EFI gurus What drives injector firing order?

[oldiron]

Just as the title reads. I'm confused as to what drives the injector firing order. Is it the ecu? Is it the wiring itself?
Example; I'm installing EFI on an '86 5.0 from a mustang, I have a Ron Francis MG80 SD non-ho sequential harness. If ecu drives the inj. order to match firing order I need an ecu from an 86-88 HO mustang..correct? I spoke with tech support at Ron Francis and am more confused than before. They suggested moving the wiring at the telorvek panel....Wouldn't doing this lead to a 25% lean 25%rich condition between bank 1 and bank2?
If the ecu determines inj. firing order couldn't you use the ho ecu for ho applications and the non-ho for non-ho applications?
Please bear with me as I learn this stuff, the learning curve is pretty steep.
Greg

 

[SevenT]

Injector firing

oldiron,

Injector Firing Order

Firing order does not effect spark at the plugs because that is still determined by what order you put the plug wires on the distributor cap. But if you have a sequential fire fuel injection computer, then the computer program opens the injectors in the same order as the camshaft timing.

taken from: http://www.fuelinjectedford.com/page92.html

1984 – 1990 EFI Car Computers

These computers are acceptable but are not as flexible as other choices. Ford was still learning about fuel injection during these years. Most of these computers have oddball features like inferred mileage sensors and dual EGR solenoids. These computers are Speed Density controlled, which limits their capabilities in stock form.

These come in 2 different “flavors.” There was a “Base” version that used the old firing order (1-5-4-2-6-3-7-8) and 14lb/hr injectors; and a “High Output” (HO) version that used the HO firing order (1-3-7-2-6-5-4-8) and larger 19lb/hr injectors. These computers will run the opposite firing order, but your idle will be a little rough. Engines built to be controlled with one of these computers need to be very close to stock.

The most desirable computer from these years is the Mustang’s DA1. The DA1 can be mildly reprogrammed with an add-on chip, but the speed density still can’t handle large cam profiles.

Taken from: 'Inject Your Horse' in Bronco Driver

Good luck,

SevenT

 

[oldiron]

Thanks sevenT
I read that article, plus about 20 others. I know that spark firing order is a product of how you choose to route the wires themselves. What I'm trying to figure out is the injector firing specifically. I've even read a couple of articles that would lead one to believe that the pip sensor in the distributor defines the inj. firing sequence. But I can't find a definitive answer yet.
Greg

 

[needsmoarturbo]

I studied the wire harness pin out between a 87 crown vic and 89 mustang long ago. If memory serves the injectors come off the same pins on the ECU connector, so I would assume the ECU itself dictates the injector firing order. I could be off on this it was a long time ago I studied it..

 

[Broncobowsher]

The ECU is programmed for the firing order. It knows cylinders 1-4 are on the right bank and matched to that O2 (when twin O2 are used) and 5-8 are on left bank. Cylinder numbers always go to the same on the ECM. The code just written for which injector goes next.

I don't know if the EEC-IV is advanced enough, but some ECMs would vary the timing of the pulse. At some times a shot on the back of a hot closed intake valve to better vaporize the fuel, or a shot while the intake is open and taking an air charge. And even when in that intake charge to put the shot of fuel based on flow modeling. But considering the EEV-IV was the first generation of port injection I doubt they got anywhere near that advanced.

 

[oldiron]

I studied the wire harness pin out between a 87 crown vic and 89 mustang long ago. If memory serves the injectors come off the same pins on the ECU connector, so I would assume the ECU itself dictates the injector firing order. I could be off on this it was a long time ago I studied it..

I did the exact same thing, and from what I've learned you're correct, all the pins are the same and control the same inj. at different times. The only way I can see that would work is if the ecu controlled the sequence.
Greg

 

[oldiron]

Just finished chatting with FRPP. They're telling me that the injector firing sequence is a product of the programming in the ecu. I'm gonna take their word for it and move along. i.e. no re-wiring.;D
Greg

 

[BroncoChicken]

You want the ECU to match the cam in your engine. You can move wires around or you can probably send EFI guy your ECU and have him change the firing order. It will idle better than if you leave the 4 cylinders mismatched.

 

[Viperwolf1]

You want the ECU to match the cam in your engine. You can move wires around or you can probably send EFI guy your ECU and have him change the firing order. It will idle better than if you leave the 4 cylinders mismatched.

It's not as simple as it seems to just move injector wires. Remember the O2 sensors are also timed to sense at specific points in the firing order which will be all screwy if you're firing an injector on the wrong bank because you moved the wires. There is a way to do it with just wiring but it is really complicated and you end up with a unique firing order that doesn't start with 1. Just have it programmed in and be like the rest of the injected world.

 

[oldiron]

I'm gonna use the da1 ecm to match the '86 ho engine I have. My confusion was with the harness itself. It's called a non-ho harness, but with the correct ecm on the correct engine, it should run the ho firing order just fine.
Greg

 

[Timmy390]

A non H.O. harness will be batch fire vs. sequential I bet.

Tim

 

[oldiron]

Its sequential.

 

[Broncobowsher]

A non H.O. harness will be batch fire vs. sequential I bet.

Tim

Truck will batch, car will sequence.

 

[Timmy390]

Was just reading over on a Stang site that was the difference between ho and non ho harnesses. Bad thread I guess.

I'll shut up now:-[

Tim

 

[DirtDonk]

The PIP only sends out one signal per rotation of the distributor, so it's not going to be telling 8 cylinders when to fire. Other than insofar as the computer uses it to help make that determination correctly.

As the others said and you confirmed with FRPP, that bit of magic is done in the computer. Being basically a variation on a cam position sensor (CPS), would be my way to describe it.
I think the old experts used to get bent out of shape when you equate it to a CPS for some reason, but it's still there to tell the computer where in the rotation the engine's distributor, crankshaft and camshaft are.

Paul

 

[Broncobowsher]

The PIP only sends out one signal per rotation of the distributor, so it's not going to be telling 8 cylinders when to fire. Other than insofar as the computer uses it to help make that determination correctly.

As the others said and you confirmed with FRPP, that bit of magic is done in the computer. Being basically a variation on a cam position sensor (CPS), would be my way to describe it.
I think the old experts used to get bent out of shape when you equate it to a CPS for some reason, but it's still there to tell the computer where in the rotation the engine's distributor, crankshaft and camshaft are.

Paul

But the PIP isn't always the same. On car distributors with sequential EFI it has signature PIP. One of the windows in the wheel is bigger. With a smaller tab to match. The edge that triggers is still evenly spaced. Once the engine starts the computer uses this signature to set the #1 cylinder.

 

[DirtDonk]

Interesting. Thanks for the info. I thought they were all the same with that one different window.

Paul

 

[73azbronco]

Real good book called ford fuel injection and engine electronic control. Can be had for $20, but when I was buying one they went for over $100 back when 5.0 swaps were big deals. Worth the price of admission to learn all the details.

 

[oldiron]

Well I just got an interesting phone call from FRPP's tech line. They wanted to verify what I was doing, and what I was using to make it happen. And they 100% verified that the ecu drives injector firing sequence. They also confirmed that the MG80 from Ron Francis could be used on HO or non HO engines, just match the cam firing order to the appropriate ecu and it'll work perfectly.
SevenT is correct.
Greg