Injectors

Site Subscriber Joined: 07 Oct 2004 Posts: 2281

How do uprated injectors actually increase performance? I notice with heavily modified engines a popular mod is uprated injectors and I regularly see "Cossie injectors" appearing in the tech specs.

Surely what is being injected is the same regardless of what car the injectors are from, since the same sensors (CAS, MAP, CTS, Lambda, etc.) are used to calculate the volume and ratio of the intake charge?

Am I right in assuming that the advantage is in the delivery or efficiency with which the charge is delivered into the cylinders?

Forum Moderator Joined: 18 Feb 2004 Posts: 7432

Different injectors have different max flow rates. If you mod the engine and require more fuel, you need bigger injectors to satisfy the demand.

Original injectors will be fine up to a point until the pulse width for each fire of the injector to deliver the required fuel becomes too long and the duty cycle becomes too high. At this point you need bigger injectors.

Site Subscriber Joined: 07 Oct 2004 Posts: 2281

Cheers for the info Neal. Wouldn't care to elaborate on what pulse width and duty cycle mean?

Site Subscriber Joined: 10 Jun 2004 Posts: 2317

Pulse width is the length to time the fuel is actually being injected on that 'pulse' ? or am i totally barking up the wrong tree?

Forum Moderator Joined: 18 Feb 2004 Posts: 7432

sure why not.

As you know the ECU uses its various inputs to decide how much fuel needs to be delivered. An injector is either open or closed. The time to open and time to close is negligible and is ignored. When open, the injector will flow a steady amount of fuel. The pulse width is therefore the length of time the injector needs to stay open to deliver the required amount of fuel.

Duty cycle is simply the percentage of time that the injector stays open. ie duty cycle of 75% would mean that the injector is open 75% of the time.

Gay Rights Activist Joined: 07 Apr 2004 Posts: 1268

right enough!
the injectors are pulsed on and off. the pulse width is the open period...say 20ms.

edit* i didnt see neals reply!

Site Subscriber Joined: 07 Oct 2004 Posts: 2281

Ah, well that's that one cleared up then! I feel enlightened.

Mr Quoter-vator Joined: 16 Feb 2004 Posts: 7405

and the more fuel your engine requires the longer the injectors have to stay open, so at higher rpms they may be open more than they are closed which can lead to them over heating as they are opened by electro-magnet. they need the closed time to cool off

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

I don't know why do I bother writing tech articles explaining this shit if no one reads them?