Using CCP1 and CCP2 to measure instant fuel consumption

[Archangel]

Here's how I monitor instant fuel consumption...

Looks great Jeremy, more on screen than my snap on scanner, what kind of display is that, a monitor? What are you measuring the fuel flow with? ( the mpg goes over 60 due to the computer shuts off the fuel completely when decellerating. Impressive work.

[skimask]

Looks great Jeremy, more on screen than my snap on scanner, what kind of display is that, a monitor?

http://www.sparkfun.com/commerce/pro...roducts_id=569
It's the same screen that I posted the color lcd code to here awhile back.

What are you measuring the fuel flow with? ( the mpg goes over 60 due to the computer shuts off the fuel completely when decellerating. Impressive work.

Straight OBD2 data, mass air, temp, pressures, etc.etc.etc. Do enough math, mainly unit conversions and a bit of integration, and you can get almost anything you want out of OBD2...although the outputs are all 'estimated' because they're all derived from formulas with a few generic numbers (i.e. fudge factors) thrown in. But based on my driving over the past 8,000-ish miles, that 'estimation' seems to be quite accurate.
And when the mileage goes over 60...
The Nissan I've got ('98 200SX) isn't very aggressive at decel fuel cutoff like todays vehicles are. Based on my datalogging and calculations, if I'm doing 65mph and I let off the gas, I only get complete cutoff under certain conditions (above 2000 rpm, above 25mph, closed throttle, MAF below 500grams/sesc, MAP below 6 in/hg, calc.load.val below 10%). Other than that, I figure it goes open loop and tries to hit an A/F of about 25:1. Apparently, today's vehicles go to decel cutoff as soon as you think about slowing down (which accounts for some of todays vehicles being a just a little bit jerky at lower throttle settings in my experience).