so i dynoed today
04-25-2008 | 04:43 PM
#32
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Joined: 08-13-05
Posts: 5,733
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From: the glove
the numbers are a bit off, one would assume, however the man above is partially on the rite track.
those ugly and large rims are costing you power. i've seen 40-60hp lost due to brake size increases, let alone bigger wheels.
its not just weight that comes into play in this case, a larger wheel can be lighter then the smaller unit its replacing, yet you'll still lose power to the weight being farther away from the focus point (the CV) thus requiring more torque to initiate its rotation, and sustain it. a heavier and larger wheel simply makes this effect exponential.
with HP being a direct relation of torque and RPM this effect is self evident. the lesser power your car comes with will only make this effect more apparent.
i, however would go to a different shop, you should be down on power, but not that amount.
EDIT- is your car a stick or auto? the loss of power that torque converters cause would play into the power loss the of the rims as well.
EDIT2- the dyno run "sounds" like its legit, the load was steady and constant across the rev range. doesnt mean that the calibration is outta wack tho either.
those ugly and large rims are costing you power. i've seen 40-60hp lost due to brake size increases, let alone bigger wheels.
its not just weight that comes into play in this case, a larger wheel can be lighter then the smaller unit its replacing, yet you'll still lose power to the weight being farther away from the focus point (the CV) thus requiring more torque to initiate its rotation, and sustain it. a heavier and larger wheel simply makes this effect exponential.
with HP being a direct relation of torque and RPM this effect is self evident. the lesser power your car comes with will only make this effect more apparent.
i, however would go to a different shop, you should be down on power, but not that amount.
EDIT- is your car a stick or auto? the loss of power that torque converters cause would play into the power loss the of the rims as well.
EDIT2- the dyno run "sounds" like its legit, the load was steady and constant across the rev range. doesnt mean that the calibration is outta wack tho either.
04-25-2008 | 04:49 PM
#37
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Joined: 08-13-05
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From: the glove
i.e. wheels that are 5lbs heavier would effect power by several factors of 5....same goes for larger rims, size wise.
it could vary well be a massively flawed dyno, i'm simply supplying you with ideas as to why the numbers are so different.
Last edited by 06black; 04-25-2008 at 04:49 PM. Reason: Automerged Doublepost
04-25-2008 | 04:55 PM
#38
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Joined: 10-01-06
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From: Maidstone, SK
I'm sticking by my theory....
Reasons;
The load is constant, which means it is applying load evenly though out the whole range... therefore it is reading the RPM/speed correct.
The torque number shown (131 ft-lb torque) is about right for the LE5. This tells me that the load cell is setup correctly, and reading properly.
Therefore, the system is simply failing to properly associate the torque value with the speed value and spit out a correct HP number.
I bet if you went and grabbed the raw data from that session, and manually entered it into excel with the correct RPM/Tq equation, that you'd get a reasonable HP number.
Edit:
The mustang dyno where I used to work did this last summer.... very similar situation... a hair puller for diagnosing, but a simple fix.
Reasons;
The load is constant, which means it is applying load evenly though out the whole range... therefore it is reading the RPM/speed correct.
The torque number shown (131 ft-lb torque) is about right for the LE5. This tells me that the load cell is setup correctly, and reading properly.
Therefore, the system is simply failing to properly associate the torque value with the speed value and spit out a correct HP number.
I bet if you went and grabbed the raw data from that session, and manually entered it into excel with the correct RPM/Tq equation, that you'd get a reasonable HP number.
Edit:
The mustang dyno where I used to work did this last summer.... very similar situation... a hair puller for diagnosing, but a simple fix.
04-25-2008 | 05:05 PM
#40
change the area in which the car has to rotate mass, and the return effect is exponential
i.e. wheels that are 5lbs heavier would effect power by several factors of 5....same goes for larger rims, size wise.
whats the weight difference then?
it could vary well be a massively flawed dyno, i'm simply supplying you with ideas as to why the numbers are so different.
i.e. wheels that are 5lbs heavier would effect power by several factors of 5....same goes for larger rims, size wise.
whats the weight difference then?
it could vary well be a massively flawed dyno, i'm simply supplying you with ideas as to why the numbers are so different.
04-25-2008 | 05:07 PM
#41
u got ripped off... i paid 60 for 2 and 3 woulda been like 75.. for that price i would expect a much better calibration or something
I'm sticking by my theory....
Reasons;
The load is constant, which means it is applying load evenly though out the whole range... therefore it is reading the RPM/speed correct.
The torque number shown (131 ft-lb torque) is about right for the LE5. This tells me that the load cell is setup correctly, and reading properly.
Therefore, the system is simply failing to properly associate the torque value with the speed value and spit out a correct HP number.
I bet if you went and grabbed the raw data from that session, and manually entered it into excel with the correct RPM/Tq equation, that you'd get a reasonable HP number.
Edit:
The mustang dyno where I used to work did this last summer.... very similar situation... a hair puller for diagnosing, but a simple fix.
Reasons;
The load is constant, which means it is applying load evenly though out the whole range... therefore it is reading the RPM/speed correct.
The torque number shown (131 ft-lb torque) is about right for the LE5. This tells me that the load cell is setup correctly, and reading properly.
Therefore, the system is simply failing to properly associate the torque value with the speed value and spit out a correct HP number.
I bet if you went and grabbed the raw data from that session, and manually entered it into excel with the correct RPM/Tq equation, that you'd get a reasonable HP number.
Edit:
The mustang dyno where I used to work did this last summer.... very similar situation... a hair puller for diagnosing, but a simple fix.
04-25-2008 | 05:07 PM
#42
04-25-2008 | 05:10 PM
#43
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Joined: 08-20-07
Posts: 2,061
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From: Irwin, Pa (S of Pittsburgh)
04-25-2008 | 05:59 PM
#45
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Joined: 10-01-06
Posts: 5,134
Likes: 0
From: Maidstone, SK
A 20ft-lb difference is nothing to be too terribly worried about.... the 60hp difference IS something to be worried about.
Look at it this way... his tq is 15% off from yours.... his power is 60% of yours....
Big difference.
04-25-2008 | 06:02 PM
#46
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Joined: 07-29-05
Posts: 7,926
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From: AZ
i bet he didn't offer any refund or the chance to come back at a later date did he? did you ask questions or maybe bring up that this doesn't sound right?
did any other cars dyno around that time that put out retarded numbers as well?
did any other cars dyno around that time that put out retarded numbers as well?
