Air/fuel ratio on overrun?

5th October 2011, 00:16

I've just installed an AFR gauge, its only connected to the narrowband lambda sensor so obvs not too accurate.

I have a bit of a concern though, on idling it sits around 14.6:1, when driving it fluctuates around between approx 12/13:1 upto 17/18:1, although if i cane it,change gear and dont accellerate after, so basically on the overrun....it will read 20:1 for a few seconds, is this a serious problem?

5th October 2011, 08:15

I'd pretty much ignore it if you're using the wrong sensor.

5th October 2011, 10:53

How do you mean the wrong sensor? Its not the wrong sensor the instructions say its meant to connect to the signal wire for the lambda on the ECU, I just connected it to the signal wire coming off the lambda which should do the same job.

I think your right however about ignoring it, this a/f gauge is just a feature of this turbo timer i've installed(its to warm the car up without keys in the morning due to it becoming winter) and after a googling many people are saying its just a "theoretical" reading that it gathers from the sensor and shouldn't really be relied on.
Also, apparently if when a car is on closed throttle the fuel is cut for economy reasons, I forget the actual name for the process...but thats apparently why it shows as lean on the gauge, that sound about right?

5th October 2011, 12:28

A narrow band lambda sensor is a switch. It switches from rich to lean, there's no way to get a number value out of it so the gauge is basically picking numbers out of its arse.

If you want a proper afr reading you need a wideband and controller, that'll give you actual afr readings.

5th October 2011, 12:52

FLOL at fitting a turbo timer to warm your (n/a) engine/car up before getting in it.

I read that starting your car from cold and leaving it to idle until it reaches 'optimum temp' increases wear on things, and uses alot more fuel than if you was to drive it slowly till it reached temp.

5th October 2011, 13:04

It should run that on overrun.....

Id be more worried bout the fluctuations you have when driving... but then again you wouldnt even know if you didnt fit the afr, it wont make much difference. Get a decent map then it will read fine and run better.

5th October 2011, 13:08

Quote:

Originally Posted by saxova

FLOL at fitting a turbo timer to warm your (n/a) engine/car up before getting in it.

I read that starting your car from cold and leaving it to idle until it reaches 'optimum temp' increases wear on things, and uses alot more fuel than if you was to drive it slowly till it reached temp.

Any links to that? Sounds like bullshit

How can driving it use less fuel than letting it idle :|

5th October 2011, 13:12

Read any car manual... they say to not let the engine idle from cold, and to drive steady/low RPM/no more than 2/3's of throttle until it's warm.

I read this in the new mk5 seat ibiza cupra manual, and it also said it in a 2000 corsa manual.

5th October 2011, 13:13

•An idling engine releases twice as many exhaust fumes than a vehicle in motion.
•If every driver in Canada avoided idling for 5 minutes a day, we could prevent 1.6 million tonnes of carbon dioxide from being emitted.
•No more than 30 seconds of idling is needed for oil to circulate through your engine. Many components, such as the wheel bearings, tires and suspension system will only warm up once the vehicle is moving.
•Restarting your car many times has little impact on engine components, adding only around $10 per year to the cost of driving, money that is recovered in fuel savings.
•Ten seconds of idling uses more fuel than restarting the engine.
•Idling can damage your engine since it is not operating at its peak temperature where fuel is completely burned. Fuel residue from incomplete burning can damage engine parts.
•Idling a vehicle for 10 minutes a day uses an average of 100 litres of gas a year. If gas costs 70 cents a litre, you will save $70 per year, just by turning your key.
•During the winter, Canadians idle their vehicles for a combined total of 75 million minutes/day. This is equal to a vehicle idling for 144 years. Although we idle our vehicles about 40% less in summer, we still waste an enormous amount of fuel and money.
•A block heater warms the oil and engine coolant, making it easier to start your vehicle and improving winter fuel economy by as much as 10%.

5th October 2011, 13:16

http://www.motherearthnews.com/ask-o...e-warm-up.aspx

http://autos.aol.com/article/warm-up-car/

5th October 2011, 14:35

Quote:

Originally Posted by saxova

FLOL at fitting a turbo timer to warm your (n/a) engine/car up before getting in it.

I read that starting your car from cold and leaving it to idle until it reaches 'optimum temp' increases wear on things, and uses alot more fuel than if you was to drive it slowly till it reached temp.

To warm the heaters mainly, i hate getting in a cold car.

And tbh, I think thats bullshit, I can sit with it idling for ages and not use any noticable fuel, when driving it clearly uses some.
Again, idling a car clearly does less damage than driving it around before the oil has warmed and circulated properly

Quote:

Originally Posted by CoolC

It should run that on overrun.....

Id be more worried bout the fluctuations you have when driving... but then again you wouldnt even know if you didnt fit the afr, it wont make much difference. Get a decent map then it will read fine and run better.

