[Diy_efi] duty cycle

[Dan Uscatu]

http://www.stealth316.com/2-calc-idc.htm

quote:

The fuel injector duty cycle (IDC) is the percentage of time the 
injector is supplied with power. The time during which the injector is 
powered (or activated) is called the injector pulse width (IPW). During 
normal engine operation, the fuel injector fires once during the four 
strokes of the Otto cycle, which last for 2 revolutions of the engine. 
As an example, at 3000 rpm it takes 0.040 seconds or 40 milliseconds 
(ms) for the engine to complete 2 revolutions (3000 rpm divided by 60 
equals 50 revs per second; invert to get 0.02 sec per rev or 0.04 second 
for 2 revs). At 6000 rpm it takes 20 ms for two revolutions. If a fuel 
injector is activated for 15 ms (the IPW) at 3000 rpm the duty cycle is 
37.5% (15 ms/40 ms), or rpm times IPW divided by 1200 equals IDC in 
percent. If an injector is powered for 15 ms at 6000 rpm, then IDC is 
75% (15 ms/20 ms). If you know the engine speed (rpm) and the IPW 
(dataloggers can provide this information), then it is easy to calculate 
the IDC.




----- Original Message ----- 
From: "Craig Dunn" <dunnbeetle at bigpond.com>
To: <diy_efi at diy-efi.org>
Sent: Thursday, 27 January, 2005 1:35 PM
Subject: [Diy_efi] duty cycle


I am confused about what injector duty cycle actually means.  Would an 
injector working at say 50% duty cycle be injecting the same AMOUNT of 
feul at say 2000rpm as at 3000rpm.

Does the % relate to the amount of time the injector is squirting feul 
per revolution in which case (with static feul pressure) there is less 
time to inject feul at 3000rpm then 2000rpm so a 50% duty cycle at 
3000rpm means that less feul is injected per cylinder?

If that is true then would you need an  duty cycle of say75% to inject 
the same amount of feul at 3000 revs as 50% DC at 2000revs?

Am i on the right track or how does duty cycle work

Thank
Beetle


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