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Can the PTU in the FF & Lusso handle the power of a 700hp V12

Discussion in 'FF/Lusso/F12/812S' started by officeline, Nov 30, 2020.

  1. officeline

    officeline Rookie

    Jul 23, 2019
    29
    Belgium
    Full Name:
    Frank Vancauwenberghe
    Ferrari's 4-wheel or PTU system is totaly different from a conventional 4-wheel or 4X4 system that is based on a single gearbox with a central differential that gradually regulates the power from one central engine to each wheel individually, allowing all wheels to handle the same forces and are equally dimensioned.

    The Lusso & FF are actually classic 2WD vehicles, a front-mounted engine with a rear-mounted gearbox that handles the full power to the rear wheels, noting that the rear is more strongly dimensioned than the front.
    The difference lies in the fact that the front wheels are now additionally driven by a 2nd gearbox called 'PTU' which is mounted at the front on and in the engine. This gearbox has at the front only 4 gears " executed in a two speed gearbox" and from the 5th gear it is disengaged and drives the Lusso or the FF as a normal 2WD.
    Both gearboxes are mounted in the same line on the crankshaft of the central engine, the PTU is directly on the front side of the engine and the rear gearbox on the other side or rotated 180° via a classic drive shaft or universal joint shaft. Both do not know mechanically about each other and function standalone. Ferrari's rear gearbox is a proven concept and is clearly an oversized design to handle large forces, but the front PTU is a different story and is remarkably smaller in size than the rear.

    If you drive the Lusso in 1st, 2nd, 3rd or 4th gear on a straight track at a constant speed, you won't create any slip, virtually no power is sent to the front wheels, you drive as if you were driving a 2WD. If you take a sharp turn and you accelerate the PTU gets in action, the front wheels get more power so they turn faster, you get more grip and the car is less likely to skid. But once in 5th gear you must realize that you are driving back in a classic 2WD because the PTU will be switched off and you will have to make sure that the car does not understeer or break out in the opposite direction of your rotation. You will then have to make sure that there is enough grip on the front wheels by taking back the throttle or by making less steering angle.

    [​IMG]

    According to Ferrari's technical director Roberto Fedeli, the PTU "in this picture" of which the internal gears between the 2 front wheels are visible, can only handle 20% of the engine power. It is small in size "4 to 5 times smaller" because there is hardly any space in the engine compartment. It controls the speed of the front wheels based on two wet oil clutches for each side of the car. They decide if there is slippage and therefore more or less power has to be sent to the left or right front wheel.

    According to Fedeli, the PTU can run the front wheels at the same speed as the rear wheels. This means that a large amount of power, or perhaps almost all of it, can temporarily be transferred to the front wheels.

    Suppose Ferrari would have limited the Lusso so that only 20% of the power can be sent to the front wheels then we can't speak of a real 4 X4 like an Audi quattro where 70% to 80% of the power can be sent to one of the 2 axles. So it is to be expected that more than 20% of the power can be pushed to the front axle to get enough grip in slip situations.

    And since the PTU of the Lusso can rotate all wheels at the same speed, this means that more than 20% of the power can be directed to the front wheels.

    So if it can handle only 20%, Ferrari should have a safety device built in if the power on the front axle is more than 20% of the torque. But this is not the case because then this system would have to be disabled at high loads and this is not done because this would be visible by driving behaviour or the instrument panel. The following situation shows the Achilles tendon of this concept:

    Suppose you drive at 200km/h in 6th or 7th gear and you want to take a left turn, you slow down before the turn and are now doing probably 4 to 5000 rpm, you want to add throttle to get back to speed. You are driving manually and you put your Lusso in 4th gear because your want to increase rpm as you want to leave the corner faster. Shifting into 4th gear activates the PTU and suddenly an important part of the power comes on the PTU. The PTU will make the right wheel turn faster than the left one because it has to travel a longer distance than the opposite wheel. Driving quickly into a corner will cause immense horizontal and vertical forces to be applied to the left front side of the car, which tends to slow this side down. The wet clutch detects slippage and orders more power to the left wheel. The power demand on the front wheels is then significantly more than 20% and probably closer to 50% as we are now easily making 6000 rpm's and from the power graph of the Lusso we can see that we are moving almost closely to full load. A conventional 4X4 now brings more then 50% of the power to the front wheels and for the Lusso that will make no difference because as long as the clutch detects slip it will increase the power to the front because it wants the left front wheel to spin as fast as the rear wheels.
    It then looks like you are driving a monster V12 that is shifted by a mini gearbox in close proximity comparable to an Alfa 156. In addition, the drive shafts of the front wheels "see picture" are lighter than the rear wheels as in a classic 2WD Ferrari where the full power is only put on the rear wheels which always process the full power. However, at this time, more power or the same forces may be applied to the front wheels as those applied to the rear wheels. It is highly doubtful that this small mini PTU can handle these monstrous forces.

    Since there is no protection to limit the power on the Lusso's PTU, it occasionally gets into situations where it is overloaded. And if there is any power limitation, this would be very unsafe because your 4x4 would fail in stress conditions where you need them high. For the PTU this situation is very stressful and moreover, these forces suddenly come through shifting from 5th to 4th gear. A classic 4x4 differential does not have this problem as it gradually builds up the distribution.

