Decat pipe and emmisions?

[markiii]

Having had teh main cat replaced with a downpipe while having my H&S exhaust fitted I was expecting the car to fail it's emissions test.

Surprising then after resetting teh 3rd CEL in a row due to havig no CAT after another 1000 miles or more it still hasn't returned.

Curious I decsended on teh MOT station and for £10 had an emmisions test.

Results Below.

Fast Idle
CO max allowed 0.3 Result 0.26%0.05%
HC max allowed 200ppm Result 2ppm5ppm
Lambda  allowed 0.9-1.03 Result 1.031.01

Natural idle
CO max allowed 0.5% Result 0.11%0%

All it passed. Surprised? I am.

I'm tempted to have an accident with my precats soon, so will be off to see what results come from having no cats at all, and no precats but with the main cat back on.

Results added in Red tio cover all cats in place boith pre and main.
Cushty  :-) :-) :-)

[Anonymous]

Close on the Lambda?

I've been thinking the same as you... accident with the pre-cats (if they don't destroy themselves first)... leaving everything else as is.

[Tem]

FWIW, at least one local 1ZZ-FE (in Corolla) passes our emission test without any cats.

Our max limits are:
BELOW 1000rpm: CO: 0,5; HC: 100; O2: 5
ABOVE 2000rpm: CO: 0,3; HC: 100; O2: 5
Lambda 1,03

[markiii]

anyone now exactly what the lambda test is?

[Anonymous]

Mark, do you remember the cost of the cat replacement pipe? Would they make up another if i needed one?

[markiii]

Mine was a cheat, I managed to get hold of a spare cat pipe, and had the cat cut out and a piece of stainless welded in.

All in costs wouldn't take 2 people to the pictures  :-) :-) :-)

I did ask about making up from scrathc.

based upon a full stainless replacement pipe with a relocated single flex joint. They were estimating £150 ish

In your case though with teh PE there is a silly little pipe linking teh turbo outlet to the cat pipe. If your going to do it I'd be tempted to follow Martins lead and replace them both with a nice wide single pipe.

[Anonymous]

Yeh i'll have to look into it, i just want to get rid of the cat before i toast it!!

Anyone have a spare cat i could buy for now?  s:wink: :wink: s:wink:

[GSB]

anyone now exactly what the lambda test is?

The lambda test is done by simply running the gas past an O2 sensor the same as in your exhaust manifold. It's a check that indicates weather your engine is running properly in closed loop mode. The numbers given as a pass mark 0.9-1.03 are a band which indicates good combustion. If the engine were to stray outside of this band it would indicate poor combustion (to rich or to lean) and thus an error with the closed loop control (usually a knackered O2 sensor)

[Anonymous]

FWIW with the 2ZZ and no cat at all and with the Power FC I pass emmisions easily.

We have limits of CO 0.5 at idle and 0.3 at 2500rpm.

Both of them passed easily.  s:) s:)

It also helps that I have access to the testing station whenever I want  s;) s;)

[Anonymous]

Following on with this a bit.Knowing an MOT will be needed on mine soon i took it too a friends garage and he hooked it up, results were

fast idle
co 7.85%   s:shock: :shock: s:shock:  
hc 401ppm   s:shock: :shock: s:shock:  
lambda .791   s:shock: :shock: s:shock:  

idle

co 1.82%   s:shock: :shock: s:shock:  

Ah crap, now i'm still running stock injectors and the e-manage is adding no more fuel at these testing points.

Looks like my cat is dead from all the rich fueling i've been running for the last 10months.Can't think what else will be causing such high emission.

Please throw in your thoughts?

[markiii]

possible.

however with the emanage there should be an easy solution.

get your decat pipe.

create a very lean map.

load the map pre-mot, change it back after.

sorted  :-) :-) :-)

[Anonymous]

possible.

however with the emanage there should be an easy solution.

get your decat pipe.

create a very lean map.

load the map pre-mot, change it back after.

sorted  :-) :-) :-)

Yes, the profec can store 3 different sets of maps to send to the e-manage, so i'll program another set just for the MOT, and just swop it to it when i'm there, then swop it back as i leave  s:D s:D  

My concern at the moment is WHY it is running so high when basically on MOT tests it runs as a std car. I can fix the problem but just interested in the reason it's doing it? Hmmmmmm   s:? :? s:?

[markiii]

not quite sure what you mean, "on MOT tests it runs liek a standard car"?

[Anonymous]

I mean on a MOT they basically rev it to 2500rpm, the car isn't running under any load so the emanage isn't altering any settings, the turbo isn't being used so basically it's test shouldn't be any different than a std car.

[markiii]

gotcha

all true, I'm surprised it's that highbut without pre-cats or and if your main cat is dead, that could be why.

