# BMW inline 6 engine design question



## 801 Radial (Nov 1, 2004)

I wanted to ask about the 2.5/3.0 inline 6 in a 3 Series. Are the cylinders slanted (say at 30 degrees) or are the cylinders vertical and the engine mounted at an angle? The location of the valve cover in 325Ci makes the engine look tilted towards the passenger side. Are all BMW inline 6s the same as far as this design aspect? 

Thanks!


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## Kaz (Dec 21, 2001)

I don't really see the difference. :dunno: The engine (probably all of em going back to the 60s) was designed to be run at an angle.


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## Alex Baumann (Dec 19, 2001)

The petrol engines are installed at 30°, the diesel at 20°


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## 801 Radial (Nov 1, 2004)

I agree Kaz, they would acheive the same packaging benefit of a lower hood line and lower CG. But the engines would be different to me. For example, the Chrysler Slant Six had cylinders cast 30 degrees off engine center line. This was obvious with the engine out of a car...think of half of a V8. Is this the way the BMW engines are? Or are the cylinders cast vertically (no angle off engine center line) and the engine mounted in the car at an angle? 

So, based on what yall are saying, the cylinders are vertical and the engines are tilted when they are installed. Is that correct?


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## Kaz (Dec 21, 2001)

The only difference I could see would be the design of the anciliaries Oilpan, intake/exhaust, etc. would have to be such that they fit at an angle relative to the car. The blocks are cast and finished vertically if you look at photos of how engines are made. Since on a inline engine, the centerline is the centerline no matter how you look at it (center of the piston/cyl, rods and crank all line up), If we were growing a tree, I'd understand the difference, but in this case I still don't understand the difference between making it slanted or slanting one made straight up and down. Maybe the old slant-6 is odd if the crank and bore centerlines aren't in line.


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## 801 Radial (Nov 1, 2004)

Kaz, maybe there is no difference to the driver or car performance. I do agree that engine accessories would have to be designed to match the engine layout. Maybe I have mispoke or haven't explained what I'm thinking well. 

How about I use a clock as a reference? To me, a traditional inline 6 would have the head mount at 12 and the pistons move up towards 12 and down towards 6. The crank would be about where the clock hands would mount in the center. Is this the layout of a BMW inline engine? Or...is the head at 10 and the pistons move up towards 10 and down towards 4 with the crank in the same location? In both examples the oil pan is down at 6. The traditional inline 6 would look like an "I" from the front, where the slanted (20 or 30 degree) engine would look like a bent "I". With the top half canted to your left.

Tilting a (12 o'clock) traditional engine (not designed for tilting) would mean the oil in the pan would be forced to the side where the pan meets the block and may expose the oil pick-up point. So, BMW could tilt the engine and have the block bottom cast so it would remain horizontal- allowing a standard pan & pick-up. Having the block cast so the cylinders are at 10 o'clock would mean the block bottom (and oil pan) would remain horizontal, but the angled cylinders would provide a lower layout.

The end result in hp/torque/driver feel may be the same, but BMW would have to design the block to match one or the other layout. It would have to have the valve cover/head mount at 12 or 10. The block wouldn't be the same assuming that the bottom end is horizontal where the pan goes. 

Whew. So, which layout has BMW chosen? Or am I barking up the wrong tree?


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## The Roadstergal (Sep 7, 2002)

The E30 has a slight kink to keep the pan level. This picture kinda shows it; the top of the intake maifold is horizontal when the engine is in the car.


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## BoyScout (Mar 20, 2004)

I found this from a 2001 issue of "European Car"

Because the M3's prodigious cornering forces and the engine's 30-degree slant as it is mounted in the engine compartment conspire to prevent oil from draining back into the pan during hard left turns, a scavenging pump has to be used to pump oil back down into the pan.

Full story: http://www.europeancarweb.com/features/0110ec_m3/


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## vm (Jul 16, 2002)

801 Radial said:


> How about I use a clock as a reference? To me, a traditional inline 6 would have the head mount at 12 and the pistons move up towards 12 and down towards 6. The crank would be about where the clock hands would mount in the center. Is this the layout of a BMW inline engine? Or...is the head at 10 and the pistons move up towards 10 and down towards 4 with the crank in the same location? In both examples the oil pan is down at 6. The traditional inline 6 would look like an "I" from the front, where the slanted (20 or 30 degree) engine would look like a bent "I". With the top half canted to your left.


There is no such thing as a bent "I" engine.



801 Radial said:


> Tilting a (12 o'clock) traditional engine (not designed for tilting) would mean the oil in the pan would be forced to the side where the pan meets the block and may expose the oil pick-up point. So, BMW could tilt the engine and have the block bottom cast so it would remain horizontal- allowing a standard pan & pick-up. Having the block cast so the cylinders are at 10 o'clock would mean the block bottom (and oil pan) would remain horizontal, but the angled cylinders would provide a lower layout.


This is it, with a caveat. The caveat is that no matter if you use your inline six vertical or slanted the bottom of the block is the same. The only changes are in the oil pan (much cheaper and simpler than changing the block) and the oil pickup point.


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