Gearing vs Horsepower
02-13-2007, 06:45 PM
#16
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Originally Posted by danglerb
I'm too busy trying to fit GTS valve caps on my wheels. What sort of rwhp gain should that have, or is it just more torque?
02-13-2007, 07:00 PM
#17
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All assume its not a joke, so here it goes:
You guys are close. Gearing is only used, and we are talking about automotive applications, so you can optimize the application of HP to the wheels
AS we have been over before:
Acceleration = Power(mass/velocity)
this means acceleration is INEXTRICABLY tied to power. look at the power curve of your vehicle, at any vehicle speed, max potential for acceleration will happen as close to max HP as possible. Gearing shifts this speed range up or down, but doesn’t give or make hp.
again, also don’t confuse engine torque with rear wheel torque that is developed through the gear box. this, also, is determined by HP. Engine torque at any speed, will determine the torque you can have at the rear wheels as multiplied through the gear box. This is why a viper V10 at 550ft-lbs of max torque and a 250ft-lbs max torque Porsche 911 RSR both, with 450rwhp, will accelerate exactly the same at all speeds! (providing they have the same gear spacing and the same hp curve shape) now, the gear box becomes a maximizer if you will for the 911 in reality. by putting the gears closer together, you effectively gain the amount of HP you can apply to the rear wheels, so that a 438rwhp 911 can be equal at all speeds to a 460rwhp viper. (if the cars weigh the same)
Gearing is used to keep your engine at or as as close as possible to max hp as possible with respect for maximizing acceleration. Now, as far as choosing rear end differntials, this has the effect of shifting the sweet spots over a given speed range using multiple gears. I have posted an example of this too, based on computer simulation. (viper 3.08 vs viper 3.54:1 rear ends)
in the end, based on the target speeds, up to 118mph,from 20mph, the 3.08 was faster, however, from 0-20, providing launch control and grip issues not taken into effect, the 3.54 gear box provides better acceleration. also, ironically, if the speed range goes to 155mph, the advantage goes back to the 3.54. its a series of trade offs needed to be examined for any and all applications of HP, weight, and speed.
Mk
You guys are close. Gearing is only used, and we are talking about automotive applications, so you can optimize the application of HP to the wheels
AS we have been over before:
Acceleration = Power(mass/velocity)
this means acceleration is INEXTRICABLY tied to power. look at the power curve of your vehicle, at any vehicle speed, max potential for acceleration will happen as close to max HP as possible. Gearing shifts this speed range up or down, but doesn’t give or make hp.
again, also don’t confuse engine torque with rear wheel torque that is developed through the gear box. this, also, is determined by HP. Engine torque at any speed, will determine the torque you can have at the rear wheels as multiplied through the gear box. This is why a viper V10 at 550ft-lbs of max torque and a 250ft-lbs max torque Porsche 911 RSR both, with 450rwhp, will accelerate exactly the same at all speeds! (providing they have the same gear spacing and the same hp curve shape) now, the gear box becomes a maximizer if you will for the 911 in reality. by putting the gears closer together, you effectively gain the amount of HP you can apply to the rear wheels, so that a 438rwhp 911 can be equal at all speeds to a 460rwhp viper. (if the cars weigh the same)
Gearing is used to keep your engine at or as as close as possible to max hp as possible with respect for maximizing acceleration. Now, as far as choosing rear end differntials, this has the effect of shifting the sweet spots over a given speed range using multiple gears. I have posted an example of this too, based on computer simulation. (viper 3.08 vs viper 3.54:1 rear ends)
in the end, based on the target speeds, up to 118mph,from 20mph, the 3.08 was faster, however, from 0-20, providing launch control and grip issues not taken into effect, the 3.54 gear box provides better acceleration. also, ironically, if the speed range goes to 155mph, the advantage goes back to the 3.54. its a series of trade offs needed to be examined for any and all applications of HP, weight, and speed.
Mk
Originally Posted by BRETT AINLEY
Hi
Not sure if this is a joke but...
Gearing gives you speed or acceleration...not horsepower...
Well to be precise ..gearing allows the hp you have already got to be used in different ways....low gearing = fast accelleration......high gearing = slower acceleration but higher top speed...
So to answer your question.....gearing gives you precisely NO extra horsepower...
All the best Brett
PORSCHE 928 S2 AUTO V8 4.7 LTR 1986 IRIS METALLIC BLUE WITH X-PIPES ,RMB ,PROMAX CHIPS, KICKDOWN SWITCH, K&N, WIZARDS OF NOS - NITROUS KIT 150 HP JETTING - 505 BHP / 500 FT LBS TORQUE
PCGB UK 928 FORUM MODERATOR - Email managingdirector@pchealthcare.co.uk
Not sure if this is a joke but...
Gearing gives you speed or acceleration...not horsepower...
Well to be precise ..gearing allows the hp you have already got to be used in different ways....low gearing = fast accelleration......high gearing = slower acceleration but higher top speed...
So to answer your question.....gearing gives you precisely NO extra horsepower...
