For some time on this dirty exhaust tip issue I've been pointing out there... |  |  |
Expect the best, and accept no substitute. |
Products for your Boxster, Cayman and Carrera. |
 | |
Laz - Saturday, 1 December, 2012, at 3:37:34 pm |
Laz - Saturday, 1 December, 2012, at 3:38:09 pm |
Minus 40 degrees... Is that Fahrenheit or Celsius?
Edited 1 time(s). Last edit at 12/01/2012 03:39PM by Laz. (view changes)
Edited 1 time(s). Last edit at 12/01/2012 03:39PM by Laz. (view changes)
| For some time on this dirty exhaust tip issue I've been pointing out there... MarcW - Saturday, 1 December, 2012, at 5:53:56 pm |
are two converters between the engine combustion chambers and the exhaust tips and any mild and it is mild soot build up is a reflection on the converters. And DFI engines are not the only P
rsche engines to soot up their exhaust tips. Both my Boxster and 996 do this.
With the older engines they are fed a rich mixture and then this excess of fuel in the exhaust is fed air -- that's what the secondary air injection pump is provided when it is running -- to burn the fuel in the converters to heat them up to there 600C operating temperature. The converters go from dead cold to 600C in around a minute or sometimes less and then once up to temp and the o2 sensors too, the mixture is dialed back to around 14.7:1 which is the ideal air fuel mixture for the converters. They are at their most efficient when fed the exhaust gases (from an otherwise) healthy engine.
So, some soot, with no CEL, no untoward engine behavior, no problem other than too much driver anxiety and imagination.
As for break in it has always been about the new engines and the much higher amount of internal friction they produce. This is why rpms are restricted to 4K or below to keep the heat build up down. Lab and field tests have found that "break in" continues for some thousands of miles long after the initial break in miles have come and gone.
rsche engines to soot up their exhaust tips. Both my Boxster and 996 do this.With the older engines they are fed a rich mixture and then this excess of fuel in the exhaust is fed air -- that's what the secondary air injection pump is provided when it is running -- to burn the fuel in the converters to heat them up to there 600C operating temperature. The converters go from dead cold to 600C in around a minute or sometimes less and then once up to temp and the o2 sensors too, the mixture is dialed back to around 14.7:1 which is the ideal air fuel mixture for the converters. They are at their most efficient when fed the exhaust gases (from an otherwise) healthy engine.
So, some soot, with no CEL, no untoward engine behavior, no problem other than too much driver anxiety and imagination.
As for break in it has always been about the new engines and the much higher amount of internal friction they produce. This is why rpms are restricted to 4K or below to keep the heat build up down. Lab and field tests have found that "break in" continues for some thousands of miles long after the initial break in miles have come and gone.
| Re: Two items: DFI dirty exhaust tips, and the reason for Porsche's break-in procedure Guenter in Ontario - Saturday, 1 December, 2012, at 6:00:22 pm |
Great article. The part I found most interesting is that in one 1/2 hour of testing on the bench, the metals in the motor don't reach maximum temperature. In summer, I make it a point not pushing the engine for at least 10 minutes after the coolant reaches operating temperature. Looks like I could wait even longer.
I've often read about varying engine speeds during break-in period. As pointed out in the article, it's not just the engine that needs a break-in period. I have a couple of routes that I've taken every new car on during the first few weeks. All 2 lane roads that allow a varied speed, including shifting the transmission. It seems to have worked for me. I've never had to have any major engine / transmission work done on any of my cars and I generally keep them for at least 150 K miles.
Nice find, Laz.
I've often read about varying engine speeds during break-in period. As pointed out in the article, it's not just the engine that needs a break-in period. I have a couple of routes that I've taken every new car on during the first few weeks. All 2 lane roads that allow a varied speed, including shifting the transmission. It seems to have worked for me. I've never had to have any major engine / transmission work done on any of my cars and I generally keep them for at least 150 K miles.
Nice find, Laz.
Sorry, only registered users may post in this forum.