with a cat cars exhaust,but can easily be modified,don't know if this is true or not

[Roberto Rica]

As I said you'd be better getting the right parts - they have been coming up on ebay recently - a friend paid 130 pounds for manifolds with lambda sensors and precats and Y-piece complete with main cat.

Why mess around with the wrong parts when the correct ones are so reasonable.

Just my opinion though.

Rob

[victormeldrew]

My decatted car has TVR supplied manidolds and Y piece with no cats, and there are no drillings for the lambdas, which have been ditched. Why would you want a closed loop system to optimise cat efficiency when there is no cat?

[TVR Thunder]

Hmmm,

So I dont really need the Lamda's??? The car has had some minor mods by the previous owner (see my profile fr details). i.e Mark adams & RR setup etc. Will this have an adverse effect without another RR session??

Thanks again,

Ian.

[poorpeet]

If you don't fit lambda sensors wont the ecu see the lack os data from them as a fault & go into limp home mode?

[blitzracing]

Simple switching of the tune resistors will allow you to run a non cat fuel map, that does not use the sensors at all. They refer to the resistors / fuel map used by the wire colour fitted to the resistor. Ie white or green map. If you do change the resistor, the car will no longer be running the Mark Adams set up you have payed for, and to make matters worse it could switch to the standard Range Rover map that runs pretty lean at higher revs. (I dont know how Mark Adams programs his maps- I think theres space for 3 - 5 fuel maps in one chip- but I dont know if the chip contains a non cat map suitible for the TVR, you would need to ask him).

[Ian_Greaney]

Ok,

Looks like I'm gonna need the Lambda's after all, so what size are the threads???

Cheers

Ian.

[that daddy]

12x1.25 thread.
Double check with an old sensor before having inserts welded into your manifolds.

Edited by that daddy on Friday 9th March 14:10

[spend]

Umm ~ where on precat manifolds can you weld a bung?, I thought there were only 4 separate runners to the manifold flange. The bung really shpould be put in the collector AFIK.

I'm of the camp why bastardize precat manifolds when there are more catted manifolds available...

I do have 2 spare sets of fully decatted manifolds + y piece if you are desperate. I think most that have been down the route which I assume you wish to take live with the precats out of their manifolds and have 2 Y pieces (1 with cat removed) and simply change the tune resistor with the Y-piece.

Dave