UK vs US dyno figures
 

Hi Guy's

I have been told by someone in the US that my rwhp 368 on my to4r 0.84 a/r
is very good figure becuase the dynapacks used inthe UK generally reads 15%
lower than the dynojet often used in the US therefore he says my 368 rwhp if it was dyno'd in the US on a dyno jet would of been approx 423rwhp can anyone confimr this is true? I have always kind of wondered why hp figures in US was generally a lot higher compared to the UK for similar setup etc..

rgds


--------------------

Brian Ellis (Rotary Imports Ltd)
www.rotaryimports.com
info@rotaryimports.com
tel:07950-693-616
fax:0208-405-9580

Dynapacks typically read lower than Dynojets (doesn't necessarily matter what country they are in). However, I've never seen an exact percentage of the difference being consistant. Most of the differences I've seen have been around 4-5% difference.

Thanks for reply,

I actually made a typo it's a dyno dynamics dynamometer not a dynopack.

rgds

Dyno Dynamics reads very accurately!
There usually about 10-15% lower then Dynojet

Thanks for clarification Enzo.

rgds

Yes, Dyno Dynamic is one of the most accurate dynos out there.

The spec's for the 450 dyno dynamics model list twin 8.5" rollers. This twin roller method increases tire flex load losses vs single 48" dynojet roller for 2 reasons:

1) drive wheel support load increase of about 15%, due to load vectoring.

2) 8.5" roller pair pinch into the tire much more than the big dynojet 48" roller.

dynojets are inertial dynos, so at best the results are a stab in the dark. In terms of using them to work out actual HP they are worthless. shops buy them because they are cheap and the unitiated like having a power run to brag about.

They have also led to this culture of quoting RWHP and thinking it means something. It doesn't. A coast down test to calculate rolling losses on an eddy current dyno is the closest you will get to a repeatable and usable figure, but even then, with an uncalibrated dyno you are still nowhere unless you are comparing 2 cars on the same day on the same dyno.

Don't believe me. Next time you do a dynojet run, repeat it with another 10PSI in the tyres. Then put 185 width rubber on and try again.