[Mircea]

Hi,

My car (2008 E92 325i N53 3.0L) is suffering from the dreaded 30E9 NOx Cat ageing code as previously it was driven with busted injectors which I have now fixed.

Instead of getting a NOXEM to fix this code I was thinking of a remap.
I've got quoted just under £400 for a remap + coding out of the NOx sensor + secondary cat delete which all together I've been assured will fix the issue while also giving some extra horsepower.

My questions are:

1. Will the secondary cat delete be an MOT fail?
2. What are the downsides of having them removed? And the upsides?
3. Will it smell much worse at standstill like some people say?
4. Do I have any alternatives of fixing that code other than NOXEM? Why can't the cats connection to the ECU just be 'unplugged'?

[Smokey33]

Secondary cats shouldn't have anything to do with any engine codes. There much further back down the exhaust, the 02 sensors are for the pimary cats surely?

[Mircea]

There are no mentions of the o2 sensors anywhere when I read about this issue.
It says NOx cat ageig, and the NOx sensor is indeed under the car, to the exhaust

[Tr1ppy]

O2 sensor and NOx sensor are separate things. The latter is just downstream of the secondary/NOx cats and hence report NOx status back to the ECU.

I've been considering this myself as I have NOx sensor related error codes. I have a 330i so a remap may not provide much of a benefit but on a 325i its definitely worth it as you'll be getting up to 330i levels of power, if not more.

I imagine it would be a lot louder if you remove the secondary cats but then they could be replaced with some form of silencer I suppose.

Not sure if they will affect MOT. I thought it was just the primary cats that are tested as they do most of the work regarding emissions control.

[Mircea]

Originally Posted by Tr1ppy

O2 sensor and NOx sensor are separate things. The latter is just downstream of the secondary/NOx cats and hence report NOx status back to the ECU.

I've been considering this myself as I have NOx sensor related error codes. I have a 330i so a remap may not provide much of a benefit but on a 325i its definitely worth it as you'll be getting up to 330i levels of power, if not more.

I imagine it would be a lot louder if you remove the secondary cats but then they could be replaced with some form of silencer I suppose.

Not sure if they will affect MOT. I thought it was just the primary cats that are tested as they do most of the work regarding emissions control.

Those guys told me that it shouldn't affect MOT sniffer tests, and I am guessing they wouldn't do it really if the car was bound to fail its MOT after their modifications lol.

I have also heard that removing the 2nd cats and coding out the NOx sensor won't allow the car to run in stratified charge mode because even though there would be no cat error message spawning back, there would be no NOx sensor to tell the ECU that everything's alright either...

I just emailed the bimmerprofs guy about this exact query and I'll let you know what he answers if he does... But then again when I had the leaky injectors and I sent him my diagnostic screenshots, asked him about what I should do to to fix what's wrong with the car he said to buy the NOXEM as there are no sign of leaky injectors in the diagnostics lol... So I think his answer might be a bit biased towards his product, and I don't blame him for that.

[Tr1ppy]

Originally Posted by Mircea

Those guys told me that it shouldn't affect MOT sniffer tests, and I am guessing they wouldn't do it really if the car was bound to fail its MOT after their modifications lol.

I have also heard that removing the 2nd cats and coding out the NOx sensor won't allow the car to run in stratified charge mode because even though there would be no cat error message spawning back, there would be no NOx sensor to tell the ECU that everything's alright either...

I just emailed the bimmerprofs guy about this exact query and I'll let you know what he answers if he does... But then again when I had the leaky injectors and I sent him my diagnostic screenshots, asked him about what I should do to to fix what's wrong with the car he said to buy the NOXEM as there are no sign of leaky injectors in the diagnostics lol... So I think his answer might be a bit biased towards his product, and I don't blame him for that.

That's an interesting point regarding the stratified charge mode operation. I was hoping it would still run after removal as then we would get the double benefit of lean operation and a free flowing exhaust giving better mpg!
I guess we would have to weigh up the pros and cons of each method. The stratified charge mode would most likely give the best mpg I would have thought as the engine is designed for this.

Yeah I can understand the bimmerprofs guy wanting to promote his own product. But then the site does have a lot of good info regarding our engines.

[Mircea]

Originally Posted by Tr1ppy

That's an interesting point regarding the stratified charge mode operation. I was hoping it would still run after removal as then we would get the double benefit of lean operation and a free flowing exhaust giving better mpg!
I guess we would have to weigh up the pros and cons of each method. The stratified charge mode would most likely give the best mpg I would have thought as the engine is designed for this.

Yeah I can understand the bimmerprofs guy wanting to promote his own product. But then the site does have a lot of good info regarding our engines.

Yeah if you go on the bimmerprofs site here you will notice at the Stratified Charge mode point it says Stratified charge: for warmed up engine, if there is no error readings regarding NOx system, in steady load conditions and if NOx sensor is Online so yeah...

In the end, the worst case would come to deciding whether I want the NOXEM to fix the issue or the remap and decat for the extra power, or both forking out a total of £700, or neither and just live with it as I don't see what damage it can cause other than to the MPG lol

[Jet1990]

did you end up getting the car mapped?

[Mircea]

Originally Posted by Jet1990

did you end up getting the car mapped?

Not yet as I've just changed brakes all round.
Will probably have it done somewhere closer to the summer as it's a £500 expense with travels that I can live without for now, but will post before/after dynos and sound videos when I do

[Jet1990]

nice one. I have the 30E9 code too and was thinking of coding out the Nox sensor but was told it couldn't be done?

I have a custom backbox for the car and it already has a lovely sound. I think getting rid of both secondary cats would make it sound mental.

[AUDELA]

Originally Posted by Mircea

Hi,

My car (2008 E92 325i N53 3.0L) is suffering from the dreaded 30E9 NOx Cat ageing code as previously it was driven with busted injectors which I have now fixed.

Instead of getting a NOXEM to fix this code I was thinking of a remap.
I've got quoted just under £400 for a remap + coding out of the NOx sensor + secondary cat delete which all together I've been assured will fix the issue while also giving some extra horsepower.

My questions are:

1. Will the secondary cat delete be an MOT fail?
2. What are the downsides of having them removed? And the upsides?
3. Will it smell much worse at standstill like some people say?
4. Do I have any alternatives of fixing that code other than NOXEM? Why can't the cats connection to the ECU just be 'unplugged'?

Hi - I know this was early last year but I've got the same NOX codes on my '07 E93 325i N53 3.0L.

Spoke to Maptech and they quoted £245 for the Stage 1 remap. £285 for Stage 2 plus another £200 for the NOX / cat delete. Seems reasonable for an extra 60hp.

Would be curious what you ultimately decided on... if anything at all.