instanious and avrage MPG computer.
 

can this be done on obd0 or 1 cars? i realy want one. i've seen the JCwitny gauge but i want somthing digital. if u read here under the trip secton this is what i want. but this one is obd2.

https://www.scangauge.com

i want somthing i could splice in do a couple sensors and addon sorta like the Zemco cruse control. (if u can remimber that far back :P) anyway all i want is a little box. i can buld and put 2 7-segment displays im my cluster or to a VFD (same as LCD) display in where my clock goes. somthing simalar to like a insight cluster that give u instauous and avrage mpg.

i am proficient in electronics and programing but i dont even know where to begin on this. what sensors to use? are they readly avalible. for ex. i'd use the gas flow sensor from the zemco system but #1 it's hard to find and #2 it's not ment for the fuel injecton presures. only for carbed. maybie even go as far as somthing that will interface with the ecu. to get the sensor data that way. simaler to datalouging.

i know this is a high and drawn out request but it's somthing that've allways wanted and i'm sure that others on this site could benifit from it.

We've talked about it.
 

We've talked about it. Either you could run the ecu open loop and datalog it (honda only) or you could splice somewhere to measure injector pulse and vss and make a little chip/board to monitor and display that.

2 things...
 

On the '98 Integra (Honda OBD-II), is there a simple wiring diagram to indicate when the engine is running in open loop (like have a red LED for open-loop, green for closed). Also, is it true that Hondas/Acuras run open-loop at full-throttle, regardless of conditions?

Secondly, again on the 'teg, is there a schematic for making a fuel-economy guage? I don't need to know the numbers, just a gauge to show to the fuel consumption, low to high with hash marks in-between. I've been trying to moderately accelerate down hills, and coast up the next hill or keep the same pressure on the gas pedal. Just trying to improve the "driving efficiently" part and need some real-time info.

RH77

Quote:Secondly, again on the
 

What you want here is a vacuum mpg gauge. They suck, so just get a vacuum gauge (generally a boost gauge that measures vacuum too). More vacuum = better gas mileage ceteris paribus, so there you go, you'll have to be mindful of other factors, but it will help for compartivity.

I'll get back to you on the other ****.

EDIT: Meh.

vacuum gauge is one way to
 

vacuum gauge is one way to go for sure.

you might be able to do it digitally if you can tie a multimeter into your MAP sensor return wire, and run the multimeter wires into the cabin so you can spy on the relative voltage in different driving conditions.

you just need to know what the upper and lower limits are (which is easy to figure out in a few minutes of "extreme" driving).

(also, i understand not all cars have MAP sensors, so this might not apply to you - some use MAF instead.)

Re: vacuum gauge is one way to
 

Thanks -- I found my multi-tester in the basement today (recently moved), so I can give that a shot.

Thanks man. I had a boost guage on my Evo and it was easy enough to install. I may try that also -- fuel is saved at "negative boost" and VAC draw pressure would translate to fuel use, I assume.

RH77

Yeah, honda fuel maps are
 

Yeah, honda fuel maps are plotted in terms of vacuum/boost versus rpm. It's just a table really. So vacuum is columns and rpm is rows. You get the idea, move to less vacuum or more rpms and you're using more fuel.

Re: Yeah, honda fuel maps are
 

Thanks again. I'm glad it's pretty much that simple.

RH77

I still have all my notes
 

I still have all my notes when I was designing a driving computer to keep track of this stuff and lot's more. I just need to be inspired again to start working on it. I'm working on a microcontroller related project at work so maybe that'll spark my interest again. Just to calculate instantenous MPG wouldn't be hard at all. I might forget about reading all the sensors (like coolant temp and intake air temp) and just do MPG. I've really been thinking more and more about how nice to would be to instantly know the effect of MPG mods and driving habits in real time as I'm driving.

Flatland... you're alive...
 

Flatland... you're alive... I'm happy that you decided to visit :)

I would be more than thrilled to have a MPG readout. It's the ONE thing my car is really missing...

I think most people (at least in our little world) would love a way to measure MPG for obd1 and obd0 cars. Hell, I'd even buy one off of you. Put me down as your first customer.