MOT Emissions Test: Which Exhaust Pipe Is Best?
#1
02-28-2016, 05:52 PM
MOT Emissions Test: Which Exhaust Pipe Is Best?
Although I've never had a problem with an Emissions Test on my XJS, I've always started to wonder, if one of the Exhaust outlets, would give a lower reading than the other one.
As they only ever take the reading (on my car) from the Left hand side Exhaust Pipe, if you were standing facing the Boot/Trunk.
In the event that the Pipe on the Left produced a too high reading, would you have any grounds for requesting that both Exhaust Pipes should be Tested to give an average reading.
As they only ever take the reading (on my car) from the Left hand side Exhaust Pipe, if you were standing facing the Boot/Trunk.
In the event that the Pipe on the Left produced a too high reading, would you have any grounds for requesting that both Exhaust Pipes should be Tested to give an average reading.
#2
02-28-2016, 06:03 PM
Veteran Member
If your exhaust is stock, then each side represents only bank A or B. If there was a significant variation from one to the other, I doubt the average would equate to a "pass". Unless the MOT center was feeling generous.
It's an interesting question, because every time I get mine smog tested, it comes in so far under the limit that I have often wondered if the limits are meant for all 12 cylinders, but that they are only testing 6.
It's an interesting question, because every time I get mine smog tested, it comes in so far under the limit that I have often wondered if the limits are meant for all 12 cylinders, but that they are only testing 6.
The following users liked this post:
orangeblossom (02-28-2016)
#3
02-28-2016, 06:58 PM
If your exhaust is stock, then each side represents only bank A or B. If there was a significant variation from one to the other, I doubt the average would equate to a "pass". Unless the MOT center was feeling generous.
It's an interesting question, because every time I get mine smog tested, it comes in so far under the limit that I have often wondered if the limits are meant for all 12 cylinders, but that they are only testing 6.
It's an interesting question, because every time I get mine smog tested, it comes in so far under the limit that I have often wondered if the limits are meant for all 12 cylinders, but that they are only testing 6.
Now that's an 'Epic' answer, if ever there was one! and I wouldn't mind betting that not too many people have ever thought about it quite like that.
As it would seem you are right!
Each exhaust, just represents a 6 cylinder engine, if your Car is fitted with 'Marelli' ignition or a 12 cylinder engine, if you have Lucas.
That could produce a 'Hornets' nest, if they ever legislated against 12 cylinder cars.
#4
02-29-2016, 01:37 AM
Veteran Member
[QUOTE=orangeblossom;1412560
In the event that the Pipe on the Left produced a too high reading, would you have any grounds for requesting that both Exhaust Pipes should be Tested to give an average reading.[/QUOTE]
OB
The factory spec emissions are miles below the UK fail level. If the thing fails, then the engine is seriously over-fuelling/not igniting the mixture correctly. SO if it does fail, it needs fixing!
Greg
In the event that the Pipe on the Left produced a too high reading, would you have any grounds for requesting that both Exhaust Pipes should be Tested to give an average reading.[/QUOTE]
OB
The factory spec emissions are miles below the UK fail level. If the thing fails, then the engine is seriously over-fuelling/not igniting the mixture correctly. SO if it does fail, it needs fixing!
Greg
The following users liked this post:
orangeblossom (02-29-2016)
#6
03-02-2016, 06:15 PM
Veteran Member
I just wanted to mention that, whenever I have some reason to suspect that the engine is not running right and I'm not sure where to start checking, I have something that's proven to be worth gold many times over and right in front of me, either with the car in the garage, or at WOT, or at 90 mph: it is my wide band air/fuel ratio gauge. It is a totally independent and highly accurate system with its own wide band oxygen sensor and digital indicator that I have located on my A-pillar.
It will always tell you what's going on with your fuel burn, whether you're running rich or lean in normal driving, or during acceleration, or even idling. Of course, most of the time you don't care that is there, but when something doesn't feel right, or sound right, there's nothing better than having it there, no different from your typical insurance. Believe it or not, it spends most of its time displaying an oscillation between 14.3:1 and 15.1:1, meaning right around the well known and ideal stoichiometric 14.7:1 reading. Then, the A/F ratio will drop to rich readings when you floor it, but you'll know if it's too rich or not rich enough. You'll get used to "what's normal" in your car, be it a 6 or a 12. The only thing is that for a V12 install it will be necessary to have a second O2 sensor for the opposite side with a switch next to the gauge to select either bank, as necessary. That should be a cinch. -- Actually, the V12 install sounds interesting because you''ll be able to compare banks that obviously should not read any different A/F ratios. Mine's a six, so I don't get to compare banks as in a V8 or a V12.
