by PrecisionBoost » Wed Jun 24, 2009 3:03 am
The other option is to increase the RPM for the peak horsepower
Horsepower = (torque X RPM ) / 5252
So if you are making 100lbft of torque all the way up to 10,000 RPM you will make 100hp at 5252 RPM and 190hp at 10,000 RPM.
So if your goal is 500hp and you manage to get the RPM redline up to 10,000 RPM then you only need 262.6 lbft of torque.
At 5000 RPM that torque would give you 250 hp
Now....again using a 100hp baseline ( at 5000 RPM ) we can say that your going to need about 3.125 BAR of boost to manage 250hp at 5000 RPM..... which should give you 262.6 lbft of torque.... which will give you 500hp at 10,000RPM.
Now.... the big problem is that we've increased pressure due to the boost by about 62.5% but we've increased the forces on the crank due to RPM by a square factor
That is to say increasing RPM from 6500 to 10,000 will increase the forces during acceleration and deceleration by 236%
Given peak power does not occur at the peak acceleration or deceleration I'm going to guess that were talking about a total increase in forces in the range of 250%.
So..... boosting it to 6.5BAR only increased the force by 125% while boosting just 3.125 BAR and increasing redline will change the forces by 250%.
Now at this point you might think the 6.5 BAR is better... but we can remove rotational mass from the pistons, connecting rods and crank to significantly reduce the issues with accelerating and decelerating the rotational mass.
So... lighter forged pistons.... lighter forged rods..... lighter knife edged forged crankshaft.... will all combine to decrease the rotational mass by a huge amount while increasing the amount of force each component will take by a very significant factor.
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