[alfa] re: 2 litre horsepower

[White Anthony <anthony.white@xxxxxxxxxxxxxx>]

Being interested in this conversation about how much power could be made from
a 2 litre Alfa engine, I'd thought I'd contribute a few numbers.  
 
I believe that the theoretical maximum torque for a naturally aspirated 2
litre running on petrol (gasoline) is 260 Nm, or 191 lbft (less frictional
losses).  This level of torque requires combustion chamber pressures of about
16.5 bar.  
 
From there, it's quite an easy thing to calculate the theoretical power a 2
litre engine could produce at any given rpm:
 
  

RPM

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000


Torque (ft/lb)

191

191

191

191

191

191

191

191

191

191


Power (hp)

36.4

72.7

109.1

145.5

181.8

218.2

254.6

290.9

327.3

363.7

 
Of course, torque curves aren't linear, so you'd have to pick your torque
peak, and there will also be frictional losses to be accounted for.  
 
The Alfa Twinspark F3 engine made torque of 240 Nm (177 lbft).  It had a 24mm
airbox restrictor that limited the revs it could use, so it made about 170 hp
at 5500 rpm.  They probably couldn't make the full 260 Nm of torque, due to
being only two valve engines.  The four valve F3s were making the full 260
Nm.  
 
Current F1 engines run with combustion pressures of about 15 bar, and are
making almost exactly 120 Nm of torque per litre capacity -- 360 Nm all up,
which gives 960 hp at 19000 rpm, 910 hp at 18000 rpm, or 858 hp at 17000 rpm
(all less frictional losses).    
 
Meanwhile, current European 2 Litre touring cars are also making about the
same 120 Nm of torque per litre capacity, giving them around 260 hp at 8000
rpm.  
 
Of course, none of this is replicable in your daily driver.  
 
Regards,
Anthony White
Wellington, NZ
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