[auf Deutsch]

I realize this topic has been discussed and debated ad nauseam throughout the years mostly because the answer is not set in stone. All dynometers are different. But I want to get peoples' input on what they think is the best or most accurate mathematical equation. I hear the "how much horsepower" question seemingly on a daily basis since I've bought my car. Most of these people couldn't differentiate an LSD from a DCT so I want to make it easy for both of us and provide a universal answer, especially since my power numbers are incrementally increasing over time.

My thoughts are as follows based upon this popular position relative to the M2:

A 6MT car assumes a 12% drivetrain loss and a DCT assumes a 15% loss. Therefore, if the typical stock M2 puts down 335 WHP, a 6MT unit should advertise 380 HP (335/.88) and a DCT unit should advertise 394 HP (335/.85). These numbers do seem high. I'd appreciate what everyone has to say. Feel free to rip apart my hypothesis if you have better sources.

[AlexCirci]

Originally Posted by auf Deutsch

I realize this topic has been discussed and debated ad nauseam throughout the years mostly because the answer is not set in stone. All dynometers are different. But I want to get peoples' input on what they think is the best or most accurate mathematical equation. I hear the "how much horsepower" question seemingly on a daily basis since I've bought my car. Most of these people couldn't differentiate an LSD from a DCT so I want to make it easy for both of us and provide a universal answer, especially since my power numbers are incrementally increasing over time.

My thoughts are as follows based upon this popular position relative to the M2:

A 6MT car assumes a 12% drivetrain loss and a DCT assumes a 15% loss. Therefore, if the typical stock M2 puts down 335 WHP, a 6MT unit should advertise 380 HP (335/.88) and a DCT unit should advertise 394 HP (335/.85). These numbers do seem high. I'd appreciate what everyone has to say. Feel free to rip apart my hypothesis if you have better sources.

My 2016 manual put down 355whp/393lbtq on a dynojet. Let me find the chart and I'll upload.

I've seen lower numbers from other posts on here... so curious if conditions were perfect when I dyno'd or if I have a factory freak. This was bone stock running 93

[auf Deutsch]

Originally Posted by AlexCirci

My 2016 manual put down 355whp/393lbtq on a dynojet. Let me find the chart and I'll upload.

I've seen lower numbers from other posts on here... so curious if conditions were perfect when I dyno'd or if I have a factory freak. This was bone stock running 93

Yeah, I did 349/367 on a Dynapack, that TQ number of yours is killer....getting a baseline done again on a Dynajet very soon.

[DKX4///M]

I personally hate the whole drivetrain loss measured in %....Yes a 400hp dct rwd car may lose a certain amount of hp that equates to 15% bt that doesnt mean when that car is modified to 800hp (crank)that it loses twice as much power to the wheels...

For example an unmodded car (x) looses 30hp to spin the drive train...You modify it and double the hp. Is it magically twice as hard to push? No...z

Maybe there are stronger drive train components, or in gear maybe the compression ratio makes it harder to push but from my experiences drive train loss is ridiculous to measure in percentages.

Different cars are more effiecient than others st putting the power down, but it shouldnt be measured in %, Hope this makes sense.

[auf Deutsch]

Originally Posted by DKM3Power

I personally hate the whole drivetrain loss measured in %....Yes a 400hp dct rwd car may lose a certain amount of hp that equates to 15% bt that doesnt mean when that car is modified to 800hp (crank)that it loses twice as much power to the wheels...

For example an unmodded car (x) looses 30hp to spin the drive train...You modify it and double the hp. Is it magically twice as hard to push? No...z

Maybe there are stronger drive train components, or in gear maybe the compression ratio makes it harder to push but from my experiences drive train loss is ridiculous to measure in percentages.

Different cars are more effiecient than others st putting the power down, but it shouldnt be measured in %, Hope this makes sense.

Should there be a flat/static figure then?

