Q5 TDI Emissions Fix experiences
02-14-2019, 04:38 AM
#491
Gasoline engines run at a stoichiometric (air to fuel ratio) of about 14.7:1. Changing that ratio within a very narrow band produces a lean or rich air to fuel mixture.
Discussion of rich and lean fuel mixtures is generally irrelevant in diesel engines for our purposes. AFR (air to fuel ratio) varies greatly in a diesel engine with engine load and speed and can range from as low as around 6:1 or 8:1 to as much as 70:1 at idle or coasting down a grade. More fuel equals more heat and more power.
Diesel engines don't have a throttle to control air intake volume as gasoline engines do. Diesel air intake is always wide open. Engine rpm and power output are controlled by the accelerator pedal which controls fueling. Again, more fuel equals more power.
Discussion of rich and lean fuel mixtures is generally irrelevant in diesel engines for our purposes. AFR (air to fuel ratio) varies greatly in a diesel engine with engine load and speed and can range from as low as around 6:1 or 8:1 to as much as 70:1 at idle or coasting down a grade. More fuel equals more heat and more power.
Diesel engines don't have a throttle to control air intake volume as gasoline engines do. Diesel air intake is always wide open. Engine rpm and power output are controlled by the accelerator pedal which controls fueling. Again, more fuel equals more power.
Interesting reading here. https://www.technology.matthey.com/a.../49/3/119-121/
02-14-2019, 05:49 AM
#492
AudiWorld Member
Yes and no. As I understand it, Diesels almost always run leaner than a gasoline’s stoichiometric fuel ratio. Thus their higher efficiency. Diesels produce more soot at richer mixture levels and more NOx at leaner mixture levels. NOX is produced by the higher combustion temperature of a lean mixture. (Smaller flame but hotter) I would also reason that our TDIs with the emmisions fix require more frequent DPF regeneration is because they produce more soot than before in the effort to reduce NOx. I have no documentation of that however.
Interesting reading here. https://www.technology.matthey.com/a.../49/3/119-121/
A very simple google search will explain the concepts better than I can.
My first (of three) Dodge Cummins was a 2001.5 HO six speed, One of the choices on the overhead digital display was instant mpg. Mpg varied continuously as I described above. I've seen it display as much asj (iiirc) 200mpg at 50mph with a tailwind or 4mpg under full load, full throttle acceleration.
Last edited by HBarlow; 02-14-2019 at 05:59 AM.
02-14-2019, 06:11 AM
#493
Harvey, I say things like “ As I understand it” in an effort to not offend and be argumentative. Peace ;-)
05-06-2019, 05:17 AM
#495
This is to follow up with those that have had emissions repairs on their Audi TDI.
It has been a while since last post, and hope that Audi figured out how to address everyone’s concerns.
We have not done ours yet and would appreciate if you can share your experiences.
thank you in advanced.
It has been a while since last post, and hope that Audi figured out how to address everyone’s concerns.
We have not done ours yet and would appreciate if you can share your experiences.
thank you in advanced.
05-06-2019, 06:15 AM
#496
AudiWorld Senior Member
This is to follow up with those that have had emissions repairs on their Audi TDI.
It has been a while since last post, and hope that Audi figured out how to address everyone’s concerns.
We have not done ours yet and would appreciate if you can share your experiences.
thank you in advanced.
It has been a while since last post, and hope that Audi figured out how to address everyone’s concerns.
We have not done ours yet and would appreciate if you can share your experiences.
thank you in advanced.
On the other hand, satisfaction that something works does not drive folks to these forums. Only problems do. Folks don’t repeatedly say, “my car still works great this week,” they say, “my car threw a code this week” or whatever.
Don’t even get me started on the placebo/nocebo effect. People experience what they expect to experience. Countless studies have proven this.
Remember the old John Prine song “Dear Abby?” I sincerely suggest you look up the lyrics, they’re great. Here’s a snippet:
Dear Abby, Dear Abby...
My fountain pen leaks
My wife hollers at me and my kids are all freaks
Every side I get up on is the wrong side of bed
If it weren't so expensive I'd wish I were dead
Signed Unhappy
Unhappy, Unhappy...
You have no complaint
You are what your are and you ain't what you ain't
So listen up Buster, and listen up good
Stop wishing for bad luck and knocking on wood
My fountain pen leaks
My wife hollers at me and my kids are all freaks
Every side I get up on is the wrong side of bed
If it weren't so expensive I'd wish I were dead
Signed Unhappy
Unhappy, Unhappy...
