Don't be Just Another Failure!

[Doctor Fishtail]

I'm not sure he actually said that. He said that uncontrolled torsional vibrations is what will cause opg to break. The engineer said the oem damper was good for factory rpm and that at 8,000prm, one is exceeding factory limits.

Probably stands to reason though, if one gets an aftermarket damper, the stock opg will be good for more power and rpm as the uncontrolled torsional vibrations should be minimized/eliminated.

On a stock engine, under normal operation, the crankshaft has predictable angular forces and thus torque. Adding abnormal operation (i.e. bigger blower, pedaling the car, on-off traction, 2 step, bouncing off the rev limiter, hole-shots, flat shifting etc.) causes excessive jerk (quick acceleration changes during the pulses) allowing forces to exceed the limitations of the engine components. In the case of the Mod Motor, timing components break, oil pump gears fracture, crank snouts break/crack, crank keys fail, etc.; anything with a mass and angular velocity can be compromised.

Ford engineers designed the oil pump gears to survive under normal operation for as long as possible. They did not design the gears for hi-performance or race engine applications. A stock set of Mod Motor oil pump gears are manufactured from powdered metal, which is quite strong by itself, but it is also very brittle and unable to sustain impacts (instantaneous changes in force).

The solution is to use gears that are constructed from a material that is not as brittle (softer) such as 10xx steel or 4340 steel. These materials are more expensive to manufacture and requires very accurate machining and surface grinding (100 millionths) versus simply pouring powder into a mold. In normal use the Ford gear will last forever as it wears well versus 4340 gears which wear much faster when left unhardened. Notice the words "For as long as possible."

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[foghat]

That, could not be more of an perfect example of cheap quality gears. Why Ford would install such an obviously inferior product is mind boggling. Crank Jerk is the reason they break in the engine. This can happen simply by hitting bumps in the road while under WOT.

The video does not prove the part is inferior or will break under factory conditions.

If anything it does show, as the ford engineer stated, that uncontrolled torsional vibration (which you get enough of when going beyond factory specs) will cause the opg to break.

As the engineer implied, a properly designed (ATI) aftermarket damper should make things safe.

If we are using the floor to mimic uncontrolled torsional vibration and proof that the oem opg is substandard, maybe I'll make a video of me dropping an OPG on a pillow (representing a damper) and when the opg does not break, that should be proof enough that a damper is all one needs.

 

[Dominant1]

Its like this you drop your caseless iphone its gonna crack. Its because its not designed to withstand such things. Same with the stock pump gears. Its not designed to be dropped nor withstand 700 hp. So with the i phone you get a good case if your constantly clumbsy. And you get a billet gears if your upping the hp. If you fall and hit your head in the right way you could be dead. None of us wear helmets where ever we go.

 

[Doctor Fishtail]

The video does not prove the part is inferior or will break under factory conditions.

If anything it does show, as the ford engineer stated, that uncontrolled torsional vibration (which you get enough of when going beyond factory specs) will cause the opg to break.

As the engineer implied, a properly designed (ATI) aftermarket damper should make things safe.

If we are using the floor to mimic uncontrolled torsional vibration and proof that the oem opg is substandard, maybe I'll make a video of me dropping an OPG on a pillow (representing a damper) and when the opg does not break, that should be proof enough that a damper is all one needs.

I did the ATI Super Damper first. Later did the gears. I was on the fence at the time when I did the damper about installing gears. By no means at all did the Ford engineer say that the damper is the fix. He is suggesting it will help the issue at hand.

 

[foghat]

On a stock engine, under normal operation, the crankshaft has predictable angular forces and thus torque. Adding abnormal operation (i.e. bigger blower, pedaling the car, on-off traction, 2 step, bouncing off the rev limiter, hole-shots, flat shifting etc.) causes excessive jerk (quick acceleration changes during the pulses) allowing forces to exceed the limitations of the engine components. In the case of the Mod Motor, timing components break, oil pump gears fracture, crank snouts break/crack, crank keys fail, etc.; anything with a mass and angular velocity can be compromised.

Ford engineers designed the oil pump gears to survive under normal operation for as long as possible. They did not design the gears for hi-performance or race engine applications. A stock set of Mod Motor oil pump gears are manufactured from powdered metal, which is quite strong by itself, but it is also very brittle and unable to sustain impacts (instantaneous changes in force).

