X-post from B5 S4 forum re: injector duty cycle.....

PSmalls::DoggieStyle · 07-24-2005, 07:21 PM

TIA for any insight you may have.

Click!

Audi2ptzero · 07-25-2005, 06:27 AM

Why do you think your running over 100% on the second graph?

PSmalls::DoggieStyle · 07-25-2005, 08:14 AM

DAP@EPL · 07-25-2005, 08:23 AM

Therefore, 20ms is 100% duty cycle at that RPM. If the specified pulse is longer than 20ms, then it just means that the injector is spraying through the full cycle (100%). You can't fit 35ms of spraying time into a 20ms cycle.

-Dave Pramanik

Audiboy · 07-25-2005, 11:28 AM

unless it detected overlean conditions and the whole system is backed off.

Having said that, how's your O2? was it lean before the swap?

PSmalls::DoggieStyle · 07-25-2005, 12:58 PM

02 voltages are fine, which is why this makes me wonder.

Audi2ptzero · 07-25-2005, 01:40 PM

Just found it funny that he said his injector duty cycle was over 130-140%, which I dont think can happen. If the injector was at 110% duty cycle at 6k rpms and the air flow was still increasing, the car would run lean in the higher rpms.

I guess a chart is needed to show how much ms at set rpms = 100% duty cycle.

PSmalls::DoggieStyle · 07-25-2005, 07:47 PM

DAP@EPL · 07-26-2005, 05:55 AM

From the RPM, you can calculate the time required for each revolution in milliseconds. Then double it for the time for the full cycle - 2 revolutions/4 strokes (intake, compression, ignition, exhaust).

Thats the maximum amount of time that the injectors can be open. Specifying a longer pulse width is pointless because you are into the next cycle (but tuners still do it).

-Dave Pramanik

Audi2ptzero · 07-26-2005, 06:26 AM

But would the car run lean if the duty cycle is over 100%? The reason I ask is because I had no problems holding 35ms readings even on my K03 and K04 setup at high rpms and the car never ran lean.

07-25-2005, 06:27 AM	#2
Audi2ptzero Elder Member Garage is empty, add now Join Date: Sep 2002 Posts: 14,369	The dbw ecu can read up to 35ms max which is 100%. Why do you think your running over 100% on the second graph?

07-25-2005, 08:14 AM	#3
PSmalls::DoggieStyle Elder Member Garage is empty, add now Join Date: Jan 2004 Posts: 30,257	I used the equation to convert and verefied with a web calculator.

07-25-2005, 08:23 AM	#4
DAP@EPL Audiworld Sponsor Garage is empty, add now Join Date: Jun 2000 Posts: 19,700	At 6000 RPMs (for example), it takes 20ms for a full cycle (2 strokes). Therefore, 20ms is 100% duty cycle at that RPM. If the specified pulse is longer than 20ms, then it just means that the injector is spraying through the full cycle (100%). You can't fit 35ms of spraying time into a 20ms cycle. -Dave Pramanik __________________

07-25-2005, 11:28 AM	#5
Audiboy AudiWorld Super User Garage is empty, add now Join Date: Mar 2000 Posts: 13,204	What was different in obtaining the two graphs? I don't think an injector swap will change WOT d/c unless it detected overlean conditions and the whole system is backed off. Having said that, how's your O2? was it lean before the swap?

07-25-2005, 12:58 PM	#6
PSmalls::DoggieStyle Elder Member Garage is empty, add now Join Date: Jan 2004 Posts: 30,257	I changed injectors and MAF housing (hombrew stage 3), basically scaling the MAF signal. 02 voltages are fine, which is why this makes me wonder.

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07-25-2005, 01:40 PM	#7
Audi2ptzero Elder Member Garage is empty, add now Join Date: Sep 2002 Posts: 14,369	I never said that it was spraying 35ms, just saying that the ecu can read up to 35ms at any rpm. Just found it funny that he said his injector duty cycle was over 130-140%, which I dont think can happen. If the injector was at 110% duty cycle at 6k rpms and the air flow was still increasing, the car would run lean in the higher rpms. I guess a chart is needed to show how much ms at set rpms = 100% duty cycle.

07-25-2005, 07:47 PM	#8
PSmalls::DoggieStyle Elder Member Garage is empty, add now Join Date: Jan 2004 Posts: 30,257	Dude, it's simple math.

07-26-2005, 05:55 AM	#9
DAP@EPL Audiworld Sponsor Garage is empty, add now Join Date: Jun 2000 Posts: 19,700	Its pretty simple... From the RPM, you can calculate the time required for each revolution in milliseconds. Then double it for the time for the full cycle - 2 revolutions/4 strokes (intake, compression, ignition, exhaust). Thats the maximum amount of time that the injectors can be open. Specifying a longer pulse width is pointless because you are into the next cycle (but tuners still do it). -Dave Pramanik __________________

07-26-2005, 06:26 AM	#10
Audi2ptzero Elder Member Garage is empty, add now Join Date: Sep 2002 Posts: 14,369	Thanks. But would the car run lean if the duty cycle is over 100%? The reason I ask is because I had no problems holding 35ms readings even on my K03 and K04 setup at high rpms and the car never ran lean.

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07-26-2005, 06:26 AM
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