4.10 gears consume horse power?
07-26-2012, 10:03 AM
#1
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4.10 gears consume horse power?
I read this on Kennebell's website. I didn't realize it was that much of a difference. They claim 18hp less with 3.73's.
http://kennebell.net/KBWebsite/Commo...esAndCures.pdf
It's under dyno tuning towards the bottom of the page. I keep thinking back to a 10 speed I had as a kid. Put it in 1st gear and it was really easy to pedal, but you had to pedal a lot to go anywhere. Put in in 10th gear and it was really hard to pedal, but you would move much faster for each revolution of the pedals.
So all things being equal, you will dyno lower with 4.10's vs 3.31 or higher. Obviously on the street you will accelerate quicker, even though a dyno would show a drop in hp.
http://kennebell.net/KBWebsite/Commo...esAndCures.pdf
It's under dyno tuning towards the bottom of the page. I keep thinking back to a 10 speed I had as a kid. Put it in 1st gear and it was really easy to pedal, but you had to pedal a lot to go anywhere. Put in in 10th gear and it was really hard to pedal, but you would move much faster for each revolution of the pedals.
So all things being equal, you will dyno lower with 4.10's vs 3.31 or higher. Obviously on the street you will accelerate quicker, even though a dyno would show a drop in hp.
07-26-2012, 04:45 PM
#6
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I had read before there was a loss, but that's the first I've seen actual numbers. I'm sure they dyno a lot of cars, so they should know.
Last edited by moosestang; 07-26-2012 at 04:58 PM.
07-26-2012, 05:13 PM
#7
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This is exactly the reason why most tuners use a dyno to tune, not for bragging rights. I would rather have a car that did well at the track or on the street, as opposed to a car that showed a higher number on a dyno.
I've known a few speed shops that will tweak little things like tire pressure, etc to make your car put down a bigger number on the dyno and make you think that they've done more to your car than they really have.
I've known a few speed shops that will tweak little things like tire pressure, etc to make your car put down a bigger number on the dyno and make you think that they've done more to your car than they really have.
07-26-2012, 05:36 PM
#8
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This is exactly the reason why most tuners use a dyno to tune, not for bragging rights. I would rather have a car that did well at the track or on the street, as opposed to a car that showed a higher number on a dyno.
I've known a few speed shops that will tweak little things like tire pressure, etc to make your car put down a bigger number on the dyno and make you think that they've done more to your car than they really have.
I've known a few speed shops that will tweak little things like tire pressure, etc to make your car put down a bigger number on the dyno and make you think that they've done more to your car than they really have.
07-27-2012, 12:29 PM
#9
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this was kind of a confusing subject to comprehend bc of so many mixed opinions and explainations, but people that have dyno'd many cars say that the gears do affect the hp, but their expaination of why would always differ.
it is in how the dynojet calculates the RWHP that the HP gets lost in the gears:
the exact numbers are most likely off. but its the basic way the dynojet figures HP.
thats the best explaination i could find.
it is in how the dynojet calculates the RWHP that the HP gets lost in the gears:
On the dynojet (DJ) 224 unloaded (inertia) dyno, it will only measure hp. It will then back calculate the tq based on the hp and rpm. It does this by calculating the hp required to spin up the 2400lb drum at specific rates. If you spin it up faster, you make more hp. If there is no rpm signal, it can only measure hp. If you have a loaded DJ, then it can measure TQ directly from the load cell attached to the eddy current "loader". This TQ cell gets calibrated (hopefully before each use!). Other dynos like the mustang dyno and the dynomax dynos can measure the TQ based on how much current the eddy current load cell is using. They do not use heavy rollers, but instead use electrical current to slow the increase in speed, basically like an electrical motor operated in reverse.
this is how the dyno figures hp/tq
wheel HP = (wheel rpm x wheel tq) / 5252
when changing gears in that equation, the wheel tq and the number 5252 will stay the same, but the wheel rpm will be lower (since you change from for instance 3.55 to 4.10), since you will lose a slight top speed with the gear change.
now since that top speed is slightly less, it will equate to less hp on the dyno.
your engine hp is the same, only the way the dyno figures hp to the wheels will be less.
but your car will go faster.
wheel HP = (wheel rpm x wheel tq) / 5252
x=rwhp, and other numbers are just for instance.
x=(5000 x 400) / 5252
x= 380.8073
now, you swap for shorter gears (3.55 to 4.10) but i'm not sure about the difference, but the wheel rpm will be lower bc of the shorter gears. the torque stays the same bc it's on a loaded dyno.
x= (4900 x 400) / 5252
x= 373.1912
wheel HP = (wheel rpm x wheel tq) / 5252
when changing gears in that equation, the wheel tq and the number 5252 will stay the same, but the wheel rpm will be lower (since you change from for instance 3.55 to 4.10), since you will lose a slight top speed with the gear change.
now since that top speed is slightly less, it will equate to less hp on the dyno.
your engine hp is the same, only the way the dyno figures hp to the wheels will be less.
but your car will go faster.
wheel HP = (wheel rpm x wheel tq) / 5252
x=rwhp, and other numbers are just for instance.
x=(5000 x 400) / 5252
x= 380.8073
now, you swap for shorter gears (3.55 to 4.10) but i'm not sure about the difference, but the wheel rpm will be lower bc of the shorter gears. the torque stays the same bc it's on a loaded dyno.
x= (4900 x 400) / 5252
x= 373.1912
the exact numbers are most likely off. but its the basic way the dynojet figures HP.
thats the best explaination i could find.
