New BMW 3 series Oil Pump

SCMPredator · May 22, 2005

hi all,

first..I just wanted to say this is a great site and i've learned so much here.

okay...now on to the good stuff. If you've read the motor trend magazine on the new BMW 3 series...I just wanted to quote page 49 of april 2005 issue...the insert that says "one engine..

"...the oil pump is pressure rather than engine speed regulated, so the engine gives more of its power to the driver and chomps through less itself".

I just wanted to understand how does this compares to other cars who have "regular" oil pumps. I am not sure how this has advantage? After all, camrys and accords V6s for example, have a proven track record on regular oil pumps. How does BMW improve on this?

V8Blitz · May 22, 2005

quote:

Originally posted by SCMPredator:
hi all,

first..I just wanted to say this is a great site and i've learned so much here.

okay...now on to the good stuff. If you've read the motor trend magazine on the new BMW 3 series...I just wanted to quote page 49 of april 2005 issue...the insert that says "one engine..

"...the oil pump is pressure rather than engine speed regulated, so the engine gives more of its power to the driver and chomps through less itself".

I just wanted to understand how does this compares to other cars who have "regular" oil pumps. I am not sure how this has advantage? After all, camrys and accords V6s for example, have a proven track record on regular oil pumps. How does BMW improve on this?

I would assume ( and I've heard nothing about this oil pump on the 3 series) that instead of driving an oil pump which is dependant on an auxiliary drive which contributes to parasitic loss, it uses a pressure pump which has less drain on the motor.

jaj · May 22, 2005

The new oil pump technology uses a special pump that pumps less oil when less oil is needed.

This may sound obvious, but the decades-old standard is a positive-displacement pump run off a driveshaft or a chain drive. As the engine rpm climbs, its output climbs as well. However the amount of oil the engine needs doesn't climb as fast as the pump output, so the excess is vented by a spring-loaded pressure-relief valve back into the oil pan. You see this if you have an oil pressure guage - the idle pressure is low, maybe 15 PSI. At a higher RPM, usually far below the red line, the pressure gets to around 60 PSI or so, and it stops climbing as the RPM increases This "leveling-off" of the pressure is the relief valve in operation. If it wasn't for the pressure relief valve, it would just keep on rising and that would eventually damage something.

Apparently, the lost power from driving oil past the spring is enough to affect fuel economy, so new engine designs include pumps that are governed without the spring relief valve - if the oil pressure climbs to its maximum level, they turn more slowly (or something - I'm not sure what) and so they pump less rather than waste the excess.

Its all about fuel economy, and I guess that it makes a noticeable difference when you have millions of cars running hundreds of thousands of miles. It adds up.

Cheers
JJ

V8Blitz · May 22, 2005

quote:

Originally posted by jaj:
The new oil pump technology uses a special pump that pumps less oil when less oil is needed.

This may sound obvious, but the decades-old standard is a positive-displacement pump run off a driveshaft or a chain drive. As the engine rpm climbs, its output climbs as well. However the amount of oil the engine needs doesn't climb as fast as the pump output, so the excess is vented by a spring-loaded pressure-relief valve back into the oil pan. You see this if you have an oil pressure guage - the idle pressure is low, maybe 15 PSI. At a higher RPM, usually far below the red line, the pressure gets to around 60 PSI or so, and it stops climbing as the RPM increases This "leveling-off" of the pressure is the relief valve in operation. If it wasn't for the pressure relief valve, it would just keep on rising and that would eventually damage something.

Apparently, the lost power from driving oil past the spring is enough to affect fuel economy, so new engine designs include pumps that are governed without the spring relief valve - if the oil pressure climbs to its maximum level, they turn more slowly (or something - I'm not sure what) and so they pump less rather than waste the excess.

Its all about fuel economy, and I guess that it makes a noticeable difference when you have millions of cars running hundreds of thousands of miles. It adds up.

Cheers
JJ

Yeah, what he said

joatmon · May 22, 2005

Yep, Hi-tech. Block is cast of a titanium-aluminum alloy.

the_oil_dealer · May 22, 2005

imagine that, a clutched oil pump. I'm not sure how the BMW's works specifically, but it might be that the oil pump drive has the ability to slip, or have a limited amount of torque applied to it. Whatever means thats used, it's sort of scraping the bucket for horsepower at the extra cost of manufacture, and increased chance of part failure. But hey, to each their own.

SCMPredator · May 23, 2005

i hope its not a ploy to meet CAFE standards similiar to the 5w20. I would hate to spend that much money on a BMW and realize later that the oil pump is not as reliable. Again this is just for discussion purposes..not to knock on BMW's quality.

SEBZX79 · May 23, 2005

The new pump is a Electric pump and is powered by an electric motor not the crank. It uses 1/10 of the power the previous pump used so it is more efficient in its operation and the motor can put more hp to the ground and get better MPG.

