# Power braking/Vacuum-assisted braking?



## Kevin Evans (Jul 11, 2014)

Not sure if this is the right subforum for this, but I have had this question on my mind all day long.

Is there power braking/vacuum-assisted braking available for EVs? Or do people just not have assisted brakes in EVs?

I've never driven a car without power brakes, so I'm kinda questioning what it'd be like driving one.


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## dougingraham (Jul 26, 2011)

My car originally had vac assisted brakes and I bought a 12 v vacuum pump for it. But I just never got around to installing it. I've driven the car 4600 miles without it and last weekend I started hooking it up. I need a couple more hours to finish the temporary installation.

If you want to know what it is like to drive this way it is easy to disconnect the manifold vacuum on your car. One hose and you probably want to plug the hose going back to the manifold. If you aren't quite that curious I can tell you that it is stiff but you can still lock up the wheels if you need to at least on my car. I finally decided to install it not because I need it but because it will be easier for others to drive the car. It will be what they are expecting or used to.

I bought my vac pump from Evolve Electrics (click the link on the right side of your screen.)


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## davidmillin (Dec 14, 2013)

> Not sure if this is the right subforum for this, but I have had this question on my mind all day long.
> 
> Is there power braking/vacuum-assisted braking available for EVs? Or do people just not have assisted brakes in EVs?
> 
> I've never driven a car without power brakes, so I'm kinda questioning what it'd be like driving one


Hi Kevin

Most conversions do have power assisted brakes particularly if the conversion car had power assisted brakes. A 12 Volt vacuum pump is fitted with a vacuum reservoir and a switch that closes when the vacuum drops below a preset level switching the pump on until sufficient vacuum is reached then as the brakes are used the vacuum will drop and the pump will switch on again. the reservoir just connects directly to the booster unit often using the same vacuum hose that connected to the engine in a petrol vehicle or the vacuum pump in a diesel vehicle. Some conversions use a belt driven vacuum pump as you would find in a diesel but as electric vehicles tend not to idle you could find yourself without vacuum when creeping along in heavy traffic etc. 12V vacuum pumps and reservoirs can be bought as off the shelf components and some people make their own reservoirs out of PVC pipe or old fire extinguishers or similar.


Hope this helps
David


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## steelneck (Apr 19, 2013)

Kevin Evans said:


> Is there power braking/vacuum-assisted braking available for EVs?


Look for a Hella UP30 Vacuum pump. It can be found in many quite new cars, like Volvo V70 for example, so they can be found used for a decent price. This is a pump that is meant to take care of all the vacuum needed for the brakes. There is also a smaller and a bigger pump. The smaller UP28 is only a helper pump, do not use that in an EV. The UP32 is a bigger unit for cars that also have other things driven by vacuum. The reason that many new cars use electric vacuum pumps is mainly because of turbo engines and diesels that do not produce vacuum enough.

http://www.hella.com/microsite-electronics/117.html

I have the UP30 in my car, it is a very quiet unit, just a small buzz if properly mounted.


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## mk4gti (May 6, 2011)

You can also get the VW passat/Audi A4 pump, there are many threads covering this subject.


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## phogan (Jun 25, 2014)

Has anyone looked into the Ford diesel truck series vacuum pump? It's Dorman part no. 904-214. For only $60 on several websites it seems too good to be true, but I believe it's the sole source of vacuum for the brakes on those trucks so that's got to be worth something.


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## nimblemotors (Oct 1, 2010)

phogan said:


> Has anyone looked into the Ford diesel truck series vacuum pump? It's Dorman part no. 904-214. For only $60 on several websites it seems too good to be true, but I believe it's the sole source of vacuum for the brakes on those trucks so that's got to be worth something.


'Designed to fit the HVAC system.'

so does not look for brakes. I believe the ford diesel trucks have a hydraulic brake booster system, not vaccum.


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## phogan (Jun 25, 2014)

"The electric vacuum pump is used to operate the ancillary functions of the truck such as power steering, power assist brakes, cruise control, heater controls, EGR functionality, and 4x4 controls just to name a few. " (from fordiesels.com)

Looks to include braking to me. Ford does seem to be going back and forth on hydroboost and vacuum. This seems like a lot of functionality to be pulling from one vacuum pump though.


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## phogan (Jun 25, 2014)

Just got an email back from Dorman. Despite the misleading quotes on their site and others, the pump is not in fact intended for power brakes.

Right you are, nimblemotors


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## evmetro (Apr 9, 2012)

Summit Racing has a pretty good variety of vacuum pumps and complete vacuum systems that are designed specifically for vacuum brakes. It would seem that vacuum is vacuum, so it would not make a difference if it was for a braking system or cow milking machine, or a ford truck that does not have vacuum brakes. I would assume you would just want to figure out just how much vacuum that you will need and get a pump that gets the job done. From my research, they get more expensive as the decibel level goes down.


