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What is the maximum injector p/w?

Old 05-30-06, 03:28 PM
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What is the maximum injector p/w?

In the logs, it can show injector p/w in milliseconds. How do you convert the injector p/w (in ms) to a duty cycle %? Im assuming the p/w number is the injector "on" time. I just want to know what is the value where your injectors maxed out. Thanks!
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Old 05-31-06, 12:38 AM
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https://www.rx7club.com/showthread.p...+cycle+formula

Future version of the logger will have an option to display D/C instead of PW. Actually I thought it was there already, but I looked and it's not.
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Old 05-31-06, 09:06 AM
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thanks for the link

so if i understand correctly, the injector pwm signal changes frequency with engine rpm? so the formula would be:

Max injector ON time (ms) =120000/RPM

the max injector duty cycle for rtek is about 60% (correct me if im wrong), so at 4000 rpm, your injectors will be maxed out at a p/w of 18ms? ([120000/4000]*.6)
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Old 05-31-06, 11:35 AM
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Buy a meter with a Duty Cycle function. Backprobe a primary injector. Observe the reading in percent and ms. Done. Easy and requires no brain strain. Even RS sells meters with duty cycle. By a Fluke though.
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Old 05-31-06, 07:28 PM
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Calculating the max open time at 4000 RPM
Code:
ms = (1 / (RPM/60) ) * 1000
   = (1 / (4000/60) ) * 1000
   = (1/66.667) * 1000
   = .015 * 1000
   = 15 ms total possible open time.
Note the order of calculations. This was not properly expressed in the other thread.

So if at 4000 RPM you were at 10ms inj PW, and we already calculated the max at 4000 is 15ms
Code:
D/C = (PW/max open time) * 100.
    = (10/15) * 100
    = 66% D/C
Rtek max DC is near 90% but that has nothing to do with any of these calculations other than if your D/C ended up being close to 90%, then you know it's time for bigger injectors.

Edit: I corrected the math as per Henrik

Last edited by turbo2ltr; 06-01-06 at 01:24 AM.
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Old 06-01-06, 01:09 AM
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That thread is not correct. For a rotary, one rotor face goes through an
intake cycle per rev of the eccentric shaft. So the intake phase is
1 / (rpm / 60) * 1000 ms in duration. ie at 6000rpm, the intake phase
is 10ms in duration.

Duty cycle is then simply the commanded injection time / time available
at that rpm.

-Henrik
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Old 06-01-06, 08:25 AM
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so i think i got it figured out:

DC = (PW*RPM)/60000

DC= injector duty cycle (decimal)
PW = injector "ON" pulse width (ms)

but from what ive read on the forums, the max duty cycle is around 60% for the stock ecu? The pocketlogger site says they only raised the injector cap by 5%? So how could it be 90%, or is it a misprint on the website?

thanks for the help!
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Old 06-01-06, 11:55 PM
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The "stock ECU only drives the injectors to 60%" is a myth. The stock ECU
will drive the injectors to ~85%, which is why the cap is only raised by
the 5%.

-Henrik
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Old 06-02-06, 10:10 AM
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ah, sweet, thanks for the info!
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