Technical thoughts about engine displacement vs engine output - BMW Forum - BimmerWerkz.com
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#1 (permalink) Old 02-10-2007, 09:56 PM
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Technical thoughts about engine displacement vs engine output

Ive been doing alot of math lately about calculating engine displacment vs engine output and calculating theoretical engine output based off using OEM replacement parts based off an initial baseline.

I also compared the dyno I have vs the dyno of lots of other e36 vehicles and figured the avg drivetrain loss depending on the dyno and conditions is a factor of .13 to .17 of total output (and thusly, for all calculations I use .15).

Utilizing the basic parameters of my engine:

84.00 bore
75 stroke
2495cc total displacement
189whp

I figure this: ((pi*((84.00/2)^2)*75)*6)/1000 = 189whp

Thusly, if using a linear line of thinking (and if you examine non-M based motors from bmw, they generally do have a linear output vs displacement) if you used a 328i crank and stock bore and the same base mods to go off of you'd get:

((((pi*((84.00/2)^2)*84)*6)/1000) * (189.5/2495))/.85 = 249.57bhp


Then, if you went a step further and used a 328i crank, non vanos m50 block bored to 86mm (it can be done) you get this:

((((pi*((86.00/2)^2)*84)*6)/1000) * (189.5/2495))/.85 = 261.59bhp

So, I figure with a 328i stroker kit, placed in a bored out m50NV block 260bhp should be very realistic with additional intake/exhaust mods (porting, etc)

Going even a step further of using a s50 crank you would get this:

((((pi*((86.00/2)^2)*86)*6)/1000) * (189.5/2495))/.85 = 267.82bhp

Only 6 more brake horse power..

Interesting, huh?

Comments? Ideas?


Last edited by nukeduster; 02-10-2007 at 09:59 PM.
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#2 (permalink) Old 02-11-2007, 05:44 PM
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Well right off the bat the dyno you have is not what you can use to compare to other cars. That dyno was doen on a chasis dyno, rather than a roller dyno. or so Ballzack tells me.


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#3 (permalink) Old 02-11-2007, 05:51 PM
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Quote:
Originally Posted by nukeduster
Ive been doing alot of math lately about calculating engine displacment vs engine output and calculating theoretical engine output based off using OEM replacement parts based off an initial baseline.

I also compared the dyno I have vs the dyno of lots of other e36 vehicles and figured the avg drivetrain loss depending on the dyno and conditions is a factor of .13 to .17 of total output (and thusly, for all calculations I use .15).

Utilizing the basic parameters of my engine:

84.00 bore
75 stroke
2495cc total displacement
189whp

I figure this: ((pi*((84.00/2)^2)*75)*6)/1000 = 189whp

Thusly, if using a linear line of thinking (and if you examine non-M based motors from bmw, they generally do have a linear output vs displacement) if you used a 328i crank and stock bore and the same base mods to go off of you'd get:

((((pi*((84.00/2)^2)*84)*6)/1000) * (189.5/2495))/.85 = 249.57bhp


Then, if you went a step further and used a 328i crank, non vanos m50 block bored to 86mm (it can be done) you get this:

((((pi*((86.00/2)^2)*84)*6)/1000) * (189.5/2495))/.85 = 261.59bhp

So, I figure with a 328i stroker kit, placed in a bored out m50NV block 260bhp should be very realistic with additional intake/exhaust mods (porting, etc)

Going even a step further of using a s50 crank you would get this:

((((pi*((86.00/2)^2)*86)*6)/1000) * (189.5/2495))/.85 = 267.82bhp

Only 6 more brake horse power..

Interesting, huh?

Comments? Ideas?
True, except for one simple thing: The S50 crankshaft is build much differently than the M52 crank. It's more balanced and it spins more easily, resulting in a revvier engine. Bore x Stroke is not everything my friend.


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#4 (permalink) Old 02-12-2007, 05:28 PM
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Quote:
Originally Posted by triggrhaapi
True, except for one simple thing: The S50 crankshaft is build much differently than the M52 crank. It's more balanced and it spins more easily, resulting in a revvier engine. Bore x Stroke is not everything my friend.
Aha, but thats where you overlooked one thing though...

Using a m52 crank, makes it undersquare using s50 pistons.. 84 stroke by 86 bore..which would make it MORE revvy.

Just knife edge the crank and balance it with the rods and pistons attached and c'est voila, you have something that would naturally like to rev even more.

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