The solution is to use gears that are constructed from a material that is not as brittle (softer) such as 10xx steel or 4340 steel. These materials are more expensive to manufacture and requires very accurate machining and surface grinding (100 millionths) versus simply pouring powder into a mold. In normal use the Ford gear will last forever as it wears well versus 4340 gears which wear much faster when left unhardened. Notice the words "For as long as possible."

If you read the engineer's email, he states it is the uncontrolled torsional vibrations that will cause the oem opg to fail. And that once you start exceeding factory limited (supercharger, increase rpm, etc), you are exceeding what the factory damper can dampen.

He pretty much implies that using a quality aftermarket damper will take care of the additional torsional vibrations caused by the aftermarket parts. No uncontrolled torsional vibrations, much less chance the opg will break.

No doubt aftermarket opg is good piece of mind, but based on what the engineer is saying, I suspect the oem damper is the real culprit when it comes to oem opgs breaking.

 

[foghat]

I did the ATI Super Damper first. Later did the gears. I was on the fence at the time when I did the damper about installing gears. By no means at all did the Ford engineer say that the damper is the fix. He is suggesting it will help the issue at hand.

No, he does not explicitly say it, but reread the engineers first two sentences...

And then the rest of the email where pretty much all he talks about is dampers and uncontrolled torsional vibration.

 

[Doctor Fishtail]

If you read the engineer's email, he states it is the uncontrolled torsional vibrations that will cause the oem opg to fail. And that once you start exceeding factory limited (supercharger, increase rpm, etc), you are exceeding what the factory damper can dampen.

He pretty much implies that using a quality aftermarket damper will take care of the additional torsional vibrations caused by the aftermarket parts. No uncontrolled torsional vibrations, much less chance the opg will break.

No doubt aftermarket opg is good piece of mind, but based on what the engineer is saying, I suspect the oem damper is the real culprit when it comes to oem opgs breaking.

The OEM damper is fine. But it has its limitations. Exceeding the limitations makes it useless. I am finding other engineers saying it is from crank jerk. Let me go read it again. Gimme a sec.

 

[mustang1]

On a stock engine, under normal operation, the crankshaft has predictable angular forces and thus torque. Adding abnormal operation (i.e. bigger blower, pedaling the car, on-off traction, 2 step, bouncing off the rev limiter, hole-shots, flat shifting etc.) ...

What's an example of these ?

bigger blower,
pedaling the car,
on-off traction,
2 step,
bouncing off the rev limiter,
hole-shots,
flat shifting
etc.) ...

 

[Doctor Fishtail]

Why Do the Oil Pump Gears Fail?

Every mechanical device is destined to fail with any amount of use; the time to failure though depends on the rate of usage or abuse. One mechanical device that tends to fail on the Ford Mod Motor is the oil pump gear. Granted, the stock gear is perfectly adequate for normal engine operation; the issue is only common when dealing with hi-performance engines. The question we receive time and time again: “Why do the oil pump gears fail?”

How the Oil Pump Gear Works

Oil pump gear operationThe oil pump used on the Ford Mod Motor is a gerotor design with an outer and inner gear setup. When the gears rotate, the intake side separates creating a void between the gears, which creates a vacuum that sucks in the oil. The oil is then moved to the discharge side through the gear motion. On the discharge side, the gears come back together squeezing the oil out. Tight tolerances and rigid design allow it to pump high viscosity liquids (e.g. Oil) at high pressures. In the Mod Motor the oil pump is driven directly by the crankshaft rotation and therefore, subject to the force oscillations of the engine.

The Forces on the Oil Pump Gears

Force

Neither power nor RPM is the culprit as neither equates to the actual forces within the engine while under operation. Force alone only explains part of the issue because torque (force with leverage) aggravates the conditions as the engine torque output increases.

The first component to examine is the engine crankshaft. On the Mod Motor the crankshaft has 4 phases per revolution with peak pulses of force every 90 degrees of crank rotation. Visually this is comparable to the human heart beat with every peak being a pulse (thump, thump, thump, thump). The blower, depending on the model it may have 5 pulses per revolution of peak force. Finally, the oil pump itself has 8 pulses per revolution of peak force. All of these are normally out of phase, but it is possible for them come into phase or close enough to increase the vector components of acceleration and velocity.

