Downpipe/Cat options

[CrazySX]

My car is running rich on bank 2 meaning in my mind that there has to be a leak in the dowpipe. I had a quick looks at it on the wknd and the flexibility bits look a but crusty although don't seem to be blowing.

What are my options for the downpipe? Are there any after market ones available at a reasonable price?

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[jvanzyl]

There's a decat on eBay that is coming up for sale.. Think it is around the £50 mark at the moment... item 152096832148 You could use it to rule out some areas? If course you might be tempted to forget about it after you'd installed it though...

[CrazySX]

There's a decat on eBay that is coming up for sale.. Think it is around the £50 mark at the moment... item 152096832148 You could use it to rule out some areas? If course you might be tempted to forget about it after you'd installed it though...

thanks for the link, however that dowpipe looks a bit ropey, looks like it is blowing under the wrap at the flexi joints, so probably won't be much better than mine  s:( s:(

I would preferably want a 2.5" with a sports cat so i can just leave it on and then modify it for use with the turbo.  However.. i may end up making something, as i haven't been able to find anything that is reasonably priced, or even available in the UK for that matter.

I would like something for now, which would allow me to start thinking about mods for turbo too  s;) s;)

[jvanzyl]

No worries man  :-) :-) :-)  would love to be able to "make stuff"!

[CrazySX]

No worries man  :-) :-) :-)  would love to be able to "make stuff"!

Its not that hard John, you just need the will and drive and tools always help!  I have been around cars/mechanics and just tend to pick things up.  I have also accumulated i number of tools over the years.  Welding was my achilles heel, but i am now learning that too.

Oh a lot of time, commitment and understanding wife also required!  s:D s:D

[wotugonado]

You need to look inside the flexis, sounds similar to mine and my flexi Inside had torn open, but looked fine from the outside.

[CrazySX]

You need to look inside the flexis, sounds similar to mine and my flexi Inside had torn open, but looked fine from the outside.

what did you do to fix it?

[wotugonado]

I haven't yet, put my standard cat back on. Will take it to a exhaust fabricator at some point and get new flexis welded in.

[CrazySX]

I haven't yet, put my standard cat back on. Will take it to a exhaust fabricator at some point and get new flexis welded in.

I don't understand, the standard cat has the flexies doesn't it?

[wotugonado]

Sorry, I had them split on my sports cat pipe, so put the standard back on for mot.

[Fin]

There's a good chance I will be getting rid of my straight through pipe in the next week or so. It needs a bit of jiggling to get it to fit a standard back-box, it's an inch or so higher at the back. If I was any good at that sort of thing, I would have 'adjusted' the hanger for a better fit.

[CrazySX]

There's a good chance I will be getting rid of my straight through pipe in the next week or so. It needs a bit of jiggling to get it to fit a standard back-box, it's an inch or so higher at the back. If I was any good at that sort of thing, I would have 'adjusted' the hanger for a better fit.

Let me know when it's up for sale and how much you're after. I could jiggle it I think. Maybe fit a sports cat  s;) s;)

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[ChrisGB]

My car is running rich on bank 2 meaning in my mind that there has to be a leak in the dowpipe. I had a quick looks at it on the wknd and the flexibility bits look a but crusty although don't seem to be blowing.

What are my options for the downpipe? Are there any after market ones available at a reasonable price?

Sent from my SM-G920F using Tapatalk

I cannot see your logic on the diagnosis?

[CrazySX]

My car is running rich on bank 2 meaning in my mind that there has to be a leak in the dowpipe. I had a quick looks at it on the wknd and the flexibility bits look a but crusty although don't seem to be blowing.

What are my options for the downpipe? Are there any after market ones available at a reasonable price?

Sent from my SM-G920F using Tapatalk

I cannot see your logic on the diagnosis?

