1/4 mile times for DCT and 6MT are the same

[sonicgrounds]

Originally Posted by CanAutM3

A well driven Miata will be quicker around a track than a poorly driven F8X

What is your point

Miata is an extreme example. I said "slightly better" driver on the 6MT will beat the DCT. The point being what all the DCT owners are so proud about is an advantage totally irrelevant in all by extreme conditions. Hope the fun factor is why you bought your car no the silly advantage BMW out in there to sell their $3000 DCT options. Can you imagine if the manual was .2 seconds quicker! They wouldn't sell a single DCT.

[gthal]

Originally Posted by CanAutM3

A well driven Miata will be quicker around a track than a poorly driven F8X

What is your point

+1

His comment made no sense to me. The ONLY way to compare the transmissions is to compare identical drivers and, as you correctly state, the DCT will be faster. Once you build in driver variability, the discussion around transmission choice is impossible to continue with any meaning.

A 6MT car might be faster than a DCT car with a better driver... well, how much better does that driver need to be?

[gthal]

Originally Posted by sonicgrounds

Miata is an extreme example. I said "slightly better" driver on the 6MT will beat the DCT. The point being what all the DCT owners are so proud about is an advantage totally irrelevant in all by extreme conditions. Hope the fun factor is why you bought your car no the silly advantage BMW out in there to sell their $3000 DCT options. Can you imagine if the manual was .2 seconds quicker! They wouldn't sell a single DCT.

I think you are just wrong

I have been tracking cars for years and am a fairly proficient MT driver. I have also tracked DCT cars and I can say I'm faster in the DCT. For you to say a driver that is "slightly" better negates that advantage has little basis in fact as you can't possibly quantify that nor can I. My point being is that the DCT is faster whether you like it or not. For some, the DCT is more fun too

Not everyone buys a DCT just because it is quicker... Lots of reasons to choose a DCT. There are only 2 things I know to be absolutely true... One, the DCT is more money and, two, the DCT is faster all else being equal. Period. Whether the performance improvement is worth it to you or not is subjective. I can promise that YOU would be quicker on a track in a DCT than you are in a MT. Now if you were slightly better driver than you are today then you would still be slightly faster in a DCT than your slightly better 6MT self

[sonicgrounds]

Originally Posted by gthal

I think you are just wrong

I have been tracking cars for years and am a fairly proficient MT driver. I have also tracked DCT cars and I can say I'm faster in the DCT. For you to say a driver that is "slightly" better negates that advantage has little basis in fact as you can't possibly quantify that nor can I. My point being is that the DCT is faster whether you like it or not. For some, the DCT is more fun too

Not everyone buys a DCT just because it is quicker... Lots of reasons to choose a DCT. There are only 2 things I know to be absolutely true... One, the DCT is more money and, two, the DCT is faster all else being equal. Period. Whether the performance improvement is worth it to you or not is subjective. I can promise that YOU would be quicker on a track in a DCT than you are in a MT. Now if you were slightly better driver than you are today then you would still be slightly faster in a DCT than your slightly better 6MT self

I think you are missing my point. I wasn't arguing that the DCT isn't quicker. I was arguing that the difference is no where near as big or relevant to owning these cars for most buyers as the DCT fanboys make it out to be here. I'll qualify that by saying, unless you track your car at least once a month. For the rest of %90 buyers, I hope it's the fun factor not the silly .2 sec advantage that made them get the DCT. Yes I get it the DCT is more expensive, but I doubt anyone buying these cars would skimp on 3k and get a manual if they really want a DCT.

[MaynardZed]

The difference between the two transmissions on a road course is close to negligible I'm guessing. Some shorter tracks might have only 1-2 upshifts per lap, so does the 0.2-0.3 second advantage per lap of the DCT get negated by the 80lbs or so weight savings of the 6MT? Maybe, maybe not? The 6MT sure is fun though!

That being said, if I were to order a theoretical quickest lap time F8x car, it would probably have a DCT.

