I'm sure some of you know the formula: bhp = (factor) x (cid) x (psi +14.7)...
03-13-2001, 11:21 AM
#2
The problem with this formula is the factor itself, but is is an ok approximation of how much gain
you will get if you are increasing the amount of air going into your cylinders via pressure. It is an approximation of how much more power you will get whether you are calculating at the wheels or at the crank.
For example, if you know that your 1.8T (115 cid) car makes 150hp at the crank with say 7psi, then you can calculate a baseline "factor" of roughly 0.06. Then if you want to see what kind of hp are possible with a 14 psi boost, you plug the numbers in and get something like 198hp. But again, the problem here is that you are using the same factor - which lumps efficiency, all conditions into a single number.
But, if you are thinking of tuning, it is not a bad formula, just start your fuel on the rich side as well, and fine tune later.
For example, if you know that your 1.8T (115 cid) car makes 150hp at the crank with say 7psi, then you can calculate a baseline "factor" of roughly 0.06. Then if you want to see what kind of hp are possible with a 14 psi boost, you plug the numbers in and get something like 198hp. But again, the problem here is that you are using the same factor - which lumps efficiency, all conditions into a single number.
But, if you are thinking of tuning, it is not a bad formula, just start your fuel on the rich side as well, and fine tune later.
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