The two different firing orders questions

[DSGcoupe]

Originally Posted by Woodz428

As has already been posted, it was indeed main bearing loading that Ford was re-distributing. I would have to look at the early order, but think it had to do with not having 2 firing pulses (one after another) on the same main.

I know this is an old thread and I am newer to this forum, but not to the automotive world. I am curious about the theory behind the above quote. When looking at the two firing orders, it appears they just moved the load to the rear two cylinders instead of the front two (front crankpin journals to the rear crankpin journals)

Old FO= 1-5-4-2-6-3-7-8
H.O. FO= 1-3-7-2-6-5-4-8

this leads me to believe that it was more of a bean counter move to save on production costs.

(I will sit back with my bucket of popcorn now. )

[eschaider]

He's a little more fodder for the fire. This is a listing of all the possible firing orders for the Ford family of engines. Out of the nine possibilities (that includes the Coyote flat crank) only four have ever been attempted in production.



It is interesting that the original Flat Head firing order was revived for the cross plane crank equipped Coyote's.

[Dumpling]

I believe that your list of possible firing orders may be incomplete with regards to Windsors.

I bought an EPEC system from SVO. This was a factory EFI system that was user-modifiable for Windsors. I had a choice if firing orders. As I was planning on using it on an FE, I picked the FE's firing order.

Also, has cylinder numbering been standardized between makes? I always thought that made Chevrolet and Ford SB's the same.

[eschaider]

It is possible the original author missed assigning a particular firing order to a particular engine style but the total number of available possible firing orders for Ford is accurate.

While I am unfamiliar with the particular EPEC system you purchased from Ford, virtually every aftermarket system will allow you to specify the firing order of your choice. The only caveat is that you need to have a cam ground to support the firing order and in the case of flat plane crankshafts you also need to have the correct crankshaft.

The most commonly used flat plane crankshaft is both end throws up and both center throws down. However, just to keep us on our toes there is also a up-down-up-down version of the crank that has yet another set of possible firing orders.

You want to achieve two broad goals with your firing order selection. The first is not to produce an intake draw where two adjacent cylinders have sequential charging draws from the intake manifold. In general after the first cylinder has drawn in its charge, the atmosphere in the intake manifold is rarefied and the second cylinder is cheated out of a full intake charge.

To avoid the intake charge cheating effect, you want adjacent firing and therefor charging cylinders to be as physically distant in the intake manifold as possible. You also want to choose firing orders that mitigate, to the extent possible crankshaft oscillations from adjacent power pulses. The more you wind up, then unwind and subsequently wind up your crankshaft again, the more work your crank damper needs to do and the shorter your crankshaft life will be.

Chevrolet and Chrysler frequently use a 18436572 firing order and number the cylinders 1,3,5,7 front to back on the driverside bank and 2,4,6,8 on the passenger side. The driverside cylinder bank always leads the passenger side cylinder bank. On Fords the numbering is 1,2,3,4 front to back on the passenger side bank and 5,6,7,8 down the driverside bank with the passenger side bank always leading the driverside bank.

The Pontiac and Oldsmobile cylinder placement and firing order data mimics the Chrysler / Chevrolet cylinder numbering, placement and firing order. The 215 inch aluminum turbocharged V8 that Olds used in their Turbo Coupes also used the same cylinder placement and firing order. The ever-popular Buick Nail Head V8's from the fifties used a very unique firing order and an equally unique cylinder numbering convention. The firing order was 1,2,7,8,4,5,6,3 and the cylinder numbering was flip flopped from the Chrysler / Chevrolet model with cylinders 1,3,5,7 front to back on the passenger side and cylinders 2,4,6,8 on the driverside. They also lead with the passenger side cylinder bank like Ford does.

[eschaider]

Duplicate

[Dumpling]

Originally Posted by eschaider

...

While I am unfamiliar with the particular EPEC system you purchased from Ford, virtually every aftermarket system will allow you to specify the firing order of your choice. The only caveat is that you need to have a cam ground to support the firing order and in the case of flat plane crankshafts you also need to have the correct crankshaft.
...

EPEC kit includes an A9P ECM and control software....
.

[eschaider]

The picture is nice but it doesn't say anything about the EPEC system, other than it is for a '88-'93 Mustang.

I did look through some old Ford strategy file documentation that I have and the generation of ECU you have there still has a number of tuning metrics with hard stops that will force scaling if you attempt to exceed those hard stops that Ford built in.

