What can be done with the oil pump gears to strengthen them? Cryo?

Yes, I know I can replace them with billet for $500. Thought I'd look for a low cost solution first.

 

He sells the gears themselves for 300 something, but you need to install them and get them machined to fit your oil pump exactly.

 

I still don't understand why horesepower supposedly kills oil pumps gears. I thought RPM was the culprit.

 

have people actually run into oil pump failures?

Ben, if you have an extra gear, cut it in half and we can do a hardness test on it to see if/what its treated to. Cause its a give and take. If you have an extra pump I could model it, then we water jet it (depending on thickness) out of a prehardened steel and voila oil pump.

 

Well, horsepower is a function of torque and RPM, after all...sounds logical to me.

Whereas 100lb-ft of torque at 8000 RPM might not kill an oil pump gear, 250lb-ft at 8000 RPM might.

I think someone really just needs to figure out a way to add cylinders to the B6/P so we can smooth out the power delivery...

 

sure, but how much of a load is an oil pump?

 

The load the fluid puts on the gear is constant (NA vs Boosted) and assuming the gears aren't misaligned and the shafts don't fail.

 

I don't have an 'extra' pump until I open up my block, as I'll be ordering a new one anyway.

We can get the off the shelf pair of replacement gears for $300 retail. I don't think we could make them for that. $500 includes a brand new pump, required machining to switch the gears out, and delivery.

 

Is this just for safe measure then?

 

Right. I don't see how load increases with more power. Oil is the same weight, and rpm is the same. I'm pretty sure that if oil pump gears really did fail at stock rpm, I would have killed them on my 16+ hours of track time post the 150k mile mark.

 

yeah the stock pump seems to be iffy >7500 rpm
Figured if sintered steel can be made stronger with shot peening or cryo or some other process I don't know about, it would be worthwhile.

 

It takes some combination of greater than stock power + high rpm. There are 2 gears and the outer gear seems to be the one that fails.

There is a guy on miata.net that lost 2 built motors in a row from oil pump gear failure. Granted, I believe he had a 400 hp drag car, but still.

 

Im wondering is thats just a freak of nature, but on a built motor i guess its good insurance.

 

The gears are made from powdered metalurgy, a form of sintering. The outside of the gears is very hard, tough, strong, etc. However, .050 below the surface of the gear, it's rather weak. Somewhere around 1/3 the strength of a true cast and machined gear of the same material. Often, since powdered metalurgy gears are made to reduce cost, they are not alloyed to be extra strong, so cryotreating will help, but not as much as it could, had the gears been made of other various alloys.

Crankshaft flex is what causes them to shatter, as they are quite brittle compared to a cast gear. It's not the power the pump takes to drive it that breaks the gear. There's not a whole lot you can do to strenghen them. If you knew what alloy they were made from, you could find out what cryo and hot/cold forming techniques would alter it's characteristics appropriately.

 

I've thought about doing this mod, but changed my mind because I didn't know crank flex was the issue.

Is 250whp enough reason to warrant one for a 99 motor?

 

Hustler-you'll probably be fine, as long as you don't make 250 whp @ 8K. I think for the cost and hassle of billet oil pump gears, I would either use and electric oil pump, or go all out with a dry sump setup.

 

yeah, because dry sump conversions are so affordable.

 

I have a buddy here that has broken two of them at 400 hp. If anyone wants a pump for testing, I have one in the garage, but it is stuck to my old crankshaft.. I cant get it off.

 

I'm seriously considering the billet oil pump gear pump for my build too. Course I also read somewhere in some thread that the ATI damper will reduce the crank issues that hurt oil pump gears. I'm not sure if that means one prevents need for the other or both is better than either or what.

I just know that when I add $500 here and $500 there it's a lot of damn coin.

 

cool. maybe throw it in your trunk for the next time you come up to DIY? I know a guy with a plasma torch that I've been dying to try

Then the next step is finding a place that can do the metalurgy. Loki or Pat, do you have a suggestion?