injector spacing
Turbo Mini Forums

The conversions I've seen for staged injection tend to have the injectors mounted parallel to each other. Would it cause issues if the second set of injectors were place behind the first set, further along the runner. Or is it advantageous to have them at the same position?

First, how are you injecting, port obviously but what ECU and what injection timing regime ?

I don't think there is a simple answer but with the MS2E siamese code, a comparison between my setup and Graham T shows we need very different injection timings to create the same result and the main physical difference is where the injectors are located relative to the inlet valves and spray pattern of injectors.

As a best guess the differences relate to the angle, both horizontally and vertically, and the spray pattern that determines which valve is favoured but - in your scenario - the transit time between injector and valve.

That is, assuming you want to inject only through an open valve rather than non-siamese engines where you inject on the back of closed valves.

If so, you will certainly get a different transit time for injectors different distances from the valves so the results of staging may be somewhat unpredictable.

Schrödinger's cat - so which one am I ???

Port injection with MS2 siamese code, Rod.

Then I think you will run into problems with the transit time with the injectors that are further away (whether the ones further away are the primary or staged).

Depending on which "value" you choose to bring the staging in you may be able to compensate, ie, if you set staging to be activated by a given RPM you could alter the injection timing tables above the staging RPM setting to still give the correct fuel even with the increased transit time (for the injector further away).

I only use RPM as the most obvious example, you have the choice of others in the siamese code but which best to choose ?

Personally I think it will be a nightmare to get right, a trade off between injector distance (transit times) and injector angle (which valve each favours and that includes wall wetting, not just where they are pointing).

I haven't finished welding up my staged manifold so I just have single (large) injectors on each runner at the moment and they are dead central, as close to horizontal as possible, and very close to the head and AFR distribution is so easy to tune.

My staged manifold (yet to be welded, let alone tested) has the staged ones the same distance from the valves, but, as it isn't finished/tried there is nothing to say if it will be any beter than what you are thinking.

Schrödinger's cat - so which one am I ???

Okay, thanks for your reply. Sounds like I'm best off going with parallel mounted injectors then.