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    E92/E9X M3 Drivetrain Losses Explained - DCT (dual clutch transmission) vs. Manual

    The question has arisen several times about what has lower drivetrain losses, the DCT or the manual M3. We have seen information being circulated suggesting the DCT has lower drivetrain losses which is why it performs better which is simply incorrect and a case of pushing personal politics over the correct information.

    The DCT performs better simply due to the shift speed despite weighing about 50 pounds more than the manual. With the way a dual clutch transmission works, it simply takes some additional engine power to operate. This is especially true in the case of wet clutches such as the Getrag unit in the M3 vs. dry as dry clutches do not have the additional loss created by pumping fluid into the housing. Dan Carney writes in this article hosted on dctfacts.com, "A dry clutch setup enjoys a 1% fuel economy benefit compared to a wet clutch DCT because of the elimination of the oil pump and its attendant losses."

    The wet clutch DCT simply takes power to run. It is a physical impossibility for it to have lower drivetrain losses than the manual. The associated systems just simply will take more power to operate. It is impossible for a wet clutch DCT to have the drivetrain efficiency of a manual but the difference is not huge. DCT's often have higher mpg ratings due to having a 7th gear not due to lower losses. They have quicker acceleration figures due to the tighter gearing and shift speed.

    We thought it would be best to not have you take our word for it but research the topic and have the experts in the field provide their thoughts. Who knows this transmission better than the manufacturers themselves and the people who work on them? BimmerBoost started by contacting Getrag who makes the DCT transmission in the M3 and asked about the drivetrain losses compared to the manual:

    Thanks for your question and for your interest in our products.

    As there is a pump in hydraulic actuated DCTs the loss of the DCT in principle is a bit higher compared to a manual transmission.

    Mit freundlichen Grüßen/ Kind regards
    Dr.-Ing. Hartmut Faust

    Chefingenieur Entwicklung Zentralbereiche
    Vice President Central PD Functions

    GETRAG
    Getriebe- und Zahnradfabrik
    Hermann Hagenmeyer GmbH & Cie KG
    GETRAG InnovationsCenter
    Hermann-Hagenmeyer-Straße
    74199 Untergruppenbach

    Fon +49 (0) 71 31.644-45 10 | internal: 45 10
    Mobile +49 (0)178.6 000 415
    Hartmut.Faust@getrag.de
    Getrag states that the hydraulic systems drain a bit of power. Ok, well, how about another manufacturer, what would Borg Warner think on the subject?

    Good question, and the answer, as with so many engineering / human interface questions is... it depends.

    From a pure physics perspective, the manual transmission is more mechanically efficient, all other factors (number of gears, ratios) being the same. The DCT must have a control system to operate and that requires either an engine driven hydraulic pump similar to a conventional automatic, an electrically driven hydraulic pump, or electrically driven motors and servos. So, some energy must be consumed to automate the DCT... approximately 2% fuel efficiency penalty for engine driven pump and an oil bath pump, only about 1% for electrically driven system and a dry dual clutch (examples are VW DQ200 sold in Europe and China, Ford's new Powershift built by Getrag, Fiat C635 just introduced in Europe).

    Bob Blakely
    Director, Marketing
    BorgWarner Drivetrain Systems
    3800 Automation Avenue
    Auburn Hills, MI 48326
    Phone: 248-754-0257
    Fax: 248-754-9257
    Cell: 248-330-2585
    bblakely@borgwarner.com
    Well, it seems that both major manufacturers are in complete agreement on the subject. What about tuners who modify these vehicles, what would they have to say? I contacted AMS with the same question:

    Dual clutch takes more power to run.

    Chris Black
    --Tuner--
    Automotosport, Inc.
    1760 Metoyer Court
    West Chicago, IL 60185
    (847) 709-0530 ext. 2014
    www.amsperformance.com
    Hmmm, ok, what about a company that specializes in aftermarket DCT's? Here is what South Side Performance had to say:

    We see a penalty of about 2% compared to a manual. The accepted standard for a manual is 15% so we would say a RWD DCT is at around 17%. AWD DCT's would be slightly higher.

    Kris@SSP
    http://www.sspperformance.com
    Well, it would seem we are seeing a pattern here. What about the website dctfacts.com? They specialize in DCT information and news, here is their take on the subject:

    In terms of mechanical efficiency, a dual clutch transmission will never quite be able to match the theoretical efficiency of a standard six-speed manual transmission, as the necessary hydraulic systems will inevitably absorb some energy, especially on a wet clutch DCT. Manuals have no such systems.

    http://www.dctfacts.com/information/...ion-works.aspx
    Well, it would seem the entire industry is in compete agreement. Now, the penalty for the DCT's added systems is not large, only about 2%. However, as you add power it does become noticeable. Here is a practical example with 2 supercharged M3's both running the same SC, same boost, same fuel, on the same dyno. The red is manual the blue is DCT:

    Click here to enlarge

    The best run vs. best run was compared and the difference between the two is just over 3% reflecting the comments of the experts in the DCT industry. So there you have it folks, a little bit of research goes a long way and count on BimmerBoost.com to provide you with the accurate and correct info, not personal politics.

    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
    : http://www.boostaddict.com/showthrea...r-kit-for-sale

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    Just a reminder to some of you, this is what was allowed to circulate and mislead people on some other "less technical" sites:

    the DCT is more efficient than the 6MT by a rather large margin.
    I hope you're not pulling out that busted myth that DCT cars have more DT loss than 6MT's.
    Whoops...