For n/a engines of about the same or similar displacement to the engine this was originally designed for, you would likely be OK for small improvements in torque and power. For significant power increases the scaling required for mass air flow calculations, injector sizing and a number of other metrics can distort the engine load metric which the ECU uses for pulse width calculations. The distortion becomes progressively more problematic the higher you go in the displacement or power domains.

Perhaps the most significant challenges with this generation of ECU are the lack of documentation from Ford, the absence of engine failure protections, traction control, launch control metrics etc. Very significantly the silicon that was used to power the ECU back then was typically 16 bit technology that ran at clock speeds around 10 Mhz. These ECU's were a significant step up from carbs but fall way short of what is commercially available today as a proletariat over the counter sale.

If you compare that generation of ECU to personal computers it is the equivalent of an old 4Mhz 8 bit CPM based PC compared to a modern symmetric multi-processor 3 GHz 64 bit Windows or Mac OSX based PC.

p.s. My words sound a bit harsh and they are not intended to be. The A9 ECU (A9L & A9P) were the highest performing mass air based ECU's Ford manufactured for the 88-93 5.0 Fox bodied Mustangs. In their day they were quite impressive systems. As time and technology marched on several things happened. Ford quit manufacturing new units and began selling refurb units taken in warranty exchanges. The aftermarket began to offer progressively more sophisticated and faster design ECU's based on modern silicon that ran at higher clock speeds, and used more sophisticated performance oriented tuning software and user interfaces. Eventually even A9x refurb units became scarce and the supply / demand dynamic caused any existing units to rapidly rise in price.

More significantly the commercially available over the counter aftermarket alternatives began to proliferate with more features, capabilities, performance and importantly documentation to adapt them to your particular ride. The A9x series of ECU's slowly began the fading into history process, partly because of availability, performance, adaptability and perhaps the most significant better, lower priced aftermarket alternatives.

[Dumpling]

Shown in the picture is a custom-calibrated mass airflow sensor. You provide cubic inches and other parameters for the engine the ECM is to be controlling and it adjusts the readings sent from the mass airflow sensor to the control unit....

[incoming]

This makes my head hurt

[eschaider]

Originally Posted by Dumpling

Shown in the picture is a custom-calibrated mass airflow sensor. You provide cubic inches and other parameters for the engine the ECM is to be controlling and it adjusts the readings sent from the mass airflow sensor to the control unit....

And your point is ...

[Dumpling]

Originally Posted by eschaider

...
I did look through some old Ford strategy file documentation that I have and the generation of ECU you have there still has a number of tuning metrics with hard stops that will force scaling if you attempt to exceed those hard stops that Ford built in.

For n/a engines of about the same or similar displacement to the engine this was originally designed for, you would likely be OK for small improvements in torque and power. For significant power increases the scaling required for mass air flow calculations, injector sizing and a number of other metrics can distort the engine load metric which the ECU uses for pulse width calculations. The distortion becomes progressively more problematic the higher you go in the displacement or power domains.

...

And your point is...

I actually read things before spewing non-sequitur replies...

[eschaider]

Originally Posted by Dumpling

I actually read things before spewing non-sequitur replies...

I think you are becoming defensive without reason. You are not being attacked. While you obviously have an ECU, that while dating back to first generation technologies, is from all appearances none the less serving you quite well. That is excellent.

Your knowledge of Ford ECUs, ECU strategies, what they support and what they allow appears somewhat limited but that does not necessarily impact the utility you realize from your ECU choice. It does however misinform those that might be reading these posts hoping to pick up knowledge to help them in their own efforts.

Because the 03/04 Cobra’s used an Eaton with a 1.9L swept volume pulleyed to supply 8psi of boost, Ford built the 03/04 EEC-V Cobra processor with a hard stop in their MAF transfer function at 64 pounds of air per minute. In round numbers it takes 10 pounds of air per minute to produce 100 HP. A MAF transfer function that can provide a 64 lb/min upper limit would handle a 640 FWHP engine. The general opinion in Ford Engineering, at the time, was that this was a robust and generous allocation.

Once the cars got into the hands of enthusiasts and larger blowers from KB and Whipple began to appear on the engines, the engines quickly eclipsed what Ford originally believed to be a very generous hard stop in their mass air flow measurement code. An early aftermarket fix was the use of a switchable resistor pack between the MAF and the CPU to modify the voltage the ECU saw so that it could be ‘fit’ into the preordained space Ford Engineering provided.

That worked, with some loss in resolution, as long as the overage was relatively small. Because substantially more air, was available with the aftermarket screw blowers, the MAF transfer function ultimately needed to be scaled to stay within the hard coded limits Ford engineering provided.rather than modifying the MAF voltage output with a switchable resistor pack.