The install, which includes the welding of one (or two) Bosch O2 sensor bung(s) on the down pipe(s), is relatively straight forward. I don't know what these gauges run nowadays, but it shouldn't be more than the $270 that I paid over ten years ago.
Again, I just wanted to share this as I read of possible concerns about over fueling and how a wide band A/F ratio meter is so convenient to have because it's like a whole combustion test station right in your cockpit to use dynamically, on the go.
Cheers,
The following 2 users liked this post by Forcedair1:
Greg in France (03-03-2016),
Gunner01 (03-03-2016)
#7
03-03-2016, 03:15 PM
Senior Member
Not sure whether anybody in this thread would really give a rat's a.. about this comment (because mine's a six, not a 12), but for whatever is worth...
I just wanted to mention that, whenever I have some reason to suspect that the engine is not running right and I'm not sure where to start checking, I have something that's proven to be worth gold many times over and right in front of me, either with the car in the garage, or at WOT, or at 90 mph: it is my wide band air/fuel ratio gauge. It is a totally independent and highly accurate system with its own wide band oxygen sensor and digital indicator that I have located on my A-pillar.
It will always tell you what's going on with your fuel burn, whether you're running rich or lean in normal driving, or during acceleration, or even idling. Of course, most of the time you don't care that is there, but when something doesn't feel right, or sound right, there's nothing better than having it there, no different from your typical insurance. Believe it or not, it spends most of its time displaying an oscillation between 14.3:1 and 15.1:1, meaning right around the well known and ideal stoichiometric 14.7:1 reading. Then, the A/F ratio will drop to rich readings when you floor it, but you'll know if it's too rich or not rich enough. You'll get used to "what's normal" in your car, be it a 6 or a 12. The only thing is that for a V12 install it will be necessary to have a second O2 sensor for the opposite side with a switch next to the gauge to select either bank, as necessary. That should be a cinch. -- Actually, the V12 install sounds interesting because you''ll be able to compare banks that obviously should not read any different A/F ratios. Mine's a six, so I don't get to compare banks as in a V8 or a V12.
The install, which includes the welding of one (or two) Bosch O2 sensor bung(s) on the down pipe(s), is relatively straight forward. I don't know what these gauges run nowadays, but it shouldn't be more than the $270 that I paid over ten years ago.
Again, I just wanted to share this as I read of possible concerns about over fueling and how a wide band A/F ratio meter is so convenient to have because it's like a whole combustion test station right in your cockpit to use dynamically, on the go.
Cheers,
I just wanted to mention that, whenever I have some reason to suspect that the engine is not running right and I'm not sure where to start checking, I have something that's proven to be worth gold many times over and right in front of me, either with the car in the garage, or at WOT, or at 90 mph: it is my wide band air/fuel ratio gauge. It is a totally independent and highly accurate system with its own wide band oxygen sensor and digital indicator that I have located on my A-pillar.
It will always tell you what's going on with your fuel burn, whether you're running rich or lean in normal driving, or during acceleration, or even idling. Of course, most of the time you don't care that is there, but when something doesn't feel right, or sound right, there's nothing better than having it there, no different from your typical insurance. Believe it or not, it spends most of its time displaying an oscillation between 14.3:1 and 15.1:1, meaning right around the well known and ideal stoichiometric 14.7:1 reading. Then, the A/F ratio will drop to rich readings when you floor it, but you'll know if it's too rich or not rich enough. You'll get used to "what's normal" in your car, be it a 6 or a 12. The only thing is that for a V12 install it will be necessary to have a second O2 sensor for the opposite side with a switch next to the gauge to select either bank, as necessary. That should be a cinch. -- Actually, the V12 install sounds interesting because you''ll be able to compare banks that obviously should not read any different A/F ratios. Mine's a six, so I don't get to compare banks as in a V8 or a V12.
The install, which includes the welding of one (or two) Bosch O2 sensor bung(s) on the down pipe(s), is relatively straight forward. I don't know what these gauges run nowadays, but it shouldn't be more than the $270 that I paid over ten years ago.
Again, I just wanted to share this as I read of possible concerns about over fueling and how a wide band A/F ratio meter is so convenient to have because it's like a whole combustion test station right in your cockpit to use dynamically, on the go.
Cheers,
Thread
Thread Starter
Forum
Replies
Last Post
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)