[gthal]

Originally Posted by sonicgrounds

I think you are missing my point. I wasn't arguing that the DCT isn't quicker. I was arguing that the difference is no where near as big or relevant to owning these cars for most buyers as the DCT fanboys make it out to be here. I'll qualify that by saying, unless you track your car at least once a month. For the rest of %90 buyers, I hope it's the fun factor not the silly .2 sec advantage that made them get the DCT. Yes I get it the DCT is more expensive, but I doubt anyone buying these cars would skimp on 3k and get a manual if they really want a DCT.

Ahhh... I think I was missing the intent of what you were saying

[Mik3ymomo]

It's fairly well documented that the DCT cars are quicker.
The reasoning is fairly well understood that the program and hardware can shift the car beyond human capacities.

The weight penalty of the DCT is a variable some would argue might even the playing field a bit for the manual. The thing that I think some people are not considering between the E9x and the F8x platform is the Forced induction.

On the E9x platform the DCT advantage was as simple as the trans shifting quicker then humanly possible.

On the F8x platform the the DCT advantage is two fold. The quicker shifts are retained but also the element of boost comes into play. The DCT will do a better job of keeping the car under boost and will have little to no boost drop between gears compared to the human operated manual.

This was always a redeeming factor for automatics on turbocharged cars.
It was somewhat surprising back in 1990 when the 300zx Twin Turbo tested faster with an auto vs the manual equipped cars.
The improvements and engineering of automatics with less parasitic losses compared to their old school heavy predecessors was the beginning of the end for manual transmissions.

Now Porsche and Ferrari have or nearly have abandoned the manual trans altogether.

[MFL]

We dyno'd two M4's back to back on the same day in the same conditions, the 6MT put down around 23 more WHP than the DCT car.

[MFL]

DCT is definitely quicker though, the shifts are near lossless and the gearing is more aggressive on the top end. I will argue that at least in the E92's, the 6MT is substantially more fun.

[FTS]

Originally Posted by sonicgrounds

I think you are missing my point. I wasn't arguing that the DCT isn't quicker. I was arguing that the difference is no where near as big or relevant to owning these cars for most buyers as the DCT fanboys make it out to be here. I'll qualify that by saying, unless you track your car at least once a month. For the rest of %90 buyers, I hope it's the fun factor not the silly .2 sec advantage that made them get the DCT. Yes I get it the DCT is more expensive, but I doubt anyone buying these cars would skimp on 3k and get a manual if they really want a DCT.

I think the whole argument is pointless, even if you track your car. You cannot look at DCT (me being a fan boy I guess since I ordered it with one), just for performance reasons. Many claim it is easier to drive for them, hence more driving enjoyment, some say they have medical issues that lead them to prefer an automatic, and in my case I want my other family members to drive the car as well and that meant it had to be an automatic.

Does any one here race their M4 or intend to race it? I would bet real money there are 0 (zero) of such people. So, what's the point of whatever the performance advantage? You are drag racing? Tracking? Even in those cases there are so many other variables that DCT vs. Manual will be a small contributor to performance if really at all.

And the topic of weight? OMG! This board is consumed with the weight of the car to a point it is laughable in my not so humble opinion. 80 Kg for a 1600+ Kg car? Pointless in any situation.

So my argument is when you state that no one would pick DCT if all else was equal is a very narrow view of how cars are driven, enjoyed and consumed. Be thankful you have the choice of selecting one or the other, and that we are not forced into a selection by the manufacturer, let's just enjoy what we have.

[xnu]

Originally Posted by MFL

We dyno'd two M4's back to back on the same day in the same conditions, the 6MT put down around 23 more WHP than the DCT car.

I can dyno two of the same model 6MT cars and show a 25hp difference.

[crashtestdummy81]

Originally Posted by CanAutM3

However, on the F8X, because of the broad power plateau of the S55, the DCT does not benefit from tighter gearing as it did on the E9X and it also suffers from a greater weight penalty. So DCT provides less of an advantage on the F8X.