All the best Brett
PORSCHE 928 S2 AUTO V8 4.7 LTR 1986 IRIS METALLIC BLUE WITH X-PIPES ,RMB ,PROMAX CHIPS, KICKDOWN SWITCH, K&N, WIZARDS OF NOS - NITROUS KIT 150 HP JETTING - 505 BHP / 500 FT LBS TORQUE
PCGB UK 928 FORUM MODERATOR - Email managingdirector@pchealthcare.co.uk
02-13-2007, 07:04 PM
#18
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Originally Posted by mark kibort
All assume its not a joke, so here it goes:
You guys are close. Gearing is only used, and we are talking about automotive applications, so you can optimize the application of HP to the wheels
AS we have been over before:
Acceleration = Power(mass/velocity)
this means acceleration is INEXTRICABLY tied to power. look at the power curve of your vehicle, at any vehicle speed, max potential for acceleration will happen as close to max HP as possible. Gearing shifts this speed range up or down, but doesn’t give or make hp.
again, also don’t confuse engine torque with rear wheel torque that is developed through the gear box. this, also, is determined by HP. Engine torque at any speed, will determine the torque you can have at the rear wheels as multiplied through the gear box. This is why a viper V10 at 550ft-lbs of max torque and a 250ft-lbs max torque Porsche 911 RSR both, with 450rwhp, will accelerate exactly the same at all speeds! (providing they have the same gear spacing and the same hp curve shape) now, the gear box becomes a maximizer if you will for the 911 in reality. by putting the gears closer together, you effectively gain the amount of HP you can apply to the rear wheels, so that a 438rwhp 911 can be equal at all speeds to a 460rwhp viper. (if the cars weigh the same)
Gearing is used to keep your engine at or as as close as possible to max hp as possible with respect for maximizing acceleration. Now, as far as choosing rear end differntials, this has the effect of shifting the sweet spots over a given speed range using multiple gears. I have posted an example of this too, based on computer simulation. (viper 3.08 vs viper 3.54:1 rear ends)
in the end, based on the target speeds, up to 118mph,from 20mph, the 3.08 was faster, however, from 0-20, providing launch control and grip issues not taken into effect, the 3.54 gear box provides better acceleration. also, ironically, if the speed range goes to 155mph, the advantage goes back to the 3.54. its a series of trade offs needed to be examined for any and all applications of HP, weight, and speed.
Mk
You guys are close. Gearing is only used, and we are talking about automotive applications, so you can optimize the application of HP to the wheels
AS we have been over before:
Acceleration = Power(mass/velocity)
this means acceleration is INEXTRICABLY tied to power. look at the power curve of your vehicle, at any vehicle speed, max potential for acceleration will happen as close to max HP as possible. Gearing shifts this speed range up or down, but doesn’t give or make hp.
again, also don’t confuse engine torque with rear wheel torque that is developed through the gear box. this, also, is determined by HP. Engine torque at any speed, will determine the torque you can have at the rear wheels as multiplied through the gear box. This is why a viper V10 at 550ft-lbs of max torque and a 250ft-lbs max torque Porsche 911 RSR both, with 450rwhp, will accelerate exactly the same at all speeds! (providing they have the same gear spacing and the same hp curve shape) now, the gear box becomes a maximizer if you will for the 911 in reality. by putting the gears closer together, you effectively gain the amount of HP you can apply to the rear wheels, so that a 438rwhp 911 can be equal at all speeds to a 460rwhp viper. (if the cars weigh the same)
Gearing is used to keep your engine at or as as close as possible to max hp as possible with respect for maximizing acceleration. Now, as far as choosing rear end differntials, this has the effect of shifting the sweet spots over a given speed range using multiple gears. I have posted an example of this too, based on computer simulation. (viper 3.08 vs viper 3.54:1 rear ends)
in the end, based on the target speeds, up to 118mph,from 20mph, the 3.08 was faster, however, from 0-20, providing launch control and grip issues not taken into effect, the 3.54 gear box provides better acceleration. also, ironically, if the speed range goes to 155mph, the advantage goes back to the 3.54. its a series of trade offs needed to be examined for any and all applications of HP, weight, and speed.
Mk
Now that was an excellent technical post..I even printed it out to read again
Thanks
All the best Brett
02-13-2007, 07:28 PM
#20
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Woo.............. knarley, man........ 
02-13-2007, 09:19 PM
#25
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Originally Posted by BRETT AINLEY
Hi Mark
Now that was an excellent technical post..I even printed it out to read again
Thanks
All the best Brett
Now that was an excellent technical post..I even printed it out to read again
Thanks
All the best Brett
I've decided to tattoo that post by mark on my inner thigh. In fact I've written the publishers of the Bible, I'd like to add it as the last chapter in Revelation. 
02-13-2007, 09:28 PM
#29
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Originally Posted by Danglerb.
I have to say, I've come to really respect Mark Kebord during my 4 months on this list. I've read every word he's ever written at least 5 or 6 times, and everytime I do, I get MORE out of it.
So, this brings me to the question: How much gearing is required to get to say, 400hp? I've been looking for a 2.20 to swap into my trans, I figure conservatively that'sll give me between 400 - 500hp. What do you guys think? Are there aftermarket gear manufacturers for the 928?
So, this brings me to the question: How much gearing is required to get to say, 400hp? I've been looking for a 2.20 to swap into my trans, I figure conservatively that'sll give me between 400 - 500hp. What do you guys think? Are there aftermarket gear manufacturers for the 928?