[arquitecto]

Originally Posted by DKM3Power

I personally hate the whole drivetrain loss measured in %....Yes a 400hp dct rwd car may lose a certain amount of hp that equates to 15% bt that doesnt mean when that car is modified to 800hp (crank)that it loses twice as much power to the wheels...

For example an unmodded car (x) looses 30hp to spin the drive train...You modify it and double the hp. Is it magically twice as hard to push? No...z

Maybe there are stronger drive train components, or in gear maybe the compression ratio makes it harder to push but from my experiences drive train loss is ridiculous to measure in percentages.

Different cars are more effiecient than others st putting the power down, but it shouldnt be measured in %, Hope this makes sense.

Originally Posted by auf Deutsch

Should there be a flat/static figure then?

From what I understand, neither a percentage rate nor a flat hp number is very accurate. Every car design will have a different level of efficiency related to drivetrain loss. There are multiple points throughout the drivetrain that contribute to the loss.

As DKM3Power correctly points out, if you double the stock hp you would not see double the drivetrain loss. However, a flat hp number would not be accurate either since this increase on hp will result in greater internal stresses that do contribute to drivetrain loss.

If you are able to pull the guts out of a drivetrain with double the hp you would expect to see higher levels of friction, heat build up, and losses due to increased angular momentum of the drivetrain components. These will increase drivetrain loss and since this increase is non-linear, it is more difficult to calculate than simply assuming a blanket hp figure.

One possibility would be to look at several stock M2's results and see what kind of figures they are putting up to then extrapolate how efficient the drivetrain of the M2 averages out. This figure could be used as a baseline for the M2 but would not be applicable to a different type of car since the design of the other car may not correlate with the design of the M2 or with highly modified M2's that may be making significantly different hp figures.

[mike@x-ph.com]

Originally Posted by auf Deutsch

I realize this topic has been discussed and debated ad nauseam throughout the years mostly because the answer is not set in stone. All dynometers are different. But I want to get peoples' input on what they think is the best or most accurate mathematical equation. I hear the "how much horsepower" question seemingly on a daily basis since I've bought my car. Most of these people couldn't differentiate an LSD from a DCT so I want to make it easy for both of us and provide a universal answer, especially since my power numbers are incrementally increasing over time.

My thoughts are as follows based upon this popular position relative to the M2:

A 6MT car assumes a 12% drivetrain loss and a DCT assumes a 15% loss. Therefore, if the typical stock M2 puts down 335 WHP, a 6MT unit should advertise 380 HP (335/.88) and a DCT unit should advertise 394 HP (335/.85). These numbers do seem high. I'd appreciate what everyone has to say. Feel free to rip apart my hypothesis if you have better sources.

the 12/15 loss is a very reasonable but keep in mind BMW always underrate their engine BHP

[SeanWRT]

Originally Posted by mike@x-ph.com

the 12/15 loss is a very reasonable but keep in mind BMW always underrate their engine BHP

That doesn't explain the fact that 6MT m2 reads normally 5~10hp lower on the wheel than its DCT counterpart.

[auf Deutsch]

How accurate is the horsepower calculator on the dragtimes site?

12.0 ET
116 trap
3600 lbs

equals 425 flywheel

[DivideBYZero]

Where's the 3% extra loss coming from with the DCT? It doesn't have a Torque Converter...

[zenmaster]

Originally Posted by auf Deutsch

How accurate is the horsepower calculator on the dragtimes site?

12.0 ET
116 trap
3600 lbs

equals 425 flywheel

What M2 does 12.0s 1/4 mi?

[auf Deutsch]

Originally Posted by zenmaster

What M2 does 12.0s 1/4 mi?

This is just a random example. All numbers are interchangeable.

[zenmaster]

Originally Posted by auf Deutsch

This is just a random example. All numbers are interchangeable.

All of these calculators are ballpark because they are not calibrated for a specific car, car setup, or conditions. Accuracy at best 5%, at worst 30%.