    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
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    always the best info here

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    Click here to enlarge Originally Posted by LostMarine Click here to enlarge
    always the best info here
    Thank you. It is because we actually try and we actually care.

    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
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    Nice post! I think its a tad more accurate/valuable information then somebody's Dyno Database. Click here to enlarge So much for that "myth" that technical info never gets posted here.

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    Click here to enlarge Originally Posted by JonMartin Click here to enlarge
    Nice post! I think its a tad more accurate/valuable information then somebody's Dyno Database. Click here to enlarge So much for that "myth" that technical info never gets posted here.
    Well, you know, actually taking the time to do research and talking to the people who build the trans may be a bit more accurate than throwing together a bunch of random dyno numbers in some pointless one-sided quest.

    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
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    Click here to enlarge Good info!

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    1 out of 1 members liked this post. Yes Reputation No
    Those this mean the hydraulic pump is providing hydraulic pressure even when the car is in gear? I understand that it takes power to run the pump when the car is switching gears but how about when it is in gear? Just something I thought of while I was reading the post. Good info btw!

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    Great info! Thanks for researching that.
    09 Alpine White E92 M-DCT / ESS VT2 Supercharger w/ NITROUS / Borla Race Exhaust
    10.87 @ 131 mph in the 1/4 Mile
    60-130 MPH in 6.23 secs (Nitrous)
    60-130 MPH in 6.87 secs (Boost only @ 7.5psi)

  10. #10
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    Click here to enlarge Originally Posted by armyav8tor Click here to enlarge
    Those this mean the hydraulic pump is providing hydraulic pressure even when the car is in gear? I understand that it takes power to run the pump when the car is switching gears but how about when it is in gear? Just something I thought of while I was reading the post. Good info btw!
    The associated systems are always a drain, not just when switching gears.

    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
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    Click here to enlarge Originally Posted by Mikewads Click here to enlarge
    Great info! Thanks for researching that.
    My pleasure, it's what I do Click here to enlarge

    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
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    Nice work Sticky, great info.

    I wonder what the ZF Step tranny is compared to the Manual for the N54s.

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    Click here to enlarge Originally Posted by Irishace Click here to enlarge
    Nice work Sticky, great info.

    I wonder what the ZF Step tranny is compared to the Manual for the N54s.
    It will have higher drivetrain losses than the manual, probably like 3-5%.

    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
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    You might want to take a read of this.
    My favorite tuner in UK uses Rototest...

    http://www.rri.se/

    About as scientific as it gets, and compared to the manufacturer:
    http://www.rri.se/popup/performanceg...p?ChartsID=647

    Steve

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    Click here to enlarge Originally Posted by m1bjr Click here to enlarge
    You might want to take a read of this.
    My favorite tuner in UK uses Rototest...

    http://www.rri.se/

    About as scientific as it gets, and compared to the manufacturer:
    http://www.rri.se/popup/performanceg...p?ChartsID=647

    Steve
    Not familiar with that dyno but the 335 is underrated from the factory to begin with.

    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
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    Is basically a high accuracy engine test dyno bolted to each hub - so no loss from wheel slip or anything else.
    Its hydraulic based and has load cells in each wheel unit. VERY accurate.

    What the figures for the above 335i AT do indeed show is that the calculated drivetrain loss is like 6% or so which is not realistic.
    What it does demonstrate therefor is that BMW have indeed underestimated the output of the n54 on 95ron.
    The real output is likely in the region of 325bhp (if we assume 15% loss on the AT tranny)
    Possibly it was benchmarked on the engine dynos with crapola fuel, 91 or less?

  17. #17
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    Click here to enlarge Originally Posted by m1bjr Click here to enlarge
    Is basically a high accuracy engine test dyno bolted to each hub - so no loss from wheel slip or anything else.
    Its hydraulic based and has load cells in each wheel unit. VERY accurate.

    What the figures for the above 335i AT do indeed show is that the calculated drivetrain loss is like 6% or so which is not realistic.
    What it does demonstrate therefor is that BMW have indeed underestimated the output of the n54 on 95ron.
    The real output is likely in the region of 325bhp (if we assume 15% loss on the AT tranny)
    Possibly it was benchmarked on the engine dynos with crapola fuel, 91 or less?
    Actually, I think it is far more simple than that. It was simply BMW protecting the E46 M3 as when the 335 launched the last E46 M3's were still for sale.

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    Nice info Sticky. This is very simple and very effective, so thank again!

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    Good post Sticky! Very informative, thanks!
    Click here to enlarge
    Click here to enlarge

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    Click here to enlarge Originally Posted by Jajima Click here to enlarge
    Good post Sticky! Very informative, thanks!
    It's what I like to do Click here to enlarge

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    2 out of 2 members liked this post. Yes Reputation No
    Sticky,

    Like everyone says, good info! Thank you for not only posting this but taking the time and effort to do the research. This is the sort of thing that makes up a quality forum!


    Cheers

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    Click here to enlarge Originally Posted by ersin Click here to enlarge
    Sticky,

    Like everyone says, good info! Thank you for not only posting this but taking the time and effort to do the research. This is the sort of thing that makes up a quality forum!
    BimmerBoost is happy to go above and beyond Click here to enlarge

    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
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    Nice thread Sticky
    Click here to enlarge

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    good reading

  25. #25
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    Click here to enlarge Originally Posted by LostMarine Click here to enlarge
    good reading
    Due to good writing.

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