EBMCS03

SON OF A B*($& I knew I should have gotten a Cayman S! :'(

kmslo530i

nuts....I'm going to find a Porsche dealer tomorrow!!

znod

How does your math imply that the 550i is 369 lbs less than the 545i? Are you violating the rules of mathematics when you are doing reverse calculations? Could you give me a set of assumed parameters for the 550i and 545i (include lbs and hp for each). Then I'll plug in my formulas and calculators and post my work.

Reducing the 550i's weight by 369 lbs while assuming it has 325 HP equates its weight-compenstated lbs/hp ratio with its actual ratio of 3800 / 360. No laws of math are violated. The calculation of the weight-compensated ratio is hypothetical, but straight forward.

Znod, I'm a bit comfused by your calculations. But first off, you can't simply compare lbs/HP between a Porsche and a BMW because other factors such such as drivetrain gearing, and rear mount vs. front engines. There is much advantage to rear mount engines. So, when we compare lbs/HP, we can only compare BMW 545i to 550i since the only difference is lbs and HP (given that all others can be the same from factory). To use lbs/hp negates other factors not including weather such as drag, drivetrain gearing ratios, tire sizes, Everybody follow me so far?

Yes, I mentioned that there are noncomparabilities, but the auto-math literature and websites are replete with calculations that ignore such noncomparabiites--e.g., weather and altitude adjusted data, and on and on and on. Assuming that the differences caused by noncomparabilities will not materially affect the validity of conclusions drawn from calculated data is necessary if one wants to draw conclusions from calculations at all. And, remember, that, as I mentioned, you can't hold everything constant even for a 545i and a 550i except HP, torque, and displacement, because the engines' HP and torque curves are different--which can affect ET's, etc., noticeably. Also, I can find other data that allow the same sorts of observations where you would agree that the cars are more comparable. And, calculating lbs/hp ratios for noncomparable cars is commonplace in trying to predict how they will perform comparatively.

At this point, we can't assume the 100 lbs more for the 550i. We need some facts to narrow our theoretical calculations.

We, of course, we can assume anything we want. What we assume may or may not be correct. The BMW USA website data once indicated that the 550i gained no weight, while, as I recall, the BMW GB (but, maybe BMW Germany) website data indicated, at one time, that the car gained 100 lbs. These data may have changed by now; I have not looked lately. So, some of my calculations were made under the assumption of a 100 lb weight gain--since the actual weight gain, if any, is unclear to me.

Give me some time later on so I can present my calculations for ET for both cars. The beautiful of this exercise is that all variables are constant except for lbs and HP; otherwise, I'd have to write a technical issue and everyone would be turned off.

Well, there are lots of ET and MPH calculators online that only consider basic differences such as weight, HP, etc. It will be interesting to see what your calculations look like. Your results can then be compared to what the online calculators give. And, anyone that doesn't want to read what someone else writes if free to ignore it. Happy formulating and calculating.

znod

But the M Roadster is faster and costs less. Still, the Cayman is awfully good looking. I have not yet seen a M Roadster in person.

EBMCS03

Like you said... the Cayman looks sooooooooo good! And Honestly... I think it drives better. I've driven M3, E39 M5 and the Cayman is better. a porsche is a porsche... :'(

EBMCS03

Then I'm going to have to pay you visit

realtyman

No trouble getting it to do what I want. Also, no trouble getting it to do what I "don't" want (like light up the right rear only by using AA). Although I will most likely get an SMG (or equivalent) again the 2 issues I have with the 545i is the lack of a limited slip diff (yeah, I know, it's not the transmission. But it is "the car" and at least in my case, it renders Accelleration Assist all but useless) and the inability to modulate the clutch on take-off (yes, it's the nature of the beast, I guess).

In the case of my previous post, it was an oddity that I was able to get one part of the AA program (the desired part - the "speed shift" that you will only get by using AA (or buying an "M")) without having to go through the undesired part of the AA program (the right rear only wheel spin). So as I said - If I can only figure out how to do that again.

EBMCS03

Wouldnt it be about the same if you put the car in D mode Sport... that'll make it shift for you... but I guess at a little slower rate than AA...

But here somthing to think about... I thought when I have the pedal down all the way... in kick down mode... not during AA but like I floor it in kick down mode in second and then shift close to read line keeping my foot down the shift seems faster.

So maybe in Sports mode D1 and flooring it past kick down you can get it to shift close to AA speeds.


Did that make any sense?

doug_999

Last month's issue I believe

http://www.roadandtrack.com/article.asp?se...article_id=3638
http://www.clublexus.com/forums/showthread...;highlight=550i

realtyman

Makes sense... But will not reproduce the result.
Sport mode will shift quicker than non-sport and the shift point is higher but....

When in AA mode the shift program is modified to a MUCH quicker shift (I'd say it is similar to a "speed shifting" sensation - or maybe clos to the "M" shifting speeds).
It'll shift at redline, however the shift is a whole lot quicker/harder/faster that the normal Sport mode shift and is accompanied with a "banging" sound and you get thrown back into the seat. Lets just say it's something you wouldn't want to do all the time (but sure is fun on occassion).