Acceleration has a time component and the above pulses are of very short duration (rapid acceleration and declaration). There is also distance (the clearance between gears/crank in this case, which seems small but things are relative) to calculate which, gives velocity and its derivative acceleration. The rapid change in acceleration can be defined as jerk or lurch:

Oil pump gear failures explained

Jerk is an extremely important component in precision mechanical operations, such as the operation of a combustion engine. Ford engineers would have spent considerable time working on reducing the jerk from normal operation (predictable behavior).

Abnormal Operation and Unpredictable Behavior

On a stock engine, under normal operation, the crankshaft has predictable angular forces and thus torque. Adding abnormal operation (i.e. bigger blower, pedaling the car, on-off traction, 2 step, bouncing off the rev limiter, hole-shots, flat shifting etc.) causes excessive jerk (quick acceleration changes during the pulses) allowing forces to exceed the limitations of the engine components. In the case of the Mod Motor, timing components break, oil pump gears fracture, crank snouts break/crack, crank keys fail, etc.; anything with a mass and angular velocity can be compromised.

Ford engineers designed the oil pump gears to survive under normal operation for as long as possible. They did not design the gears for hi-performance or race engine applications. A stock set of Mod Motor oil pump gears are manufactured from powdered metal, which is quite strong by itself, but it is also very brittle and unable to sustain impacts (instantaneous changes in force).

The solution is to use gears that are constructed from a material that is not as brittle (softer) such as 10xx steel or 4340 steel. These materials are more expensive to manufacture and requires very accurate machining and surface grinding (100 millionths) versus simply pouring powder into a mold. In normal use the Ford gear will last forever as it wears well versus 4340 gears which wear much faster when left unhardened.

The Bottom Line

This market is not standard operation; today’s hi-performance applications are pushing the limits of engines more and more. Ford engineers have taken the time to account for what happens during normal operation, but they have no control over owner operation or the conditions created by modifications.

Real World Examples

Crank snout damageThe photo to the right shows a crank snout that has been completely destroyed by hitting the rev limiter. As the engine blew past the soft limiter in the tune, it proceeded to bounce off the hard limiter. This action caused repeated acceleration and deceleration in short intervals (jerk). Since the crankshaft has angular momentum it was compromised by quick changes in force.

 

[Doctor Fishtail]

What's an example of these ?

bigger blower,
pedaling the car,
on-off traction,
2 step,
bouncing off the rev limiter,
hole-shots,
flat shifting
etc.) ...

For me the On and Off traction is a big one at WOT. It creates havoc on everything from the 3:73 gears all the way up through the drivetrain to the crankshaft.

 

[foghat]

Interesting. Seems to be a couple elements at play here then. 'uncontrolled torsional vibrations' and 'jerk'.

 

[Doctor Fishtail]

Interesting. Seems to be a couple elements at play here then. 'uncontrolled torsional vibrations' and 'jerk'.

Yea the vibrations the Super Damper will take care of. The Crank Jerk not so much. For the jerk problem is why I chose to install gears.

 

[MyLilPony]

I thought the OEM OPG would require more than just a drop, even if on concrete. Maybe a throw or a hammer strike to simulate "shock loading".

Anyone have an MMR gear they can test on?

My first concern was whether the OEM OPG was really that fragile. My second concern is what happens if the Chevy / Dodge people see this video. :lol:

The shop had a used mmr gear he dropped a few times, never had an issue. In all honesty I am sure this is their sales pitch. I only brought my car there for the labor but when we got to talking he told me it was a good idea none the less then we did the drop test

Chevy and dogs he people have enough to worry about, like having to drive a Chevy or especially a dodge. My Camaro was a piece of crap the picture here shows how it looked 60% of the time. Matter of fact this is how it looked as it went to the ford dealer to trade in. POS!

 

[mustang1]

For me the On and Off traction is a big one at WOT. It creates havoc on everything from the 3:73 gears all the way up through the drivetrain to the crankshaft.

Same here. Maybe this is less of a concern for those with automatic transmissions.

I am not concerned at present as I have warranty. But my friend would be concerned about even installing headers and a tune, given his driving habits.

 

[Dominant1]

Yeah i have an automatic my car is going to my tuners shop in a couple of weeks for a complete n/a build and tss opgs are scheduled to be installed. The car will have a 7500 rpm redline ...

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