[SteveJ]

I mean on a MOT they basically rev it to 2500rpm, the car isn't running under any load so the emanage isn't altering any settings, the turbo isn't being used so basically it's test shouldn't be any different than a std car.

Here's the problem.....

The O2 sensors in the stock car are prior to the pre-cats, so they adjust the mixture to give the optimum output for the cat's to 'eat' with the final result being the required emissions.

Take away the cat's and the ECU keeps trying to create the right 'food' for the cat's, which are no longer there to eat it, so it comes out of the exhaust with too much unburnt fuel - hence the high HC's and CO

[mph]

Here's the problem.....

The O2 sensors in the stock car are prior to the pre-cats, so they adjust the mixture to give the optimum output for the cat's to 'eat' with the final result being the required emissions.

Take away the cat's and the ECU keeps trying to create the right 'food' for the cat's, which are no longer there to eat it, so it comes out of the exhaust with too much unburnt fuel - hence the high HC's and CO

La la la, don't believe you!
The O2s are there to allow the car to run safely at a much leaner (read: less fuel) levels than older vehicles which had to always run richer than was necessary to have a built in safety level against leaning out. Emissions are a bonus, but the saving the manufacturer is really after is l/100 - after all, the majority of the masses are more interested in fuel consumption than emissions. IMO.

[markiii]

your both right to an extent, however, with where th 02 sensors now sit the reading isn't going to be accurate. Whether that affects the longevity of th engine is debateable, but it does mean fuelling will be out.

this could well be the reason.

did you do the 02 sensor mod?

[SteveJ]

Here's the problem.....

The O2 sensors in the stock car are prior to the pre-cats, so they adjust the mixture to give the optimum output for the cat's to 'eat' with the final result being the required emissions.

Take away the cat's and the ECU keeps trying to create the right 'food' for the cat's, which are no longer there to eat it, so it comes out of the exhaust with too much unburnt fuel - hence the high HC's and CO

La la la, don't believe you!
The O2s are there to allow the car to run safely at a much leaner (read: less fuel) levels than older vehicles which had to always run richer than was necessary to have a built in safety level against leaning out. Emissions are a bonus, but the saving the manufacturer is really after is l/100 - after all, the majority of the masses are more interested in fuel consumption than emissions. IMO.

But also consider this.....

If the engine run's too lean, oxygen is still present in the exhaust gas (which is what the O2's are there to detect) Also the cat's will start to produce some really nasty oxides, which would be worse than having no cat's at all. So (and this is all theory as I lack the chemical knowledge to prove it) the engine is run rich to ensure no oxygen in the exhaust gas, and also to ensure there are HC's available for the cat to turn into H2O and CO2. So the ECU adjusts the fuelling to ensure little or no oxygen in the exhaust gas, then adds a little extra fuel for the cat's to munch on.

Just my 2cents - now we need an analytical chemist to help us out - anybody seen one 'in da house?   s8) s8)  '

[Anonymous]

Well it doesn't matter too much who's right here,i can cure the problem for the MOT, i'm just interested to hear theories on the cause of this. Some have gutted their pre-cats and to my knowledge this hasn't caused high emissions, so it seems strange why this has happened.

Yes i've got both O2's linked together to read from the first one.  s:wink: :wink: s:wink:

[SteveJ]

Well it doesn't matter too much who's right here,i can cure the problem for the MOT, i'm just interested to hear theories on the cause of this. Some have gutted their pre-cats and to my knowledge this hasn't caused high emissions, so it seems strange why this has happened.

Yes i've got both O2's linked together to read from the first one.  s:wink: :wink: s:wink:

How are they linked - I assume you are using some form of signal buffer or conditioner. Without it the very high impedance output from the O2 sensor will be affected by having 2 relatively low impedance loads (aka the ECU inputs) attached to it.

[markiii]

Well it doesn't matter too much who's right here,i can cure the problem for the MOT, i'm just interested to hear theories on the cause of this. Some have gutted their pre-cats and to my knowledge this hasn't caused high emissions, so it seems strange why this has happened.

Yes i've got both O2's linked together to read from the first one.  s:wink: :wink: s:wink:

your right but I'm not sure how many are running with no cats at all?

[Anonymous]

Simply, at the ECU the signal from the 2nd O2 into it is cut and the end is spliced into the signal from the 1st. Thus both banks get the same reading from 1 sensor.No conditioner is needed.

[SteveJ]

Simply, at the ECU the signal from the 2nd O2 into it is cut and the end is spliced into the signal from the 1st. Thus both banks get the same reading from 1 sensor.No conditioner is needed.

Nope - that won't give the right reading (it will read low - hence your very high HC's) As I explained, the O2 is a very high impedance output, and will be overloaded (and pulled low) by having 2 ECU inputs connected to it.

Martin has a signal buffer between his O2 and the ECU inputs to alleviate this problem.

[markiii]

so what is he using as a signal buffer?