znod

Weclome. I am glad your car performs so well. I am hoping that you will take it to a dragstrip and let us know how you do. But, note that the issue with getting good strip times is now whether one can produce tire smoke. Many can easily smoke their tires with relatively few RPM, but good strip times often take many RPM--especially with a low-torque engine like the M5's. I am interested in an M5, but definitely will wait for the manual to even think about getting serious.

Centurion

Don,
I know you place straight-line acceleration very high on your list. Here's something I thought might be interesting, but honestly have not given it much thought...

Speaking only in terms of launching from stand still, the M5 with SMG will be slower off the line than the same car with a manual (assuming with the manual you are holding the motor at the optimal RPM before engaging the clutch). However, the SMG equipped M5 will have quicker shifts between gears. You'll probably need to shift to 4th gear in a 1/4-mile run, hence AT LEAST 3 shifts).

Here's the question: Do you think those 3 shifts are quick enough to catch up to the manual shifting M5 which, theoretically, is already out in front?

My initial assumption is, "No". The jump at the line is enough to take the manual shifting M5 across the quarter-mile first.

Any thoughts, or am I just drinking too much of Grandma's eggnog?

znod

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znod

Don,

Great issues to think about Pennyurion.

I know you place straight-line acceleration very high on your list. Here's something I thought might be interesting, but honestly have not given it much thought...

Yep, I got stuck in the 50's and 60's. Yea! I'm kidding, of course. I like curved lines too. But, I find time and places for straight lines.

Speaking only in terms of launching from stand still, the M5 with SMG will be slower off the line than the same car with a manual (assuming with the manual you are holding the motor at the optimal RPM before engaging the clutch). However, the SMG equipped M5 will have quicker shifts between gears. You'll probably need to shift to 4th gear in a 1/4-mile run, hence AT LEAST 3 shifts).

I think a good driver with a manual can launch better than an SMG with LC disabled at least. I am not sure what would happen with a full load of LC. I still think the manual driver still would have a slight advantage if a launch above 4k is indicated, given track conditions, and because of the manual driver's ability to use his accelerator/clutch combo, perhaps, closer to optimally than the SMG driver can. In this regard, I am assuming that the SMG will shift at the optimal RPM, but I am unsure that this scenario will play out since shifting below redline actually might be optimal. In sum, I think that at least a good power shifter can keep up with an SMG in shifting--closely enough no matter what. And, from the C&D results, it looks like both cars would need to shift 3 times.

Here's the question: Do you think those 3 shifts are quick enough to catch up to the manual shifting M5 which, theoretically, is already out in front?

As my thoughts above imply, I don't think the SMG would catch the manual. I do think that the race should be a very close one. And, I think the manual driver needs to be a good driver and maybe would need to powershift. I would like to think that powershifting would not be required because, if I ever get an M5, then I would want the theoretically fastest one without having to powershift. In this regard, I don't want an SMG since I want smooth shifting most of the time and relatively few problems and complexities out of my tranny.

My initial assumption is, "No". The jump at the line is enough to take the manual shifting M5 across the quarter-mile first.

My "best" opinion is that the manual will win without powershifting given a good driver. But, it should be very close. In this regard, I am not convinced that the SMG would be catching even the non-powershifter. I know that I, for one, can shift very quickly without powershifting--and I have no reason to think that I am the fastest non-powershifter.

I have one more thought supporting the close-race idea--with the manual winning. I doubt that BMW chooses the rear-end ratio for the manual cars optimally. I suspect BMW doesn't want the manuals to be faster than the SMG's. And, note that BMW's times for manuals and SMG's always seem to be the same in recent history. One the other side of the coin, I'd bet that BMW's drivers don't dirve the manuals as well as good old US drag racers do--even without powershifting.

Any thoughts, or am I just drinking too much of Grandma's eggnog?

I think that one can drink too much of anything. But, I know you would not do so. I liked your thoughts.

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P.S. I don't think it would matter except for the optimal shift-points issue, but are you assuming the SMG will be shifted manually or automatically?

cobradav

It don't recollect this being mentioned associated with the NA crippled LC but there is another feature that is apparently missing. An automatic shifting at optimal RPM all hands off courtesy of LC. If available as it is in ROW M5s would appear to me to further optimize a ? mile time/speed. Not having either M5 it is hard for me to judge. That to me would be the best litmus test is to pit the two versions of M5 against each other (and swapping drivers) rather than having to depend on times in different locations or antidotal stories about beating this 997 this or SL that.

znod

Excellent point. I mentioned that possibility above, if I am understanding you correctly, assuming automatic shifting implicit. In general, I was assuming either manual or automatic shifting for the SMG. Add 2, manual-shift car. Game, set, and match (maybe ).

Centurion

Sorry, looking back I see that I neglected to mention that. I was referring to an SMG tranny being shifted manually.

At any rate, I believe the actual time it takes for the SMG tranny to lift the clutch, select a gear, and re-engage the clutch (in other words, the dead-time between gearshifts) is the same whether it is being shifted manually or automatically. I'm not sure of the current SMG III technology, but the previous SMG II took 0.8seconds between upshifts (as reported by BMWNA).

Now here is what I've got from the "2006 M5 Product Information" catalog:
In the sportiest program of all, S6, the minimum shift time has been reduced 20% from that of the existing SMG, which was already very fast.

Therefore, approximately 0.6seconds between shifts in SMG III. (?)

All that being said, I still think the manually shifting M5 would take the 1/4 mile.
You bring up an interesting point about the rear-end ratio. I wonder what BMW will do with the gearing of the manual shifting M5 because that introduces yet another variable.

znod

Sorry, looking back I see that I neglected to mention that. I was referring to an SMG tranny being shifted manually.

At any rate, I believe the actual time it takes for the SMG tranny to lift the clutch, select a gear, and re-engage the clutch (in other words, the dead-time between gearshifts) is the same whether it is being shifted manually or automatically. I'm not sure of the current SMG III technology, but the previous SMG II took 0.8seconds between upshifts (as reported by BMWNA).

Now here is what I've got from the "2006 M5 Product Information" catalog:
In the sportiest program of all, S6, the minimum shift time has been reduced 20% from that of the existing SMG, which was already very fast.

Therefore, approximately 0.6seconds between shifts in SMG III. (?)

All that being said, I still think the manually shifting M5 would take the 1/4 mile.
You bring up an interesting point about the rear-end ratio. I wonder what BMW will do with the gearing of the manual shifting M5 because that introduces yet another variable.
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Yep, and it is "the" critical variable--game, set, and match possibly to the car that comes closest to having the optimal ratio--assuming BMW does not try to more or less equate the performance levels of the two cars. The outcome of the race will be something of a crap shoot if BMW wants to "equate the ratios."