BigDaddyBry

iTrader: (15)

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):

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???

BigDaddyBry

iTrader: (15)

Yeah, I saw that too. I was told it was a third gear pull, but that is something to consider.

Dyno: Clayton Eddy current.

jimbob

iTrader: (4)

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....

BigDaddyBry

iTrader: (15)

Thanks for the info and feedback Jimbob. I think I found a place in Colton. I should be able to get it there by the end of January. In the meantime, I sure would like to know what could have caused the elevated numbers. Just curious.

slow

iTrader: (7)

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.

BigDaddyBry

iTrader: (15)

Thanks for info 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?

DynoDR

iTrader: (1)

The load cell or strain gauge is a small device that measures the force applied. The conterweight is exactly that, a conterweight to help with the sudden changes in load or "soften" the shock of the dyno. The eddy brake is a large magnetic device that looks like an electric motor. That is what provides the resistence in simple terms.

The calibration of the dyno does not need to be changed or reset between vehicles. The vehicle weight number that you input will change it some but you do not need to worry about actual vehicle weight if you use a constant accel/sec rate to test with. I know I keep saying this but if people would forget all the different vehicle weight inputs of the eddy current dynos and use a set accel alot of the large varying numbers would be history. Vehicle weight or vehicle simulation is great for driveability testing or tuning but for power curve comparing it gets you all over the place.

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....

slow

iTrader: (7)

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

BigDaddyBry

iTrader: (15)

Thanks for the info and education guys.

Yes, the proof will be on the track. This is educational and the dyno numbers will be verified nonetheless.

BlackHawk T/A

iTrader: (3)

If those numbers are correct I think you should trap around 120mph, give or take a couple.