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## nimblemotors (Oct 1, 2010)

Brakes use a lot of vacuum compared to opening a vent flap.
Noise is a big issue for an EV.
I would think a car OEM pump would be quieter. 

I seem to recall someone modified their power brakes to use pressured air instead of vacuum, plumbing it to the other side of the booster. 



evmetro said:


> Summit Racing has a pretty good variety of vacuum pumps and complete vacuum systems that are designed specifically for vacuum brakes. It would seem that vacuum is vacuum, so it would not make a difference if it was for a braking system or cow milking machine, or a ford truck that does not have vacuum brakes. I would assume you would just want to figure out just how much vacuum that you will need and get a pump that gets the job done. From my research, they get more expensive as the decibel level goes down.


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## piotrsko (Dec 9, 2007)

The Ford diesel / Dorman pump will make enough to run the brakes. Takes 5 minutes, however, to turn off. Maybe 2 applications of brakes depending on size of reservoir. Tried it, gave up.

The summit ones are just plain expensive, and noisy. Got one. Good for cruising Wal-Mart parking without honking horn.

No matter which way you go, make sure booster holds vacuum. If you're running hydraulic power steering, hydroboost works pretty well.


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## dougingraham (Jul 26, 2011)

I am using the older VBS pump I got from Evolve Electrics. No reservoir was needed. When I turn on the car it runs about a second and from that point on it runs perhaps 1/4 second when ever you release the brake pedal. You can pump the brake pedal and you never run out of assist. I can only hear it when I am stopped and there is no traffic around. If the car is moving at all the gearbox noises mask it.


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## dladd (Jun 1, 2011)

I have this vacuum pump in my car, and it's not shutting off. And it's too loud. I could fix the shutting off with a new switch, but the too loud part i can't fix. I've isolated it as best I can, and it's still loud. 

So I want a new pump. I want the quietest pump there is, at any cost. lol. In the scheme of what I've dumped into this car, a few hundred to solve a problem that bugs me at every stop light is totally worth it. 

The problem seems to be that most people have only tried the one pump they own, so there are no real comparisons out there. I don't want to waste money buying a new pump that is just as loud as this one, and I've never seen anyone else that uses this pump so I have no idea how it compares relatively speaking to the other pumps available.

All the online EV shops sell one, they all seem to claim they have the quietest pump, and they all look different... I don't know which to buy!

this one says 50db, but so does my Honda Generator and it is not exactly silent... 

this one says, "the quietest pump we've ever tested" but doesn't list any db level. But it's a factory Ford part, I'd think they would go with a good pump, right?

sigh. I dunno.


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## nimblemotors (Oct 1, 2010)

Eliminate the power brakes. What you need is a new master cylinder that has a smaller bore size, so it uses a longer stroke on the pedal to achieve the same braking force. It is not a fun process to figure it out and find the right master cylinder, but that is what I did when I built my race car as it had little vacuum with a big camshaft and I didn't want the weight of the booster and the clutter of the lines.


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## DavidDymaxion (Dec 1, 2008)

Better brake pads can make a surprising difference. Even with power brakes, my gasser would not lock up the front wheels (no antilocks in front), or engage the rear antilocks even if I pushed the brake pedal with all my might. I estimate I could push with about 200 lbs of force. This was with whatever pads the previous owner had installed (or possibly they were original). At first I was sure the antilock brakes were broken, but they did work on snow.

I switched to Hawk HPS brake pads, and wow was the pedal effort reduced. I can now get a front wheel skid or get the rear antilocks to engage with firm but not all out pressure.


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## steelneck (Apr 19, 2013)

dladd said:


> So I want a new pump. I want the quietest pump there is, at any cost. lol. In the scheme of what I've dumped into this car, a few hundred to solve a problem that bugs me at every stop light is totally worth it.


I have a Hella UP30, you can find it in many quite new cars, mine came from a Volvo V70 2008. I can hear it buzzing when standing still, but as soon as i drive, the EM, transmission sounds or the tires will make more sound, i cannot hear it while driving, just as you wont hear it in Volvos or whatever car it is used in. This pump is made to take care of all brake vacuum on its own, many cars have the smaller UP28 that is only a helper pump, do not use that. There is also a bigger unit called UP32 and that is made to also be able to supply all vacuum in cars that have other things driven by vacuum, like things in the heater system.

Edit:
Here is a link:
http://www.hella.com/microsite-electronics/117.html


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## Roderick (Dec 8, 2013)

i've been looking for Hella UP30 for a month now on ebay and nothing!
I've checked all vacuum pumps but most of them are up28 even on later cars like V70..

anyone got suggestion of where to get them cheap?


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## Woodsmith (Jun 5, 2008)

Buy an afte-rmarket vacuum gauge and check the vacuum on the ICE set up.
Then get a pump that can achieve the same vacuum quickly.


