Archive for category Porsche cayenne hybrid
Below is a dyno chart showing power of the combustion engine alone and combined power with the hybrid motor on a VW Touareg hybrid. The Porsche Cayenne hybrid S uses the same drivetrain in a slightly different body (same underlying chassis).
As you can see, power from the 3.0L supercharged engine is quite good. Where the hybrid motor’s additional power really shines is at the low end. This is due to the characteristic of a hybrid motor. They provide maximum torque at 0 rpm which decreases as friction and other limitations rise with rpm. Horsepower provided by the hybrid motor is more or less constant as rpm increases.
In the last 3 sections, http://www.evwaudi.com/2011/02/how-to-safely-disconnect-vw-hybrid-battery-high-voltage-line/ , the safety connector at the engine was shown. This article will show the High Voltage System Maintenance Connector at the battery pack. Always disconnect this when working on the high voltage electrical system.
You disconnect it by removing the cover flap and then pulling it up in a perpendicular position.
This is under the orange flap in the picture below.
How to remove the high voltage line on the VW Touareg hybrid or Porsche Cayenne hybrid. May also apply to Audi A6 hybrid, VW Jetta hybrid
In the last article, part 2 of a series: http://www.evwaudi.com/2011/02/how-to-safely-work-vw-touareg-hybrid-disconnect-electrical-system/ on how to disconnect the battery pack on the VW Touareg hybrid and Porsche Cayenne hybrid, the safety line and how it works was discussed. This article is the final part on this topic and shows how the mechanical lock on the high voltage line works.
Again, the official literature says that only a trained VW High Voltage technician can remove the maintenance connector. First, remove the safety connector. This prevents the high voltage lock from moving. It also prevents the high voltage system from being supplied with current. If you read part 1 and 2, you will see how this interrupts the safety line. The battery management unit then decouples the high voltage battery through the relays. As long as all systems work as intended, there will be no voltage at the high voltage line and you won’t get shocked when removing the high voltage line.
The safety connector also physically blocks the locking bar from swiveling out of the way. Then swivel back the locking bar. The cable can then be removed. This is shown in the illustration below.
In the last article: http://www.evwaudi.com/2011/02/how-to-safely-work-vw-touareg-hybrid-disconnect-battery-pack/ the main safety switch was described.
This article will describe how the safety line works to disconnect the electrical system on the VW Touareg hybrid and Porsche Cayenne S hybrid.
Safety line closed:
The VW Touareg hybrid’s high voltage elements are linked by a separate low voltage loop line. Each connection with the safety line is designed to act like a contact breaker point. When all components are ready to operate, the contact breaker points are closed. When the safety line sees voltage, current is able to flow because the line is not interrupted. The presence of current indicates that all of the safety line’s components are ready to operate. The function of the safety line is comparable with cold monitoring in the case of bulbs.
Safety line open:
If any point is open the safety line is interrupted. This could be if any component is not ready to operate or because the safety connector has been removed. In this case, there will be no current. This indicates that the high voltage system is not ready to operate. The check to determine whether the safety line is closed or interrupted is carried out by the voltage converter. If the control unit determines that the line is interrupted, it actuates the protective relays and interrupts the high voltage battery’s connection to the high voltage system.
Below is an illustration from VW’s literature showing the safety line.
One concern of working on hybrid cars for DIY’ers is how to work around the hybrid electrical system. It’s not only amps or only volts that is dangerous, it’s enough of the combination of enough either volts or amps that can injure you. Comparing electricity to water, you can think of amps as the volume of water and volts as the speed that it moves. You’re not going to get swept away in a river unless there’s enough water and it’s flowing fast enough.
The electric safety line in the VW Touareg hybrid and Porsche Cayenne hybrid
The battery pack in these cars is 288 volts and more than enough amps to cause serious injury. If it has enough energy to move a car it has enough energy to jolt you. Therefore, take safety precautions when working on them. There are a few safety measures:
• The electric safety line with safety connector
• The ignition lock
• The battery regulation control unit relay
• The airbag control module
• The maintenance connector
In this first post in a series, let’s look at the safety line and connector. The safety line guarantees that the entire high voltage system’s voltage is turned off as soon as a high voltage component is disconnected from the system. Together with a locking bar, the safety connector forms a mechanical lock, which prevents the high voltage lines from being disconnected while voltage is present. The safety line is an electrical circuit that is closed by safety connectors. If this circuit is opened by removing the safety connectors, the high voltage system shuts off.
The safety connectors have to be removed before high voltage lines can be disconnected from the high voltage components. This guarantees that the system is not conducting voltage when the lines are disconnected. It is shown below.
