First of all, sorry if this topic already exists, I spent a few minutes searching and couldn't find anything related.



I am building up an s5 using megasquirt to control everything. I do not have the original ECU, I got the engine for free.

does the s5 (or any 13b for that matter) do sequential or batch fuel injection? i know there is virtually no time for the mixture to dwell in the runners due to the nature of the intake cycle of the rotary. in either case of batch or sequential, the second question is: is there one injector pulse (per injector) per intake stroke, or are there several that fire during this time? Which leads to the question: is it required that one "time" the injection event to correspond to the appropriate rotor position, or does one merely set up the duty cycle at any given rpm/load and ignore the "start time" of the injection event? This configuration makes sense at low rpms, but at high rpms it seems a little fishy. for example, (if my calculations are correct) one rotor will have an intake stroke begin every 0.0075 seconds at 8000 rpm. this means that you have to have AT LEAST 1 pulse of fuel during this time. this means that if you only have one pulse per intake stroke, the time from the beginning of one pulse to the beginning of the next would have to be either EXACTLY 0.0075 seconds (to get one pulse per intake), or at least double that fast (at half the duty cycle). anything else and you could end up with an intake stroke with no fuel in it, right? and some intake strokes might have double the required fuel in them, right? for this reason it seems that one does not "time" the injection events, but rather makes sure the frequency is much higher than your intake frequency at a given rpm, and then controls the amount of fuel with the duty cycle.



i am confused, and any help would be much appreciated

thanks in advance.

the s4 and s5 ecu's are a little different, and a little more advanced, than most 80's computers.



the mazda ecu runs sequential injection on the primary 2 injectors, up until the "staging point" which is kinda odd, or about 3500-3800rpm, at which point they go batch fired.



the injectors are phased to the engine, although playing with it on a stock port engine, and aftermarket ecu, it doesnt seem to matter much.



the injector timing info is in the "1986 training manual" section 4, page 4-36



less than 3000rpm fuel injection occurs at 95btdc

more than 5000rpm fuel injection occurs at 185btdc



between 3-5k rpms its scaled between the two

ok, i'll take a look at that manual...

for thoes interested this manual can be found here:

RX7 and Miata manuals