Oppo I need your help

"6cyl" (6cyl) 09/10/2013 at 18:33 • Filed to: help!

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As many of you know BMW is famous for their inline 6's that sit in the engine bay at a slant like this m50. I am struggling to find out more information on the angle of these motors specifically the m20 and m30. From what I have found so far the word seems to be that the m20 sits at around a 30°-33° angle off vertical. Unfortunately I have not found any source that seems credible and I've found nothing on the m30.

Does anyone have any insight into this matter?

GhostZ > 6cyl 09/10/2013 at 18:38

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I have nothing to add, but I do have another question: what is the advantage of a slant engine? It can't be for packaging purposes, unless you really need to shorten the height of the engine. I would think balance issues and the added width would be more of a problem than the height.

BiTurbo228 - Dr Frankenstein of Spitfires > GhostZ 09/10/2013 at 18:41

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It is usually to get them to fit under a low bonnet. No real reason otherwise.

HammerheadFistpunch > GhostZ 09/10/2013 at 18:43

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yeah, packaging. Almost all engine are installed on the slant, if its a v engine, your v angle is the slant, if you want to think about it that way. There are exception though, my Land cruiser's I6 is bolt upright because...well, no need to slant it, there is plenty of room.

Z_Stig > GhostZ 09/10/2013 at 18:43

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Mostly packaging issues, as it allows for a lower hood height.

lonestranger > GhostZ 09/10/2013 at 18:44

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I believe it is indeed done for packaging purposes. It allows for a lower hood height than if the engine were upright and the same size. Even on a slant, it's still not as wide as a vee engine.

6cyl > GhostZ 09/10/2013 at 18:45

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They are rather tall motors and slanting them keeps the hight of the hood and weight of the motor lower. The exhaust is also on the bottom side keeping engine bay temperatures down.

It is not ideal for oiling or perfect balance but I suppose they have weighed the pros and cons.

Z_Stig > 6cyl 09/10/2013 at 18:45

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I've always wondered what the exact angle is too. Everything I've seen on virtually every BMW forum says approximately 30 degrees.

6cyl > Z_Stig 09/10/2013 at 18:47

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Any idea if it is the same for all the motors or all the inline 6's? Some of the 4 cylinder's seem to be even more slanted but it's hard to know for sure.

dogisbadob > 6cyl 09/10/2013 at 18:47

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Probably 30 degrees. It seems legit. And like others said, most likely for packaging reasons.

I think Chrysler's slant 6 was slanted 45 degrees.

Z_Stig > 6cyl 09/10/2013 at 18:49

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I have no idea on the I4s, but all of the I6s seem to be the same.

BiTurbo228 - Dr Frankenstein of Spitfires > 6cyl 09/10/2013 at 18:49

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Unfortunately not either. However, I do have another question you might have an answer to. Do you know how much a fully dressed M30 weighs?

I've seen the 156kg floating around, but I strongly suspect that's the weight for a short-block, as that's what's quoted in the BMW parts catalogue.

I'm compiling a list of engines including bhp/kg, lb-ft/kg, bhp/l, lb-ft/l, construction and maximum known displacement among other things).

What I've found is that it's bloody difficult to find reliable engine weights on the internet.

The man in the iron mask > 6cyl 09/10/2013 at 18:57

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talk about slant in this mercedes 300 SLR '55

The man in the iron mask > The man in the iron mask 09/10/2013 at 18:59

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6cyl > Z_Stig 09/10/2013 at 19:03

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Awesome, thanks! I had read some where on maybe r3vlimited that someone thought the m20 and m50 were 11° different so I 've been very courious

Z_Stig > 6cyl 09/10/2013 at 19:10

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Wow! 11 degrees is quite a bit. This thread almost makes me wanna grab a protractor and start measuring inline-six Bimmers! hahaha

Z_Stig > The man in the iron mask 09/10/2013 at 19:11

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Yea, that was like 50 degrees?

Rows His Own > GhostZ 09/10/2013 at 19:11

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Packaging. Also, oh god do you know how hard it is to work in the engine bay of a 3 series? When I did the crank case vent on my 330, virtually the entire intake side of the motor had to come off. If it were vertical, it would have been impossible. But it works well with the engine bay at a slant. Bmw engineers do nothing without a well thought out reason.

Rows His Own > 6cyl 09/10/2013 at 19:14

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I can try to measure my m54 and s54 but I'm almost certain they're the same. Ill eye around a junkyard at some e30s and maybe a 2002 an see what I can find out.

The man in the iron mask > Z_Stig 09/10/2013 at 19:18

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wikipedia says:The engine was longitudinally mounted and canted at a 33-degree angle to lower its profile for aerodynamic reasons, resulting in the distinctive bonnet bulge on the passenger side of the car.
i think they mean 33 off horizontal, so 57 degrees, you were close

6cyl > Rows His Own 09/10/2013 at 19:29

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I agree I think the m/s5x motors are all the same angle.

If you do want to check them and any you find at a junk yard that would be great! Let me know what you find out.

Brian, The Life of > 6cyl 09/10/2013 at 19:34

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Only one thing to add: Beware of oil starvation in long sweeping turns. Baffled oil pans are your friend if you track an M30-equipped car.

6cyl > BiTurbo228 - Dr Frankenstein of Spitfires 09/10/2013 at 19:46

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Here ya go :)

m10 - 180lbs

m20 - 258lbs

m30 - 315lbs

m42 - 220lbs

Rows His Own > 6cyl 09/10/2013 at 19:46

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Also I wonder of its the same across different models with the same engine. Ill check an e60 and an e39 to be sure. Hmmmm

Rows His Own > 6cyl 09/10/2013 at 19:47

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And every excuse to open the hood on the m is worth it to me.

BiTurbo228 - Dr Frankenstein of Spitfires > 6cyl 09/11/2013 at 04:41

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Very helpful post, but they seem like short blocks to me as well. Considering that the M30 can be punched out to 3.5l, 315lbs seems like a very optimistic weight. Especially seeing as it's got a cast-iron block.

For instance, the all-alloy Alfa V6 (which can also be punched out to mid 3.0ls) weighs 374lbs, and the cast-iron block M20 weighs 397lbs dressed, and that's a physically smaller engine than the M30.

There's more info on BMW engines than most, but a lot is taken from the parts catalogue which inly lists short-blocks (the block, head, pistons, crank etc. but not the intake, alternator etc.).