Quote:
Originally Posted by RobertSmalls
I'm going to disagree with you on the emissions merits of an ignition cut over a fuel injector cut.
(gee, that's a surprise)
sure , but who said best case, engineering is about worst case.
Imagine coasting down that long grade, I80 East to the Reno Area.
I never once said factory car designed for fuel cut , were wrong or dirty.
Gee,they have a special cat , to it lights back off fast (low mass element and a short path to the exh. ports .)
this is a modding forum. (again worst case , and Emission mods are illegal or did you forget to notice the rules in the EPA, regs. i can quote them,but why, this is nothing, new. Just do your own search for the word "modification")
The engine is going to turn over only a few times between when you hit the kill switch and when it comes to rest. An injector cut will save a few pulses worth of gas vs. an ignition cut.
If you dump those few mg of gas into the exhaust and it doesn't get ignited, then you've created HC emissions. If it does get completely burned on the cat, you've raised the cat temperature a degree or two... but it's going to cool off a few dozen degrees anyway while you coast to a stop and wait for your light to turn green. The cat will get back up to operating temperature soon enough after you take off, no sense in pouring fuel on it to make that happen faster. Sure, why not.?
My Honda hybrid leaves the factory with auto-stop, wherein the engine comes to rest when it's not needed, and the cat begins to cool down. Yet the car meets with EPA and CARB approval. ( imagine that )
As far as FI PW >0 during DFCO, huh. That's a head-scratcher. Are you sure? It kind of makes me want to measure it with a multimeter, not a scantool. The Scangauge reports that my Subaru uses 0.04gal/hr at 0rpm, which is clearly not the case.
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Depends on what car , what year, your experience is limited to just a few cars,and you need to read more about ScanGuage.
you dont understand the Scanguage. Sorry, (read the calibration white papers"
in most cases, it uses , Airflow from the MAF AND THEN reverses the calculation back to the injector PW.
with poor accuracy at all times and horrible accuracy at low fuel rates !!!
It says that in their write ups.(ScanGuage)
many cars with obd2 do not have injector , PW logged.
what your car OBD2 ,does varies by brand and year.
Some cars , cut full totally. DFCO
some keep the CAT , tickled with fuel. (year and models vary)
I have a 91 TBI car, that cuts 100%
to find out the truth takes a scope. no better way.
attached to the injector and drive.
first print out you Injector Dead-time spec, and the flow characteristics.
this action prevents you from getting confused by all the layers for software/firmware.
hope that bods well with your Physics degree.
look up too , how non linear the injector is at low PW just after deadtime.
read up on that.
and most cheap Multimeter do not measure PW accurately ,there sample rates are way too slow.
Get GMM /DSO or real scope and look at accurate measurements.
the whole point of SCANGUAGE is to find the sweet spots for MPG
accuracy is not even close.
It is not an instrument nor is it traceable to the NIST.
However it does a great job at finding the sweet spot in all gears.!
I use Palmer software and it too suffers from the same issues.
cheers.