I spliced some long wires into the signal wires, ran them threw a hole in the firewall, and to the DMM in my cup holder.
Anyway the planned test wasn't going to give any useful results, and there was far too much traffic. It seemed to only turns off over 35mph, but then I tried down shifting... My car seems quite quick to respond, under a sec to see change in the O2 reading from .335V(where it like to stabilize) to .450V.
The thing to determine is how much can we push the envelope on the lower RPM range past what the computer allows (engineers almost always give things some cushion room to prevent problems)
The thing that I learned from this test is that down shifting can really save fuel with some cars. It was cutting off even under 20mph if in 2nd.
it doesn't cut off at a particular mph but a particular rpm. that is what to look for.
the scangauge will show you this without having to splice wires or pull out ye olde fluke meter. I know I keep pushing this but you can see actual open/closed loop along with instantaneous mpg. I have been meaning to do a video on this showing where it cuts off on my wife's car but haven't had the time.
maybe this is the push I need. I know that we give margin or buffer zones but that is to keep warranty and yourself intact. you may want to rethink the manual switch if you plan to do that because if you forget to turn it back on, it may damage all sorts of goodies.
Be the change you wish to see in the world
A scangauge sounds like a excellent toy, which I hope to soon own. Do they make one that can plug into a laptop to make graphs and show derivatives and integrals of said graphs, that just seems too cool to be in production...
Most modern fuel injected cars can DFCO, but each has different behavior.
The ScanGauge is a specific model of OBDII product and does not connect to a computer. There are plenty of other brands that do.
There's a link in my sig to a DIY fuel rate meter. That is the most accurate and fastest-responding way to detect DFCO. Using that, I've gotten a pretty accurate understanding of DFCO behavior in my VW and my GMC. My GMC usually has an 8 second delay before DFCO!
How can you spot DFCO with a scangauge? I've heard it wasn't possible.
It's laggy and inaccurate, but it's useful enough. The quickest seems to be open/closed loop; when you see open loop you're in DFCO. You can also just watch instant MPG; when it goes to 9999 you're in DFCO, but it tends to take a few seconds of DFCO before it shows 9999.
From my understanding if the motor stops spinning the transmission fluid pump the transmission will fry.
The engine will stay spinning under fuel cut unless either rpm falls to a point where there isn't enough hydraulic pressure to keep the transmission in gear or the transmission is shifted into neutral.
Also, you will get a check engine light with a cutoff switch unless you put a dummy load for each injector for the ecu to see.