99 civic mpg gauge ?

[user102]

Hi I have a European 99 civic 1.5 sohc vetec-e that I am planning on setting up a mpg computer + lcd to fine tune my journeys.It has a obd2a ecu with no 16 pin obd2 connector but has 1x2 pin connector (service check) and 1x3 pin connector(datalink).The goal is to go with something like a diy OBDguino type system if possible as I have the parts.I'm looking for a system that works with my car and which can calculate current/average mpg and is reasonably accurate ?



I can provide any more information if required.

Any ideas ?
Thanks

[Ecky]

Check out the instrumentation section. I believe MPGuino is what you're looking for.

[user102]

Originally Posted by Ecky

Check out the instrumentation section. I believe MPGuino is what you're looking for.

Ok thanks.Quick question given this ecu is it possible to interface with it using an arduino based system to gain access to some other engine parameters such as throttle position,engine temperature etc and if so what compatible system am I looking for ?

[Ecky]

Originally Posted by user102

Ok thanks.Quick question given this ecu is it possible to interface with it using an arduino based system to gain access to some other engine parameters such as throttle position,engine temperature etc and if so what compatible system am I looking for ?

Beyond me. I haven't read about any tools that can use a datalink connector to get that information but that doesn't mean they don't exist.

[user102]

How does the mpguino calculate fuel consumption without knowing any manifold pressure data from the map sensor ?

[Ecky]

Directly - you tap one of your injector grounds and it measures how long your injectors are open. Combine that with a connection to the VSS and you have fuel used and distance. You have to calibrate it, but there's a table in the wiki that should get you very close to start with. 2-3 tanks should get you within 1%.

An MPGuino is actually the only accurate way to measure fuel used in lean burn engines (and possibly for those who use engine-off coasting too). OBD port based meters can't account for these things.

[backpacker3]

Originally Posted by user102

Ok thanks.Quick question given this ecu is it possible to interface with it using an arduino based system to gain access to some other engine parameters such as throttle position,engine temperature etc and if so what compatible system am I looking for ?

That sounds more like a OBDuino. There is a thread on it but a lot of the information in it was out of date for me so I'm slowly working on a new version. If you have arduino experience i don't mind the help if you're interested. The thread I started is called OBDuino 2 you can search it or I can link to it later.

[user102]

Originally Posted by Ecky

Directly - you tap one of your injector grounds and it measures how long your injectors are open. Combine that with a connection to the VSS and you have fuel used and distance. You have to calibrate it, but there's a table in the wiki that should get you very close to start with. 2-3 tanks should get you within 1%.

An MPGuino is actually the only accurate way to measure fuel used in lean burn engines (and possibly for those who use engine-off coasting too). OBD port based meters can't account for these things.

Hi If the amount of fuel going though an injector at any given time also depends on engine load ie reading from map sensor and mpguino doesn't take this into account then how does it do the consumption calculation within 1% accuracy ?

My car has a map sensor on the intake manifold will mpguino still work accurately ?

I was thinking of going the obdguino route however there is no 16 pin obd connector present only the ones i mentioned about previously would a 3 pin to 16obd adaptor cable work?

[Ecky]

Originally Posted by user102

Hi If the amount of fuel going though an injector at any given time also depends on engine load ie reading from map sensor and mpguino doesn't take this into account then how does it do the consumption calculation within 1% accuracy ?

My car has a map sensor on the intake manifold will mpguino still work accurately ?

I was thinking of going the obdguino route however there is no 16 pin obd connector present only the ones i mentioned about previously would a 3 pin to 16obd adaptor cable work?

By measuring the injector ground, you're measuring how much fuel the injector lets through. You don't need any more information.

MAP sensor and O2 sensors are what the computer uses to calculate how long and much to open the injectors (that, and tables under certain conditions), but you can just as easily read the injectors themselves to see how much it decided to open them.

As I understand it, something like a scangauge can give you a wider variety of information, but these meters read inaccurately under some circumstances because they just use manifold pressure to calculate fuel used, which will be incorrect under certain conditions, ie. lean burn (different AFR) and engine-off-coasting, because they're assuming a stoichometric burn is always happening - that is, making assumptions about how much the injectors actually open. If you're looking to find out how much fuel is being used over a given distance, the best way to do it is to measure the fuel being used directly, and the speed traveled over time, which is exactly what these do.

As for whether or not you can plug any of these other meters into a 3-pin port, that I have no idea.