EFI And 302/HO Firing order

[Toddml]

I am getting ready to do the MAF EFI Swap. Stock 302 with 15426378 firing order. Computer is from a mustang with the HO 13726548 firing order. I have read that it is not much of an issue with the old firing order. Will it work?

 

[Viperwolf1]

Absolutely. Keep spark plug firing order the same as the cam.

 

[Toddml]

So I just hook everything up and as it is now. Stock 302 with 1975 firing order? From what I have read the articles mention to not change the spark plugs around or any of the injectors.

If the cam is set for the old firing order and the computer is designed for the HO firing order, how does the engine still run? Any insight would be great.

 

[Toddml]

Absolutely. Keep spark plug firing order the same as the cam.

So I just hook everything up and as it is now. Stock 302 with 1975 firing order? From what I have read the articles mention to not change the spark plugs around or any of the injectors.

If the cam is set for the old firing order and the computer is designed for the HO firing order, how does the engine still run? Any insight would be great.

 

[Viperwolf1]

Computer doesn't care or even know anything about the ignition firing order. It only controls the injector firing order. You'll have 4 of 8 injectors firing at a less efficient time in the valve cycle but it will run fine. Ford made millions of motors that fired all the injectors at the same time and they work ok.

 

[Toddml]

Computer doesn't care or even know anything about the ignition firing order. It only controls the injector firing order. You'll have 4 of 8 injectors firing at a less efficient time in the valve cycle but it will run fine. Ford made millions of motors that fired all the injectors at the same time and they work ok.

So if I understand it, the computer will fire the injectors at the new firing order, which I assume then fuel will just sit in that cylinder a little longer before it gets any spark? And by being a little less efficient you may loose some fuel through an open valve due to the firing order being different? Makes sense, most of the comments made is that the idle is a little rough, which would be the case, but as the engine RPM increases this timing gets much closer and in turn rough running goes away? Plan to do a rebuild and at that time will go to the new firing order, for now just want to get the system in and all of the bugs worked out.

 

[Viperwolf1]

The fuel mist will hang in the intake port until the intake valve opens. Not really much different than fuel delivery from a carb. I don't think you'll even notice any roughness.

 

[Toddml]

The fuel mist will hang in the intake port until the intake valve opens. Not really much different than fuel delivery from a carb. I don't think you'll even notice any roughness.

Thanks Viperwolf. I can't wait to get the EFI system in. It has been fun so far reasearching and gathering up all of parts.

 

[brianstrange]

You can rearrange the injector discharge in order to meet you cam firing order by swapping the pins in the ecu. There is some talk that this can cause 02 sensors to improperly read the exhaust, and I'm not sure which route is better.

 

[Toddml]

You can rearrange the injector discharge in order to meet you cam firing order by swapping the pins in the ecu. There is some talk that this can cause 02 sensors to improperly read the exhaust, and I'm not sure which route is better.

That is what I have read. Is changing the injector firing order makes for bigger problems than a slight rough idle. I think I will run it as is. I plan to upgrade the motor soon anyway, just want to get the EFI installed and working now, that way when I do the rebuild there will be less to deal with.

 

[Viperwolf1]

You can rearrange the injector discharge in order to meet you cam firing order by swapping the pins in the ecu. There is some talk that this can cause 02 sensors to improperly read the exhaust, and I'm not sure which route is better.

You cannot fix it by just swapping injector firing order. That will cause problems with the O2 sensors. There is a way of changing the injector order and the cylinder number configuration to make the O2 sensors happy but it just isn't worth the effort. There's a thread on here somewhere. You'll end up with an engine with a strange cylinder number configuration that will cause confusion to everyone that works on it until it is dead. Either run it as is, change the cam, or re-program the ECM. Chances are you'll never be able to tell the difference.

 

[Toddml]

You cannot fix it by just swapping injector firing order. That will cause problems with the O2 sensors. There is a way of changing the injector order and the cylinder number configuration to make the O2 sensors happy but it just isn't worth the effort. There's a thread on here somewhere. You'll end up with an engine with a strange cylinder number configuration that will cause confusion to everyone that works on it until it is dead. Either run it as is, change the cam, or re-program the ECM. Chances are you'll never be able to tell the difference.

Thanks, that is the plan to run it as is.

 

[brianstrange]

You cannot fix it by just swapping injector firing order. That will cause problems with the O2 sensors. There is a way of changing the injector order and the cylinder number configuration to make the O2 sensors happy but it just isn't worth the effort. There's a thread on here somewhere. You'll end up with an engine with a strange cylinder number configuration that will cause confusion to everyone that works on it until it is dead. Either run it as is, change the cam, or re-program the ECM. Chances are you'll never be able to tell the difference.

Considering that Bank fire worked fine and was equal to having one cylinder per bank/cycle timed properly, and three out, .....having two cylinders timed, and two out , per bank is no big deal......this makes a lot of sense as long as the fuel discharge timing is the same. I have heard that the sequential delivery time was different, but not from a reliable source. It would be nice to somehow get that data...

 

[jw0747]

here's what you need to do. leave everything on your stock engine as is and just add your efi. mine was done this way and you'll notice nothing different and there'll be no rough idle. very simple. been running like this for 4+ yrs now.