Question on a Dyno Conversion Factor?
11-19-2009, 08:17 AM
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Question on a Dyno Conversion Factor?
Ok so say a car makes 230whp on a Dynopack stock and then makes 414whp. The stock crank hp is 287 so 230 is about 80% of that. Would that mean that my 414whp is like 520 crank hp? (287 * .80 = 230, 520 * .80 = 416) The reason I ask this is because my car doesn't feel like it has 500+ hp (even though it supercharged and only makes this from 6000 and up lol). Never has. Doesn't even feel like it's making 450hp. And yes I know the torque is linear because of the supercharger and all of that. Is my way of looking at this dyno correction off?
11-19-2009, 08:43 AM
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You might just be getting use to the power and that's y it doesn't feel like u have all that hp. Thats what happened to me (quick). After not driving it for awhile, when i did drive it it felt like it was a rocket... Now that im building i haven't driven it in so long that my other slow **** cars feel like rockets..lol.
11-19-2009, 09:17 AM
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Same thing happens to me...i have to remind my self every now and then... and i do that by reving to about 4000 slowly on the road and then punching it. That reminds you exactly how much power you have
11-19-2009, 09:44 AM
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a few trips down the drag strip will remind you. or just drive without the cog belt for a few days. i could never believe how much different the car was without the belt.
Also your crank HP is way over 500 then bc the supercharger is very inefficient. prolly closer to 550 crank hp.
Also your crank HP is way over 500 then bc the supercharger is very inefficient. prolly closer to 550 crank hp.
11-20-2009, 04:46 AM
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Ok so say a car makes 230whp on a Dynopack stock and then makes 414whp. The stock crank hp is 287 so 230 is about 80% of that. Would that mean that my 414whp is like 520 crank hp? (287 * .80 = 230, 520 * .80 = 416) The reason I ask this is because my car doesn't feel like it has 500+ hp (even though it supercharged and only makes this from 6000 and up lol). Never has. Doesn't even feel like it's making 450hp. And yes I know the torque is linear because of the supercharger and all of that. Is my way of looking at this dyno correction off?
Using your example, your baseline dyno gives 57bhp loss to the drivetrain (this is the friction and inertia of the transmission, driveshaft, differential, axles and wheels). Now if you drop in a new powerplant, i.e., supercharged 3.5l 6 cyl, what has changed in the drivetrain? Nothing. It still takes the same 57bhp to overcome the friction and inertia. In other words, drivetrain loss is a constant, not a variable.
So your engine is really making approx. 470 bhp, which is probably closer to what your butt dyno is telling you.
Last edited by arizzee; 11-20-2009 at 04:47 AM.
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11-20-2009, 05:04 AM
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Some folks like to use a % to calculate backwards to get a bhp number from a whp but this type of calcuation ignores the physics of what going on from the flywheel to the wheels.
Using your example, your baseline dyno gives 57bhp loss to the drivetrain (this is the friction and inertia of the transmission, driveshaft, differential, axles and wheels). Now if you drop in a new powerplant, i.e., supercharged 3.5l 6 cyl, what has changed in the drivetrain? Nothing. It still takes the same 57bhp to overcome the friction and inertia. In other words, drivetrain loss is a constant, not a variable.
So your engine is really making approx. 470 bhp, which is probably closer to what your butt dyno is telling you.
Using your example, your baseline dyno gives 57bhp loss to the drivetrain (this is the friction and inertia of the transmission, driveshaft, differential, axles and wheels). Now if you drop in a new powerplant, i.e., supercharged 3.5l 6 cyl, what has changed in the drivetrain? Nothing. It still takes the same 57bhp to overcome the friction and inertia. In other words, drivetrain loss is a constant, not a variable.
So your engine is really making approx. 470 bhp, which is probably closer to what your butt dyno is telling you.
11-20-2009, 06:38 AM
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Not many, I guess I just always thought 500hp was a ***** ton of power and it just doesn't feel like a lot now that I have it. I think part of it may be the linear torque and power curve of the supercharger though. I have gone up against some 05-09 Vetts (Which have about 440hp) on the highway and pulled away from them pretty well so I guess that confirms my doubts. I guess it's just never enough.
11-20-2009, 11:53 AM
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Not many, I guess I just always thought 500hp was a ***** ton of power and it just doesn't feel like a lot now that I have it. I think part of it may be the linear torque and power curve of the supercharger though. I have gone up against some 05-09 Vetts (Which have about 440hp) on the highway and pulled away from them pretty well so I guess that confirms my doubts. I guess it's just never enough.
That is the very reason I dislike centrifugal superchargers. I don't like waiting until redline for all of my boost.
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