    Today there are reports of dozens of broken PTU's because the seals and forks have failed due to high pressure and stress factors on the forks while driving as in this situation.

    PTU failure is related to the use of the car. For example, the PTU is more prone to tarmac than snow. The FF/Lusso is originally presented in a snow environment where it has to work much less than on asphalt. In a wet or modulable surface the forces to be transferred to the PTU are smaller. The daily use of the Lusso in city traffic and cornering by shifting to lower gears is much more stressful than cruising at constant speed or long distances. It is doubtful that the concept can cope with this. Driving on freeways puts almost no strain on the PTU unless one accelerates and decelerates continuously. This also explains why some cars with many kilometers have escaped PTU failures where cars with very few kilometers that are only used to make short trips in city traffic are much more likely to have PTU failures.

    The current PTU concept is too fragile and cannot cope with the high forces at these heavier loads or with people who drive sportily. The Lusso is a combination of a mouse and an elephant. I you ride it like a mouse with an elephant you will have no problems, but if you ride it like an elephant with a mouse, the PTU will probably fail. The problem is that as a driver you don't always know in which mode you are driving.

    The first thing to go are the seals, which are under very high pressure. If you are saddled with a defective PTU it is advisable to grade it up with better seals and stronger forks as one of these specialists recommends.

    https://www.ssautotech.co.uk/ferrari-ff-ptu-rebuild.html

    It is clear that the current PTU concept is a dead end street story for Ferrari. Despite the fact that the Lusso is a fantastic car to drive or own, you should be aware of this Achilles tendon of your car if you want to keep it in good condition. Entering the circuit with such a fragile concept does not seem to me a good idea. It is equivalent as asking for PTU failure given the high stress your PTU will have to endure unless you manage to complete your lap only in 5,6 or 7th gear as if you were driving a classic Ferrari.
     
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  3. ANOpax

    ANOpax Formula Junior

    Jul 1, 2015
    664
    The Netherlands
    Thanks for the summary Frank. How’s your legal case against Ferrari going?
     
  4. Magnus Kanerfalk

    Sep 12, 2020
    22
    Full Name:
    TioMango
    Interesting, this is the main reason why I'm looking at a "T" now when I'm buying a Lusso.
     
  5. gilly6993

    gilly6993 Formula 3

    Aug 20, 2009
    2,237
    Longmeadow, MA
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    Eric
    #4 gilly6993, Dec 1, 2020
    Last edited: Dec 1, 2020
    Great write up and very informative. Thank you

    I am someone who has had a replacement on my 2017, about 5K miles ago, and no issues since.

    Is the new PTU that was put in, which was the summer of 2019, different than the original? Stronger seals or otherwise?


    Sent from my iPhone using Tapatalk
     
  6. ttforcefed

    ttforcefed F1 World Champ
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    Aug 22, 2002
    16,498
    wld be nice to eliminate the ptu
     
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  8. otakki

    otakki Formula 3

    Mar 24, 2016
    1,558
    Great summary!
     
  9. papou

    papou Formula 3
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    May 18, 2012
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    daniel ross
    Magnus Kanerfalk likes this.
  10. SeattleStew

    SeattleStew Formula Junior
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    Apr 10, 2020
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    Stew
    Interesting read. I laughed at the first comment about a lawsuit as when I read the original post I said to myself “I think this guy is suing Ferrari”.
     
  11. ANOpax

    ANOpax Formula Junior

    Jul 1, 2015
    664
    The Netherlands
    Don’t laugh. He is suing Ferrari.
     
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  13. SeattleStew

    SeattleStew Formula Junior
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    Stew
    I'm not laughing at him suing Ferrari. I was laughing at the irony of I thought based on that post he was suing them, and the first comment is exactly that.
     
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  14. Moopz

    Moopz F1 Rookie
    Rossa Subscribed Owner

    Jun 29, 2004
    4,619
    Orlando, FL
    I've been looking at Lussos. My local service manager said he has replaced a handful of them (he calls them PTOs), varying mileage range. He didn't recommend getting a Lusso without the power warranty or without $23k saved for out-of-pocket replacement.

    Sent from my SM-N975U using Tapatalk
     
  15. MotorMouth

    MotorMouth Formula 3
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    Jan 6, 2010
    1,074
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    Dave
    I’ve read through the entire ptu design flaw thread and have concluded that the answer is for someone to come up with a delete kit. PLEASE someone come up with a delete kit! It’s such a bummer. These would otherwise make the best DD ever.
     
  16. Moopz

    Moopz F1 Rookie
    Rossa Subscribed Owner

    Jun 29, 2004
    4,619
    Orlando, FL
    There is a kit sold in the UK that addresses the internals so it can be repaired and not replaced.

