what hp does the oil pump gears break. I just wondering i know the turbo the blower guys lose sleep over that

 

Probably 600+, it would make sense to replace them if you are thinking about making power of any kind IMO. Some will probably say it isn't needed but I would think it is cheap insurance since a new motor is about 8k.

 

Just replace the gear...

 

Question: Why would increasing the HP output of the engine have any bearing on the oil pump? It’s as an engine driven accessory that would not see any greater stress as HP increases. I can see where an increase in engine RPM red line or heavier viscosity oil could potentially have an effect on its durability. What am I missing?

Thanks,
John

 

An increase in HP is going to increase the stresses on all of your engines moving parts. If this wasn't so then people could run 2k+ HP on stock internals and you would never hear of a failure.

 

Not quite the same thing comparing the oil pump drive gear to the internals of the engine.
Once you raise the RPM's you start running the chance of the stock gear breaking. The oil pump gear turns off the crankshaft. The faster the engine spins, the faster the pump spins. The gears are not made of a strong metal.

 

So what your saying is, if the RPM's are never raised from stock then the stock oil pump gears will be fine? If the oil pump gears run off the crank and your HP increase then the stress on the crank will increase and so should the stress on whatever the crank is attached to. I am sure people are breaking gears if they run to 9k RPM but at the same time I am sure people who don't increase their RPM and simply increase power also blow gears.

 

We know the oil pump's gear is driven by the crank's rotation. That's four pulses per revolution as the cylinders fire. While it's not hydraulically locked, the oil pump does not want to turn easily when pushing oil through the engine. Adding more force to those impulses is what is putting the strain (torque) on the part. Even at the same RPM, you can beat the hell out of the gear by adding power.

 

Thank you, someone who makes sense.

 

Nick is correct...read on....

The load placed on the oil pump and its drivetrain will stay the same unless one or more of the following changes: the oil viscosity, the pumps bypass pressure (If equipped with a variable bypass valve), is operated beyond its maximum designed speed. The two caveats would be: 1) component flex or movement under greater stress loads of higher output engines such as the crank or block flexing potentially changing the gear lash as an example, and 2) harmonics at increased HP or RPM. Both are very real and documented failure modes in other engines.

Hypothetical: On a completely stock engine, say the pump requires 5 crank HP to pump 12gpm at 80psi to the engine at 7500 RPM. Increasing the engines total power output will not change the pumps load at all (unless one or more of the variables listed above are changed), it still requires 5hp because it is still pumping the same 12gpm at 80psi at 7500 RPM.

Following Brandon’s or El Coyotes line of thinking, adding hp to the engine would increase stress on the coolant pump, alternator, AC pump, etc. It won’t. They’re all “Slaves” or accessories powered BY the engine.

John

 

I think we mostly agree. More RPM does cause more stress load on the gear. And you acknowledge the increased flex and harmonics, I was eluding to, with simply an increase in power while RPM and viscosity remain the same.

In your hypothetical, both engines would have the same load at that RPM. But there would be a significant difference in load rate when getting to that RPM. That's the added force I was referring to.

The other accessories also feel the increased force from the change in rate, but not as much. The belt drive helps reduce the damaging forces a lot.

 

Then why on the 03-04 Cobra's did the alternators fail religiously? My other argument has no basis but stick with me, the alternator on cars with root or centrifugal cars may burn up because of the strain from the blower, so then if you add a turbo to the car which shouldn't increase anything but HP do you then need to switch to better gears or leave them alone?

 

I'm assuming the gears on the Coyote are similar material to the older 4.6 Cobras. The pump gear failed twice on my 98 Cobra. First time was after a day at VIR car was mostly stock engine wise. Tune and exhaust. All my mods were suspension. There were times I would hit 7500 rpms. The gear split in half...second was when I upgraded to the MMR 5.0 stroker. I didn't go with the MMR pump. Just went with the Ford Racing one. Same result...engine was only making 500 RWHP but I routinely spun the engine to 8500. If your car has loose tolerances or a weakened crank. Then I could see elevated horsepower causing the crank to vibrate would cause a failure. When I ordered my MMR pump...they told me I needed it for the rpm I was spinning my car. And even the ford racing pump which is an upgrade for my Cobra was insufficient.