As I've mentioned in another thread, the gearing of the DCT actually provides a significant advantage , especially in the lower gears, due to increased wheel torque (17% 1st,12% 2nd,10% 3rd & 8% 4th)

Originally Posted by CanAutM3

In the end, it all very much depends on the track. The more shifts around a track, the more the F8X DCT is likely to have and advantage. On a track that requires very little shifts (or none at all), I agree, the F8X 6MT has the edge.

Originally Posted by MaynardZed

The difference between the two transmissions on a road course is close to negligible I'm guessing. Some shorter tracks might have only 1-2 upshifts per lap, so does the 0.2-0.3 second advantage per lap of the DCT get negated by the 80lbs or so weight savings of the 6MT? Maybe, maybe not?

The point where the DCT loses its advantage is the brief periods where the DCT is required to up shift at marginally earlier road speeds than the MT due to the gearing between 36-42, 67-75, 102-113 & 136-147mph assuming you hold the gear to the red line. The length of time the MT has the advantage also decreases the earlier you up shift, assuming same shift rpm for both transmissions

[CanAutM3]

Originally Posted by crashtestdummy81

As I've mentioned in another thread, the gearing of the DCT actually provides a significant advantage , especially in the lower gears, due to increased wheel torque (17% 1st,12% 2nd,10% 3rd & 8% 4th)

Wrong.

The car is traction limited in 1st, the shorter gearing of the DCT provides no advantage in that gear.

Both transmission are able to keep the engine in the power plateau (5500-7300RPM) from 3rd gear up, so the shorter gearing of the DCT does not provide any advantage.

There could be a slight advantage in 2nd gear (almost negligible), but that is about it.

The DCT gains on the 6MT because the car does not stop accelerating during shifts, where the 6MT loses 0.2~0.3sec for each shift. How much the DCT loses back due to the increased weight and drivetrain loses is another debate.

Originally Posted by crashtestdummy81

The point where the DCT loses its advantage is the brief periods where the DCT is required to up shift at marginally earlier road speeds than the MT due to the gearing between 36-42, 67-75, 102-113 & 136-147mph assuming you hold the gear to the red line. The length of time the MT has the advantage also decreases the earlier you up shift, assuming same shift rpm for both transmissions

Also wrong, for the same reason as above. As long as the engine is kept in power plateau, torque at the wheels remains the same.

Note that only 1st and 2nd gears need to be shifted at red line. All other gears need to be short shifted (7300RPM) for optimal acceleration.

[dhoggm3]

Originally Posted by gthal

I think you are just wrong

I have been tracking cars for years and am a fairly proficient MT driver. I have also tracked DCT cars and I can say I'm faster in the DCT. For you to say a driver that is "slightly" better negates that advantage has little basis in fact as you can't possibly quantify that nor can I. My point being is that the DCT is faster whether you like it or not. For some, the DCT is more fun too

Not everyone buys a DCT just because it is quicker... Lots of reasons to choose a DCT. There are only 2 things I know to be absolutely true... One, the DCT is more money and, two, the DCT is faster all else being equal. Period. Whether the performance improvement is worth it to you or not is subjective. I can promise that YOU would be quicker on a track in a DCT than you are in a MT. Now if you were slightly better driver than you are today then you would still be slightly faster in a DCT than your slightly better 6MT self

Well said. Still, I'll take the 6MT. Different strokes...

[MasterC17]

The main advantage I see to DCT on this particular platform in a straight line is its ability to hold boost during shifts. Obviously, the faster shifting also helps, but the gearing is negligible due to traction issues and power plateau.

[shortseller]

Originally Posted by MFL

DCT is definitely quicker though, the shifts are near lossless and the gearing is more aggressive on the top end. I will argue that at least in the E92's, the 6MT is substantially more fun.

Rowing through gears puts a smile on my face all the time. Auto mode or paddles is nice but does take some fun out of it all for me. That being said, DCT is faster on the street especially in straight line runs, off a stop light. I agree, just be thankful we have the choice!

[dmk08]

Originally Posted by MasterC17

The main advantage I see to DCT on this particular platform in a straight line is its ability to hold boost during shifts. Obviously, the faster shifting also helps, but the gearing is negligible due to traction issues and power plateau.

Luckily you can change the tires and negate traction issues.