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      03-16-2007, 08:45 AM   #243
hotrod2448
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Quote:
Originally Posted by DrM View Post
Shiv's car made 355 whp and 405 ft-lbs of torque at the wheels. This is most likely about 400ps. But, it is close to Alpina levels. Alpina is about 20% over stock levels. Shiv's car is about 33% over stock levels. Hopefully the engine has that much margin built in. 30% in a regularly driven car shouldn't be a problem (fingers crossed...)

I would worry about the AA turbo M3 though. They push more than double the power of the factory motor. Things MUST break at that level (600+whp)
OK, so Alpina rates their stuff at crank power like OEM. I'm used to pretty much discussing only WHP. There's were I went wrong.

Do most BMW tuners rate power using crank power? It seems that is mostly a Euro thing. If I recall a lot of the Audi guys do it that way as well.
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      03-16-2007, 10:03 AM   #244
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Originally Posted by hotrod2448 View Post
OK, so Alpina rates their stuff at crank power like OEM. I'm used to pretty much discussing only WHP. There's were I went wrong.

Do most BMW tuners rate power using crank power? It seems that is mostly a Euro thing. If I recall a lot of the Audi guys do it that way as well.
To me, crank numbers are worthless, and can be misleading. The E46 M3 and 335i put down fairly comparable rwhp numbers, yet their crank rating is 33hp different.

Lots of tuners quote a crank figure based off estimates. Good for marketing, but doesn't really give you a clear picture of power being made. I'd be real curious what the N54 puts at crank, stock. Probably more than 300/300. That makes Alpina's gains less impressive, particularly if they are using 16 psi boost.
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      03-16-2007, 10:12 AM   #245
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Quote:
Originally Posted by catm3 View Post
To me, crank numbers are worthless, and can be misleading. The E46 M3 and 335i put down fairly comparable rwhp numbers, yet their crank rating is 33hp different.

Lots of tuners quote a crank figure based off estimates. Good for marketing, but doesn't really give you a clear picture of power being made. I'd be real curious what the N54 puts at crank, stock. Probably more than 300/300. That makes Alpina's gains less impressive, particularly if they are using 16 psi boost.
If they are the stock turbos there may not be a whole lot of top end power to be gained from increasing boost before they run out of efficiency.
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      03-16-2007, 10:20 AM   #246
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Originally Posted by Corey View Post
If they are the stock turbos there may not be a whole lot of top end power to be gained from increasing boost before they run out of efficiency.
True, you can see that on Alpina's dyno. After 6K, the engine starts to fall off. Interestingly, their peak torque is somewhere around 5K. 5K is where the HP peaks and stays at peak till 6K. My guess is that max boost hit 16psi at around that 5K RPM range, then drops off quickly to 6K.

http://www.blogsmithmedia.com/www.au..._dyno_1280.jpg

Shiv did mention that he thought they could hit that level of boost in mid RPM range, but wouldn't sustain it up top because of the turbo limitation. If Alpina did indeed change the pistons, the compression ratio may be lower allowing boost levels of 16psi on pump gas.
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      03-16-2007, 05:02 PM   #247
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Quote:
Originally Posted by catm3 View Post
To me, crank numbers are worthless, and can be misleading. The E46 M3 and 335i put down fairly comparable rwhp numbers, yet their crank rating is 33hp different.
Reporting numbers from the crank or from the wheels provides different feedback to different people. Not to mention that the numbers significantly differ between automatic and manual transmissions. While power at the wheels may be all you are looking for, an engine tuner can find the power at the crank to be a more meaningful number.

When doing engine performance modeling through calculations the numbers only deal with what is happening in the engine. Adding in the drivetrain (meaning transmission, wheels, etc.) variables adds in unwanted uncertainties. I often crunch numbers to model how a turbocharger will perform on a particular engine. The more accurately I can model the numbers the more accurately I can predict how an engine will respond to a particular turbocharger. Having a simple dyno chart of an engine's output at the crank is one of the best tools I can have.

