DCT vs. 6speed for track use

[CanAutM3]

Originally Posted by d k

Its interesting to note that the F8x has the same final drive where the E9x got the shorter drive with the DCT.

On the E9X, comparing final drive is irrelevant because the DCT and 6MT had drastically different gear ratios. On the E9X DCT, 7th gear was the 1:1 ratio !! Hence why it needed a much shorter final drive.

[CanAutM3]

Originally Posted by SYT_Shadow

I hope I'm not pissing you off. I haven't bought the next track car and at times question if it should be DCT. This discussion seems interesting, but I do not expect to 'win' or 'lose' anything here

Per the graph posted above, at 5000rpm you have 400hp, 95% of max power. So, if you shift at 6000 you are in a pretty good spot.

Random dynos will show different things as they're not steady state like the OEM dyno, but more or less, this is good. Maybe instead of shifting at 6000 you shift at 6500, but it seems like there's tons and tons of rev space where you're at max hp.

Cheers

No you are not pissing me off at all, it is an interesting discussion and it is why I keep entertaining it.

I agree, no one is out there to win the HPDE cup. However, HPDE is about perfecting the art of driving fast around a track. And driving fast around a track is just as much about driving the proper line, car control and maximizing the mechanical abilities of the vehicle. So yes, you can drive without optimizing the powerband, just as you can miss all your apexes by half a car width . But what is the point in that .

As for the S55 power curve, I posted this many times myself, the absolute numbers provided by chassis dynos are pretty meaningless. However, the shape of the power curve is not. Our cars operate in transient when going around a race track, not in steady state. Hence the shape of the curve on chassis dynos is more representative of what is going on in real life. So if the majority of chassis dynos indicate that the S55 keeps building power past 5500RPM, I tend to believe them.

[CanAutM3]

Originally Posted by SYT_Shadow

The E92 DCT was a bespoke model specifically tailored to the S65. It was codeveloped with the Ferrari California DCT if I remember correctly

The DCT in the E9X is indeed bespoke. But the DCT in the California is not really related.

IIRC, the DCT in the California is a transaxle (diff included) and has completely different gear ratios.

[SYT_Shadow]

Originally Posted by CanAutM3

The DCT in the E9X is indeed bespoke. But the DCT in the California is not really related.

IIRC, the DCT in the California is a transaxle (diff included) and has completely different gear ratios.

Somewhere I read they were developed together but indeed do not share parts

[d k]

I have all 4 ratio sets in a spreadsheet somewhere...

It would be interesting to see the F8x dct with a shorter final drive where you could use 2/3/4/5/6 gaining effectively a gear although 2nd would be very short and only useable because it was a dct (slam down in the middle of a hairpin).

Ill try to have a more inteligent responce by tomorrow

Originally Posted by SYT_Shadow

The E92 DCT was a bespoke model specifically tailored to the S65. It was codeveloped with the Ferrari California DCT if I remember correctly

The F80 gets a hand me down, which is a shame as it's not meant or designed around the S55. CanAut had a nice thread on this

[MaynardZed]

Originally Posted by BMW M4 PWR

...and sorry, making it a practice to post videos of my racing endevours on a public forum is ignorant on many levels. (i.e. Insurance coverage, Warranty claims, even life insurance) Ask me how I know^^😒 You'd be surprised at who watches & monitors public forums and how many have got put into a stink from not being smart about what they post up... been there done that :/ )

What companies offer insurance and warranties for "racing". Sign me up please👍

[CanAutM3]

Originally Posted by d k

I have all 4 ratio sets in a spreadsheet somewhere...

It would be interesting to see the F8x dct with a shorter final drive where you could use 2/3/4/5/6 gaining effectively a gear although 2nd would be very short and only useable because it was a dct (slam down in the middle of a hairpin).

