How much *REAL* (Crank) HP does the N55 motor make?

We have this debate going on, on the F10 Boards, and am curious to see what you guys may have experienced on the matter.

We all know the N55 is underrated, presumedly due to keeping insurance costs on volume models down (as I can attest to as the insurance rate on my 535i was pleasantly surprisingly lower than my previous car) but "how much" is the question, My theorizing and calculations give me the impression we're seeing anywhere from 325-340 crank HP from them.

My reasons for drawing those conclusions:

-A brand new, non broken in 535i was video'd to dyno at 277 RWHP/283 RWTQ (with some miles over 280 will be attainable). Using a 17-20% drivetrain loss, you get over 330+HP.

-The 535i is a 4100 lb car, which has been documented by magazines to attain a Trap Speed from 99-101 MPH regularly (Trap Speed IMO is the most honest indicator of HP). Using "Drag Time Calculators", a car that weighs that much needs about 336 (Crank) HP to trap that high.

-My "real life" experiences dragging older Manual SN-99 Mustang GT's (260 crank HP, dyno's at 225 RWHP, with less drivetrain loss due to not being automatic, but obviously far less efficient than newer BMW's) showed those 3200 lbs GT's did 14.0 @ 100 MPH drag runs, which is about identical to some F10 535i "Magazine runs". Therefore using the "100 lbs = 10 HP rule", a 535i which weighs 800-900 lbs more would need 80-90 more HP to trap at the same times. Which would = around 340 crank HP (280-ish RWHP).

-And finally, I've heard people say 3-Series N55's have dyno'd at around 290 RWHP, which would mean these cars dyno at the wheels closer to their "marketed" HP numbers.

Any experiences from you guys on the matter?

Originally Posted by K-A

...My theorizing and calculations give me the impression we're seeing anywhere from 325-340 crank HP from them.

...

-And finally, I've heard people say 3-Series N55's have dyno'd at around 290 RWHP, which would mean these cars dyno at the wheels closer to their "marketed" HP numbers.

Any experiences from you guys on the matter?

I believe you are dead-on with your guess. As to why this is important, I have no clue.

I can only tell you that PPK stage 1 added that much thrill to my ride that I would easily exchange it for minus 30-50 hp at the crank for it (instead of adding 15 hp). What was the thrill? Exhaust note. Because I really don't know what to do with 30-50 hp "extra" in this country (U.S.), but that exhaust note puts the large grin on my face every day over 40 degrees F.

Originally Posted by Mark K

I believe you are dead-on with your guess. As to why this is important, I have no clue.

I can only tell you that PPK stage 1 added that much thrill to my ride that I would easily exchange it for minus 30-50 hp at the crank for it (instead of adding 15 hp). What was the thrill? Exhaust note. Because I really don't know what to do with 30-50 hp "extra" in this country (U.S.), but that exhaust note puts the large grin on my face every day over 40 degrees F.

Haha. Yeah, "crank HP" is really BS anyway, we know what the car dyno's at, and what it traps at, so I guess it's just an interesting thing to "guess" the crank HP, as insanely unimportant to the factual statistics we do have at hand.

I agree with you, it's really pointless to have high HP in this country. I live in a congested area and to me it's even "too much" to try and get the most of this 535i. Proof in that? I've already got a speeding ticket, my first in years, and something I never got close to getting when I was happily and purposefully granny driving my sub-270 HP Merc's.

Your 17-20% drivetrain loss is high for a modern engine. Today manuals are more in line with 10-12% and automatics are more like 15%. The n55 I saw dyno in person put down about 268whp. My guess is crank is 315 or so.

Originally Posted by Jamesonsviggen

Your 17-20% drivetrain loss is high for a modern engine. Today manuals are more in line with 10-12% and automatics are more like 15%. The n55 I saw dyno in person put down about 268whp. My guess is crank is 315 or so.

Interesting. Was that a Mustang Dyno or Dynojet (Mustang Dynos are always much lower). It's good to see more results from N55 dynos.

I can see 15% on a modern auto. 20% does seem pretty high. Some dyno sheets I've seen tell you to divide by a certain number (.something), and when you do, you usually get the same figure as you would if you just factored in a 15-18% drivetrain loss.

Here's the 277 RWHP Insideline dyno:

Originally Posted by K-A

Interesting. Was that a Mustang Dyno or Dynojet (Mustang Dynos are always much lower). It's good to see more results from N55 dynos.

