1.8 T rough idle at start-up explained (thanks to April)......
10-04-2002, 09:53 AM
#1
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1.8 T rough idle at start-up explained (thanks to April)......
See also earlier posted thread related to 3.0 rough idle.
Lot's of people complain about the rough idle. While I agree it's annoying, after reading this article, I came away with a different mindset.
It's pretty damn impressive at the engineering that went into making our cars Ultra Low Emission Vehicles (ULEV). In fact, that's one of the reasons I like my car so much.
The air in Atlanta is really bad. With urban sprawl reigning supreme around here, there's little hope that it's going to improve.
With my A4, I admit I feel a little less guilty that I'm contributing to the problem.
My friends are amazed that a sports sedan like this is so eco-friendly.......way to go Audi!!!
Anyway, here's an excerpt from the article:
-------------------------------------------------
<i>"In particular immediately after the engine has been started from cold, the untreated emissions can be reduced considerably by warming up the intake ports and the cylinder fill. The intensified evaporation of the fuel results in improved mixture preparation. This can be achieved without additional input by specifically diverting hot exhaust gas back into the intake port (internal exhaust gas re-circulation). This is done by advancing intake-valve opening (IO) when the engine is cold. The control times of the unadjusted valve gear, with ramp, produce an effective valve opening overlap of 40° crankshaft (CS).
With increasing advance of the intake control times, the HC emissions decrease noticeably. At the same time, the engine's smoothness deteriorates due to the higher residual gas in the cylinder caused by the greater valve opening overlap. The standard deviation of the indicated mean pressure spmi, which consequently rises, serves as a measure of this.
The development objective is to achieve an optimum
balance between maximum introduction of heat and
acceptable smoothness. A deterioration in
smoothness can be counteracted by advancing the ignition point."</i>
-------------------------------------------------
I'm no engineer, but to me it sounds as if, based on the last sentence, that the ignition coils have a pretty advanced and tough job.
Could this theoretically be why some of them have been failing??
Just a thought.....<ul><li><a href="http://www.emitec.com/pdf/SAE-Audi.pdf">click here for full article</a></li></ul>
Lot's of people complain about the rough idle. While I agree it's annoying, after reading this article, I came away with a different mindset.
It's pretty damn impressive at the engineering that went into making our cars Ultra Low Emission Vehicles (ULEV). In fact, that's one of the reasons I like my car so much.
The air in Atlanta is really bad. With urban sprawl reigning supreme around here, there's little hope that it's going to improve.
With my A4, I admit I feel a little less guilty that I'm contributing to the problem.
My friends are amazed that a sports sedan like this is so eco-friendly.......way to go Audi!!!
Anyway, here's an excerpt from the article:
-------------------------------------------------
<i>"In particular immediately after the engine has been started from cold, the untreated emissions can be reduced considerably by warming up the intake ports and the cylinder fill. The intensified evaporation of the fuel results in improved mixture preparation. This can be achieved without additional input by specifically diverting hot exhaust gas back into the intake port (internal exhaust gas re-circulation). This is done by advancing intake-valve opening (IO) when the engine is cold. The control times of the unadjusted valve gear, with ramp, produce an effective valve opening overlap of 40° crankshaft (CS).
With increasing advance of the intake control times, the HC emissions decrease noticeably. At the same time, the engine's smoothness deteriorates due to the higher residual gas in the cylinder caused by the greater valve opening overlap. The standard deviation of the indicated mean pressure spmi, which consequently rises, serves as a measure of this.
The development objective is to achieve an optimum
balance between maximum introduction of heat and
acceptable smoothness. A deterioration in
smoothness can be counteracted by advancing the ignition point."</i>
-------------------------------------------------
I'm no engineer, but to me it sounds as if, based on the last sentence, that the ignition coils have a pretty advanced and tough job.
Could this theoretically be why some of them have been failing??
Just a thought.....<ul><li><a href="http://www.emitec.com/pdf/SAE-Audi.pdf">click here for full article</a></li></ul>
10-04-2002, 09:59 AM
#2
Nah, I don't think it's related to the coil failures; Their job shouldn't be any more difficult (m)
just from the ECU varying the ignition timing. Their rate of "fire" is cotinuously varied depending on RPMs anyway... The ECU is what handles telling the coil when to do that.
But yeah, it is interesting how much the ECU has to do just with the idle routine now. ugh...
But yeah, it is interesting how much the ECU has to do just with the idle routine now. ugh...
10-04-2002, 10:01 AM
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indeed they do, thing is, that is pretty much the job of any coil, and altering the timing is
the least of their worries, the timings altered by fractions of a second...
the charge build up and transfer itself involves a lot, but thats the job of a coil.
the charge build up and transfer itself involves a lot, but thats the job of a coil.
I just wish we could get more info about these coil failures
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10-04-2002, 10:23 AM
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No! I'm serious though. You contribute a lot of accurate info, and I think I speak for the others
when I say we appreciate it! You seem to be very knowledgeable about Audi and its products. Didn't mean to sound sarcastic.