alpha6164

ISF is rated at 100ms or .10 sec (tenth of second) but not 0.1ms. That would make it a millionth of a second DCT is 8ms which is significantly faster.

dsg03svt

iTrader: (3)

^^^ I thought this too...?

MRxSLAYx

Can you show a source for this?

MR_F1

"Shift times" don't always take into account the time to do a complete shift. I'll assume different Manufacturers quote this differently, and only include the time to engage/disengage gears, but don't include response time, shift logic calculations, etc...

Scoll down about halfway on page 2 to see what I mean.
http://www.lexus.com/models/ISF/feat...sion_Story.pdf

alpha6164

Here is the source. Getrag uses similar transmission in the VW DSG and Porsche PDK and the other two are also quoted at 6-8ms.


http://www.autozine.org/technical_sc...ear_manual.htm

alpha6164

I understand. The time it takes for you to pull the paddle and electronic signal to get to transmission ECU is a whole separate issue. In the article you posted Lexus themselves state 100ms shift time which is very fast for single clutch time manual transmissions. In a twin clutch setup since the next gear is already selected the 8ms quoted time is the time it takes after the signal from the paddle shifter has already gotten to the transmission ECU and just to activate the next gear that is already in place.

mr2fast

shift times aside (after all we're talking very small fractions of a second), the IS-F has over 100tq more than the M3. So even with the 'slower' shift times and extra weight you should still be coming out ahead.

alpha6164

Where did you get this information? ISF is rated at 371 ft/lb tq and M3 is 300 ft/lb. That is only 70ft/lb difference. Torque will help you getting off line but is not going to help on a roll or at higher speeds. F1 cars have made 750-900hp but only make 200 ft/lb of torque. I want to see a C6 Z06 try to race one of those F1 cars.

matt310

iTrader: (1)

8ms? You guys are crazy. That's faster than the seek time of most hard drives. I would say 100-200ms is a better estimate. All you have to do is drive one - the gear change speeds (depending on your definition) are almost exactly the same as those in the IS-F, only they're much harsher. Do a search on "M-DCT lag" and you'll find volumes of thread of disgruntled owners unhappy with those transmissions. There are also multiple class action lawsuits on the matter, for example, http://www.utahjusticelaw.com/bmw-m3...-failures.html

MRxSLAYx

Dont mean to put you out there but your wrong. A zo6 will beat an F1 car if it was at the same weight and power level. Torque is a very big part of a roll race. Put your supra up against a similar power C6 z06 that can hook and you won't have a chance. Torque is evident during all stages of a roll race, even the top end.
someone correct me if I'm wrong. But I've seen live examples that support my opinion.

alpha6164

Sorry i am well aware of the "DCT Lag" but that was an issue with the 2008 models and it had to do with "deceleration." The lag has nothing do when accelerating. Read the article yourself.

And the numbers quoted are not by BMW. They are they same numbers also quoted for VW and Porsche. Why do you think it would take 200ms in a transmission that the gear is already selected. The next gear is already engaged and just needs to be activated. The last generation single clutch SMGIII shift times were 65ms, do you think they went backwards in shift times? The Ferrari F430 that also had the single clutch sequential is listed at 60ms.

Also, i have driven the DCT and the shifts are not harsh at all like the M6 my buddy used to own. In the M6 and fastest shift mode when and i would shift at red line i would literally look at the rear view mirror to make sure the transmission is not laying on the road. The kick is brutal. Anyone that has driven the M5/M6 in the S6 mode will tell you. The DCT is super smooth since the next gear is already selected.

alpha6164

Please clarify "similar power level." What does that mean? Are you talking about hp or torque? You mean if the Z06 had 750 horsepower and same weight of the F1 car? Well no ****** shirlock. IF the z06 or any vehicle weighted the same as F1 car had same power BUT also more torque of course it would win. Who can argue against that. Same with my MKIV. My supra makes 952whp and about 750ft f/lb torque. Of course if a Z06 made 950whp i would have no chance since he is a little lighter, has same whp and more torque than my 750 ft/lb most likely. Having said that it would have to be one bad *** Z06

The M3 is 4.4L vs 5.0L and makes 70 ft'lb torque and in every official review i have seen including Road and Track, Top Gear, Fifth Gear, the M3 has edged ahead the ISF (except 0-60mph). That by itself tells you that torque does not make you win.

matt310

iTrader: (1)

I'm not going to get into a ridiculous argument over this. The M-DCT lag has everything to do with a pause in acceleration when the transmission logic is confused, causing delayed acceleration and the issue is not limited to the 2008 model year; it's still happening in some cases post-flash which is why there are lawsuits about it. Directly from the lawsuit filings:

"The new transmission problem, known to the M3 owners as the DCT lag or hesitation problem, presents during deceleration or a rolling stop situation which is followed by any acceleration, such as a changing traffic light or a left or right hand turn. When the driver tries to accelerate, there is a lag, hesitation or delay in the transmission and the vehicle has the feeling of an engine stall and loses all power for one to two seconds before finally regaining power and accelerating."


In terms of the 8ms "shift" time, this is worth the read:

"The 8ms figure has been discussed here on the forum extensively. It was given on some article on some website (again exact references are here in the forum) for the DSG unit. The vast majority of those that have either thought about, measured and or compared this figure to other units and other information realize this number is absurd.

Furthermore the SMG figures that have been floated of both 80 and 65 ms are deceptive. IIRC those figures are from BMW directly. They likely only cover the shift and conveniently leave out the clutching. SMG shift times were at best about 0.2 seconds (200 ms) which about the same as a good but fast human can shift. Again the article that shows the actual testing that concludes this figure of about 200 ms for a good typical upshift it referenced in prior posts on the forum. If you are really interested use google to search this forum rather than the forums built in search function. Just append a good boolean search with "site:m3post.com".

I've seen test data for a human in a MT at 0.25 s (250 ms). Shift time really vary for all DCTs and many of the good current units are in the range of tens of ms for ideal upshifts to tenths of seconds for non ideal multiple downshifts (maybe even 0.5 s or longer)."

Full post here: http://www.m3post.com/forums/showthr...=328813&page=2

MRxSLAYx

Lol ya you get my point. At the end of the day... There is a reason why everyone here knows the isf is faster from a roll.

mr2fast

sorry I was wrong about the M3's tq it's 295 not 262. Regardless that is a SUBSTANTIAL difference in power. Torque is the measure of rotation force while HP is a theoretical number derived from torque (tq * rpm / 5252). Since the whole game is power to weight torque is the most important figure while HP is mostly for bragging rights (lol i feel some flames coming my way).