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Is Injector latency affected by the use of resistors?

EFI Tuning Fundamentals

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Hi,

Is the injector dead times affected by the use of resistors?

I´m asking because I´m about to tune a car with some peak and hold injectors with an early vipec v44, which require resistors to limit the current.

the car is running 1680cc lucas injectors.

The short answer is yes, it will be affected. A peak & hold injector is designed to operate with a peak & hold injector drive that can provide a high peak current to quickly open the injector and get fuel flowing - The whole idea behind the peak & hold injector drive is to reduce latency. If we try driving the low impedance peak & hold injector with a saturated injector drive directly, there is insufficient impedance to limit current flow and hence the injector drive can be damaged, hence it's common to use a ballast resistor to control current.

So ultimately if the injector has been characterised with a peak & hold injector drive and then you operate it using a saturated drive and a ballast resistor, it's reasonable to expect that the latency may increase slightly as the injector won't benefit from the high initial opening current. How much the latency is affected is a question I can't answer though - If you had no other data and you've got no way of extracting actual data based on your installation, I'd probably recommend running the published dead time data to start with and accept that there's going to likely be some inaccuracies. The reality is that those injectors are quite an old design and offer quite poor linearity at low pulse widths anyway so your'e going to find they do some odd things at idle/cruise even with perfectly accurate latency data.

Also understand that the latency data can vary depending on the ECU or more specifically the injector drive circuit being used to operate the injectors, so it's quite likely that published data may still not be 100% accurate in your particular ECU.

Not sure if this helps or adds more confusion though?

I have the data, for peak and hold. And I know they are unlinear so I was considering trying to compensate for the unlinear flow using pulse with corrections. But desided not to since the data is not correct for the injectors when using resistors.

Thanks for the reply

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