Duty Cycle on overrun

[tbourner]

Does anyone know what the injector duty cycle drops to during engine braking? This is on a 1.0L if that helps!!

Just interested to see how much fuel I'm saving down sliproads in gear in comparison to coasting!!

 

[squigbobble]

Does anyone know what the injector duty cycle drops to during engine braking? This is on a 1.0L if that helps!!

Just interested to see how much fuel I'm saving down sliproads in gear in comparison to coasting!!

I don't know if anyone's certain on this... who's got the definitive answer? :suspect:

I can give u half an answer though (maybe a third )-
To my knowledge, the ECU will always try to maintain the air/fuel ratio it's been set to under all circumstances (except for cold starts), 'cos of that an engine running at idle will consume less fuel than one running at a higher speed with the same amount of throttle as it'll be taking in more air.
'Cos of the need to maintain the a/f ratio (to avoid toasting valves/bore wash/emissions/whatever) the ECU can't just turn down the fuelling during overrun, it's forced into choosing 1 of 2 options- on or off. So, if ur lucky to have an ECU that can do an overrun duty cycle, the injector duty cycle drops to zero.

Don't forget to resist the urge to sit on the clutch and leave it in gear, u're just taking a bit more off the lifespan of ur clutch release bearing. Popping it in neutral's better for the clutch.

*awaits being shot down in flames* :blush:

 

[tbourner]

I never sit on the clutch..... or the brakes for that matter so I have no idea how I keep warping front discs!!!

Anyway - I know that in the Supra the duration is about 2.0ms at idle, and drops to 1.5ms on overrun - therefore saving approximately 25% fuel. Like you say the stoichiometric AFR is (attempted to be) maintained at all times, but on overrun there is vaccum in the inlet manifold (technically that's not true - but less air than during running - hence engine braking). Just thought someone might know a bit about the ECU control and how clever it is.

 

[Craig]

Micra_pete is the man you need to ask

 

[micra_pete]

stoichiometric AFR is not targetted through-out the rev range, in fact the cg13 ecu only aims for it once or twice in its entire fuel map, its not a straight cut answer this one, see Table below

See where i dropped of the throttle

Time RPM MAF v Thr v Inj Duty
09:15:27 6525 4.69 4.1 14.75 80.2
09:15:27 6550 4.66 4.1 14.75 80.51
09:15:27 6600 4.69 4.1 14.75 81.12
09:15:27 6625 4.62 4.1 14.13 78.01
09:15:27 6675 4.73 4.1 14.75 82.05
09:15:27 6725 4.69 4.1 14.57 81.65
09:15:27 6775 4.76 4.1 14.75 83.28
09:15:28 5462 1.84 0.42 0.43 1.96
09:15:28 5462 1.86 0.42 0.43 1.96
09:15:28 5650 1.86 0.42 0.43 2.02
09:15:28 5688 1.9 0.42 0.43 2.04
09:15:28 5800 1.94 0.42 0.43 2.08
09:15:28 5875 1.92 0.42 1.43 7
09:15:28 5975 1.92 0.42 1.43 7.12
09:15:28 6162 1.96 0.42 1.51 7.75
09:15:28 6200 1.96 0.42 1.59 8.22
09:15:28 6325 2.03 0.42 1.65 8.7
09:15:28 6412 2.14 0.42 1.69 9.03
09:15:28 6538 2.44 0.42 2.69 14.66
09:15:28 6700 3.3 0.66 6.41 35.79
09:15:28 6662 4.37 1.98 12.75 70.78
09:15:28 6775 4.65 3.14 13.81 77.97
09:15:28 6550 4.66 3.82 13.77 75.16
09:15:28 6675 4.72 4.06 14.75 82.05
09:15:28 6700 4.66 4.06 14.63 81.68
09:15:28 6762 4.7 4.06 14.71 82.89
09:15:28 6800 4.74 4.06 14.53 82.34

this is a nearly stock standard 1.3 ecu (number 16)

 

[micra_pete]

i know the table is a little hard to read, but the forum doesn't like extra spaces

 

[tbourner]

Jeez that's a bit confusing with no spacing!! Am I right in saying that it doesn't really help in relation to idle though? Clearly WOT then lift off then WOT again will show a pretty huge change in manifold AF reading? Nice figures nonetheless thanks m8!

 

[micra_pete]

--Time--------RPM-----MAF-v----Thr-v----Inj------Duty
09:15:27-----6525-----4.69-----4.1------14.75-----80.2
09:15:27-----6550-----4.66-----4.1------14.75-----80.51
09:15:27-----6600-----4.69-----4.1------14.75-----81.12
09:15:27-----6625-----4.62-----4.1------14.13-----78.01
09:15:27-----6675-----4.73-----4.1------14.75-----82.05
09:15:27-----6725-----4.69-----4.1------14.57-----81.65
09:15:27-----6775-----4.76-----4.1------14.75-----83.28
09:15:28-----5462-----1.84-----0.42-----0.43------1.96
09:15:28-----5462-----1.86-----0.42-----0.43------1.96
09:15:28-----5650-----1.86-----0.42-----0.43------2.02
09:15:28-----5688-----1.90-----0.42-----0.43------2.04
09:15:28-----5800-----1.94-----0.42-----0.43------2.08
09:15:28-----5875-----1.92-----0.42-----1.43------7
09:15:28-----5975-----1.92-----0.42-----1.43------7.12
09:15:28-----6162-----1.96-----0.42-----1.51------7.75
09:15:28-----6200-----1.96-----0.42-----1.59------8.22
09:15:28-----6325-----2.03-----0.42-----1.65------8.7
09:15:28-----6412-----2.14-----0.42-----1.69------9.03
09:15:28-----6538-----2.44-----0.42-----2.69------14.66
09:15:28-----6700-----3.30-----0.66-----6.41------35.79
09:15:28-----6662-----4.37-----1.98-----12.75-----70.78
09:15:28-----6775-----4.65-----3.14-----13.81-----77.97
09:15:28-----6550-----4.66-----3.82-----13.77-----75.16
09:15:28-----6675-----4.72-----4.06-----14.75-----82.05
09:15:28-----6700-----4.66-----4.06-----14.63-----81.68
09:15:28-----6762-----4.70-----4.06-----14.71-----82.89
09:15:28-----6800-----4.74-----4.06-----14.53-----82.34

thats easier to read, do you want some figures at idle?

 

[Napster]

micra pete, im just interested to know how you know that data? hope you dont mind me asking?
napster

 

[micra_pete]

i just stream it over consult

cables are available over the net, i can recommend the plms development cables as i know the guys that make them

mention pete rushton if you order

 

[tbourner]

do you want some figures at idle?

If you could mate that'd be cool!

You're more helpful than the Supra techies were when I asked how to work out radiator size mathematically!

 

[Napster]

i just stream it over consult

cables are available over the net, i can recommend the plms development cables as i know the guys that make them

mention pete rushton if you order

i have no idea what this means mate :upside: ?? lol

heres my technical knowledge lol ---> "are you talking about the thing that is under the fuses by the door, behind the plastic holder??? its grey has HOLES where you could put a cable, which is probably linked to the ECU"
or something with a LAPTOP / PC??-

if you laugh at what i wrote then fair enough lol cause i am.
naps

 

[Ed]

From my data logs (not precise from the ecu like petes) in over run above a certain rpm with throttle closed, the fuel cuts compleatly, and the AFR meter reports AIR!