Instead of vacuum gauge: multimeter on MAP sensor

[modmonster]

does anyone know of a portable data logger or adding machine? -let me explain

i've been thinking that if we can monitor the MAF sensor, air flow is proportional to fuel flow at 14.7:1 so we basically have a fuel flow gauge. now if we could add up these voltage values in real time (integration) this would give us the trip fuel used. we know mileage from the dash so we could then easily have a very basic mpg calculator.

[Nevyn]

Would I be out of line to suggest an Arduino? you could probably use it to monitor the voltage and do the math.


Or just turn it into an MPGuino......

[dichotomous]

its a very rare thing for a car to be running 14.7:1..... on accelleration it uses much more fuel, more like 12-10:1, on deccel it uses less fuel, it almost never uses 14.7:1 though.
to know your fuel, you need something to monitor the flow of fuel per mile, which likely only the computer will tell you

[modmonster]

i don't have an electronic spedometer in my car. if i just install the mpguino to the injectors will that give me any usefull fuel related information?

e.g. gallons per hour, total trip gallons ?

[top_down]

dcb, is there another analog input available on the MPGuino and enough space for some code to monitor the MAP voltage and display a live bargraph display of the engine vacuum? It might be asking too much, but I'd love to see a slightly smaller font on the MPGuino "big" displays, and a bargraph underneath showing a live vacuum reading. I hate the big ugly mechanical vacuum gauge in my Metro, but love having that additional piece of info while I'm driving.

I suppose I could do something with the appropriate parts and 10-20 LEDs, but it would be so clean to have it all on the one display.

[dcb]

A mega168 vacuum effort, done right, would need some code space. You can always gut out the code you don't like to make room (someone should start a code tweaks wiki) but given that it complicates hookup, and there is precious little code space left with the current arrangement, I doubt it would ever be "core" on the base unit.

You do want to update the bar graph as often as possible, so it looks "analog" not just once per 1/2 second, so the whole program might need redoing to do more than one thing at a time with it. There are a couple analog ports available (analog 1 and 2), might just want to build a second one for vacuum/wideband o2/???

[Clev]

dcb, do you forsee any issues using the Atmega328P? I bought the new rev MPGuino kit (I still want to order some stuff so I can socket-mount the LCD instead of soldering it, so I haven't put it together yet.) FL has the 328P-20P preprogrammed for $6.25, so I added it to the order. I wanted the room to be able to add my own project stuff later (I second the code wiki!). Do you think there will be any porting needed to run the existing code on the 328?

[Daox]

Originally Posted by dichotomous

its a very rare thing for a car to be running 14.7:1..... on accelleration it uses much more fuel, more like 12-10:1, on deccel it uses less fuel, it almost never uses 14.7:1 though.
to know your fuel, you need something to monitor the flow of fuel per mile, which likely only the computer will tell you

I totally disagree. Any modern car will likely run at 14.7:1 a good majority of the time if not more. I've monitored closed vs open loop on my matrix (which also has a wideband O2 sensor in it which I've monitored) and that sucker stays in closed loop 95%+ of the time. Only at 3000+ rpm and WOT does it break into open loop. If you back off the throttle a small amount you drop back into closed loop unless you are at very high rpms. Maybe its just a very well designed engine, but I can't believe others would be that much worse.

[dcb]

Originally Posted by Clev

dcb, do you forsee any issues using the Atmega328P?

For experimental purposes, no issues. You have to tweak your arduino installation, and I'm hoping they will cut the bootloader back down to 1k or less, but it should be pin compatible. I have not tried the 328 yet, not sure if/where mpguino is going after 1.0, or if it even needs to go anywhere, but the 328 is a distinct possibility. Gotta see how this first batch of boards goes and see where things stand after that.

[Clev]

Originally Posted by dcb

For experimental purposes, no issues. You have to tweak your arduino installation, and I'm hoping they will cut the bootloader back down to 1k or less, but it should be pin compatible. I have not tried the 328 yet, not sure if/where mpguino is going after 1.0, or if it even needs to go anywhere, but the 328 is a distinct possibility. Gotta see how this first batch of boards goes and see where things stand after that.

Cool. I'll let you know how it goes once I get it together.