I know, I need to block the tail pipes with a rag and check properly at the wknd. However wknd gone, I replaced a stud and nut on the 3 amigos and I cranked up some of the bolts on the manifold. So I know there are no leaks at the joints that would cause a rich ltft on bank 2 but.. the flexis are the only suspect thing before the sensor on bank 2 so my logic tells me it's got to be a leak at the flexis.

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[ChrisGB]

My car is running rich on bank 2 meaning in my mind that there has to be a leak in the dowpipe. I had a quick looks at it on the wknd and the flexibility bits look a but crusty although don't seem to be blowing.

What are my options for the downpipe? Are there any after market ones available at a reasonable price?

Sent from my SM-G920F using Tapatalk

I cannot see your logic on the diagnosis?

I know, I need to block the tail pipes with a rag and check properly at the wknd. However wknd gone, I replaced a stud and nut on the 3 amigos and I cranked up some of the bolts on the manifold. So I know there are no leaks at the joints that would cause a rich ltft on bank 2 but.. the flexis are the only suspect thing before the sensor on bank 2 so my logic tells me it's got to be a leak at the flexis.

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There are three oxygen sensors in the exhaust system, two of which monitor the fueling:
Sensor 1 Bank 1
Sensor 1 Bank 2

These are the ones above / before the pre cats, so a leak in the downpipe is very unlikely to have any effect on their readings. The third sensor after the main cat is for catalyst efficiency and a leak would possibly cause a code there, but not a bank 2 rich code.

Can you hear any exhaust blow?

[lamcote]

I agree with Chris about the location of the leak.  

Can I check, is it the Bank 2 O2 sensor reading or the fuel trim you are saying is rich?

If it's the fuel trim it may be an exhaust leak but it would have to be before the O2 sensor to have any effect. If the O2 sensors are before the precats then that would be a leak very near the engine.


If it's the O2 sensor reading :

1, if you are looking for a leak in the exhaust at a point after the Bank 2 Sensor, this can't be affecting the reading from that O2 sensor
2, an air leak in the exhaust before the sensor may cause the O2 sensor to read lean (or erratic) but not just rich. The ECU would respond by making the fuel trims run rich, but that would just bring the mixture back to stoichiometric as far as the O2 sensor is concerned, so an exhaust leak should really only result in either a lean or erratic O2 reading. It would cause rich settings in the fuel trims.

A rich reading on the Bank 2 O2 sensor could be :
1, broken O2 sensor
2, leaky injector on cylinders 3 / 4 (ie bank 2)

A rich reading on Bank 2 fuel trims could be :
1, exhaust leak BEFORE the O2 sensor on cylinders 3/4
2, an inlet leak on cylinders 3/4
3, broken O2 sensor

[CrazySX]

I cannot see your logic on the diagnosis?

I know, I need to block the tail pipes with a rag and check properly at the wknd. However wknd gone, I replaced a stud and nut on the 3 amigos and I cranked up some of the bolts on the manifold. So I know there are no leaks at the joints that would cause a rich ltft on bank 2 but.. the flexis are the only suspect thing before the sensor on bank 2 so my logic tells me it's got to be a leak at the flexis.

Sent from my SM-G920F using Tapatalk

There are three oxygen sensors in the exhaust system, two of which monitor the fueling:
Sensor 1 Bank 1
Sensor 1 Bank 2

These are the ones above / before the pre cats, so a leak in the downpipe is very unlikely to have any effect on their readings. The third sensor after the main cat is for catalyst efficiency and a leak would possibly cause a code there, but not a bank 2 rich code.

Can you hear any exhaust blow?

Hi Chris,

Thanks for clearing this up, firstly i was under the impression that bank 1 was the left sensor and bank 2 the right (facing the engine), however looking at a diagram (exploded view of exhaust manifold side from Toyota) someone posted up last week, i only saw bank 1 on there and not bank 2.  This lead me to believe that bank 2 was in the main cat.  I guess i should have just asked   s:oops: :oops: s:oops:  its just that on V engines i can see how you have bank 1 and 2, but on a 4 pot its a bit confusing as technically its only 1 bank on the exhaust side :p

I was under the car at the weekend and i couldn't hear a blow, but when i touched the flexis they did seem a bit crusty.  I need to investigate further.  Issue is i have a TTE so hearing a little blow among the burble proves difficult.

