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Old 02-13-2012, 12:43 PM   #132 (permalink)
SentraSE-R
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Join Date: Jun 2009
Location: Bay Area, California
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Mean Green Toaster Machine - '06 Scion xB
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We have to remember the cat temp display isn't accurate. There's no way a 1000 degree F lump of metal is going to drop to 100F in 25 seconds (during a glide) with no liquid or air being pumped through it. My guess is it's a UG programming artifact - something like: count six V1s in 1/5 second and add their total to the total of the previous 60 V1s; if <6 V1s are available, start totaling new V1 data log. Cutting the fuel injector signal (going into EOC) interrupts the voltage signals (V1) being counted (DFCO apparently doesn't interrupt the signal). That would explain why each pulse starts from ~100F cat temperature, and it leaves us in the dark as to what the actual cat temp really is.

The DFCO cooling pattern gives us more of a clue to what's really happening to the cat temps, although DFCO is pumping air through the cat, unlike the EOC glide. I'm guessing the O2 passing through the cat during DFCO keeps it lit longer: ergo, the cat stays warmer during DFCO.

So, maybe the thing to do is, do a pseudo P&G on a downhill, using DFCO. It might give us some insight as to how much the cat actually cools during a series of P&G cycles.

Another thing I might be able to do is program Scangauge xgauges for cat temps for the CANSF communications protocol used by my xB, if those data are available. Then I could log the cat temp data for 24 seconds of a P&G cycle using the SG v. 4.1.5 performance features. It's just possible the SG uses a different algorithm to calculate cat temps.

I guess I know what today's project is .
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Boycotting Exxon since 1989, BP since 2010
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac? George Carlin
Mean Green Toaster Machine
49.5 mpg avg over 53,000 miles. 176% of '08 EPA
Best flat drive 94.5 mpg for 10.1 mi
Longest tank 1033 km (642 mi) on 10.56 gal = 60.8 mpg

Last edited by SentraSE-R; 02-13-2012 at 12:58 PM..
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