MSefi.com read only forum (Jan.15,2018)

Hey guys, Just wondering how exactly the duty cycle is calculated? Reason I ask is I was playing with a 2.6L Rodeo today, pretty much stock motor just a mild cam and exhaust and while doing a full power run the injectors went over 100% duty cycle... Reason im confused is as far as I can tell its a stock injection setup with the stock size injectors and I would not have thought the factory use injectors right on their limit?

So im wondering if anything else can effect it? Does changing the number of squirts or injector staging effects this?

Altho the fuel curve on the graph did start to lean out so seems they are indeed too small...

ReaperCustoms wrote:Hey guys, Just wondering how exactly the duty cycle is calculated? Reason I ask is I was playing with a 2.6L Rodeo today, pretty much stock motor just a mild cam and exhaust and while doing a full power run the injectors went over 100% duty cycle... Reason im confused is as far as I can tell its a stock injection setup with the stock size injectors and I would not have thought the factory use injectors right on their limit?

It's the calculated pulse width divided by the available injection time. Usually, anything over 90% will make the injectors stick open.

So im wondering if anything else can effect it? Does changing the number of squirts or injector staging effects this?

Slightly. The more squirts per engine cycle, the more times you have the injector dead time added to the pulse width. 1 / simultaneous and 2 / alternating produce the lowest duty cycles.

Altho the fuel curve on the graph did start to lean out so seems they are indeed too small...

A real possibility.

Turns out the fuel pump was slowly dieing and pressure was progressively dropping until the car would not even start... Fit a new fuel pump and bingo.