I can't get my head round a comparison of two dyno plots, what am I missing? Is one of the sets of results not correct - here is the detail.

 

i'm looking at the Shark plots for the 2.0TSI 280/300 hp engine. The topline figures are 350bhp and 475Nm torque. I put mine on the Group B motorsports dyno with a bunch of other Briskodians on a group session. The topline numbers were 310 bhp and 510Nm (give or take a few as I've rounded the numbers up/down). That is not confusing as it's written, but I plotted the power and torque readings from my plot onto the Shark graphs as I am interested in comparing the two, on the basis of the headline numbers.

 

What is confusing, is that all the way up the rev range (on both runs) my car is making more torque than the Shark plots, yet, at all of the corresponding points on the curve, the power is lower? I might not be the smartest physicist on the planet, but power is a function of force and distance (watts = force x distance travelled); i.e. bhp is a function of torque and engine speed.

 

I'm guessing here that a typical dyno measures forces through a resistive roller, and the power is calculated from that, so that you'd expect the torque figure to be correct, if one of the two wasn't?

 

I used a conversion of 1.49 from lb/ft to Nm

Cant compare different dynos on different days , that way lies madness

Hi Steve. Power = torque x rpm /5252

So 300ftbls at 3000 = 171 bhp

150ftlbs at 6000 = 171 bhp

What toque did your produce at peak power. Then what torque does shark produce at peak power. Sharks should be more if it's more power.

Thanks John I'll try that.

I was told years ago that the area under the curves is more important than the peak figures.  So a car which makes power early and holds it can be better than a car with another 50hp but gains it later on and doesn't hold on to it.

Which is all related to the torque curve. Personally, I L keep the feel of a flat curve, as it gives the engine a manic feeling top end.

Which is all related to the torque curve. Personally, I L keep the feel of a flat curve, as it gives the engine a manic feeling top end.

Just like a NA petrol

But the advantage of a turbo is the lower down peak torque which creates a broader powerband.

Don't talk to me about dyno runs haha. Should be able to get some logging done soon though, just mega busy. Got a service kit for the forge 007 but can't get the bloody top off by hand and have no vice. Got the oem dv on see if it makes a difference but still waiting for a clip for the top vacuum hose. Will zip tie it tomorrow and try a little run. Anyway sorry for the slight hijack!

I was told years ago that the area under the curves is more important than the peak figures.  So a car which makes power early and holds it can be better than a car with another 50hp but gains it later on and doesn't hold on to it.

 

True om road cars. Racing machines are tuned differently and have to make top power at certain rev range so they work with gearing suitable for a particular track i.e. they would go for additional 50 bhp any day:)

With a daily you track from time to time the are under a very smooth curve is the king as this governs the all illusive driveability.

 

Dynos also have different parasitic loss settings and it is perfectly normal to have the same car producing completely different numbers on two different dynos. I personally do not care that much for the overall figures, that is a second thing to look. The most important is how smooth the curve is imho.

Edited 14 April, 201511 yr by Jabozuma

If i want a Dyno Reading to know what an engine with a DSG box is producing i want it on a Hub Dyno.

Roller Dynos are fair enough, but then so variable on the Wheels / Tyres getting it doing what you want.

 

 

On the 5th Gear test more recently with VBH they use the Rollers.

Edited 15 April, 201511 yr by goneoffSKi

Tesco Momentum 99 & Shell V-Power Nitro now 99 ron Minimum.

Edited 15 April, 201511 yr by goneoffSKi

If i want a Dyno Reading to know what an engine with a DSG box is producing i want it on a Hub Dyno.

Roller Dynos are fair enough, but then so variable on the Wheels / Tyres getting it doing what you want.

On the 5th Gear test more recently with VBH they use the Rollers.

Hub dyno's only tell you the hub output , the ONLY accurate figure is an engine dyno , lot of work then though .

If you use a chassis dyno and use the figure at the wheels then that should be accurate enough for most people and offer excellent repeatability, of course most people don't like that because the number is smaller . Ultimately it's the only figure that is relevant , we drive our cars with the engine under the bonnet and the wheels on , after all .

We drive them on the road if they are road cars, wheels on tarmac, dirt, grass, snow or whatever you are using it for.

So if you want to know what the engine does, that is one check you might want.

 

Roller Dynos are great,

but you will not be driving to work or sitting at traffic lights with a cold air blower facing your front grill, 

dry tyres, & a controlled humidity.

 

Dynos are lovely, but as we know, no traction no action, and Strap your car down to ensure your tyres are getting traction 

is all very nice, but its Figures & graphs on paper and an Aid to tuning, 

but often does not equate, to Rpm, NM, and Road Speed in the real world.

Or even on the strip or track.

 

http://crailraceway.co.uk/recordscrail.php?recclass=8

Edited 15 April, 201511 yr by goneoffSKi

Simple answer - 2 different dynos in 2 different buildings on 2 different days gives 2 different power and torque curves.

We drive them on the road if they are road cars, wheels on tarmac, dirt, grass, snow or whatever you are using it for.

So if you want to know what the engine does, that is one check you might want.

 

Roller Dynos are great,

but you will not be driving to work or sitting at traffic lights with a cold air blower facing your front grill, 

dry tyres, & a controlled humidity.

 

Dynos are lovely, but as we know, no traction no action, and Strap your car down to ensure your tyres are getting traction 

is all very nice, but its Figures & graphs on paper and an Aid to tuning, 

but often does not equate, to Rpm, NM, and Road Speed in the real world.

Or even on the strip or track.

 

http://crailraceway.co.uk/recordscrail.php?recclass=8

 

 

I dont get the cold air blower nor controlled humidity but I get your point , of course we dont tend to drive at maximum rpm in third or fourth gear driving to work but its the best we have

 

Horsepower is directly linked to trap speed on a drag strip though and thats as useful a guide as anything