Oppo Challenge. Highest BMEP for an engine. 

"BJohnson11" (brettjohnson01) 01/25/2015 at 20:12 • Filed to: None

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The professor for my Internal Combustion Engine design class has challenged us to find the engine with the highest brake mean effective pressure. BMEP is related to (Power)/(displaced volume*engine speed at peak power).

Specifically, for BMEP in psi for four stroke engines BMEP = power(hp) * 396000 / N(rpm) * displaced volume (cubic inches).

Who can find the highest BMEP?

For Sweden > BJohnson11 01/25/2015 at 20:14

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Mechanical engineers are weird

/Aerospace engineer master race

PowderHound > BJohnson11 01/25/2015 at 20:15

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Math? Pass.

bob and john > BJohnson11 01/25/2015 at 20:19

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your definatly looking at high-boost engines.

DrJohannVegas > BJohnson11 01/25/2015 at 20:20

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If you can get reliable data on it, the BMW F1 turbos are probably up there.

BJohnson11 > DrJohannVegas 01/25/2015 at 20:23

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Yea the first engine I tried was the 1.5l BMW turbo from 86. Went with a conservative 1100 hp at 12000 rpm. Got close to 400 psi.

I'd be curious how a top fuel dragster or other high displacement high hp engine measures up.

Drakkon- Most Glorious and Upright Person of Genius > BJohnson11 01/25/2015 at 20:27

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the problem with Top Fuel is there is no direct way to measure the horsepower. No dyno can handle them. Most engine engineers will guess about 10,000 HP, but it's just a guess.

davedave1111 > BJohnson11 01/25/2015 at 20:29

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Am I misreading that? Power is torque * rpm, and you seem to have power/rpm in there, which would cancel back to torque. So aren't we just looking at torque*displacement? That doesn't sound quite right. Should there be brackets round the last two terms? That would mean we're looking for high power at low rpm and displacement, which makes more sense.

By the way, you might find this interesting if you scroll down slightly.

http://en.wikipedia.org/wiki/List_of_a…

ETA:

Oh, and this - http://en.wikipedia.org/wiki/Mean_effe…

If only EssExTee could be so grossly incandescent > BJohnson11 01/25/2015 at 20:29

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is that (396000/(rpm*displacement)), or ((396000/rpm)*displacement)?

this is not matt farah's foxbodymiata > BJohnson11 01/25/2015 at 20:35

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You might have luck with modern rally cars.

The VW Beetle GRC car's 1600cc (~98ci) turbo 4 makes 544hp at 7,800 rpm

that would be (544*396000)/(7800*98) = 281.82

No idea what a good number and not sure I did the math quite right, but it's a pretty damn good power plant, especially with anti-lag and so on. Faster to 30mph than an f1 car.

edit: source

BJohnson11 > davedave1111 01/25/2015 at 20:35

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It's (power) /(displacement*rpm). So Torque/displaced volume essentially.

BJohnson11 > If only EssExTee could be so grossly incandescent 01/25/2015 at 20:37

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The first one.

Drakkon- Most Glorious and Upright Person of Genius > BJohnson11 01/25/2015 at 20:37

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porsche 962 is 187.6

680hp, 175ci, 8200 rpm.

I'm not good enough at math to guess will a crazy HP but crazy rpm lose out to a more moderate HP, but a lower speed engine.

jariten1781 > BJohnson11 01/25/2015 at 20:40

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Wouldn't a big ol marine diesel contend? Puts massive power in the numerator and very low RPM in the denominator in exchange for huge displacement. A 14 cylinder WS RTA96C does about 100,000 HP at about 100 RPM.

davedave1111 > BJohnson11 01/25/2015 at 20:41

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Ah, I knew I must be reading something wrong. Hey, it's - oh, shit, it's - nearly 2 am here :)

If two strokes are allowed I reckon that mammoth Wartsila-Suza ship engine will win.

Drakkon- Most Glorious and Upright Person of Genius > BJohnson11 01/25/2015 at 20:47

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geoff page built Ford BDT-e for the RS200

1150hp

146.5ci

9000rpm

Index: 345.4

BJohnson11 > jariten1781 01/25/2015 at 20:48

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Huge displacement though. I'll see how it stacks up.

BJohnson11 > davedave1111 01/25/2015 at 20:49

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Yea I'll run that in a bit. Huge displacement might hurt it though.

7:07 > PowderHound 01/25/2015 at 20:53

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davedave1111 > BJohnson11 01/25/2015 at 20:57

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Could be, but it has enough torque to do the Kessel run in less than twelve parsecs.

PowderHound > 7:07 01/25/2015 at 20:58

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I'm just incredibly lazy today

If only EssExTee could be so grossly incandescent > BJohnson11 01/25/2015 at 21:01

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That second part of the equation is problematic. the division means that (rpm*displacement) causes a reduction in BMEP number, so you want to keep that second half low. Ideally you want an engine with high power, low displacement, and low peak power. Unfortunately that doesn't really exist. Your options for high power engines are either low displacement and high rpm (race cars), or high displacement and low rpm.

...have you looked into truck engines?

BmanUltima's car still hasn't been fixed yet, he'll get on it tomorrow, honest. > BJohnson11 01/25/2015 at 21:37

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BMW M12, 2.0L I4 Turbo:

1400*396000/9500*122= 478

Kharkiv model V-2:

500*396000/1800*2367= 46

Ariel V8, 3.0L V8:

500*396000/10500*183= 103

FS52AR ASP, 0.00852L one cylinder RC nitro engine:

.5*396000/11000*.52= 35

BJohnson11 > If only EssExTee could be so grossly incandescent 01/25/2015 at 23:16

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I agree, engineering problem solving in a nutshell. Gotta have tradeoffs somewhere.

I'll look into big rigs and as others mentioned, large marine diesel engines.

samssun > If only EssExTee could be so grossly incandescent 01/25/2015 at 23:57

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It's not so much "problematic" as "by design" that BMEP is scaled by RPM & displacement...its whole point is to measure output independent of speed or size, ie how hard you can get your fuel to push on the pistons. Adding revs or cylinders just means doing work more frequently, but BMEP tells you what that base unit of work is.

BJohnson11 > samssun 01/26/2015 at 01:45

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Right, I totally agree. Hence why BMEP is considered by many to be one of the best measurements with which to compare engines. But I think what EssExTee was saying was that you can't optimize both low displacement and low rpm and somehow make power.

BJohnson11 > davedave1111 01/26/2015 at 01:50

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Just FYI, the Wartsila engine fell fairly far short. Truly done in by it's massive size. Has a BMEP around 275 psi. Not bad, but not great either.

samssun > BJohnson11 01/26/2015 at 07:18

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Oh I read it as him starting with BMEP, trying to reverse engineer the highest value from the equation, and finding our the two easiest ways to add power (displacement & rpm) don't help...which of course is the point.

I think of BMEP as TANSTAAFL for engines: there's no easy way to maximize it, besides "build a better engine".

briannutter1 > BJohnson11 01/26/2015 at 10:32

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You may want to look at commercial tanker ship engines. Except some of those are 2 strokes

If only EssExTee could be so grossly incandescent > BJohnson11 01/26/2015 at 10:59

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I did a quick calculation on the Detroit Diesel series 60 and got 296.6.

specs: 14 liters, 575hp @ 1800rpm

If you change 396000 to 13000, you can plug liters directly ito the equation instead of first converting to cubic inches. Thus:

(hp*13000)/(rpm*liters)=BMEP