What Are They?
First let me say, there’s nothing new about accumulators. Many pieces of equipment/machinery use them. So in that regard to, let me just use a Wikipedia definition. I’m not re-inventing something here when these have been used for years. Their definition is perfect already:
“A hydraulic accumulator is a pressure storage reservoir in which a non-compressible hydraulic fluid is held under pressure by an external source. The external source can be a spring, a raised weight, or a compressed gas.”
In sum, an accumulator is similar to a battery. If you didn’t have a battery in your vehicle, outside of it not starting, if it was running, the alternator would be constantly working to keep all of the electrical loads satisfied. As soon as the alternator failed in this situation, the car would die as well. (We are not using old mechanical combustion ignition vehicles in this scenario).
It could also be compared to an air compressor. You have a motor electrically powered that’s usually belt driven, that turns the air compressor pump. That pump fills the air compressor tank (or air accumulator in this instance). There are many different sized air compressor tanks, shops have upwards of 90 gallon units. It holds all of that stored air under pressure so that multiple pieces of pneumatic equipment can be run at one time. If you tried to do the same thing without a storage reservoir or accumulator it would be impossible to do.
This is what the accumulator is for on an F1 or E gear system. Again very similar to a battery or air compressor. You have a voltage regulator in a vehicle system so as not to over charge a battery, you have an air pressure switch that turns off the pump motor on the air compressor when it reaches its set limit, for example 150 psi. Once 150 psi is reached, this is sensed by the pressure switch, and turns it off.
Likewise in a F1 system, the F1 pump cycles, this fills either the bladder or piston type accumulator (explain in a minute), once the pressure is up to where it’s supposed to be, sensed by the pressure switch that’s on the valve body, it is mandated off. This is all a hydraulic accumulator is. It stores hydraulic fluid under pressure for the system to use.
Various Types of Accumulators?
Let’s deal solely with Ferrari, Lamborghini and Maserati accumulators. The two types usually used in these cars are either bladder type accumulators or piston type. You usually see bladder type accumulators used in F cars, and piston type in Maserati.
These photos above show you both types in these cars.
First, the bladder type accumulators you will see in F cars or Lambos, they are normally mounted vertically or straight up and down from the valve body.
Second the piston type accumulators in the second picture above, mainly in Maserati you see them mounted on top of the gear box horizontally.
Now I cannot say exactly why one was used in the Ferrari/Lambo and the other in Maserati. I can speculate if you’d like. I would postulate that bladder types are used in one car because of their mounting location allowed for the space, and for them to be vertical. When you mount a bladder type accumulator horizontally it has a slightly loss of efficiency, additionally, they seem to be away from heat zones.
If you notice in the Maserati the piston accumulators are laid flat on the gear box, they are thinner, and required less diameter space to be placed there. Additionally, because it’s exactly where all the heat from the gear box would rise to the piston type accumulators are known to work better with higher heat ratings.
A few of the down sides to each though are: The bladder type accumulators when they fail usually fail immediately injecting whatever pre-charged gas the bladder uses right into the F1/E gear system. Air injected into a closed hydraulic system is never good.
The piston type accumulator on the other hand fails more slowly as the seals deteriorate, it doesn’t release the gas the same way.
The flip side to this is bladder type accumulators can handle more particulate or dirtier fluids than piston types. Piston types have to make sure the fluid is clean or it could damage the seals.
I am going to hyper-link some videos here by Parker, a leader in the hydraulic industry to show you how these accumulator actually work:
Signs of Failure
I suppose the most important part of this article as it pertains to these cars is what are the obvious signs of failure.
As we have previously discussed, the different type of accumulators do fail differently.
In a Ferrari, you will have the air injected into the system, so this could cause the car not to shift, or have problems with the actuator/clutch. This will be accompanied by a constant priming of the F1 pump. This could be confused with a stuck relay, diagnostic checks should be performed to nullify this. If the pump is constantly cycling it’s because you have lost your storage cell. You will need to both replace the accumulator, and completely bleed the system.
The consistent sign with either accumulator that it has failed or is failing is the F1 pump constantly priming.
With a piston type accumulator like the Maserati you don’t have to worry about an immediate failure. You need to time your pump cycles. Sitting in neutral car running, the pump should not cycle more than once a minute. Once you get under this you know you are starting on the last legs of the accumulator. I’ve personally had clients where the pump cycled every 8 seconds. Another client a Maserati Dealership installed a brand new pump, without proper diagnostics, and 5 miles later the pump burned up again.
Accumulators don’t have a forever shelf life and are considered maintenance items. Checks should be performed to maintain the health of the system. If not you could ended up burning up your F1 pump or worse damaging parts inside the actuator, or thrust bearing getting stuck mid-shift.
Additionally, I might add, the fix to this is not to install a more powerful pump. That’s not how this works. You need to address the hydraulic cell responsible for storing the energy it needs. That pressure is between 40-50 bar for example with Maserati. So, the minimum pressure is 580 psi, the switch triggers the F1 pump it pumps it to psi. It takes all of about three shifts to deplete the system back down to 580 psi of hydraulic pressure again. As far as I know, there isn’t a hydraulic pump that you can retrofit in any of these cars that automatically pump at the bare minimum of 580 psi.
I am all for making things better but the way to do that is to make sure you are in “good hands” mechanically with whatever shop/dealership you are using. These cars are way too expensive to try to band-aid a F1 system with a more powerful pump. Obviously, I’m not talking about the F430 with the E-Diff system. I’m more referencing making sure the health of the system is good before putting an aftermarket pump on the system that’s really not necessary.