You have no complaint
You are what your are and you ain't what you ain't
So listen up Buster, and listen up good
Stop wishing for bad luck and knocking on wood
05-06-2019, 08:28 AM
#497
AudiWorld Member
The answer to the question of whether to trade driveability issues, degradation of performance and reduction of fuel economy for cash is in the mind of each individual owner not the pages of this forum.
The issue can be displayed on a horizontal line. One end, lets say the left side of the line is those who want or need the money and do not care or may not even notice slight driveability issues or loss of performance and economy. On the other end of the scale is those who value the performance and fuel economy of their car over other considerations and don't need or can do without the cash payout from VWAG. Other possibly relevant factors are time you will keep the car, emissions laws and inspections in your state, or other cnsiderations.
I'm on the extreme right end of the scale. I bought the Audi for the performance and economy of the TDI and will keep it for many more years. I was born a car guy and am tuned into the feel and performance of my car. I'm not a wealthy man but I don't need the money. My state does not inspect emissions equipment. I can ignore the cash payout and enjoy the car as Audi buillt and programmed it.
Where are you on the scale?
The issue can be displayed on a horizontal line. One end, lets say the left side of the line is those who want or need the money and do not care or may not even notice slight driveability issues or loss of performance and economy. On the other end of the scale is those who value the performance and fuel economy of their car over other considerations and don't need or can do without the cash payout from VWAG. Other possibly relevant factors are time you will keep the car, emissions laws and inspections in your state, or other cnsiderations.
I'm on the extreme right end of the scale. I bought the Audi for the performance and economy of the TDI and will keep it for many more years. I was born a car guy and am tuned into the feel and performance of my car. I'm not a wealthy man but I don't need the money. My state does not inspect emissions equipment. I can ignore the cash payout and enjoy the car as Audi buillt and programmed it.
Where are you on the scale?
05-06-2019, 12:29 PM
#498
AudiWorld Member
Thread Starter
2015 TDI original owner and underwent the "fix" early 2018, and generally haven't experience any performance degradation.
But what we have experienced is a couple of check engine lights issues which were resolved, but I continue to have this experience.
At wholly random times, and there isn't a clear scenario to cause this: upon the end of a ride the fan continues to run for an extended amounts of time (3+ minutes, never the same).
Additionally, find with this, but not every time, an odd smell that forces me to open a garage door to air it out.
My SA claims they cannot see a related code, but admits it's odd behavior. Are others seeing this, is it normal, anything to be concerned about?
Along with some issue related to having to replace the sunroof frame and the resulting rattles and hassles - I'm beginning to get at wits end with a truck we initially really loved, sell it and retain whatever equity we have it from DieselGate.
But what we have experienced is a couple of check engine lights issues which were resolved, but I continue to have this experience.
At wholly random times, and there isn't a clear scenario to cause this: upon the end of a ride the fan continues to run for an extended amounts of time (3+ minutes, never the same).
Additionally, find with this, but not every time, an odd smell that forces me to open a garage door to air it out.
My SA claims they cannot see a related code, but admits it's odd behavior. Are others seeing this, is it normal, anything to be concerned about?
Along with some issue related to having to replace the sunroof frame and the resulting rattles and hassles - I'm beginning to get at wits end with a truck we initially really loved, sell it and retain whatever equity we have it from DieselGate.
BTW, does the extended warranty cover check engine light issues? Coming up on 4 years soon . . .
05-06-2019, 12:34 PM
#499
Wife has been getting yellow check engine light as well. First time dealer claimed no codes. Most recent time diagnosis was a fuel pump issue (low level fuel pump or something - i..e, when tank is closer to empty). That was replaced, and the light has come on again. Appointment pending.
BTW, does the extended warranty cover check engine light issues? Coming up on 4 years soon . . .
BTW, does the extended warranty cover check engine light issues? Coming up on 4 years soon . . .
Good luck with diagnosis and repair.
05-06-2019, 06:29 PM
#500
Thanks for all responses and hope to hear from more from those that got their TDIs fixed.
Our 2015 Q5 TDI remains stock (unfixed), and need to decide whether to get the fix in the next few months.
The engine light came on, and the dealer says that it is the DEF pump. He told us that it would be covered if we do the fix, otherwise is out of warranty (and hundreds of dollars to fix).
The interesting thing is that we do not see any difference in the car’s performance.
again, thx in advanced for your input.
Our 2015 Q5 TDI remains stock (unfixed), and need to decide whether to get the fix in the next few months.
The engine light came on, and the dealer says that it is the DEF pump. He told us that it would be covered if we do the fix, otherwise is out of warranty (and hundreds of dollars to fix).
The interesting thing is that we do not see any difference in the car’s performance.
again, thx in advanced for your input.