Where's your cat?

So I was talking to an exhaust shop today and he was telling me you can only really replace from about halfway down the original exhaust because the cat is under there and there are sensors everywhere, I couldn't picture what he was on about so he showed me another one they had done, sure enough there was a dirty great big cat sitting approximately under the front passengers seat. MIne doesnt have that so I am assuming it is in the dump pipe? Even when we looked under the bonnet though we couldnt see any wires or sensors going in there? Mines an 08 and I have sinse seen another with the cat under the car and both were 07's (all dual cab's)

Did nissan discontinue with that set=up or is it just a case of being built in a different place/made slightly different? Mines a South African one.


Any help would be appreciated,
Cheers
Matt

hes proberly shown you a petrol model.
the diesel cat don't have any sensors.
the only one with sensors would be the later auto models with DPF and i think its all built into the cat which is bolted to the back of the turbo.

Matt76 said:

So I was talking to an exhaust shop today and he was telling me you can only really replace from about halfway down the original exhaust because the cat is under there and there are sensors everywhere.

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Thats correct, I had a S/S 3" system just fitted and you can now only do that from the rear flange of the DPF.

i have a petrol 4.0L and looks like i have 4 cats, two off each manifold a bit of pipe past the box another two cats into a y piece then to the rear through what seems to be a 44 gallon drum or similar and a resonator, WTF is with that?
cant wait to rip that off and fit a 3" S/S system

Bosshog said:

Thats correct, I had a S/S 3" system just fitted and you can now only do that from the rear flange of the DPF.

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Is yours an auto mate?

Matt76 said:

Is yours an auto mate?

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Yup Matt it is

If your's is a 08 2.5 diesel auto you have much more than a cat....you have a dirty great Diesel Particulate Filter (DPF) which is in essence a catalytic converter. This thing has pressure sensors fore and aft and when the pressure differential exceeds a certain figure (don't know what that is) the ECU gets the message to increase fuel and the temp in the DPF skyrockets to burn off all the captured particulates. You can read more about the DPF at this site: Diesel particulate filter - Wikipedia, the free encyclopedia

i thought the DPF was built in wit the cat and it was just behind the turbo rather than underneath the vechile ???

i'll bet those "pressure sensors" are actually temp sensors. it makes sure it hot enough to regen and checks the drop across it to tell that its working.

if it was mine i would be reducing the amount of egr which will reduce the amount of soot made therefore there won't be much to clean out and less issues of it blocking up.

tweak'e said:

i thought the DPF was built in wit the cat and it was just behind the turbo rather than underneath the vechile ???

i'll bet those "pressure sensors" are actually temp sensors. it makes sure it hot enough to regen and checks the drop across it to tell that its working.

if it was mine i would be reducing the amount of egr which will reduce the amount of soot made therefore there won't be much to clean out and less issues of it blocking up.

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Yes the DPF is just aft of the turbo...and there are temp sensors but I have been told that sensors are then to detect when the DPF is starting to choke up and these read the pressure difference accross the DPF to kick the regen off. Never pulled one apart and would prefer to toss the bloody thing really so can't say for certain.

Pete22 said:

Yes the DPF is just aft of the turbo...and there are temp sensors but I have been told that sensors are then to detect when the DPF is starting to choke up and these read the pressure difference accross the DPF to kick the regen off. Never pulled one apart and would prefer to toss the bloody thing really so can't say for certain.

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it detects the heat change when it starts to block up.

if someone worked out what signals the ecu is expecting you could actually fool the ecu (make it think its working perfectly all the time) and have the DPF removed.

YouTube - dodge ram 6.7 cummins dpf delete in stacks

The yanks have kits for all the pick ups to remove the DPF, there are ways around it.

Dave.

looks like they retune the ECU. get the ecu to turn off the egr and ingnore the exhaust sensors.

In the d40 it goes from the back of the turbo, Cat then DPF. The dpf does have sensors before and after and the obviously sense when the dpf is blocked.

The autos that I know of that have removed the dpf have had conflicting results as it looks like the computer still tries to do a burn off anyway. Obviously this is not good for fuel economy.

I am unaware of anyone yet able to fool the computer in these.

I know with the new unichip you can do it in petrols but nothing like this available as far as I know with diesels.