When Ford built the Cobra version of the EEC-V ECU they built upon the success they had realized with their previous generation EEC-IV ECU’s. By setting the MAF Transfer function ceiling at 64 pounds of air per minute they believed they were safely above any air demands their customer’s engines might see. In retrospect we now know they were not. The air flow limits on the EEC-IV ECU’s like you are using were lower compared to the EEC-V supercharged Cobra limits — which, as it turned out, were themselves restrictive.

The EEC-IV processor and piggyback EPEC you are running will use either an A9L or an A9P ECU in the EEC-IV. The last strategy Ford released for the A9L ECU’s was the GUF-B strategy which was used in 5 speed versions of the car. If the car came with an automatic, the ECU was labeled an A9P and was delivered with a GUF-1 strategy supporting the automatic version of the vehicle. Performance fans typically opted for the GUF-B strategy unless they used an auto, in which case they would use the GUF-1 strategy.

Irrespective of strategy used, the maximum air flow OEM software can recognize is below the 64 pounds per minute that the supercharged 03/04 Cobra strategies supported. The fix for this is to scale the MAF xfer function and also a number of additional parameters, including injector flow stats. If you do not do this then you will have an unpleasantly tuned engine. Additionally if you repeatedly bang into the MAF transfer curve’s ceiling flow rate, because you did not scale the MAF xfer function, then you will lean out the engine and eventually do damage to it even though it is not supercharged.

Your implementation apparently does not do this which means the ECU + EPEC package at least accommodates your power level fairly well. The Ford supplied EPEC MAF transfer software package most likely scales the original MAF transfer function and the associated functions it interacts with. Just like on the later EEC-V ECU's when you scale this metric you experience a reduced resolution in the MAF transfer function, and potential load aberrations depending on the amount of scaling required. The load aberrations directly impact the fidelity of the fueling model at any given point in the engine's operating range.

For guys who are only now electing to transition to EFI they would be much better served with an aftermarket package than any of the packages Ford has offered over the years. They are faster, have more tuning features, more capabilities, do not require scaling internal fueling metrics and definitely provide more engine save routines.

And by the way this whole discussion is off topic for this thread.

[Dumpling]

The EPEC was an UNLOCKED version of Ford's mass air EFI system.
You seem to be locked into some idea that there are built-in limits to it. Think Tweezer or Quarterhorse...

[eschaider]

Originally Posted by eschaider

... Your knowledge of Ford ECUs, ECU strategies, what they support and what they allow appears somewhat limited but that does not necessarily impact the utility you realize from your ECU choice. It does however misinform those that might be reading these posts hoping to pick up knowledge to help them in their own efforts ...

Originally Posted by Dumpling

The EPEC was an UNLOCKED version of Ford's mass air EFI system. You seem to be locked into some idea that there are built-in limits to it. Think Tweezer or Quarterhorse...

I have owned and tuned both Tweezer and Quarterhorse enhanced EEC systems. You are simply uninformed about the way the add on units interact with the base system processor. Your assertion that add-on electronics can change the basic strategy limits engineered in by Ford is incorrect. Add on processors simply do not change the basic architecture of the OEM strategy code. Their primary benefit is that they allow you access to the features in a less painful manner and in the case of Quarterhorse virtually everything in the OEM ECU, in a real time fashion as the engine is running.

That said, this whole discussion is still off topic for this thread and adds nothing to the OP's original discussion about firing order(s). If you want to pursue this sort of topic why not start a thread of your own for discussion purposes and stop misusing the OP's firing order thread?

[bubbagump]

Original post:
1) Is there any differance in performance, all else kept the same?

2) Any differance in the sound of the engine?

3) Why did Ford change the firing order? Did they ever say why they did this?

I'm unaware of answer to question 1.
If there is a difference in sound it is subtle.

#3. Ford changed the firing order when they brought out the 351's both Windsor and Cleveland. The change was to address the earlier firing order, 15426378 the OVERLOADED the front main bearing.

[msinc]

Over the years I have heard and read so many different answers to the two firing order question of why? that I either quit caring or just no longer give a GD....I like Ford and always will, but they have, over the years, done some strange things that are not worth trying to explain....like the fact that every 351 Windsor block was cast with the bosses to accept or enable the use of four bolt mains. Yet Ford never made one with them. The bosses are cast straight like a 4 bolt Cleveland, yet most aftermarket caps are splayed....again, go figure. Who makes these "decisions"??? if we can call them that....

[CompClassics]

The 351W firing order is less stressful on the engine block and crank.