The new block is Magnesium-Aluminum alloy with a internal block sleeve saving additional 20 or so lbs I believe. The whole block is not made of Magnesium because at high temps Magnesium burns.

nascarnation · May 23, 2005

1/10 the power, eh?
somehow the physics of this eludes me

BTW variable displacement vane pumps have been in automatic transmissions for decades....

moribundman · May 23, 2005

Whatever happened to KISS? An electrically driven oil pump increases chance of failure.

Geoff · May 23, 2005

quote:

Originally posted by moribundman:
Whatever happened to KISS? An electrically driven oil pump increases chance of failure.

Prolly there is an ignition cut out in case of failure, but watch those big puddles!

segfault · May 23, 2005

quote:

Originally posted by moribundman:
Whatever happened to KISS? An electrically driven oil pump increases chance of failure.

I'm sure there is some sort of fail-safe. The 2006 3-series also does not have a dipstick, you check the oil level from the on-board computer (standard model) or via iDrive (navigation model). Interesting that they went that route because the oil level sender was a common failure on the E46 (1999-2005) models.

Ray H · May 23, 2005

quote:

Originally posted by SEBZX79:
The new block is Magnesium-Aluminum alloy with a internal block sleeve saving additional 20 or so lbs I believe. The whole block is not made of Magnesium because at high temps Magnesium burns.

It's not magnesium-aluminum alloy. BMW figured out how to cast a magnesium alloy outer casing around an inner aluminum cylinder block - in effect an aluminum block with a magnesium outer "block" with the coolant jacket seperating them. Given the different expansion rates of the dissimilar metals, it'll be interesting to see how well BMW anticipated and managed potential long-term sealing problems where the aluminum head and the dual metal block mate.

Yes, magnesium burns at incredibly high temperatures. BUT, getting a large chunk of magnesium to ignite is a challenge due to its low density. The stuff sloughs off heat even better than aluminum. (Aluminum can burn, too.)

Gary Allan · May 23, 2005

No puddles will be fine ..but it will go through 5 evolutions in 5 years. Yours will quit in year 8 and will be an hard to find item. Well, yes, it's available ..but will cost $680 jobber. An internet enthusiest site will advertize a "better" unit for $1269 U$D and will give you the impression that you're a fool to willingly put the same thing back on.

unDummy · May 23, 2005

Nice picture of a variable oil pump(not electric):
http://www.germancarfans.com/news.cfm/newsid/2040623.001/page/3/lang/eng/bmw/1.html

moribundman · May 23, 2005

quote:

I'm sure there is some sort of fail-safe. The 2006 3-series also does not have a dipstick, you check the oil level from the on-board computer

"Captain, we've lost the warp drive!"
"Full impulse, reverse thrusters! Brace for impact!"

Right.

If the electric pump fails, what fail-safe could there possibly be? I wouldn't want my engine to commence an emergency shutdown procedure while I'm on a highway on-ramp. Not having a dipstick is silly, but having a dipstick is not something essential. While driving, an electronic monitoring system is far more uselful than a dipstick. As for an electric oil pump...

mechtech · May 23, 2005

I guess the engineers have to think obscure things up in the interests of fuel economy, or to just show how high tech. BMWs are.
Similar gains would be shown with oil of the proper viscosity, and a properly sized/relieved standard pump.
No way would I want the added complication, expense, and inevitable failure of the electric oil pump.

unDummy · May 23, 2005

The WATER pump is electric.

oilyriser · May 23, 2005

So many neat things can be done, if you have electric oil and water pumps. Not only do you only pump as much as the engine needs (no oil bypass valve), saving power, the drive electronics can monitor the load on the pump, to make sure it is pumping something. If you run out of oil, the driving electronics will sense this, and sound an alarm. You could have a readout, showing oil flow rate, and you could tell if your bearings are wearing out, since the flow rate at a given rpm/pressure would increase. If it happened quickly, it might mean the oil has sheared, and the viscosity has dropped.

You could also switch on the oil pump for a few seconds, before the engine is started.

neat stuff!

If an electric oil pump failed, you'd only have a minute or two to pull over, so reliability would have to be very good. You could have two pumps with check valves, so one pump could take over if the other one shut down. But that makes it more expensive and more complicated.

[ May 23, 2005, 06:21 PM: Message edited by: oilyriser ]

Jay · May 23, 2005

I don't see how an electric oil pump would be more efficient than a mechanical one. If you look at the efficiency curves of a typical automotive alternator, best efficiency is about 25%--and that's at high rpm. At lower rpm, efficiency falls to 10% to 15%. Combined with the inefficiency of the electric motor of the pump, I don't see how you come out ahead.

New BMW 3 series Oil Pump

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