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Old 02-08-2012, 04:12 AM   #90 (permalink)
Piwoslaw
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Join Date: Oct 2008
Location: Warsaw, Poland
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Svietlana II - '13 Peugeot 308SW e-HDI 6sp
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Quote:
Originally Posted by SentraSE-R View Post
I drove the car 900 miles RT to/from SoCal last week, and the cat stayed lit, between 1101-1185 degrees F. When I do my normal low speed P&G, cat temps are 285-550 degrees F, too low to light the cat.
As mechman600 mentioned, new turbodiesels have a exhaust temperature sensor to monitor DPF regeneration. I found a site which shows how to tap into that signal to monitor the temps yourself (for PSA HDi - FAP Sensor Regeneration & Turbo temperature - exhaust gas temperature monitoring). From the data there it appears that diesel exhaust is quite cool compared to a gasser (maybe because turbodiesels are more efficient?). The main temperatures of interest are:
  • Below ~200°C (400°F) - idle,
  • 200°-400°C (400°-750°F) - normal driving temp,
  • >450°C (840°F) - natural DPF regeneration,
  • 500°-600°C (930°-1110°F) - forced DPF regeneration.
The bottom line is that for the diesel's egt to be close to what lights up Sentra's cat the ECU must force the regeneration of the DPF (preheating intake air, increasing EGR, dumping extra fuel, increasing engine load by turning on rear window heater, etc.), in normal driving the exhaust temps wouldn't light Sentra's cat. In fact, "forced" exhaust temps can't be kept for long since they could damage the DPF. But new diesels still have to pass European emissions standards, so their cats must work at lower temps.

So my questions are:
  1. Do diesel catalytic converters differ from their gasser counterparts?
  2. If so, ie if they light at a lower temp, then could a gasser's cat be replaced by a diesel cat for cleaner emissions while hypermiling?
  3. Could a "universal" cat be constructed with elements from both gasser and diesel cats, so that it works in a broader temperature range?

Slightly OT, but still in emissions, I there was an article in Popular Science (October 1995, page 40) about coating car radiators with catalytic materials, thereby turning your car into a "pollution eater". I know this thread is about reducing emissions, not emitting them then cleaning someone else's, but I thought this is interesting. Of course, it probably wouldn't work well while hypermiling (cool, partially/fully blocked radiator). On the other hand, if there are materials which work on a radiator with temperatures below 100°C/212°F, then why not use them in a low-temp exhaust cat?
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