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Selecting injectors

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Hello guys, I use a CBR 600 rr engine, N/A air intake restricted, for Formula student competition. We use injectors with 179cc/min and we run sequential injection. At high load for example at 12.000 RPM at WOT ,the injection pulse is 6,25 ms , this means that injection last about 450 degrees((12.000/60.000)*6,25*360) of crank rotation. Actually , I am not dealing any problem neither at load nor at high load. But isn't is weird when injection last 450 degrees , at about 2 and a half strokes? Does sequential injection is cancelled during this process? I think that I should change to bigger injectors in order to inject the fuel only during intake stroke or little time before. What do you think?

450 degrees is only 62% of the 720 degree cycle time. You can run injectors up to 85%+ duty cycle without issue normally. Your injection is still running sequentially.

Testing with larger injectors (and lowering the duty cycle) is a good idea, and it allows you to move the injection timing. Be aware than may mean less ability to control the mixture at low duty cycles with short injection times -- it depends on the ECU, injector spray pattern, injector location, etc.

^^^Yep, as they say - "if it ain't broke, don't fix it".

Motorcycle engines are very finely developed and, while the restrictor 'may' affect the top end, you should very carefully consider any changes you make.

You will likely make it harder to get a clean idle if stepping up in size unnecessarily. The reality is with the restrictor you are unlikely to gain any more top end power as you might by mounting injectors well away from the valve and firing only very close to the intake stroke.

You may however wish to consider bumping the throttle stop and running a rotational fuel cut idle to reduce fuel consumption.

Im not sure how much influence the restrictor will have but on highly tuned ITB NA engines there is quite a bit to be gained from getting duty cycle down so that the injection event can be more ideally timed. In some of the touring car engines I have played with it is common practice to use 2 x moderately sized injectors per cyl, staged, and with relatively high fuel press (~100psi), the inj DC at peak power will be about 35%. Peak power will drop by ~5% just by turning off one set.

With FS, one of the biggest problems is actually completing the competition - I do think the time spent may be better applied, at least until the priorities

are taken care off.

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