Neutral at stop lights, save gas??

[skewbe]

Originally Posted by cfg83

skewbe -

Do you really think so? I was hoping to *infer* gas consumption from SG behavior.

2 reasons why I think so (I've been meaning to hook up an LED to my injector leads to prove that it ISN'T getting voltage when the scangauge says it is delivering fuel, but haven't gotten to it)

1. in my car, when it is cold and I'm in overrun, I can feel the effects of turning the injector kill switch on and off, but not when it is warmed up. The scan gauge still will read .2 gph in both cases.

2. The scangauge will read .2gph with the injector kill switch held in, though this is understandable as a pulse is still being created, just intercepted on the way to the injector.

It could be that the metro ECU is a little stupid about it? It could be the scangauge is. Or maybe it's an obdII limitation? Or I'm hallucinating?

I don't worry about it too much since I don't normally have any downhills that require engine braking and I try and drive in a style that doesn't require ANY kind of braking.

[JanGeo]

The engine size relates to the injector size - bigger engines use bigger injectors that inject more fuel per msec of pulse so by setting the engine size they can calculate the amount of fuel injected.
I have seen 500-600 mpg on my scangaugeII when I get the idle down to .1gph and am coasting at 50-60 mph.
Keep in mind that all the data that the SG uses is from the ECU an dwe don't know exactly what that info contains.
The Liters setting sounds interesting I may try that.
ALSO DON'T play with the SG with the engine off - seems that can make it crash and lock up - happened to me again this week had to unplug but didn't loose the data this time at least. My remote door locks activated the SG and I didn't turn the ignition key on and it locked up.

[ELF]

My scan gauge lights up when I hit the remote door locks too.

[rh77]

Originally Posted by ELF

My scan gauge lights up when I hit the remote door locks too.

I've had some wierd SG behavior, but it gets around (plugging it into all sorts of rental vehicles). On the '06 Kia Spectra, the car's ECU or the SG malfunctions and loses the ability to calculate MPG and the TPS position. It worked on a new one, so I'm thinking the car didn't like it.

It still is a great, simple, instant-feedback device for OBD-II'ers. The engine displacement is a good question, but seems to be accurate. I've driven everything from a 6.0L V-8 on the SG, down to a 1.6L -- and the pump calcs aren't that far off (as accurate as pumps calcs can be).

I also have a data logging chip for sensing and diagnosis a variety of variables -- to spot trends, etc. I bought it before I heard about the SG -- it uses the same OBD-II port, so I should've waited. I'd like a direct link to a laptop, but I can't see getting much use out of it. With the logger, I can come back and crunch the raw data if I want to.

RH77

[skewbe]

Originally Posted by JanGeo

The engine size relates to the injector size - bigger engines use bigger injectors that inject more fuel per msec of pulse so by setting the engine size they can calculate the amount of fuel injected...

I think that's right. Then they multiply the calculated amount by however far off the tank was when compared with a fillup, to account for variances i.e. different injectors, different fuel pressures.

[cfg83]

rh77 -

Originally Posted by rh77

I've had some wierd SG behavior, but it gets around (plugging it into all sorts of rental vehicles). On the '06 Kia Spectra, the car's ECU or the SG malfunctions and loses the ability to calculate MPG and the TPS position. It worked on a new one, so I'm thinking the car didn't like it.

It still is a great, simple, instant-feedback device for OBD-II'ers. The engine displacement is a good question, but seems to be accurate. I've driven everything from a 6.0L V-8 on the SG, down to a 1.6L -- and the pump calcs aren't that far off (as accurate as pumps calcs can be).

I also have a data logging chip for sensing and diagnosis a variety of variables -- to spot trends, etc. I bought it before I heard about the SG -- it uses the same OBD-II port, so I should've waited. I'd like a direct link to a laptop, but I can't see getting much use out of it. With the logger, I can come back and crunch the raw data if I want to.

RH77

Does the logger help you to monitor the Air/Fuel ratio over time? That way you could see if your Hot Air Intake was working (right?).

CarloSW2

[occupant]

Speaking of Hondas...I worked at the Civic factory in 1996 and 1997, in the VQD (vehicle quality department or something to that effect), and 2 of my 5 stations required me to drive the car from one line to the next, either out of the water pressure booth and onto final inspection, or from final inspection to the exit line which applied a black wax coating to the underside. We were instructed to start the car, drive it to the next line, and shut it off as fast as possible. This was an effort which allowed two benefits...1) saves fuel, and those guys running around the plant in the older '93 Civic sedan HATED to go get gas for us...2) keeps exhaust temperatures down to avoid setting off the heat alarm because the black wax is flammable until it sets. The automatic cars benefitted more from this procedure than the manuals, according to data collected by me when letting the car idle for x seconds and seeing what readout the temperature gauge on the exit line gave me.

Without question, the Saudi/UAE/Kuwaiti EX coupes with manual transmission could idle the longest time before exceeding the maximum allowable safe temperature. So I would assume the least fuel was being burned in those if the temperatures were lower. That or maybe they didn't have cats.

[brucepick]

Originally Posted by omgwtfbyobbq

All modern FI cars should have the injectors turn off (or maybe pulse depending on the post cat O2 reading) above a certain rpm with no throttle, depending on coolant temps (maybe other things too?), when the vehicle is above a certain rpm in any gear...

Cool. Do you know when they started doing that? My car is an '89 Volvo 240 auto trans; can you guess whether the injectors shut off?

[rh77]

Originally Posted by cfg83

rh77 - Does the logger help you to monitor the Air/Fuel ratio over time? That way you could see if your Hot Air Intake was working (right?). CarloSW2

It doesn't show A/F ratios but does show long and short-term fuel trim. During inital tests, it showed that higher IA temps improved the trim into a leaner condition, but would tend to enrich the mix at very hot IATs. It's a great device that I rarely use anymore because it plugs-in where the SG does Lots of parameters to choose from. Davis Carchip E/X.

(Wondering) Hmmm...is there an OBD-II splitter out there? like a 1 into 2 deal?

RH77

[omgwtfbyobbq]

Originally Posted by brucepick

Cool. Do you know when they started doing that? My car is an '89 Volvo 240 auto trans; can you guess whether the injectors shut off?

I think they started around OBD1, and that pre OBD systems like VW's digi2 didn't, but don't quote me on that. You could hook up an led to an injector circuit pathway and see if it's blinking behavior changes. Or better yet, I've noticed on downhills that are steep enough to coast down in gear at 55mph, the engine temps drop a lot because there's no fuel being injected, but if I'm coasting in N, they stay pretty consistent. Find a big enough hill and watch what happens to the coolant temperatures.