Electric brake booster as an alternative to hydroboost or vacuum brakes?

[Steel City 06]

So in setting up my keep for flat towing I was looking for an electric vacuum pump to power the brake booster while the engine was off.

During my search I came across this kit:
https://www.jegs.com/i/JEGS/555/631250/10002/-1https://www.speedwaymotors.com/Comp...r-Booster-Master-Cylinder-Disc-Disc,8335.html
Like hydroboost, the kit replaces the vacuum brake booster. The difference is it uses electric, rather than power steering pump pressure, to power.

The kit claims a master cylinder diameter of 1-3/16”, which I suspect would work with most big brake kits, given that the stock TJ cylinder is 15/16”. (The disadvantage of the larger cylinder is that less pressure is available when the brakes are applied without boost.) The kit claims a max PSI of 2000 psi.

According to Vanco PBS, a stock vacuum booster puts out 1000-1100 psi of brake line pressure (assuming dual diaphragm). The Vanco hydroboost kit claims a max pressure of 2400-2700 PSI, with a master cylinder diameter of 1-1/8 for the 1/2-ton and 3/4-ton kits, and 1-5/16 for the 1-ton kits.

So based on that information, the electric booster would be a moderate upgrade over the vacuum booster, but not quite to the level of the hydroboost. It would eliminate the need for a vacuum source for factory brakes and/or a need for power steering pressure for hydroboost.

One distinct advantage there is that the electric booster brakes can be used at any time, even with the engine off and no auxiliary vacuum pump. So unlike hydroboost, it would be useful for flat towing.

A big unknown would be the reliability of the included pump. If that fails or a fuse blows, you have a dozen, maybe a few more, stops before you lose pressure and end up with manual brakes.

Not arguing that this should be used to replace all hydroboost or vacuum brake applications. But it could be an interesting alternative for a few cases.

Thoughts?

 

[Steel City 06]

Another option that I looked at out of curiosity was an OEM retrofit of a factory electric brake booster.

I did find some information on the Tesla brake boosters, which are the Bosch iBooster. Apparently they have a displacement of 15cc, which is very close to a stock TJ master cylinder, assuming 1.25” travel (not confident on this number).

Hence the Tesla booster may not have the displacement needed to drive a big brake kit, but could be used on factory brakes.

 

[srimes]

Had one on a turbocharged car. Factory built it that way, worked fine. Should be very reliable.

 

[Steel City 06]

Had one on a turbocharged car. Factory built it that way, worked fine. Should be very reliable.

What car was it? Curious to find about other OEM options that might have more displacement than a Tesla

 

[srimes]

ford thunderbird turbo coupe. Any turbocharged car with power breaks needs some way to maintain break boost so I imagine it's quite common.

As for the tesla booster, they're pretty heavy and I believe have big breaks so I'd guess it would be fine. Might also look at the chevy volt while you're at it. I know it has big breaks.

 

[IAmTodd]

I had a 2011 4Runner than used electric assist for the brakes. There was no vacuum assist.

 

[mrblaine]

The kit claims a master cylinder diameter of 1-3/16”, which I suspect would work with most big brake kits, given that the stock TJ cylinder is 15/16”. (The disadvantage of the larger cylinder is that less pressure is available when the brakes are applied without boost.) The kit claims a max PSI of 2000 psi.

Hydroboost has lots of horsepower to push on the master with. It struggles with anything larger than 1 1/8" and even then you wind up with a high hard pedal into 54mm dual piston calipers.

According to Vanco PBS, a stock vacuum booster puts out 1000-1100 psi of brake line pressure (assuming dual diaphragm). The Vanco hydroboost kit claims a max pressure of 2400-2700 PSI, with a master cylinder diameter of 1-1/8 for the 1/2-ton and 3/4-ton kits, and 1-5/16 for the 1-ton kits.

I have measured pressures from 1000-1700 psi out of the stock TJ master which is 1" bore. Another reason why TJ brakes are all over the map. I have built a vacuum boosted TJ system that put out 2800 psi. I do not recommend it, but I did it. I have since moved to a 1 1/16" as a test and now have a 1 1/8" master in it and it really needs more to get rid of some pedal travel. I took it up and let Van drive it. On a back road he was reaching down with his hand to push on the brake pedal and locking up the fronts.

So based on that information, the electric booster would be a moderate upgrade over the vacuum booster, but not quite to the level of the hydroboost. It would eliminate the need for a vacuum source for factory brakes and/or a need for power steering pressure for hydroboost.