I have found that vacuum is much more difficult to achieve then pressure and so small and cheap pumps may not be able to achieve the required vacuum quickly enough, if at all.

A pump that is too small will just run non stop and a few presses of the brake will leave it 'gasping'.


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## favguy (May 2, 2008)

Regarding the UP28, Until reading steelnecks comment above, I'd not realised the UP28 was a helper pump! 

Having now looked the specs. up ( http://www.hella.com/microsite-electronics/43.html?rdeLocale=en ) I'd agree the UP30 is the better pump for the job. 

However, I've been using the UP28 in my car for 2 years now and must say it's been flawless, it initially takes around 6 seconds to pull down the vacuum when initialising the car, then is switched on by the vacuum switch detecting a drop in vacuum about every 2 pedal pumps and runs for about 2-3 seconds. This keeps the vacuum between -20Hg & -16Hg. I've never run low on vacuum even in heavy breaking, so these smaller pumps will do the job just fine, at least in a small car braking system


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## timthefinn (Mar 29, 2017)

Looking around, it looks like Hella has put out a UP5.0 pump that is 73db compared to the UP32's 78db, bit less amperage and better capacity. Problem is, I can't find it for sale anywhere. Anyone seen this thing in the wild yet?


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## ndplume (May 31, 2010)

Do these Hella vacuum pumps have an integral vacuum switch ? 
What about a check valve ?

Otherwise, can someone recommend a vacuum switch for braking?


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## oudevolvo (Mar 10, 2015)

The Hella UP-28 does not have a build in switch. I initially thought to use the UP-28 but found it quite noisy. After some further research I listed the Ford A426C and the Mes Dea 70/6E2 as alternatives.
I've compared the Hella with the Mes Dea.







The Mes Dea is more silent and I have chosen to use that one.
It has a build in pressure switch.
More details of my comparison and conclusion in my blogpost: Further details of my electric Volvo Amazon wagon
I've not further explored the Ford pump.


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## favguy (May 2, 2008)

Out of interest, I discovered the UP-28 is not meant for use as a sole method of vacuum, it's meant as an assister pump in ICE applications. The UP-32 is designed for solo use and is a lot faster to pull vacuum.

That said, I've been successfully using a UP-28 in my conversion without issue for several years now, but I tend to drive quite steady and don't need to use the brakes excessively so it has an easy life!


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## timthefinn (Mar 29, 2017)

oudevolvo said:


> The Hella UP-28 does not have a build in switch. I initially thought to use the UP-28 but found it quite noisy. After some further research I listed the Ford A426C and the Mes Dea 70/6E2 as alternatives.
> I've compared the Hella with the Mes Dea.


I do want a quiet pump, but I've heard that diaphragm pumps fail over time as discussed in Tim Catellier's post: 

http://evz3.blogspot.jp/2013/11/brakes-car-shows-and-solar-power.html

Is your experience different? Do you replace the diaphragm on a regular basis to avoid an in transit failure? The Hella sound levels of some 70db or higher is a bit severe, so am willing to listen to other options.


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## timthefinn (Mar 29, 2017)

Hydrobooster? I already need an electric hydraulic pump for my power steering. If I can trade out my vacuum brake booster for a hydraulic one, I wouldn't need a vacuum pump at all. Anyone try this? Biggest challenge for me is I'm converting a BMW Z3, so conversion kits are probably not off the shelf. Might just change out the whole assembly (booster and master cylinder) but not sure how that'll work with the ABS or car in general.


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## oudevolvo (Mar 10, 2015)

You might also consider an iBooster made by Bosch and for example used by Tesla.
Some info in http://www.diyelectriccar.com/#/topics/170770?page=1 post #11 and a little further some more.
Just apply 12V and you have assister brakes.
In the Netherlands getting it registered with that booster can be a challende (too much changes). So I’m converting to electric with traditional brakes first and perhaps upgrade later.


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## timthefinn (Mar 29, 2017)

Thanks for the lead. Hadn't heard of the iBooster from Bosch. Sounds a little tricky to procure and utilize. Sounds like people have gotten them from parted out Teslas. Do you work through junkers to find that type of thing, or does someone carry them?


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## oudevolvo (Mar 10, 2015)

Yes, they mostly come from parted out Teslas.
I found one listed on eBay https://m.ebay.nl/itm/263303202070
John from Edisonmotors has some available too.
And I found them from a Chevy too https://m.ebay.nl/itm/132156455001


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## tinkeringgreg (Mar 27, 2008)

i know the Oldsmobile diesel 350 V8 engines back in the 90s had a very similar pump that rad all of the vacuum powered devices in the car including the power brakes. it looked like the very same pump unit with a different mount/ drive system. Gm trucks withe the 6.2 diesel had a belt driven one similar to what ford used


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