how does the MS know which injector to fire?

[Jecsd1]

I am wanting to run a MS with a port injection setup on a Ford 351W. My question is if the MS only sees ignition events how does it distinguish cylinder or even bank? I'm thinking I will need a crank sensor/wheel. Is this correct? I will be using the MS only for fuel. I already have the MSD dizzy and 6A-L. The way I am thinking, w/o a crank sensor I can only run it in batch injector mode. Any suggestions?

[trakkies]

Do a search here on sequential injection.

[turbo355]

Batch fired injection dosent need to know witch side to fire first , it fires the injectors as soon as it sees a tach input either all at once or alternating bank to bank.
Now for sequential it needs more than just a simple tach signal to fire the injectors.
Most likely batch fire will be more than adequate for your needs unless you need per cylinder fuel trim and are shooting for ultimate HP.
I would suggest if your just getting started in tuning EFI to start with batch fired injection and once your comfortable with that, then look into sequential if your application requires it.

( sequential dosent necessarily mean you will make more HP, mostly your low end fueling will improve but if your motor requires certain cylinders to be trimmed to match all cylinders EGT's and AFR's then sequential will be work nicely)

[Matt Cramer]

( sequential dosent necessarily mean you will make more HP, mostly your low end fueling will improve but if your motor requires certain cylinders to be trimmed to match all cylinders EGT's and AFR's then sequential will be work nicely)

Yes, most of the improvements we've seen with sequential have been at idle or at low RPM and part throttle. Horsepower is generally unchanged.

[Jecsd1]

Thanks for the responces. If the MS is injecting one bank at a time how can it know which bank to inject?

The way I'm thinking, Doesn't the MS need to know which cylinder is firing in order to inject the correct bank? What I mean is the firing order of a 351W is 1-3-7-2-6-5-4-8. If is injects bank 1 (1,3,5,7) first then the first ignition event will be injected at the correct time. Then on the next ignition event the MS injects bank 2 (2,4,6,8) but cylinder 3 fires after cylinder 1 so the MS will inject bank 2 when bank 1 is firing again. Then they go back and forth and like 4 out of 8 ignition events do not receive injection pulses.

Is this making any sense?? I'm just having trouble understanding how the MS can fire one bank at a time if it doesn't know which bank needs injection per a given spark event.

Thanks in advance for any clarification you can provide. I am really into making the MS work on my hotrod project I just want to understand it first.

Jason

[turbo355]

I understand what your saying if you turn the motor off then start it back up it may not be firing the injector banks at the same time as it was the last time it was running.

Well thats the draw back of batch fired injection you not going to fire the injection on the actual firing of the cylinder you will be firing either 4 at a time or all 8 at once.

MS first looks for the tach signal, once it sees the signal it fires injector A first, then injector B second, so if you hook one bank of injectors to inj.A, then the other to inj.B ,this is as good as your going to get, your motor is not going to be too picky about when it fires the fuel into the port the valve will control when it gets into the cylinder.

Now you can wire up your injectors like this, on one injector bank wire cylinder 1,7,6,4 and the other bank 3,2,5,8 this is how you would wire up a wasted spark setup this might help some with the idle fueling but most likely it wont make a huge difference, i have wired small block chevys by just hooking all 4 injectors on one side to a driver, and the other 4 injectors to the other driver with no ill effects and this is with 42lb injectors with a MS1.

Dont worry about the actual time it injects the fuel into the port, unless you have HUGE injectors that make your idle quality horrible, or you need individual cylinder trim you wont need to worry about the injection time.

[Jecsd1]

I guess that makes sense.

I know almost all cars now are sequential but where there any factory vehicles in the past that batch fired in this manner? Do new sequential systems spray into an open valve or just before the valve opens?

The way I figure it each injector will have 3 pulses worth or fuel waiting to enter the cylinder when intake opens. The more I think of it that makes perfect sense. Thats exactly what a carburetor does. It is spraying fuel into the manifold and the cylinders that use the available fuel are the ones that happen to be on intake stroke and for every other cylinder they are just "collecting" fuel and waiting to intake. right?

[turbo355]

I guess that makes sense.

I know almost all cars now are sequential but where there any factory vehicles in the past that batch fired in this manner? Do new sequential systems spray into an open valve or just before the valve opens?

The way I figure it each injector will have 3 pulses worth or fuel waiting to enter the cylinder when intake opens. The more I think of it that makes perfect sense. Thats exactly what a carburetor does. It is spraying fuel into the manifold and the cylinders that use the available fuel are the ones that happen to be on intake stroke and for every other cylinder they are just "collecting" fuel and waiting to intake. right?

Yes most all new cars are sequential to meet emissions standards now days, and it helps some with fuel mileage, plenty of cars in the past have been batch fire, Mustangs from the 90's and ford trucks from the 90's were all batch fire, tons more were batch fire till the mid to late 90's . Usually they will fire before it opens but you have the option to time the squirt to where you want.

Yes you will have fuel waiting on the valve face to enter the cylinder, this helps cool the intake valve before it enters the cylinder thats why you will see coking on high millage motors, the hot valve will vaporize the fuel and carbonize it on the valve , it works like a carburetor only the FI injects the fuel into the port helping to atomize it better than a carb in most cases.

[Jecsd1]

very helpful! thanks for the info

[PSIG]

I would suggest wiring your injector banks 1-4-6-7 and 2-3-5-8 as Ford, and 1-4-6-7 and 2-3-5-8 as most GM and Mopar did with obviously good success. Note that the layout is the same for all the engines when you take cylinder numbering into account.

David

[Jecsd1]

David,
Thanks for the input. What effect does this have on the engine versus wiring up each bank? Does firing order need to be considered?

[trakkies]

David,
Thanks for the input. What effect does this have on the engine versus wiring up each bank? Does firing order need to be considered?

I'm quite interested in this too. I've just connected my RV8 as two banks - left and right. I'm fairly certain this is how the factory setup was with the original injection. But I've got to remove the loom for some mods in the near future so could easily alter it then.