    Sent from my SM-N975U using Tapatalk
     
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  17. Jaguar36

    Jaguar36 Formula Junior

    Nov 8, 2010
    541
    Cherry Hill, NJ
    Why would you want to delete one of the headline features of the FF for the slight risk of a ~$8k repair? If you've read through the full thread you'll know these cars aren't time bombs or anything, its just a small risk. Besides if you are really that afraid of it, just get a Lusso T instead.
     
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  18. Moopz

    Moopz F1 Rookie
    Rossa Subscribed Owner

    Jun 29, 2004
    4,619
    Orlando, FL
    It's more like $20-30k repair from what I've seen.

    Sent from my SM-N975U using Tapatalk
     
  19. ttforcefed

    ttforcefed F1 World Champ
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  20. ANOpax

    ANOpax Formula Junior

    Jul 1, 2015
    664
    The Netherlands
    In the UK it's a $8,800 repair (excluding sales tax). The price includes all labour and a 12 month warranty.
     
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  21. ttforcefed

    ttforcefed F1 World Champ
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    Aug 22, 2002
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    wow thats a great price. to think some poor souls out there paid $40K USD
     
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  22. papou

    papou Formula 3
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    May 18, 2012
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    daniel ross
    The uk price is £8000 = just under $11000 ,that includes re-engineering the forks..
     
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  23. papou

    papou Formula 3
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    Modified Ferrari FF / GT4C Lusso PTU rebuild
    By Martin Parkes & Simon Stojsavljevic
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    Modified Ferrari FF / GT4C Lusso PTU rebuild
    This is a joint venture between Martin Parkes and myself. Martin has a wealth of knowledge working on supercars, having over 22 year’s experience, working at main dealer levels and independents alike.

    He was brave enough to take on the task of stripping a customer’s PTU to work out a way to repair it, as opposed to Ferrari’s only option of fitting a new one at huge cost. Between us, we spotted the weaknesses and failure points inside the box.

    Over the last year, we spent a vast amount of time, effort and finance researching and modifying the PTU internals to find a firm solution to its weakness.

    We have thoroughly investigated the root cause of this problem, and have found several flaws in the design of the mechanical parts making up the hydraulic fork assemblies.

    These assemblies have been re-engineered to eliminate the weak areas and give as maximum strength to them as we saw possible.

    Image Unavailable, Please Login
    Complete New Hydraulic fork assemblies ready to install.
    Parts are not available ‘off the shelf’. Even if they were, we would not be happy to fit these as they would be like for like – only giving the PTU the same service life.

    Our aim was to find a long-term solution to this problem and not just a temporary fix that would certainly fail again.

    Our CNC machined selector fork assemblies have been re-engineered from far stronger billet materials, to exacting blueprint tolerances, and offer far greater mechanical strength over the standard forks.

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    Billets of Aircraft grade aluminium being formed into forks.
    Aerospace grade forged billets of high strength aluminium is used in the Fork redesign. A stronger modified version of chromoly billet steel, (as used in billet race crankshafts, input shafts etc), was selected for the hydraulic shafts; and, Aircraft grade Nickel Bronze, (as used for landing gear bearings), was selected for the modified seal housings.
     
  24. papou

    papou Formula 3
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    May 18, 2012
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    plantation Fla
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    Hi Daniel,


    Have you had the PTU diagnosed with internal F1 fluid leakage?


    I don’t have any affiliate there in the US.


    The rebuild of the PTU does require specialist tools. It is easy to damage the forks on assembly, and I wouldn’t be able to guarantee the workmanship unless the work is done in house here.


    I would think a good workshop would be able to carry out the job, but they need to be able to bleed the system after assembly, and place the two gearshift forks in N.


    If you can get the PTU removed, you can ship it over to me, or I can arrange DHL to come and collect it.

    It will need to be boxed in a wood crate, and protected inside and braced up so it doesn’t move.


    We have just rebuilt a PTU that’s going back to Saudi this week, delivery and return shipping, with insurance, came to a cost of just under GBP £1000.00


    Let me know what you’d like to do,


    Thank You,

    Best Regards,

    Simon


    Email: contact@ssautotech.co.uk

    Tel: 0044(0)7711 080991

    https://www.ssautotech.co.uk/
     
  25. papou

    papou Formula 3
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    It’s great that we all have looked into solving this issues my FF hasn’t had the issue as yet.
    But it disgust me that Ferrari has not resolved this for us in the first place,
    This was the signature selling point of the FF at its launch.
    Stay safe everyone and enjoy your Ferrari..
     
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  26. MotorMouth

    MotorMouth Formula 3
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    #23 MotorMouth, Dec 7, 2020
    Last edited: Dec 7, 2020
    not such a headline feature. As you point out they make a v8 that doesn’t have the feature at all. Everyone wants the V12 one though. I took away that it’s an 8 k fix plus the labor which is at least the same. At least part of it has to be done by a dealer etc. Unless your in the UK and you have that outfit do the whole job for a bit more. After exchange rate its a 20k+ job.
     
  27. papou

    papou Formula 3
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    Considering the price we can now buy a FF the cost if you have to repair a PTU shouldn’t be a deal breaker now..
     
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  28. ttforcefed

    ttforcefed F1 World Champ
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    Aug 22, 2002
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    Ok i was looking at the $ sign
     
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