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fuel main injector pulse width

EFI Tuning Fundamentals

Discussion and questions related to the course EFI Tuning Fundamentals


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Hi so i have watched the whole of the efi fundamentals course. and understand how to calculate everything in the topics including the injector pulse width. however how do I know what I should set my master fuel ms to? and also master fuel trim ? im using link g4 plus and the injections im running are Siemens deka 80lb injectors.

let me add a bit more detail. the engine is a cosworth 4 cylinder yb engine that uses map sensor and IAT sensor to measure air density. should I be using modelled fuel mode or traditional for this set up or does it not mater ? as this will change the way the injectors are set up, as in setting the injector cc etc or the ms ? or am I way other thinking this ?

just trying to work out the best place to start. and aim for the correct setting from the get go. thanks.

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It's not as critical to have this right as you think when you're first starting out your tune. You can adjust it later in order to get good resolution in the fuel table. As a guide I'd suggest you start with the master pulse width around 6-8 ms. There is a webinar that covers this quite nicely here: https://www.hpacademy.com/previous-webinars/011-master-injector-pulsewidth-fuel-table-resolution/

Thanks Andre! I am learning. getting there. next step is your practical course. I think I understand it its just putting all the pieces together and in order. im just trying to build a safe map at the moment so that I can drive the car on the road to the rolling road. which is all motorway driving. so no real load.

also forgot to ask what fuel mode would you advise I use on this vehicle. its running a link g4 monsoon ecu. and I can use modelled fueling or traditional ms based ?

Honestly it's a coin toss and a lot comes down to personal preference. VE based tuning has become a bit of a buzz word and hence a lot of ECU manufacturers feel they need to offer it now. The reality is you can get great results in either mode. If you want to use modelled mode then you will need good data for your injectors though to get the best results. It is nice with a properly tuned VE model that you can change target AFR just by adjusting the AFR target table but in reality once the engine is tuned this isn't something we tend to do so becomes a moot point. Modelled mode does however make flex fuel tuning very simple, provided all your parameters are correct.