Traditionally power brakes rely on motor vacuum to operate. However in particular in diesel setups or modern cars where there is not much vacuum or should be left undisturbed, often there already is an additional electric vacuum pump in place. When converting to electric, there no longer is any motor vacuum for power brakes available. The easiest and most straightforward solution is to add such a electric vacuum pump. They have one big disadvantage: they are noisy!
Of course next to a diesel engine you will not even notice it, but in an electric vehicle you do. Personally I could not stand the idea of the sound of a vacuum pump kicking in to build up a vacuum buffer as soon as you enable the car so I implemented electric power brakes. However, before doing so I did some research on vacuum pumps and looked for a ‘silent’ one.
The quest for a silent vacuum pump
In my longlist I compared some pumps from Hella and a Mes-Dea. The Ford A426C was left out of the equation since it was more difficult to source (although it should be a silent one). In the below table you will find the specs of the Mes-Dea and the four Hella pumps.
| Type | Current | 70% from ambient pressure | Volume | Acoustics |
|---|---|---|---|---|
| Mes-Dea 70/6E2 | < 5 A | 5 sec (2 liters tank) | < 64 dB (A) | |
| Hella UP28 | < 10 A | ≤ 11 s | 3,2 l | < 70 db (A) |
| Hella UP30 | < 15 A | ≤ 7 s | 4 l | < 77 db (A) |
| Hella UP32 | < 18 A | ≤ 6,2 s | 5 l | < 78 db (A) |
| Hella UP5X | < 15 A | ≤ 4,4 s | 4 l | < 73 db (A) |
The UP28 is the smallest Hella pump and found in many cars like Volvo and Opel. The UP5X is really a beefy pump and found in the Aston Martin Vantage. The Mes-Dea is found in a.o. the Tesla Roadster.
In any case it is recommended to add a vacuum tank as a buffer. The Mes-Dea 70/6E2 features an internal pressure sensor allowing the pump to switch on and off automatically. The Hella pumps require an external vacuum switch (available in the webshop).
Bench testing vacuum pumps
I tested the two pumps:
- Hella UP-28
- Mes-Dea 70/6E2
While it was a bit difficult to keep the Mes-Dea running continuously during the test due to the integrated sensor I managed to compare the two.
dB versus dB(A)
I measured in dB(A), so with a correction for the sensitivity of our ears. In absolute dB’s the pumps are equally loud but the tone of the Hella is higher and we are more sensitive to that freqency.
There is a difference of 2,5 to 3 dB between the pumps. This seems little but the scale is logarithmic and the experience of noise is subjective. So in practice the difference is a factor 3 on experienced intensity.
The verdict
So if you’re not into implementing electric power brakes, I’d suggest to use a Mes-Dea 70/6E2 if you can find one. Officially the UP-28 is a helper pump. The UP30 and UP5x are stand alone pumps.
Update: After the Mes Dea 70/6E2 the Tesla Vacuum pump and after that the Hella UP5x is the next best option
While the Mes-Dea 70/6E2 is hard to find nowadays, the Tesla vacuum pump (used) or after that the newly available Hella UP5x is in my view the best available alternative but I no longer stock the latter.
I managed to find some new Tesla Roadster vacuum pumps. Grab one while you can! And I have a vacuum pump from an early Tesla Model S available. That is a dual diaphragm pump and (therefore) also relatively silent.
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Product on sale
Tesla style vacuum pump brake boosterOriginal price was: €175,00.€75,00Current price is: €75,00. (inc. VAT €90,75)
For the Mes Dea and the Hella UP5x a connector kit is available.
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Mes Dea 70/6E-2 connector kit€6,00 (inc. VAT €7,26)
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Connector kit for Hella UP5x vacuum pump€5,50 (inc. VAT €6,66)
Vacuum sensor / switch
And you need a vacuum sensor. I can recommend either the Multicomp PSF109S-81-330 or the Mater XV600
Multicomp PSF109S-81-330
Vacuum set point range is -2.9 to – 11.9 psi (= -200 to -822 mbar). It is a single pole dual throw (SPDT) switch so it can be used as normally open (NO) or normally closed (NC). The port is 0,25″ (=6,35mm). Temperature range is 4 degrees to 65 degrees.
Dimensions can be found below:
It is rated for 15A at 250 VAC. It does not have specs for VDC. So if you want to be sure, using a relay in between the vacuum pump and this switch is needed. It will not be able to handle the vacuum pump current draw over longer periods of time.
Mater XV600
I have some available and will add them to my webshop soon. Will be the last ones in stock.
Using a relay
Below you will find an example wiring diagram for using the sensor(s) with a relay.
Hello,
I am doing a conversion and have purchased a Tesla vacuum pump booster for my power breaks. Do I need to install a relay as well? If so, do you sell them?
Thank you.
You need a circuit that controls the vacuum pump.
The Tesla roadster vacuum pump has an internal control mechanism.
The Tesla Model S vacuum pump needs an external circuit.
You can for example use an adjustable vacuum switch and for that one you indeed need a relay. I do not stock and sell relays.