Ah I see, I did wonder.

I wouldn't say fluctuates a lot, it obviously changes depending on how hard you accellerate though, for example if i absolutely cane it it will head towards 12:1.

As mentioned by that other lad I think its far form accurate, but give a bit of an idea as to whats happening.

5th October 2011, 21:53

Normally cars cut fuel on overrun and will lean right off

5th October 2011, 22:07

TU engines don't though I heard

As Ryan explained - gauge is picking arbitrary values - only a wideband sensor and controller will give an accurate AFR reading

5th October 2011, 22:40

It deffo seems like its doing that raunchez...because the o2 sensor voltage drops to 0.00v when it does it...so either that or it just doesn't give a reading on overrun and the gauge assumes cos 0 is closest to 0.1 that its lean.

N ah I see Gareth....like i say i only installed it as it was a feature on the timer.

5th October 2011, 23:10

got a link to wot youve fited?

5th October 2011, 23:16

Quote:

Originally Posted by Gareth_R

TU engines don't though I heard

As Ryan explained - gauge is picking arbitrary values - only a wideband sensor and controller will give an accurate AFR reading

I'd be suprised if they didn't have fuel cut on overrun especially on 3plugs, but stranger things have happened!

5th October 2011, 23:28

Ax's definitely don't, But yeah potentially with the 3 plugs they might have changed it

6th October 2011, 08:44

If you are using a narrow band sensor --the std one --then the sensor is only very accurate around 13.5 to 15 to 1
thats why its called a narrow band .
20.1 is probably the leanest value the sensor can show on over run .
all std cars shut off fuelling on over-run --eg closed throttle .
exactly where it happens depends on how the ecu protocols are set-up
eg below 3%throttle angle and rpms dropping 300rpm per millisecond --something like that .
as for theother posts about idling and pollution --what a load of american --yank tank 8v gas guzzling crap.
the whole point of modern eucs and lamda control is that the fuelling is contorlled ALL the time ,with the exceptions being wram up phase .
even this is controlled to a value .
to get cars to warm up qucikly is why water rads are getting smaller ,so is the oil sump capacity and why the cat is now very close to the exhaust ports..
a huge chunk of cast iron in v8 will take for ever to warm up ,not like a lightweight alloy small capacity engine
you want to what the afr is doioing buy a w/b unit

6th October 2011, 10:58

Ah I got it now, cheers people

And yeah I only fitted this as it was a feature of the device, but its got me tempted to fit an accurate wideband, as its interesting to watch whats happening as you drive lol

6th October 2011, 13:24

Quote:

Originally Posted by saxova

FLOL at fitting a turbo timer to warm your (n/a) engine/car up before getting in it.

I read that starting your car from cold and leaving it to idle until it reaches 'optimum temp' increases wear on things, and uses alot more fuel than if you was to drive it slowly till it reached temp.

Letting it idle when its cold to 'warm up' can only really fuck the cat, it needs hot gasses passing through quickly to warm optimally, idling on your drive the hot gasses just amass in the cat chamber and sit there clogging the cells

EDIT: just saw your post about "an idling engine produces twice as many fumes and an engine in motion" same shit (kinda)

6th October 2011, 13:40

Quote:

Originally Posted by Oc2

Letting it idle when its cold to 'warm up' can only really fuck the cat, it needs hot gasses passing through quickly to warm optimally, idling on your drive the hot gasses just amass in the cat chamber and sit there clogging the cells

EDIT: just saw your post about "an idling engine produces twice as many fumes and an engine in motion" same shit (kinda)

Good job i've got a decat then

haha

6th October 2011, 18:41

Quote:

Originally Posted by saxova

An idling engine releases twice as many exhaust fumes than a vehicle in motion.
If every driver in Canada avoided idling for 5 minutes a day, we could prevent 1.6 million tonnes of carbon dioxide from being emitted.
No more than 30 seconds of idling is needed for oil to circulate through your engine. Many components, such as the wheel bearings, tires and suspension system will only warm up once the vehicle is moving.
Restarting your car many times has little impact on engine components, adding only around $10 per year to the cost of driving, money that is recovered in fuel savings.
Ten seconds of idling uses more fuel than restarting the engine.
Idling can damage your engine since it is not operating at its peak temperature where fuel is completely burned. Fuel residue from incomplete burning can damage engine parts.
Idling a vehicle for 10 minutes a day uses an average of 100 litres of gas a year. If gas costs 70 cents a litre, you will save $70 per year, just by turning your key.
During the winter, Canadians idle their vehicles for a combined total of 75 million minutes/day. This is equal to a vehicle idling for 144 years. Although we idle our vehicles about 40% less in summer, we still waste an enormous amount of fuel and money.
A block heater warms the oil and engine coolant, making it easier to start your vehicle and improving winter fuel economy by as much as 10%.

Bull Bull Bull!