The Porsche Cayenne S hybrid mpg has been confirmed to deliver 21/25 mpg
Porsche’s first hybrid, the Cayenne S goes on sale November 2011 and start at $67,000.
Like all Cayenne, it’s based off the VW Touareg chassis but unlike past Cayenne, it uses the same hybrid drivetrain and system as the Touareg. Past Cayenne used unique to Porsche suspension and engine combination. Therefore, it shares many of the features of the Touareg hybrid including electric only drive up to 37 mph, and coasting with the engine off and decoupled. Below in the gallery is a picture of the hybrid drive system.
Peak power is also similar. The Cayenne S hybrid’s engine is rated at 333 hp and 44 electric motor for a total of 380 combined horsepower. Peak torque is 428 lb-ft at only 1000 rpm.
While the rated mpg is 21/25 doesn’t sound very impressive, the base engine’s mpg is only 14/20 which is an improvement of 50% and 25%! 25 mpg is certainly achievable without the Cayenne hybrid but not with this amount of style and speed.
As you can see from the dyno graph chart showing horsepower (red line) and torque (blue line), most of the VW Touareg hybrid and Porsche Cayenne hybrid electric motor’s assist is at low engine rpm.
With the electric motor’s assist, the combined torque curve is almost flat up to 4000 rpm and then begins to trail down. This means the engine will have tons of pick-up and throttle response down low. The engine by itself is a supercharged V6 used in the Audi S4, the sport version of the A4, so it is no slouch.
The transmission is rated to handle up to 627 lb-ft of torque so there should be room for tuners to increase the boost and fueling on the supercharged engine. The question is can the rest of the drivetrain take it?
Click the image to enlarge the thumbnail.
In the last post describing the basic layout of the battery ( http://www.evwaudi.com/2010/how-the-battery-works-vw-touareg-and-porsche-cayenne-hybrid ) , we learned that the VW Touareg hybrid and Porsche Cayenne S Hybrid use a 288 volt NiMH battery. This article describes more of the power control systems and battery.
VW uses a “power electronics unit” to control the energy flow between the electric motor and the high voltage battery. It contains a pulse controlled inverter and DC/DC converter so that the 288V battery it can also supply the regular 12V car electronics systems.
The battery consists of 240 individual cells which give an energy density of 1.7 kWh. It’s under the rear of the car where the normal spare tire is and is protected by a protection box, shown below. It does take up a little cargo space though. Cargo room with the seats up in the normal Touareg is 580 liters vs. 493 liters in the Touareg hybrid. The big orange cables which run from the battery to the power control unit and the electric motor are called traction lines. The rear part of the hybrid system, the battery assembly, weighs 79 kilograms (175 lbs).
In the below gallery you can see an illustration of the fans and an actual picture of the box removed from the car. You can also see the relation ship of its position to the exhaust.
The Porsche Cayenne S Hybrid, VW Touareg hybrid, and the just announced Porsche Panamera hybrid all use the same Audi S4 supercharged engine. With older supercharged engines, it was as easy as changing the pulley to increase boost and increase power. Does this this work on the engines in the aforementioned models? Will a chip tune also work? This is part 1 of an ongoing series of articles of how to increase the power of your hybrid.
Long story short, at this time, a smaller pulley will not increase the power of your VW Touareg, Cayenne, or Panamera hybrid.
The pulley is small to begin with so it would be a challenge to make it much smaller. Eaton makes the TVS r1320 supercharger that is on the hybrid and S4 engine and does not make smaller pulleys for it. Each supercharger is designed to operate most efficiently within a performance envelope (if you chart effiency on a graph it forms a “box”, really more of a blob) and going outside of the envelope is inefficient. Physically, the supercharger might be able to make up to 20 psi but it’s ecu limited to about 11.6 psi (0.8 bar). Any extra is recycled back to the supercharger through a bypass valve. ECU changes can close this valve and direct all the air to the engine. The reason the bypass valve is often open is to complement the design envelope of the supercharger with the engine performance for both high and low end power. Below is a video showing the insides of the supercharger showing the bypass valve.
Below is the compressor map for the r1320 supercharger (from eaton.com)
Some tuners for the Audi S4 have made up to 420 hp with just a chip and tune so I don’t see why the hybrid engine can’t be tuned as well. However, will the hybrid motor’s decoupler stand up to the abuse? The decoupler is essentially a clutch – can it hold the extra power? This is completely unknown and other than the additional engine tuning, will be the unknown factor in tuning the Cayenne Hybrid or VW Touareg Hybrid.
See the next article for more information on the supercharger and chip tunes.