Rolling Road Day!! 8th September ***UPDATED WITH DETAILS***

KevinB10 · Post by **KevinB10** » Sun Sep 09, 2007 8:30 pm

They are attached to the photos - but may be changed!

nealpina · Post by **nealpina** » Sun Sep 09, 2007 11:29 pm

Thanks Kevin. Are they on the site, as I can't find them

GrahamP · Post by **GrahamP** » Mon Sep 10, 2007 12:17 am

Try here

Post by **Charles** » Mon Sep 10, 2007 10:21 am

D4 wrote:Dunk
I'm not sure if i understand or agree with your calculations of adding 25%
my calc of yours is 202 = 252.5

using this method
202 / 4 x 5
or
202 x 1.25
or
202 / 100 x 125
or
202 + 25%

If you use 100 as an example
on your calc 100 / 3 x 4 = 133
this is a 33% uplift not a 25% one...

It depends which way the loss is being attributed.

As I understand it, the rear wheel figure is 75% of the crank figure (i.e there is a 25% loss of power from crank to rear wheel.

Therefore Wheel HP = 0.75 x Crank HP

So Crank HP = Wheel HP / 0.75

As such the factor is 1/0.75 = 1.333 to convert Wheel HP to Crank HP

Whilst this may look like a 33% uplift, it is actually the correct factor to restore a 25% loss from the original base figure at the wheel.

Hope this clarifies things on the conversion front

alpina46 wrote:But i'm sure it is possible that Charles B3s could put out more power than the Roadster S as the B3s is well & truly run in & has been very well maintained by North Oxford.

It's possible.

The Roadster S was a clear point of reference for my car and using the conversion above this puts my car at about 312hp against the Roadster S at 309hp which is about right.

What struck me as interesting is that there was a clear consistency of outputs for each engine type (where comparions are possible). Sure, we had a couple of cars where there was clearly something not quite right, but the V8's were similar, the 3.3's were similar and the 3.4's were similar.

For a low volume manufacturer to deliver that sort of consistency is testament to ALPINAs engineering skills.

chad5k1 · Post by **chad5k1** » Mon Sep 10, 2007 10:55 am

Charles wrote: As such the factor is 1/0.75 = 1.333 to convert Wheel HP to Crank HP

Whilst this may look like a 33% uplift, it is actually the correct factor to restore a 25% loss from the original base figure at the wheel.

Hope this clarifies things

And what that shows Charles is a 3.4S engine produces about the same figure regardless of if it has 40k or 125k on the clock! Very good going!

Or it could mean that my accurate wheel figure of 256 actually increases to 341 at the crank! Holy mackeral that is a lot and surely not right?!

Thanks for organising Dunk and good to meet you all.

Post by **Charles** » Mon Sep 10, 2007 11:07 am

chad5k1 wrote:
Charles wrote: As such the factor is 1/0.75 = 1.333 to convert Wheel HP to Crank HP

Whilst this may look like a 33% uplift, it is actually the correct factor to restore a 25% loss from the original base figure at the wheel.

Hope this clarifies things
And what that shows Charles is a 3.4S engine produces about the same figure regardless of if it has 40k or 125k on the clock! Very good going!

Agreed

Or it could mean that my accurate wheel figure of 256 actually increases to 341 at the crank! Holy mackeral that is a lot and surely not right?!

If you are using the 25% loss factor (which you are) then that is wrong. This applies to the auto boxes. Transmission losses on a manual box are lower (about 18%). Your chart had a converted figure to 309hp at the crank which Charlie could do accurately because it is a manual box.

What you can be sure about is that your engine is putting out at least the 300hp ALPINA quote for it.

chad5k1 · Post by **chad5k1** » Mon Sep 10, 2007 11:25 am

Charles wrote:What you can be sure about is that your engine is putting out at least the 300hp ALPINA quote for it.

Indeed, and what really matters is that the car is a hoot to drive and I love it

300 or 310 doesn't really matter, 10bhp is hardly noticeable - it's 3% and the car feels quite quick regardless.
The really impressive thing is the torque curve. So much for so long and - as you've already said - the consistancy of the outputs on different cars.

Post by **neil** » Mon Sep 10, 2007 12:20 pm

OK I've added Kev's photos too...

I also added the second calculation to the page (if you haven't already noticed)

N

Post by **neil** » Mon Sep 10, 2007 3:46 pm

Added Tony's photos too.

Petrolhead · Post by **Petrolhead** » Mon Sep 10, 2007 5:33 pm

Looks like everyone had a great time.

Just wondering, seeing as the Surrey Rolling Road states it can only go up to 150mph and 4th gear finishes at about 160mph on the B10 V8, then the torque converter can't have been locked up when the runs were done, seeing as it only locks in 4th and 5th. If it wasn't locked then the losses would have been greater. Alpina say a loss of 25%, is that with the TQ locked or unlocked?

Food for thought

Myfirstbeemer · Post by **Myfirstbeemer** » Mon Sep 10, 2007 10:07 pm

Thanks for organising everything, Dunk. It was great to put names to faces, but I'm still a bit gutted about my car's performance, but at least I made my excuses up front!

Just out of interest, why is the torque on a B10 3.3 much higher than a B3 3.3?

chad5k1 · Post by **chad5k1** » Mon Sep 10, 2007 10:17 pm

Should be the same should it not?
And hopefully you car will be easily sorted so then it will feel so much better and you didn't even know anything was wrong

blacky · Post by **blacky** » Tue Sep 11, 2007 12:25 am

looked a good day
bit sad i couldnt make it
maybe next time

johnsb10 · Post by **johnsb10** » Wed Sep 12, 2007 8:42 pm

I may be missing something obvious, but I can't find Kev or Tony's pictures. A clue please...

Petrolhead · Post by **Petrolhead** » Wed Sep 12, 2007 8:55 pm

I too wondered that John, but I'm just assuming that they're all mixed in together. If they're not, then could someone please point us in the right direction. Ta!

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Rolling Road Day!! 8th September UPDATED WITH DETAILS