[MORRWheels]

Supposely the appropiate gear ratio to dyno is the closest to 1:1.

Manual gear ratios - I/II 4.32/2.46 :1
Manual gear ratios - III/IV 1.66/1.23 :1
Manual gear ratios - V/VI/R 1.00/0.85/3.94 :1
Manual gear ratios - Final drive ratio 3.23 :1

In the E90, that would make fifth gear the appropiate gear ratio. And so many people getting crazy numbers dynoing in 3rd and 4th... shame...shame..

[kt157]

damn, then the wheels will be spinning about 130+mph
that would suck for the people without zsp

[sdorn]

1. What is zsp?

2. You are supposed to dyno in the gear closest to 1:1, but it won't give way out of line numbers if you dyno in another gear. The final drive ratio also goes into the equation, and not all cars have the same final drive ratio. The dyno measures torque, and torque isn't affected by the transmission or the final drive ratio.

[MORRWheels]

Originally Posted by sdorn

1. What is zsp?

2. You are supposed to dyno in the gear closest to 1:1, but it won't give way out of line numbers if you dyno in another gear. The final drive ratio also goes into the equation, and not all cars have the same final drive ratio. The dyno measures torque, and torque isn't affected by the transmission or the final drive ratio.

My friends, closest to 1:1 is the most appropiate for accurate numbers.

[ksfrogman]

Originally Posted by sdorn

1. What is zsp?

2. You are supposed to dyno in the gear closest to 1:1, but it won't give way out of line numbers if you dyno in another gear. The final drive ratio also goes into the equation, and not all cars have the same final drive ratio. The dyno measures torque, and torque isn't affected by the transmission or the final drive ratio.

ZSP = Sport Package.

ABBREVIATIONS THREAD:

http://www.e90post.com/forums/showthread.php?t=11465

[HRC]

Originally Posted by carlitosz

My friends, closest to 1:1 is the most appropiate for accurate numbers.

Painfully obvious!!!

Danny

[Itchy Foot]

Originally Posted by sdorn

1. What is zsp?

2. You are supposed to dyno in the gear closest to 1:1, but it won't give way out of line numbers if you dyno in another gear. The final drive ratio also goes into the equation, and not all cars have the same final drive ratio. The dyno measures torque, and torque isn't affected by the transmission or the final drive ratio.

I agree. You are SUPPOSE to, BUT the peak powers won't vary too much.

[lux.sh]

Originally Posted by carlitosz

My friends, closest to 1:1 is the most appropiate for accurate numbers.

CAPTAIN OBVIOUS!!!!! THANKS FOR LETTING US KNOW, SIR!

Originally Posted by carlitosz

In the E90, that would make fifth gear the appropiate gear ratio. And so many people getting crazy numbers dynoing in 3rd and 4th... shame...shame..

what crazy numbers?

[MORRWheels]

Originally Posted by lux.sh

CAPTAIN OBVIOUS!!!!! THANKS FOR LETTING US KNOW, SIR!



what crazy numbers?

200whp - 205whp.

[lux.sh]

Originally Posted by carlitosz

200whp - 205whp.

ohhh. for the 325i?

why? whats wrong? you own a 325, you should be happy about it. no?

And I don't get it. Normally, 1:1 direct gear will show best reading because you aren't expericing any loss through the gear teeth. So it should read better numbers if the dyno was done in 5th gear.

[sdorn]

Originally Posted by carlitosz

200whp - 205whp.

I don't think those are crazy numbers. These cars are supposed to be much more efficient than other cars, so I could see using a 10% or 12% estimate for drivetrain loss. Generally (at least from what I have read) you use between 15% - 20% for drivetrain loss depending on the car and the transmission. I would also assume that BMW slightly underrates the horsepower on their cars as many other manufacturers do.

If the 325i was actually putting out closer to 225 hp at the crank, then at a 12% loss you would be pretty close to 200rwhp. Using the same logic, I wouldn't be surprised to see 330i's putting down around 235 - 240rwhp.

It is also common for a car manufacturer to exaggerate the difference between two different models to make it seem like they are further apart than they are. For example, back in 2000 and 2001 when Chevrolet was selling the Camaro and Firebird, they would often dyno at over 300rwhp completely stock. They were only rated at between 300 and 320hp at the crank by Chevy. The reason was that Chevy didn't want it to be so obvious that the Corvette and Camaro had virtually the exact same horsepower.