If you're thinking about boosting your MX-5 NA 1.6 115 HP, there's one thing you need to know – the stock injector setup might give you some trouble.
Why?
In this engine, the injectors run in a semi-sequential setup, meaning they are paired: 1-3 and 2-4. When one injector fires, the other in the pair fires as well. This means that for a given pulse width, paired injectors deliver twice as much fuel as in a fully sequential system.
And here’s the catch – because paired injectors deliver fuel in double doses, the required injection time in semi-sequential mode has to be shorter than in a sequential setup. When you install higher-flow injectors (which is necessary for turbocharging), the required pulse width becomes so short that the injectors may struggle to operate consistently, especially at low loads (idling, cruising).
The fix?
Easy - rewire injectors 3 and 4 to separate outputs. If you're using my Speeduino PnP NA, you - apart of rewiring which is necessary - just need to switch the firing mode.
Stock injector wiring in the MX-5 NA 1.6 115 HP:
- Pin 2U - injector 1 and 3
- Pin 2V - injector 2 and 4
Corrected wiring (same as NA 1.6 90 HP & 1.8 130 HP models):
- Pin 2U - injector 1
- Pin 2V - injector 2
- Pin 2Y - injector 3
- Pin 2Z - injector 4
How to do it?
For injectors 3 and 4, simply move the signal wire from the ECU (originally coming from pin 2U or 2V) to the new dedicated output. The 12V power wire stays unchanged.
A simple mod that can save your turbo project from low-RPM headaches! 🚀
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It would seem that an alternative way to extend the injector opening time is to change the "Squirts per engine cycle" z 2 na 1. Wtedy wtryskiwacze pracują dwa razy rzadziej, więc wymagany czas otwarcia dla dostarczenia danej ilości paliwa będzie dłuższy. Jednak nie wydaje się by silnik mógł pracować równo w takim przypadku. Średnia ilość paliwa w czasie będzie prawidłowa ale chwilowa nie - kolejne cykle pracy będą miały naprzemiennie za ubogo-za bogato. Nie wydaje się to dobrym pomysłem, zwłaszcza na doładowaniu. Zdecydowanie warto używać sekwencyjnego sterowania wtryskiwaczami jeśli jest to możliwe