[CrazySX]

I agree with Chris about the location of the leak.  

Can I check, is it the Bank 2 O2 sensor reading or the fuel trim you are saying is rich?

If it's the fuel trim it may be an exhaust leak but it would have to be before the O2 sensor to have any effect. If the O2 sensors are before the precats then that would be a leak very near the engine.


If it's the O2 sensor reading :

1, if you are looking for a leak in the exhaust at a point after the Bank 2 Sensor, this can't be affecting the reading from that O2 sensor
2, an air leak in the exhaust before the sensor may cause the O2 sensor to read lean (or erratic) but not just rich. The ECU would respond by making the fuel trims run rich, but that would just bring the mixture back to stoichiometric as far as the O2 sensor is concerned, so an exhaust leak should really only result in either a lean or erratic O2 reading. It would cause rich settings in the fuel trims.

A rich reading on the Bank 2 O2 sensor could be :
1, broken O2 sensor
2, leaky injector on cylinders 3 / 4 (ie bank 2)

A rich reading on Bank 2 fuel trims could be :
1, exhaust leak BEFORE the O2 sensor on cylinders 3/4
2, an inlet leak on cylinders 3/4
3, broken O2 sensor

Hi Lamcote, your explanation makes a lot of sense.  It is my LTFT on bank 2 that is reading high.  here are my logged averages on my last run:
 Fuel Trim Bank 1 Long Term(%) -8.381966272        
Fuel Trim Bank 2 Long Term(%)   -14.26277718
Intake Air Temperature(°C)   32.75098672

if the sensor is the one you are saying on the right, then it can't be a leak before it, as i cranked the bolts up and all seemed ok.  This leaves 2 possible causes then, either a leak on the inlet side, or a broken O2 sensor.  Both O2 sensors were only fitted last year so i can kinda rule that out.

So.. inlet leak!!! Argh!! please don't be an inlet leak! I will try the trusty spray of carb cleaner around the back of the engine and see if we get a change in engine note.

However.. to counter this, my Vacuum average is -11.46341358 (PSI), shouldn't this be lower if i had a leak? on idle it sits at  about 12.3psi  which translates to 25.03 Hg.

[lamcote]

Could you swap the two O2 sensors round to see if it changes the result? That would be a free way of testing the sensors. Either way it looks like both banks are rich, bank 2 is just more rich than bank 1 so it it could be something that affects everything, not just bank 2, eg MAF, fuel pressure, charcoal cannister etc

[CrazySX]

Could you swap the two O2 sensors round to see if it changes the result? That would be a free way of testing the sensors. Either way it looks like both banks are rich, bank 2 is just more rich than bank 1 so it it could be something that affects everything, not just bank 2, eg MAF, fuel pressure, charcoal cannister etc

Now that's an idea. Although the cable is a bit shorter on bank 2. I will see if I can make it work on the wknd.

I forgot to mention I have the MAF mod in with 2zz yellow injectors. According to CAP on Spyderchat the LTFT should average around -7 or higher. This is within tolerance.

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[lamcote]

Maybe you don't have too much of a problem then, that makes Bank 1 spot on and Bank 2 running less than 6% too rich, I bet a lot of cars run like that all the time, I don't think that would be even close to triggering a code?

Do you know that the injectors are all working properly ie all delivering the same flow? I did read your comments about the Mod now you mention it, was it you that got the yellow injectors refurbished before fitting?

To state the obvious, it's worth remembering that your car isn't actually running rich, the fuel trim is doing its job and getting the mixture spot on by pulling back the fueling. You would only be running rich if there was no fuel trimming taking place (then the O2 sensor would start complaining, hence the closed loop), so there shouldn't be a problem for the engine running as it is, this kind of variation is exactly why the car has been designed to be capable of applying trims to two separate banks and I am sure 6% variance is well within tolerances, especially on cars as old as ours.