One distinct advantage there is that the electric booster brakes can be used at any time, even with the engine off and no auxiliary vacuum pump. So unlike hydroboost, it would be useful for flat towing.

A big unknown would be the reliability of the included pump. If that fails or a fuse blows, you have a dozen, maybe a few more, stops before you lose pressure and end up with manual brakes.

Not arguing that this should be used to replace all hydroboost or vacuum brake applications. But it could be an interesting alternative for a few cases.

Thoughts?

I've been looking at the iBoost stuff but info is hard to find. I think if we can get it figured out, it will be a good thing to know and figure out.

 

[mrblaine]

Another option that I looked at out of curiosity was an OEM retrofit of a factory electric brake booster.

I did find some information on the Tesla brake boosters, which are the Bosch iBooster. Apparently they have a displacement of 15cc, which is very close to a stock TJ master cylinder, assuming 1.25” travel (not confident on this number).

Hence the Tesla booster may not have the displacement needed to drive a big brake kit, but could be used on factory brakes.

Displacement like that is going to be hard to translate. We need the bore size to know much.

 

[Steel City 06]

The iBoost units can be bought off Ebay for a few hundred bucks. Search for Tesla brake booster.

The displacement was a figure I found on an EV forum. I assumed displacement was equal to piston surface area times travel. A TJ 15/16” piston has a surface area of 0.689 in^2, so assuming a travel of 1.25” (I actually do not know this number), the displacement would be 0.862 cubic inches, or 14.1cc.

So I would assume the bore size of a Tesla iBoost would be very close to that of a stock TJ, assuming similar travel.

The aftermarket kits linked fortunately do have a lot of info, and are theoretically bolt-in, plus they have a larger bore size than we would normally use.

 

[mrblaine]

The iBoost units can be bought off Ebay for a few hundred bucks. Search for Tesla brake booster.

The displacement was a figure I found on an EV forum. I assumed displacement was equal to piston surface area times travel. A TJ 15/16” piston has a surface area of 0.689 in^2, so assuming a travel of 1.25” (I actually do not know this number), the displacement would be 0.862 cubic inches, or 14.1cc.

So I would assume the bore size of a Tesla iBoost would be very close to that of a stock TJ, assuming similar travel.

The aftermarket kits linked fortunately do have a lot of info, and are theoretically bolt-in, plus they have a larger bore size than we would normally use.

Again, the TJ has a 1" bore. You can't assume anything when the number is only displacement. You need one more factor to calculate it out. Way too many assumptions.

 

[reddvltj]

So in setting up my keep for flat towing I was looking for an electric vacuum pump to power the brake booster while the engine was off.

During my search I came across this kit:
https://www.jegs.com/i/JEGS/555/631250/10002/-1https://www.speedwaymotors.com/Comp...r-Booster-Master-Cylinder-Disc-Disc,8335.html
Like hydroboost, the kit replaces the vacuum brake booster. The difference is it uses electric, rather than power steering pump pressure, to power.

The kit claims a master cylinder diameter of 1-3/16”, which I suspect would work with most big brake kits, given that the stock TJ cylinder is 15/16”. (The disadvantage of the larger cylinder is that less pressure is available when the brakes are applied without boost.) The kit claims a max PSI of 2000 psi.

According to Vanco PBS, a stock vacuum booster puts out 1000-1100 psi of brake line pressure (assuming dual diaphragm). The Vanco hydroboost kit claims a max pressure of 2400-2700 PSI, with a master cylinder diameter of 1-1/8 for the 1/2-ton and 3/4-ton kits, and 1-5/16 for the 1-ton kits.

So based on that information, the electric booster would be a moderate upgrade over the vacuum booster, but not quite to the level of the hydroboost. It would eliminate the need for a vacuum source for factory brakes and/or a need for power steering pressure for hydroboost.

One distinct advantage there is that the electric booster brakes can be used at any time, even with the engine off and no auxiliary vacuum pump. So unlike hydroboost, it would be useful for flat towing.

A big unknown would be the reliability of the included pump. If that fails or a fuse blows, you have a dozen, maybe a few more, stops before you lose pressure and end up with manual brakes.

Not arguing that this should be used to replace all hydroboost or vacuum brake applications. But it could be an interesting alternative for a few cases.

Thoughts?

