ive ben told today that the "dyna pack" hub based dyno can and does read up to 60 or 70 bhp higher than other types of dynos and that the "dyno dynamics" dyno which holds the wheels to the a set of rollers is far more accurate,

is this possible that this much bhp is over quoted and thus leaving owners with nothing more than pub bhp????


this is just what i heard so dont shoot the messenger

 

I've seen these before. i was told they are good for high power cars as there can be no wheelspin so give accurate figures, also they can be used on 4x4 cars. i suppose its the same as any dyno though it depends on how well its calibrated.

but i'll stick my neck out and say 60 - 70hp is bullshit.

 

Any dyno operator can make any dyno read anything they want.

 

i would have thought with not having the drag of the tyres and rotational mass of the wheels then the readings would be higher yes but that seems a little extreme, i wouldnt trust dyno figures anyway as its all down to who operates them as to what figure you will get anyway they are allright for a ballpark figure but thats about it
i personally couldnt give a toss what bhp and torque my car makes all i care about is that its setup right and isnt going to melt when i give it some!

 

A properly operated hub dyno should give no different readings to a regular set of rollers, The advantage is that you get no wheelspin, and it's portable. The downside is that it's more of an arse to get cars on and off.

No idea where your 60bhp figure comes from.

 

i found it hugely weird as well, i thought how could you lose 60bhp, i know that setings can be messed with but surely there is an upper or lower levels at which point the operater can no longer influence surely?????

 

who told you this, someone who has a vested interest in a dyno dynamics set of rollers i presume?

as above, you definitely should get a higher reading with a hub dyno than a chassis dyno as you don't have the losses of the tyre/roller contact, which is not unreasonable to estimate at around 70hp - in fact you could check it by putting the same vehicle under the same conditions on both a hub dyno and a chassis dyno and it will tell you.

 

99% of dyno figures are just pub talk. Even more so these guesstimated flywheel figures everyone insists on using.

If you are going to quote numbers, at least use those the dyno measures. Wheel figures. Yes they will be lower and may hurt your ego more...but its only a number anyway.

As long as a dyno can give repeatable results, before and after numbers whilst tuning...that is the most important thing.

Stupid flywheel guesses are a waste of time IMO, and its virtually only the UK that uses them !!

And trying to compare different makes of dynos is also a waste of time. They read different...big deal.

 

[quote=stevieturbo;4847548]

Stupid flywheel guesses are a waste of time IMO, and its virtually only the UK that uses them !!

[quote]

Totally agree, i've never understood why we use flywheel hp and most other countries use wheel hp. Is there a decent reason to explain this?

 

probably because most manufacturers use flywheel figures when describing thier engine which is likely to go into a number of vehicles/transmissions.

an example, rs2000 fwd and 4wd have same power output from the engine but the power at the wheels is less on the 4wd due to transmission drag etc. How do you explain that as a salesman to your average punter??? If your qouting engine fly power then you just say its slightly slower due to 4wd and the driver nods. If your trying to explain why one puts out 130bhp at wheels and the other 115bhp, yet has same engine then you need to explain about transmission losses etc.

Plus obviously from a sales perspective 150bhp sounds better than 130

 

Because Wheel HP can be easily manipulated by not only the dyno operator but the car owner

 

people want high numbers...its as simple as that.

ive them a high number and they are happy...regardless of how the car performs.

Give them a low number, and suddenly they are under the belief there is something wrong with their car...again regardless of how it performs.