Ill try to have a more inteligent responce by tomorrow

IMO, the problem with the F8X does not lie with the final drive, but rather with the individual ratios themeselves. The DCT 1st is already too short, rendering it rather useless.

[BMW M4 PWR]

Originally Posted by MaynardZed

What companies offer insurance and warranties for "racing". Sign me up please👍

Few to none, which was my point as to why I don't make it a practice of posting videos of myself (and cars) racing on a public forum. I had a track buddy of mine literally nearly get prosecuted for insurance fraud from an on track incident he had posted internet photos of prior to the claim... :/ Go racing, but if you don't want garanteed insurance or even warranty related issues, just don't posted it. So no, I don't have videos of my track endevours where I beat prepped DCT's on a regular on track. (Which frankly I don't even find a big deal bc there're not faster anyway And even if they were a trace its neglible in the hands of a skilled driver in manual)👍

[d k]

I'm enjoying this discussion and hopefully learn something along the way!


Yes, its true that the 1st is a useless gear. More so in the DCT (16.6:1) vs. the manual (14.22:1)

The manual is much closer to the ideal - which I believe is around 12:1.

In my time attack car I'm at 12.9:1 and it's a nice long gear, but still something that you won't use at the track.
What it does do, is help spread out the rest of the gears much nicer.

The E9x transmissions (DCT and manual) were much closer to each other in 1st - 15.614 vs. 15.07 respectively.



The rest of the gears on the DCT are not THAT bad.

Particularly how the final 2 gears are spaced in relation to each other.

In the E9x DCT the drop from 6th to 7th was much bigger than the drop from 5th to 6th.

In the current DCT, the drops are very close and quite small.

But still to achieve the 'ideal' overall ratio pack which is around 7.5:1 - 3.5:1 - with as many gears in the middle as possible - will take some doing.


I found the ideal combination to be the current DCT with the E9x final drive.
This will give 4 good, useable gears on track.

As a reference, I speced out my time attack car (500+hp, 2800lbs) as follows: 12.9/8.11/5.9/4.6/3.875/3.375

That's an excellent ratio pack for the track and the drops from 4/5/6 are really small. 2nd gear is just a little bit too short, but I had to choose from available ratios and that was the closest they had.

Originally Posted by CanAutM3

IMO, the problem with the F8X does not lie with the final drive, but rather with the individual ratios themeselves. The DCT 1st is already too short, rendering it rather useless.

[d k]

Another good combination would be to use the E9x DCT with the F8x 3.46 final drive.

That would give you 3-7 useable track gears.

[S65V8]

Re: building power between 5500 - 7500 rpm, I do find if I reach a higher ultimate speed faster if I shift at 6500 ish vs. revving out to 7300 the gear prior. (3->4, shift).

Not transmission related, but this car is so confidence inspiring in turns I realized due to the rigidity and bolted on rear sub frame, you can trail brake into turns harder/looser or easily go into turns off line very hot and not feel like the car will be out of sorts...

[CanAutM3]

Originally Posted by SROC5

Re: building power between 5500 - 7500 rpm, I do find if I reach a higher ultimate speed faster if I shift at 6500 ish vs. revving out to 7300 the gear prior. (3->4, shift).

Is your engine running an aftermarket tune?

[S65V8]

Originally Posted by CanAutM3

Is your engine running an aftermarket tune?

None, there's this one bulb, turn going into a straight where I multiple times shifted earlier in 3rd -> 4th (@ around 6500 - 6800rpms) and laid into 4th, at the end of the straight I was at least 5 mph faster than if I wring it out to 7500 ish on 3rd then into 4th.

I will say though, shifting at 7500 rpms feels more exciting and zingy vs. shifting a tad before

[CanAutM3]

Originally Posted by SROC5

None, there's this one bulb, turn going into a straight where I multiple times shifted earlier in 3rd -> 4th (@ around 6500 - 6800rpms) and laid into 4th, at the end of the straight I was at least 5 mph faster than if I wring it out to 7500 ish on 3rd then into 4th.

