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Old 09-16-2020, 03:54 PM   #46 (permalink)
Aero Wannabe
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Join Date: Dec 2007
Location: NW Colo
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TDi - '04 VW Golf
90 day: 55.54 mpg (US)
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Originally Posted by pete c View Post
On the topic of EOCing, I am considering it for a few reasons.

1. There is some efficiency gains. Not as much as a gasser, for sure, but something.

2. When it is in DFCO, I wonder if all that cool air moving through the cat and dpf have an effect on them? Do they cool off much? Does idling cool them or contribute to them clogging?

I don't know. I do know that driving them for economy all the time does lead to DPF issues. I have a friend that had one. His wife drove it, primarily and he told me ended up getting rid of it because of DPF headaches, which he attributed to the wife's conservative driving.

So, my thought is that perhaps it is best to just shut the damn thing down during extended coasting opportunities.

Of course, I would be cognizant of things like turbo temp. I would not do it shortly after a hard pull and when I did do it, I would likely give it a good 5-10 seconds of idling or better yet DFCO before shutting down.

Does scanguage give turbo temps? Would be a nice thing to know.

Odds are I won't do this, but I am giving it some thought.
I do not have a DPF so I cannot speak to that concerning the TDI. VW has done a lot with EGR to keep NOX emissions down in the newer TDIs so there may be a throttle plate that closes to pull in more EGR. IMHO your engine should not create much soot in the DPF at idle because the computer injects only enough fuel to maintain 900 RPM.

I find that if I can coast, it is usually for a minute or less. If I am on a longer hill I pick up too much speed to coast, therefore I am using engine braking. The loss of power brakes and steering and possible steering lock and wear from using the key switch make me very reluctant to use EOC. I suspect any gains from EOC would be minuscule.

On my car, the ScanGuage will not read turbo or exhaust temperature. I read somewhere that you can double your intake temperature reading to get a rough idea of how hot your turbo is running. In my experience, on long Colorado climbs the intake temperatures rise steadily so there may be some truth to that.
60 mpg hwy highest, 50+mpg lifetime
TDi=fast frugal fun

Originally Posted by freebeard View Post
The power needed to push an object through a fluid increases as the cube of the velocity. Mechanical friction increases as the square, so increasing speed requires progressively more power.
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