Plus since you mention the fact that while the E46 M3 and the 335i have similar outputs to the wheel but the difference gets larger when reported at the crank you can see right there where you can pick up some power to the wheels in the 335i. The 335i could benefit from a lighter flywheel, driveshaft, wheels, etc...
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      03-16-2007, 05:51 PM   #248
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Originally Posted by merritt View Post
Plus since you mention the fact that while the E46 M3 and the 335i have similar outputs to the wheel but the difference gets larger when reported at the crank you can see right there where you can pick up some power to the wheels in the 335i. The 335i could benefit from a lighter flywheel, driveshaft, wheels, etc...
The crank numbers for the N54 are underrated. And your statement is backwards. The difference in crank vs wheel wold show that the M3 could benefit from a lighter drive train since the loss is greater from crank to wheel. Thats assuming that the crank numbers are accurate for the N54, which I doubt they are.
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      03-17-2007, 09:29 AM   #249
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      03-18-2007, 12:15 AM   #250
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Wow, a couple of days away, a plethora of posts. I never cease to be amazed at the vitriol that appears on forums sometimes, it doesn't matter what make of vehicle or what price, people have an investment in their car, (something that is very precious to them) so they choose to defend their investments. That's cool.

Well, at least finally we get some real technical discussion..I was hoping that might surface eventually! :rocks:

Quote:
Originally Posted by merritt View Post
Reporting numbers from the crank or from the wheels provides different feedback to different people. Not to mention that the numbers significantly differ between automatic and manual transmissions. While power at the wheels may be all you are looking for, an engine tuner can find the power at the crank to be a more meaningful number....
I would agree that the numbers at crank and wheels mean different things to different people and crank HP/TQ numbers are paramount in design and development as Merritt said. As part of a good final result, a whole package is developed with many different criteria considered, engine power/torque as well as drivability and long term reliability. Different tuners, different methods and results - everyone benefits from that sort of competition!

Cheers
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BTW, Welcome Merritt etc.
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      03-18-2007, 01:19 AM   #251
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Quote:
Originally Posted by catm3
After 6K, the engine starts to fall off. Interestingly, their peak torque is somewhere around 5K. 5K is where the HP peaks and stays at peak till 6K. My guess is that max boost hit 16psi at around that 5K RPM range, then drops off quickly to 6K.
After I'd upgraded my old '93 RX-7 (twin turbo) ignition system, its dyno results (310whp @ 9.5PSI) showed a noticeably extended power band compared to similarly modified car w/ stock ignition. The theory provided was that more boost needs more spark. Not sure if any of that translates to the N54.
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      03-18-2007, 02:01 AM   #252
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Quote:
Originally Posted by LOK11atXEDE View Post
Wow, a couple of days away, a plethora of posts.

Hope you're more accurate on other matters than you are on the passage of time.

Quote:
I would agree that the numbers at crank and wheels mean different things to different people . . .
I guess we all could agree on that - even me, and I'm an ignoramus on this particular subject matter.

Quote:
. . . and crank HP/TQ numbers are paramount in design and development as Merritt said.
Paramount . . . hmm, searching . . . nope, merritt never used that word.

Quote:
As part of a good final result, a whole package is developed with many different criteria considered, engine power/torque as well as drivability and long term reliability.
I wish I understood what you just said.

Quote:
Different tuners, different methods and results - everyone benefits from that sort of competition!
Don't know if I agree that everyone benefits from different methods and results - unless we all somehow benefit if one or more methods produces bad or unfavorable results.

However, I agree that competition is good. But since I'm an ignoramus on the foregoing subject matter, I don't know if you want to be in agreement with me.
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      06-24-2007, 12:38 PM   #253
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Quote:
Originally Posted by RDSport View Post
Sorry, I forgot to mention that I am currently in Europe and this coming Friday I will be at BMW to discuss a few technical issues, one of which is the subject of my previous post. I will try to remember to give you an update after the meeting. Should I forget, please send me a PM as a reminder. I may be flying back to California, but I will do my best to share the information.
Any news on this? Waiting for your feedback
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