I can see 15% on a modern auto. 20% does seem pretty high. Some dyno sheets I've seen tell you to divide by a certain number (.something), and when you do, you usually get the same figure as you would if you just factored in a 15-18% drivetrain loss.

Here's the 277 RWHP Insideline dyno:

Yeah, Insideline got nearly 240whp on he n20 F30 dyno.

The 268whp was at Rogue with a 135 with an exhaust. My car with an exhaust did 220whp on the same dyno. It's load bearing, I think its a Super Flo which is like a Mustang. My car on a Dynojet would be more like 250whp(more now that I have a tune, 280ish)

Originally Posted by Jamesonsviggen

Yeah, Insideline got nearly 240whp on he n20 F30 dyno.

The 268whp was at Rogue with a 135 with an exhaust. My car with an exhaust did 220whp on the same dyno. It's load bearing, I think its a Super Flo which is like a Mustang. My car on a Dynojet would be more like 250whp(more now that I have a tune, 280ish)

Ah, ok that makes senses. Seems like Mustang Dyno's (or equivalents) are showing N55's with under 270 RWHP while the Dynojet's are the ones we see quoted as basically 280+ RWHP.

Of course, with some break in miles, it's normal to see those numbers go up a bit.

Originally Posted by K-A

Ah, ok that makes senses. Seems like Mustang Dyno's (or equivalents) are showing N55's with under 270 RWHP while the Dynojet's are the ones we see quoted as basically 280+ RWHP.

Of course, with some break in miles, it's normal to see those numbers go up a bit.

Yep!

I take my cars to the heart breaker dynos. They emulate more the actual power that is reaching the ground. Dynojets are best for bragging rights and swinging E-penies lol.

The key was to dyno the other BMW before and after the boost on the same dyno. So reading low or high is one thing, but showing gains is really nice. I picked up 150whp one winter lol. Things get muddled when you start mixing dynos.

I've pondered the same question as the OP. It sounds like you need a copy of cartest2000. Great simulation program.

A few thoughts regarding the OP comes to mind you can prove-out with that program by simply customizing shift speeds and transmission parasitic losses and other losses.

See,

1) Drag Time Calculator of old is likely invalidated by the most recent crop of transmissions and other efficiencies today's vehicles have over cars of old. They are far more efficient (having far less speed-based and rpm-based parasitic losses) than just a few years ago, let alone from what was the norm from decades ago when that algorithm Drag Time Calculator is based on; that stands for both the manual and automatic tranni.

2) The in addition, shift times are far faster in the automatics, so the loss that could accumulate measuring up to hundreds of milliseconds (if not over a second plus some) when shifting from 1 to 2 then from 2 to 3 then from 3 to 4 (tho many cars today pass the 1/4 mile right before the 3-4 shift) is only a fraction of what it was even just 5 or 10 years ago.

3) The F31 is quite slippery. Air resistance is really starting to play a role up at the trap speed of 100 or so mph. And the F3x of today is far slipperier than what was factored in to the algorithm Drag Time Calculator was based on.

4) I'm sure there are other things, like stock tire rolling resistance is far less than that of old?

But anyway, every one of those points will make a car get down the track far quicker requiring less power than Drag Time Calculator thinks it needs to attain the time and speed it does.

Here is a link to a interesting article comparing N55 to N54 on the Dyno:
http://www.automobilemag.com/reviews.../photo_01.html
If I had to take a guess, on average the N55 should make around 310-320 hp at the crank.

Originally Posted by LegendsNeverDie

Here is a link to a interesting article comparing N55 to N54 on the Dyno:
http://www.automobilemag.com/reviews.../photo_01.html
If I had to take a guess, on average the N55 should make around 310-320 hp at the crank.

Great link, thanks! I assume that's a Mustang Dyno?

WOW at the torque of the N55. 302 lbs at the wheels. I always said this car reminds me of a V8 during day to day driving. it may not be as rev friendly as some N/A classic I6's, but it is definitely tuned to give you some real down low TQ.

Originally Posted by K-A

Great link, thanks! I assume that's a Mustang Dyno?

WOW at the torque of the N55. 302 lbs at the wheels. I always said this car reminds me of a V8 during day to day driving. it may not be as rev friendly as some N/A classic I6's, but it is definitely tuned to give you some real down low TQ.

Looks like a Dynojet but nevertheless it is still pretty good.