I have a compund question

Can anyone explain what pulse width is (in simple terms)?

What is the pulse width setting for DSM 450cc injectors?

thanks

 

Well, pulse width is a measurement of the amount of time that injectors stay open per firing. Usually measured in milliseconds(ms) at a given RPM.

Another item related to pulse width you may want to know about is the "Injector Duty Cycle". This is a % taken from the amount time the injectors is open versus your RPM. This is important in determining how hard the injectors are working.

 

Okay...I know what the duty cycle is, but how do I determine the optimum pulse width fro my setup..?

 

Pulsewidth is a value the injector stays on each time the cylinder fills with air. The cylinder is going to take in a different amound of air at different loads (open throttle vs. closed throttle) and rpm's. If the cylinder is revving high and is under full load, then its going to need alot of fuel, because there's going to be alot of air moving into the cylinder. at low rpm and closed throttle, the engine's fuel requirements are miniscule, so the injector doesen't have to stay open very long. Pulsewidth has to be determined to your fuel requirements, so depending what size engine you have and how much, if any, boost you're running, you're going to have to figure out how much fuel the engine needs.


[Modified by Canuk_SiR, 7:30 PM 1/16/2003]

 

I think it would be better said that pulse-width is a determination of how long to open the injectors to give enought fuel needed based on the size of the injectors, load/rpm of motor, and desired air/fuel ratio at said load/rpm. In other words, there's not set pulse-width if you're running 10 psi of boost on a 1.8L engine. I dunno if anyone has seen a grid for any standalone management out there, but I can tell you that my PowerFC has a 20x20 grid that covers pulse-width. That's 400 points of pulsewidth calculations based on rpm/load on the engine. 400 points is not fun to change when tuning on a dyno, but must be done to get it perfect. Kinda makes you think why R&D takes so long for a stock engine ECU to be designed to fit a majority of driving styles/weather conditions/grade of fuel/altitude/etc.

 

Very good He's right to get the optimum fueling you're gonna need some dyno time. Or the best bet would be some wideband O2 street tuning.

<--- Who has a widebandin his car for this purpose.

 

I have a PFC as well...and it basicall has one setting for the injector pulse in milliseconds. I currently have it set for +50ms with DSM injector.. I arbutrarily tuned it there because the engine seemed to idle the smoothest at that setting...for those who has the PFC, tell me if this is ok...

 

ttt...any others?