Edit. Just read a great quote on the Internet, "less than 10% of anything ain't worth worrying about"!

[shnazzle]

Just to be clear...
bank 1 sensor 1 = top right
bank 1 sensor 2 = bottom of engine, after main catalytic converter
bank 2 sensor 1 = top left

The official story is that bank 1 sensor 2 sensor does not affect fueling, as it's just there to measure cat efficiency.
Load of crap. It totally affects fueling. Experienced this first hand.

Also, I've pretty much never seen the same fuel trim values in bank 1 and bank 2 (i.e. bank 1 sensor 1 and bank 2 sensor 1). You'd expect them to be the same logically, but combustion is a fickle beast.
If you had an o2 sensor per exhaust port, all 4 would differ.

Your idling vacuum is spot on. Start worrying when the vacuum bobs up and down or has delays when letting go of throttle quickly.

SOunds like all is ok. Enjoy  s:) s:)

[CrazySX]

Maybe you don't have too much of a problem then, that makes Bank 1 spot on and Bank 2 running less than 6% too rich, I bet a lot of cars run like that all the time, I don't think that would be even close to triggering a code?

Do you know that the injectors are all working properly ie all delivering the same flow? I did read your comments about the Mod now you mention it, was it you that got the yellow injectors refurbished before fitting?

To state the obvious, it's worth remembering that your car isn't actually running rich, the fuel trim is doing its job and getting the mixture spot on by pulling back the fueling. You would only be running rich if there was no fuel trimming taking place (then the O2 sensor would start complaining, hence the closed loop), so there shouldn't be a problem for the engine running as it is, this kind of variation is exactly why the car has been designed to be capable of applying trims to two separate banks and I am sure 6% variance is well within tolerances, especially on cars as old as ours.

Edit. Just read a great quote on the Internet, "less than 10% of anything ain't worth worrying about"!

No its not triggering any codes, i just started monitoring things after the MAF mod as per CAP's advice.  In hindsight, if i did this exercise before the MAF mod then i would be in a better place now.  Although i think the car ran rich before the mod anyway, as on start up u can smell fuel, the exhausts are black as! and MPG was always around 240 to a tank, i got 270 once (mainly motorway).

The injectors are defo good, i sent them off to SIMTEK and had then tested and cleaned, also fitted all new O rings.

Yes as i understand it, the car thinks its running lean so compensates by chucking in more fuel to achieve stoichiometry.  However the tolerance is supposed to be with the 10% mine is at 12-14 on bank 2.  Plus i have noticed that when i use ultimate 99ron the car pops and smells more on start up than on standard 95ron.

[CrazySX]

delete

[CrazySX]

Just to be clear...
bank 1 sensor 1 = top right
bank 1 sensor 2 = bottom of engine, after main catalytic converter
bank 2 sensor 1 = top left

The official story is that bank 1 sensor 2 sensor does not affect fueling, as it's just there to measure cat efficiency.
Load of crap. It totally affects fueling. Experienced this first hand.

Also, I've pretty much never seen the same fuel trim values in bank 1 and bank 2 (i.e. bank 1 sensor 1 and bank 2 sensor 1). You'd expect them to be the same logically, but combustion is a fickle beast.
If you had an o2 sensor per exhaust port, all 4 would differ.

Your idling vacuum is spot on. Start worrying when the vacuum bobs up and down or has delays when letting go of throttle quickly.

SOunds like all is ok. Enjoy  s:) s:)

thanks for the re-assurance Pat, but i still think the car could run a bit leaner.  John had major issues when he MAF modded his car, he had starting issues. He put his back to stock and shared his LTFTs and they near enough the same.
Fuel Trim Bank 1 Long Term(%)   1.028437954   Fuel Trim Bank 2 Long Term(%)   -0.318245041   Intake Air Temperature(°C)   18.48063892