when the secondaries kick in what rate do the primary's run at?


I am trying to do some serious fuel caculations here.. but I need to know what % of flow rate the primaries run at once the secondaries have kicked in?

anyone know?

 

The primaries fire sequentially up to 3800rpm, then (if the load is high enough) all four batch fire at half the pulsewidth the primaries were firing at before the changeover.
So say the primaries were running at 70% duty cycle, at 3800rpm all four would then fire at 35%. This means the amount of fuel flowing increases linearly without a dip or jump as the secondaries come in.

 

no ****!!!! didn't know that.

 

NZ, how does that work if you are using a S-AFc to "fool" the computer? does a 5% cut at a rpm range cut it 5% across the board? or just cut the secondaries? I was caculating total CC, minus normal injectors total CC, and creating my percentage, at a typical 5.5 PSI setup .. then I was going to go from there .. just to test my "running too rich" theroy.

total 2200cc Base, 1440+2000 = 3440, subtract and divide that buy the original.

550 and 720 = 23.6% but do a 550 550 720 720 and get 13ish

then do 720 720 1000 1000 with 550 550 550 550
and you need to know % load.

 

An S-AFC alters the airflow meter signal, not the fuel injector signals. So the ECU will just fire the injectors based on the "tricked" airflow signal it's receiving.
Things become tricky with staged injectors of different sizes. With a normal injector set-up if you put in bigger (but identical) injectors you could apply the same correction accross the boord and the car would run as it had before. But with different sized injectors coming in at 3800rpm you need to change that correction at that point.
To get 2 x 720's to perform like 2 x 550's you need to apply a -24% correction below 3800rpm. To get 2 x 720's and 2 x 1000's to perform like 4 x 550's you need to apply a -36% correction above 3800rpm. That should have everything acting like stock. Use those figures as a base and tune from there.

 

Too bad stock ecu's can't handle bigger injectors, because they already have some very nice abilities, batch firing etc.

 

since the safc only modifies the afm signal,wouldnt you only be able to run injectors up to the stock ecu's limit of about 64% no matter what size the are? ive been wondering about this for a while,does anyone know?

 

I've yet to see anybody prove the ECU can't run past this figure, particularly since I've never heard of any other stock ECU having this problem. I think this figure is just what the primary injectors are doing at 3800rpm at stock power levels.

 

I thought that all 4 ran at 50% if the load was high enough for the secondary pair to come on... guess i have been living a lie... i'm going to end it all

 

Actually, batch firing is the "old" way of doing it, and is much simpler. Modern EFI use sequential injection for better idle, lower emissions and more power.

 

Explain how the flow rate works on the '84 and '85 GSL-SE's since they are of a two injector design. Curious as they also are of a 6 port design.

Does the flow rate vary at different RPM levels?

 

They work just like any other EFI engine. They have one injector per rotor just like piston engines have one injector per piston. Remember two those injectors are each much bigger than the four fitted to FC's. The 12A Turbo ran a similar two-injector set-up using even bigger (800cc/min) injectors. These are great drop-in upgrades for modded FC's, as four of them will support over 450hp! It makes no difference since the injectors are mounted in the primary ports just like the primary injectors in the FC. Again, just like any other EFI engine, the ECU controls injector opening to adjust fuel flow according to load and rpm.

 

Interesting thread... I've replaced the stock ECU in my n/a 86 with the Megasquirt kit. This controller has two injector drivers, bank1, bank2. The system can be set to batch fire or alternate fire the two banks. This works well on most efi systems, but not on the rotary as its system is designed for staged injection. I've been experimenting a modified version of the embedded code that allows for two VE maps to be entered, one for each injector bank. Using this method, I can now define the rpm/map combination which will bring the secondaries on-line, just like the stock system.

Question1: In my staged injection setup, the primaries are batch fired. The car seems to run and idle fine. Do other standalone systems typically batch-fire as well? Anyone try to get a batch-fired primary system through an emissions test?

Question2: I've got my setup configured now to feather in the secondary injectors, starting at extremely low pulse widths, and essentially adding to flow of the primaries. Again, what is commonly done with aftermarket ecus on this front? Advantages/disadvantages of 'feathering' secondaries vs Mazdas method?