Holdener F/I power calculation formula
05-22-2006, 06:49 AM
#1
6600 rpm clutch dump of death Administrator
Thread Starter
Holdener F/I power calculation formula Holdener is an contributing author in the Ford Magazines. I saw this formula, and figured some folks might find it useful. You can take the power a motor made in N/A form, and then using this formula come up with a pretty good idea of what it should make in a boosted application. This is good for the folks doing bolt on superchargers.
F/I power = original power * pressure ratio
original power = N/A HP
pressure ratio = (boost pressure/14.7) + 1
Now, from this number, you have to factor in and subtract the hp loss from supercharger. That will vary, and that is a key factor on making this all jive. As an example.
An engine making 365 run at 8.7 psi should make 581 HP
365* ((8.7/14.7) + 1)
365 * 1.59 = 581
When checked on the dyno it actually made 533 (subtract blower loss, in this case 48HP). An average blower can loose you anywhere from 50-75 HP on the average street car. The bigger the blower, etc... the more ploss you may see. This isn't an absolute, but it gives you an idea of where you'll end up at.
F/I power = (original power * pressure ratio) - blower loss
(365 * 1.59) - 48 = 533
F/I power = original power * pressure ratio
original power = N/A HP
pressure ratio = (boost pressure/14.7) + 1
Now, from this number, you have to factor in and subtract the hp loss from supercharger. That will vary, and that is a key factor on making this all jive. As an example.
An engine making 365 run at 8.7 psi should make 581 HP
365* ((8.7/14.7) + 1)
365 * 1.59 = 581
When checked on the dyno it actually made 533 (subtract blower loss, in this case 48HP). An average blower can loose you anywhere from 50-75 HP on the average street car. The bigger the blower, etc... the more ploss you may see. This isn't an absolute, but it gives you an idea of where you'll end up at.
F/I power = (original power * pressure ratio) - blower loss
(365 * 1.59) - 48 = 533
05-22-2006, 12:48 PM
#4
(# of boost / 14.7 = % gained), original hp + % gained = new hp
ex... 8.7psi / 14.7 = .59 or 59%, 365hp(na) + 59% = 580hp, you need to dyno the car na in like conditions to make sure the starting hp is correct, dont forget that you may have more loss in the tune keeping the motor together than accual blower loss, your hp would be much higher running a 12.5 afr and more timing but **** might scatter on a stock bottom end...
ex... 8.7psi / 14.7 = .59 or 59%, 365hp(na) + 59% = 580hp, you need to dyno the car na in like conditions to make sure the starting hp is correct, dont forget that you may have more loss in the tune keeping the motor together than accual blower loss, your hp would be much higher running a 12.5 afr and more timing but **** might scatter on a stock bottom end...
