[mirlock]

Hi all

On a 156 v6 cf3 with 4 o2 sensors which one would be best to take a reading from for my nitrous system Front or rear, Note that im using a cf2 exhaust system so the rear 2 are reading from the same pipe.
So im guessing i should use one of the rear sensors.

The purpose for the reading is the nitrous Ecu can alter the mixture when executed or auto shut down if critically bad fuel ratio

Thanks in advance

 

[115686]

The manifold sensors are reading what the engine is actually burning. The post cat sensors are reading what the total burn is (engine + catalyst).

Say you go catastrophically rich - a coil pack fails, so you are chucking unburnt fuel into the exhaust. The manifold cat will say "rich" - I've got more O2 than expected in the gas stream. The post cat sensor will be reading what it always reads - but the cats will be getting very hot as the fuel is burning in there rather than the engine.

Simplest way of saying it is the post cat sensor tells you what the overall mixture is doing. You've chucked x Kg of air in and y kg of petrol and that is the right ratio. Tells you nothing about where it is being burnt, or whether cylinders are misfiring etc. It will tell you if an injector has failed.

Pre cat sensor tells you exactly what is happening in the engine, tells you nothing about the cats.

 

[Gertie]

So to get the engine running correctly - you have to use the pre-cat signal

 

[mirlock]

Thanks guys for the reply.

I was a bit confused as i have no Cats before any of the sensors.

But its all good thank you i shall use one of the pre sensors

 

[115686]

No cats anywhere? Cat after the last sensor would mean that the secondary sensor would be screaming "rich".

 

[scottyf]

Yeah but who gives a monkey about that one.DDoesn't change the fuel mixture anyway...

 

[115686]

Wouldn't the ECU get annoyed? If that goes out of whack, it lights the MCSF surely?

 

[scottyf]

It does. But doesn't mean it doesn't run.

 

[mirlock]

Im just going to get the dummy Cats for them sensors, but not high on list at the moment:biglaugh:

Edit..

You planted the seed now i had to go buy some. these are not the best ones but i cant remember the shop name where i saw the real good ones for alfas.

one of you guy can tell me how to spell it i got my eibach coilovers from them Alfetti or something in italy my mind gone blank

but for now ill try these see if they work as the good ones cost near £30 each but they have little cats inside them.

http://www.ebay.co.uk/itm/182062214111?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

 

[Gertie]

Wouldn't the ECU get annoyed? If that goes out of whack, it lights the MCSF surely?

NO Ecu does NOT get annoyed. Most V6s here in SA have been de catted without problems just put the lambda back +/- where it used to be... All good.

I have heard of errors where they put cat foolers in. Leave that too... install straight to the pipe (welded bung)

 

[mirlock]

NO Ecu does NOT get annoyed. Most V6s here in SA have been de catted without problems just put the lambda back +/- where it used to be... All good.

I have heard of errors where they put cat foolers in. Leave that too... install straight to the pipe (welded bung)

Gertie your a good man , always there with the right answers :thumbup:

There is a question i need to ask you Gertie but i can not remember what it was :biglaugh:

 

[mirlock]

I found the mini cats for sensors to fit into . not too cheap though , i will only get these if i do get errors as last resort

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