If you're primary purpose for doing this is setting it for flat towing why not just go with a flat to system like these:

https://www.roadmasterinc.com/products/braking/sys_for_me.php

 

[Steel City 06]

If you're primary purpose for doing this is setting it for flat towing why not just go with a flat to system like these:

https://www.roadmasterinc.com/products/braking/sys_for_me.php

This was kind of just a rabbit hole I went down.

I plan to install the Brake Buddy Stealth at some point, which requires a vacuum pump. The kit includes a really crappy one, so I was looking for a better one, one that can run with a higher duty cycle and a deeper vacuum.

I plan to wire it differently than the instructions say so I can use the vacuum pump at other random times, such as to supplement the vacuum during near-constant WOT for more accurate cruise control and to power brakes and other items if I want to use them without firing the engine.

I was even considering using the breakaway function of the Brake Buddy Stealth as a sort of redneck mico-lock, but I'm increasingly seeing how that might be a bad idea.


I came across this and it was a whole new product category I didn't know existed, and I couldn't find a single thread on it. It seems like a great option for those who want hydroboost-like characteristics without the complexity of hydroboost.

I've been doing quite a bit of research on Electro-Hydraulic Power Steering (EHPS) as potentially a way to supplement a CBR pump volume at idle or low RPM to increase steering speed, and this caught my attention as it is very similar.

 

[mrblaine]

. It seems like a great option for those who want hydroboost-like characteristics without the complexity of hydroboost.

Not sure how you figure hydroboost is complex. It plumbs in between the power steering pump and the steering gear on the pressure side. Then there is a return hose to the reservoir. Very basic installation. Very simple plumbing. None of the brake stuff has to be touched.

 

[reddvltj]

This was kind of just a rabbit hole I went down.

I plan to install the Brake Buddy Stealth at some point, which requires a vacuum pump. The kit includes a really crappy one, so I was looking for a better one, one that can run with a higher duty cycle and a deeper vacuum.

I plan to wire it differently than the instructions say so I can use the vacuum pump at other random times, such as to supplement the vacuum during near-constant WOT for more accurate cruise control and to power brakes and other items if I want to use them without firing the engine.

I was even considering using the breakaway function of the Brake Buddy Stealth as a sort of redneck mico-lock, but I'm increasingly seeing how that might be a bad idea.


I came across this and it was a whole new product category I didn't know existed, and I couldn't find a single thread on it. It seems like a great option for those who want hydroboost-like characteristics without the complexity of hydroboost.

I've been doing quite a bit of research on Electro-Hydraulic Power Steering (EHPS) as potentially a way to supplement a CBR pump volume at idle or low RPM to increase steering speed, and this caught my attention as it is very similar.

My parents have the InvisiBrake in their 2016 JKU and it has worked flawlessly for the last 3 years since we installed it. The only real drawback is how long it takes to generate vacuum if the booster is depleted. Although I don't think under any normal driving/braking situations (save a vacuum leak) you would ever deplete all the usable vacuum.

I see the direction you're working towards, and just to add angle for you to look at, there are hydro-boost systems that have 12V backup pumps. GMC Kodiak Chassis trucks I have driven in the past have them, you step on the brake without the engine running and the 12 pump kicks in to pressurize the brakes...

 

[ColoJeep]

Not sure how you figure hydroboost is complex. It plumbs in between the power steering pump and the steering gear on the pressure side. Then there is a return hose to the reservoir. Very basic installation. Very simple plumbing. None of the brake stuff has to be touched.

So true . Hydroboost is powerful and simple, no more complex than power steering.
There is a reason many OEM truck manufactures use it.

 

[Steel City 06]

My parents have the InvisiBrake in their 2016 JKU and it has worked flawlessly for the last 3 years since we installed it. The only real drawback is how long it takes to generate vacuum if the booster is depleted. Although I don't think under any normal driving/braking situations (save a vacuum leak) you would ever deplete all the usable vacuum.

I see the direction you're working towards, and just to add angle for you to look at, there are hydro-boost systems that have 12V backup pumps. GMC Kodiak Chassis trucks I have driven in the past have them, you step on the brake without the engine running and the 12 pump kicks in to pressurize the brakes...

I came across those dual applications too. Those seemed pretty interesting as well. If I had an EHPS supplemental pump for the power steering, that could also serve as the backup for powering the brakes through the mechanical pump.

Though it would seem normal hydroboost and flat tow braking are at odds with each other. Because hydroboost requires a spinning engine or some form of pump, and EHPS sucks up a lot of amperage. EHB on the other hand requires much less amperage, the kind that could be supplied through a 12v trailer charge circuit.

