Dyno'd high...why? Dyno experts needed.
#1
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I searched and searched but can't seem to find a reasonable explanation that would account for what appears to be excessively high numbers. I read that if the weight is off on this type of dyno, it skews the results, but not by more than a few points (the example I saw was using 500lbs of weight difference). I now turn to the experts...
Here are the details:
01 Firebird A4 3.23
GM Hotcam*, LS6 heads (no other head work)
LT headers, ORY, catback
*Cam Doctor specs for this cam are 221/228 instead of the GM advertised 219/228.
Dynoed on a Clayton Eddy Current dyno. Max rwhp/rwtq = 432.1/383.9 My high expectations were 380/370.
Here is the graph (personal data removed):
Here are the details:
01 Firebird A4 3.23
GM Hotcam*, LS6 heads (no other head work)
LT headers, ORY, catback
*Cam Doctor specs for this cam are 221/228 instead of the GM advertised 219/228.
Dynoed on a Clayton Eddy Current dyno. Max rwhp/rwtq = 432.1/383.9 My high expectations were 380/370.
Here is the graph (personal data removed):
![](http://img273.imageshack.us/img273/7614/dyno1a8ij.jpg)
#3
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Originally Posted by SideStep
The Dyno-graph reads MAX speed 40MPH. Did you dyno in 1st gear??? That would result in very high numbers.... What kind of dyno is it???
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Dyno: Clayton Eddy current.
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It's real hard to convert that dyno to a dyno jet type dyno. Just find closest Dyno jet and try again, make sure it's SAE corrected numbers too....That combo might surprise you...380-400 on dyno jet is my guess...Don't know the closest but LAPD (Los Angeles Performance Division) in Chatsworth and Mech Tech (if it's still there) in Escondido have them...You always dyno higher nearest 1 to 1 ratio (less friction) lower gear ratios (like 1st or 2nd) will dyno less....
Last edited by jimbob; 01-02-2006 at 07:07 PM.
#5
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Originally Posted by jimbob
It's real hard to convert that dyno to a dyno jet type dyno. Just find closest Dyno jet and try again, make sure it's SAE corrected numbers too....That combo might surprise you...380-400 on dyno jet is my guess...Don't know the closest but LAPD (Los Angeles Performance Division) in Chatsworth and Mech Tech (if it's still there) in Escondido have them...You always dyno higher nearest 1 to 1 ratio (less friction) lower gear ratios (like 1st or 2nd) will dyno less....
#6
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wrong factors on a eddy current dyno can really alter the hp numbers of the device, if the load cell is not calibrated correctly, the output can vary HUGE.
For example, my car has put down 171, then 420, then finally 297 with a miscalibrated eddy current dyno when I was calibrating it. Once calibrated correctly, the numbers were what I expected, (about 10-15% lower than a dynojet)
Fortunately, I have a friend with a dynojet, so I can just use that to verify the numbers, but most people don't have that luxury
Ryan.
For example, my car has put down 171, then 420, then finally 297 with a miscalibrated eddy current dyno when I was calibrating it. Once calibrated correctly, the numbers were what I expected, (about 10-15% lower than a dynojet)
Fortunately, I have a friend with a dynojet, so I can just use that to verify the numbers, but most people don't have that luxury
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Ryan.
#7
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Originally Posted by slow
wrong factors on a eddy current dyno can really alter the hp numbers of the device, if the load cell is not calibrated correctly, the output can vary HUGE.
For example, my car has put down 171, then 420, then finally 297 with a miscalibrated eddy current dyno when I was calibrating it. Once calibrated correctly, the numbers were what I expected, (about 10-15% lower than a dynojet)
Fortunately, I have a friend with a dynojet, so I can just use that to verify the numbers, but most people don't have that luxury
Ryan.
For example, my car has put down 171, then 420, then finally 297 with a miscalibrated eddy current dyno when I was calibrating it. Once calibrated correctly, the numbers were what I expected, (about 10-15% lower than a dynojet)
Fortunately, I have a friend with a dynojet, so I can just use that to verify the numbers, but most people don't have that luxury
![Winky](https://ls1tech.com/forums/images/smilies/LS1Tech/gr_wink.gif)
Ryan.
Is the load cell like the counterweight providing the resistance?
Yeah, the guy who dyno-tuned the car (who did an excellent job btw) said they checked the calibration because they were in shock at the numbers and didn't believe them at first either. He also said it appeared legit due to the results on subsequent vehicles. These vehicles had dyno'd there before and 1 also went to the track and the results were what was expected given his numbers.
Are the factors and calibration that you speak of change or need recalibration/resetting between vehicles? Or is it just the weight of the vehicle that needs to be changed?
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#8
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Originally Posted by Big Daddy Bry
Thanks for info Ryan.
Is the load cell like the counterweight providing the resistance?
Is the load cell like the counterweight providing the resistance?
Yeah, the guy who dyno-tuned the car (who did an excellent job btw) said they checked the calibration because they were in shock at the numbers and didn't believe them at first either. He also said it appeared legit due to the results on subsequent vehicles. These vehicles had dyno'd there before and 1 also went to the track and the results were what was expected given his numbers.
Are the factors and calibration that you speak of change or need recalibration/resetting between vehicles? Or is it just the weight of the vehicle that needs to be changed?
Are the factors and calibration that you speak of change or need recalibration/resetting between vehicles? Or is it just the weight of the vehicle that needs to be changed?
You still do not want to get hung up on comparing dyno numbers or dyno racing although you can get the spread tightened up if everyone would use a test standard. I know, keep dreaming....
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#9
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Typically, it is a set, and forget for a while for the calibration.
I reformatted, installed windows XP, and then installed an updated version of the software for the dyno computer, which is why recalibration was necessary. Just showing what 'can' happen if the calibration is off.
Ryan
I reformatted, installed windows XP, and then installed an updated version of the software for the dyno computer, which is why recalibration was necessary. Just showing what 'can' happen if the calibration is off.
Ryan