Questions about block 002 and duty cycles..
04-20-2004, 05:19 PM
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Questions about block 002 and duty cycles..
I was just looking over an old VAG-COM log and something occured to me.
Block 002 showed that the fuel injector average time was about 14ms @ 6000 rpm.
It was my understantding that fuel injector average time was eqivalent to the duration of each injector pulse. However, this can not be true because...
At 6000 rpm the time of one revolution is 10ms.
If the pluse duration was 14ms, then the duty cycle would be greater than 100%
In short, what the hell is fuel injector average time? TIA?
Block 002 showed that the fuel injector average time was about 14ms @ 6000 rpm.
It was my understantding that fuel injector average time was eqivalent to the duration of each injector pulse. However, this can not be true because...
At 6000 rpm the time of one revolution is 10ms.
If the pluse duration was 14ms, then the duty cycle would be greater than 100%
In short, what the hell is fuel injector average time? TIA?
04-21-2004, 04:54 AM
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We've found that (at least with S4 chips) the tuning tends to request injector times...
greater than physically possible (in some cases 140%+ greater). Guess it really doesn't matter much as 100% is the max that you can get. So you can request 500% if you want, though it seems kinda pointless.
-Dave Pramanik
-Dave Pramanik
04-21-2004, 07:01 AM
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Someone on another forum reminded me that the injectors only fire on every other turn of the motor.
This would explain the request for 14ms pulse duration.
DC=(14ms = requested pulse duration)/
(20ms = time of 2 full revolutions @ 6k rpm)
70% duty cycle
DC=(14ms = requested pulse duration)/
(20ms = time of 2 full revolutions @ 6k rpm)
70% duty cycle
04-21-2004, 03:13 PM
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If you look at the specs of a camshaft....
the intake duration is usually in the 250-280 degree area (depending on motor and setup) I think the A4 is somewhere around 260
So for every cam rotation (360 degrees), the intake is open 260 degrees (keep in mind not fully open, but open none the less)
The crank spins twice as fast as the cam, so at 6000 RPM, you have 20ms for every cam revolution.
So open valve time => 260/360 * 0.02 = 14.44ms
BUT, keep in mind that if you spray fuel outside of intake-open window, it will still collect and enter the combustion chamber once the valve opens, plus it can cool the incoming air.
So for every cam rotation (360 degrees), the intake is open 260 degrees (keep in mind not fully open, but open none the less)
The crank spins twice as fast as the cam, so at 6000 RPM, you have 20ms for every cam revolution.
So open valve time => 260/360 * 0.02 = 14.44ms
BUT, keep in mind that if you spray fuel outside of intake-open window, it will still collect and enter the combustion chamber once the valve opens, plus it can cool the incoming air.
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