Stage 2 Cosworth Kit Preview!!!!

[350matt]

So thats an 85Bhp uplift at the wheels then?, thats a bit more than Cosworth claim isn't it? as I though t the kit was + 80Bhp at the crank?

[tahdizzle]

Originally Posted by 350matt

So thats an 85Bhp uplift at the wheels then?, thats a bit more than Cosworth claim isn't it? as I though t the kit was + 80Bhp at the crank?

Brake horsepower at the crank?

[LucidMomentum]

Originally Posted by JerryIII

1.2 was my base but 165 would be a good estimation

I got my stock car dyno'd and hit around 163. Granted I had lightweight pulleys but also larger tires. 165 sounds about right for stock WHP.

[350matt]

Originally Posted by tahdizzle

Brake horsepower at the crank?

uum yes? Hp is usually measured against a brake or dynometer

hence the term brake horse power

if its not measured and calculated the its just HP

[tahdizzle]

Originally Posted by 350matt

uum yes? Hp is usually measured against a brake or dynometer

hence the term brake horse power

if its not measured and calculated the its just HP

Crank horsepower, as you mentioned is measured at the crank.

Engine not in a car. So when they advertise "Brake Horsepower" why would you think it is crank horsepower?

But thank you for teaching me how people measure Horsepower.

[ajc209]

Originally Posted by 350matt

So thats an 85Bhp uplift at the wheels then?, thats a bit more than Cosworth claim isn't it? as I though t the kit was + 80Bhp at the crank?

85bhp at wheel is pretty much 85bhp increase at fly. The drivetrain takes a fixed torque to rotate it; adding 40% power wont make drive train losses much bigger. Perhaps a fraction due to slightly higher friction losses in the gearbox, but certainly not a massive mount.


FWIW on the Cosworth engine dyno, the stock fa20 was 185-190bhp. Abbey motorsport measure about 160 hub bhp in the UK.


According to Cosworth graphs; stock ~190bhp, stage 2.3 ~290bhp


UK fuel, RON99 V power is superior to US AKI91 (~RON95).

[cdrazic93]

Originally Posted by ajc209

85bhp at wheel is pretty much 85bhp increase at fly. The drivetrain takes a fixed torque to rotate it; adding 40% power wont make drive train losses much bigger. Perhaps a fraction due to slightly higher friction losses in the gearbox, but certainly not a massive mount.


FWIW on the Cosworth engine dyno, the stock fa20 was 185-190bhp. Abbey motorsport measure about 160 hub bhp in the UK.

That dyno reads ridiculously high.

[ame="https://www.youtube.com/watch?v=BOFVnkrkQ6k"]Engine Horsepower vs Wheel Horsepower - Explained - YouTube[/ame]

Drivetrain loss is always a percent. It's not fixed, not based on a set torque rating.

[s2d4]

Originally Posted by cdrazic93

That dyno reads ridiculously high.

HINT: "Engine dyno"

[cdrazic93]

Originally Posted by s2d4

HINT: "Engine dyno"

did not see that....lol

[ajc209]

Assuming drive train losses is a fixed percentage is incorrect. People often apply one to make their car look more powerful. An frs has about 30hp loss. If you double engine output power to 400hp, drive train losses will not be 60hp. Doesn't happen; gearboxes and diffs do not double their friction coefficient with double torque. Also some of that 30hp is going to auxiliary equipment which os unaffected buy more engine power

[ajc209]

Originally Posted by cdrazic93

did not see that....lol

Cosworth Have a state of the art calibrated engine dyno. Same one they use to test their 20,000 rpm 800hp 2.4l V8 Naturally aspirated Formula one engines....

[cdrazic93]

Originally Posted by ajc209

Assuming drive train losses is a fixed percentage is incorrect. People often apply one to make their car look more powerful. An frs has about 30hp loss. If you double engine output power to 400hp, drive train losses will not be 60hp. Doesn't happen; gearboxes and diffs do not double their friction coefficient with double torque. Also some of that 30hp is going to auxiliary equipment which os unaffected buy more engine power

Coefficient of friction is not what I'm talking about, neither Mu K or Mu S. When you have friction what else comes from that? Heat. What is heat? Heat is energy.

The faster you spin a transmission, while the friction may not change from one gear on another, the friction of the clutch does. And so does the friction of the fluids inside the transmission, the diff and everything else. Increased friction is increasing heat. The more heat you produce the more energy is lost.

Transmissions are fairly efficient. Usually between 98-99%. The torsen diff we have on this car is fairly efficient as well, the lowest efficiency being 95%. These percents are because it takes heat and friction (parasitic loss from energy and the transferring hp) to move them.

Take all the Effiencies of the rotating parts from the flywheel, down to the wheels and you'll get your whp rating. @stugray @Koa @Ultramaroon

[Ultramaroon]

Let's start by throwing out the clutch. Not relevant to this discussion.

You are correct in how you quantify the efficiencies but are overlooking the fact that they are not a fixed value. Frictional losses increase as a function of both speed and load so efficiency of the transmission and differential are highest at low speed and low load.

Don't get me started on the magical properties of tires. Uggh!

[bfrank1972]

Originally Posted by cdrazic93

Coefficient of friction is not what I'm talking about, neither Mu K or Mu S. When you have friction what else comes from that? Heat. What is heat? Heat is energy.

The faster you spin a transmission, while the friction may not change from one gear on another, the friction of the clutch does. And so does the friction of the fluids inside the transmission, the diff and everything else. Increased friction is increasing heat. The more heat you produce the more energy is lost.

Transmissions are fairly efficient. Usually between 98-99%. The torsen diff we have on this car is fairly efficient as well, the lowest efficiency being 95%. These percents are because it takes heat and friction (parasitic loss from energy and the transferring hp) to move them.

Take all the Effiencies of the rotating parts from the flywheel, down to the wheels and you'll get your whp rating. @stugray @Koa @Ultramaroon

You know - I always thought of losses as a fixed % as well, but what he says does make sense. Then it struck me that we're talking about a pretty complex set of interactions, which is likely not fixed loss nor a fixed percentage loss... rather somewhere in between varying in a complex way. Then I turned to Google and found lots of articles about it, like:

http://www.superstreetonline.com/how...in-power-loss/

http://www.hotrod.com/how-to/transmi...in-power-loss/