I plan to stick with vacuum brakes for now. But EHB does look interesting, and I'm surprised nobody has made an explicit EHB jeep kit yet, seeing how so many other options are available aftermarket.


My flat tow case is a bit odd. This jeep will almost exclusively be flat towed behind a 1/2 ton truck for the purpose of shuttling cars for longer hiking, running, backpacking, and canoeing expeditions. A trailer is not at all practical due to the typical trailhead access. This solution is intended to save many hours, if not days, of shuttling cars for these kinds of trips. So it's not the stereotypical jeep behind a motorhome towing. It will be flat towed on narrow, twisty mountain gravel roads that require frequent brake application. Hence my concern that a tiny vacuum pump meant for motorhome freeway towing with sparse braking might not be able to keep up. But a bigger vacuum pump would have no problem

 

[Steel City 06]

The holy grail for my particular use case would be an EHB system that has some sort of autonomous input, much like if the electro-hydraulic actuators used for trailer disc brakes were combined with a pedal actuated master cylinder.

I haven't found any applications yet, but I strongly suspect cars with both EHB and AEB must have some sort of brake-by-wire system that could be tapped into while still having a mechanical master cylinder connection.

If I could find something like that, I could build the flat tow actuation into the brake booster itself as opposed to buying some $1,000 mechanical actuator that still requires a functioning booster.

Note:
EHPS - Electro-Hydraulic Power Steering
EHB - Electro-Hydraulic Brakes
AEB - Autonomous Emergency Braking

 

[reddvltj]

I came across those dual applications too. Those seemed pretty interesting as well. If I had an EPHS supplemental pump for the power steering, that could also serve as the backup for powering the brakes through the mechanical pump.

Though it would seem normal hydroboost and flat tow braking are at odds with each other. Because hydroboost requires a spinning engine or some form of pump, and EPHS sucks up a lot of amperage. EHB on the other hand requires much less amperage, the kind that could be supplied through a 12v trailer charge circuit.

I plan to stick with vacuum brakes for now. But EHB does look interesting, and I'm surprised nobody has made an explicit EHB jeep kit yet, seeing how so many other options are available aftermarket.


My flat tow case is a bit odd. This jeep will almost exclusively be flat towed behind a 1/2 ton truck for the purpose of shuttling cars for longer hiking, running, backpacking, and canoeing expeditions. A trailer is not at all practical due to the typical trailhead access. This solution is intended to save many hours, if not days, of shuttling cars for these kinds of trips. So it's not the stereotypical jeep behind a motorhome towing. It will be flat towed on narrow, twisty mountain gravel roads that require frequent brake application. Hence my concern that a tiny vacuum pump meant for motorhome freeway towing with sparse braking might not be able to keep up. But a bigger vacuum pump would have no problem

I'm not well versed on the terminology is this set up the same as what you were talking about?

 

[Steel City 06]

I'm not well versed on the terminology is this set up the same as what you were talking about?

View attachment 257955

That's exactly the image I was thinking of when speaking of the dual mode boosters. Not sure of the actual name for those units, but they're hydroboost with electric backup like you describe. The one you have pictured runs off of the power steering pump, but has electric backup.


I wouldn't trust that electric motor for high duty cycles, but as an occasional or emergency backup it is be fine.

The kits I originally linked are 100% electric, though they use hydraulics as an intermediary. Basically they're electrically driven hydroboost units that do not tap into the power steering. The motors are designed for much higher duty cycles as a result.

The Jegs link will show what the electro-hydraulic units look like:
https://www.jegs.com/i/JEGS/555/631250/10002/-1
They basically look like a hydroboost except with an electric hydraulic pump in place of power steering hookups.

 

[Mike_H]

@Steel City 06 Have you looked into an electric over hydraulic set-up that would be used for boat trailers? Typical electrically applied brakes, such as those on car haulers, travel trailers, etc. don't work on boat trailers, due to their use case (submerging into water). But...we all agree that surge brakes (those brakes that are applied by a master cylinder in a sliding coupler) suck pretty bad. They work..but they aren't great. So, there is an electrically controlled master, which uses some sort of prop valve to apply a variable force to a master cylinder. I'm probably oversimplifying, but you get the idea. You could probably work something out like that to accomplish what you're trying to accomplish. I didn't get more than a passing familiarity with the system, because I got out of boating and they were ridiculously expensive when the systems first came out.