I will say though, shifting at 7500 rpms feels more exciting and zingy vs. shifting a tad before

Going all the way to 7500 is not worth it for all gears except 1st and 2nd. However, the vast majority of dyno charts tend to indicate that it worth to wind the S55 up to ~7300RPM. Try that next time.

[S65V8]

Originally Posted by CanAutM3

Going all the way to 7500 is not worth it for all gears except 1st and 2nd. However, the vast majority of dyno charts tend to indicate that it worth to wind the S55 up to ~7300RPM. Try that next time.

Cool, will play around that range as well.

[MaynardZed]

Interesting conversation, but remember gearing is very track specific. What might be best for one track could be a bad setup for a different track. In real racing, they have multiple gear sets and put the best one in for a specific track. Ideally you'd be just about at redline before every braking zone, but it doesn't always work out that way. In my E36, I don't have different gear sets, but have 3 different diffs that I switch around depending on what track I'm going to.

[BMW M4 PWR]

Originally Posted by MaynardZed

Interesting conversation, but remember gearing is very track specific. What might be best for one track could be a bad setup for a different track. In real racing, they have multiple gear sets and put the best one in for a specific track. Ideally you'd be just about at redline before every braking zone, but it doesn't always work out that way. In my E36, I don't have different gear sets, but have 3 different diffs that I switch around depending on what track I'm going to.

Well said^^ 👍🏼

[CanAutM3]

Originally Posted by MaynardZed

Interesting conversation, but remember gearing is very track specific. What might be best for one track could be a bad setup for a different track. In real racing, they have multiple gear sets and put the best one in for a specific track. Ideally you'd be just about at redline before every braking zone, but it doesn't always work out that way. In my E36, I don't have different gear sets, but have 3 different diffs that I switch around depending on what track I'm going to.

It's all about the engine producing the maximum average power around the lap. On a tighter lower speed track, you usually want shorter and tighter ratios to keep the engine revs as cose as possible to the power peak. On higher speed track, it's usually preferable to sacrifice some acceleration to gain top speed. On a 6MT, you also need to factor the time lost due to the shifts, meaning that the power gained from the tighter ratios could easily be lost in the shift time.

Since the S55 has such a flat power curve, ratios are not that important. As long as the engine is kept above 5500rpm (some could argue above 6000rpm) and below 7300rpm, the engine makes max power. With the avenue of the CP tune, the S55 now makes a peakier power curve, so ratios will matter a little more.

As for being "at redline", that depends on the engine characteristics. A good example is most tuned S55, where the power peak is well short of redline. On those engines, optimizing the gear ratios to maximize average power will most likely not result in having to redline the engine.

[MaynardZed]

Yup, no doubt the S55 is very forgiving with its broad torque plateau. In the case of our F8X cars, where we're obviously not going to be switching gear sets or diffs between tracks, I agree the DCT has the advantage overall. If you need to "throw away" a gear towards the end of a stretch for example, not much is lost with the DCT since it's such a quick shift.

Referencing my S52 in regards to being at redline. With the tune and S50 manifold it needs to live between 5000-7000 rpms. I usually shift the S55 at 6500-6800 when I'm tracking my Dinan tuned M4.

[CanAutM3]

Originally Posted by MaynardZed

Yup, no doubt the S55 is very forgiving with its broad POWER plateau. In the case of our F8X cars, where we're obviously not going to be switching gear sets or diffs between tracks, I agree the DCT has the advantage overall. If you need to "throw away" a gear towards the end of a stretch for example, not much is lost with the DCT since it's such a quick shift.

Referencing my S52 in regards to being at redline. With the tune and S50 manifold it needs to live between 5000-7000 rpms. I usually shift the S55 at 6500-6800 when I'm tracking my Dinan tuned M4.

Fixed that for you

[tomtang]

DCT = Faster
6MT = Joy