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

[Steel City 06]

@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.

I've thought about that, and in fact that's sort of the driving idea behind converting to EHB.

However I'm not sure I could safely (and legally) plumb in a trailer brake actuator directly into a vehicle's brake lines in parallel with the existing master. I would have to get really fancy with check valves and solenoids to make it work, and if it's becoming that complex I'm not sure I could ever fully trust the brakes.

With vacuum brakes, hydroboost, or EHB, all of those will default to manual brakes should something fail. But plumb in a separate trailer brake actuator, and in at least one failure mode (such as an incorrect valve lineup) you wouldn't even have manual brakes as you'd simply be pumping fluid from one reservoir to another every time you push the pedal.

Even the Mico lock I've long wanted to add still allows for braking if it were to get stuck shut (the brakes would be stuck but you would still stop).

 

[Steel City 06]

So I came across a new and different option than the Bosch iBooster.

ZF makes an Integrated Brake Control that is equipped in many vehicles, particularly the 2019+ Chevrolet Silverado.

https://www.ebay.com/itm/2019-2020-...d=link&campid=5337789113&toolid=20001&mkevt=1
I would image a 1/2 ton truck would have a master cylinder with adequate diameter for a TJ. But I can’t find any specifications.

 

[mrblaine]

So I came across a new and different option than the Bosch iBooster.

ZF makes an Integrated Brake Control that is equipped in many vehicles, particularly the 2019+ Chevrolet Silverado.

https://www.ebay.com/itm/2019-2020-...d=link&campid=5337789113&toolid=20001&mkevt=1
I would image a 1/2 ton truck would have a master cylinder with adequate diameter for a TJ. But I can’t find any specifications.

No, a 1/2 ton pick-up would not have a master that would work for the TJ front calipers. The calipers we use for the 17" and Super 16 are from a 1/2 ton and have a lot more combined piston surface area than the TJ calipers have. The average late model 1/2 ton is running a big booster and a 1 3/16" bore master or larger.

Again, we can make no assumptions, we have to know what the sizes are or it just gonna be fucked up.

 

[Steel City 06]

No, a 1/2 ton pick-up would not have a master that would work for the TJ front calipers. The calipers we use for the 17" and Super 16 are from a 1/2 ton and have a lot more combined piston surface area than the TJ calipers have. The average late model 1/2 ton is running a big booster and a 1 3/16" bore master or larger.

Again, we can make no assumptions, we have to know what the sizes are or it just gonna be fucked up.

Looking more at that ZF IBC, it actually claims to not use a master cylinder during normal operation. Instead, fluid displaced by the master is metered and the resulting measurement is used to actually drive the motor to apply the brakes.

Thus in normal operation, it is essentially drive by wire, and the pedal feel is entirely simulated.

It appears if power is lost or the unit fails, then it actually sends the fluid in the master cylinder to the brakes. But otherwise the master cylinder fluid is only there to measure and create brake feel.

 

[mrblaine]

I chatted with a buddy who went to a few tech classes on that stuff and the integration of the booster into the overall vehicular control system is so high that the chance of a mere mortal figuring out a driver for the electric side is about zero.

 

[Steel City 06]

Yeah the more I looked into it the worse it gets. That ZF unit apparently is the brain for the entire traction control system, not just the brakes. It has like a 30 pin harness.

I also looked at the possibility of using a JL EHPS in parallel with a factory CBR pump to boost power steering flow at idle and maybe also run a hydroboost with the engine off. Plumbing and doing the basic wiring would be super easy. A couple of tees, a pair of check valves, power, ground, and turn-on wiring and it would be done. But if you want speed control on the JL EHPS, you'd have to set up an arduino or something to simulate the CAN bus signals.

But one thing I am still considering as a possibility is the Hydromax unit. If the electric motor is actually reliable enough to use for a good amount of time, it might be a best of both worlds scenario. Run it off the PS pump when the engine is running, and use the motor for toad and emergency braking.

Plus the Hydromax is not much more difficult to install than a normal hydroboost. Just a normal install plus maybe three or so wires.

 

[Steel City 06]

Also be careful when Googling "Hydromax" and any combinations, especially "hydromax pump". There is a NSFW product by the same name...

 

[Steel City 06]

So digging a bit more into the Hydromax, I can only find versions that either have a 1.75" or 2" bore. That may be way too large for normal usage on a TJ, unless the goal is to stop in like 0.1" of pedal travel.

The unit appears to have no issue building pressure to support TJ brakes, though I'm not sure how far the 800 PSI limit on the electric backup would get you.

If the unit with the 1.75" bore uses the same booster, then that 1900/800 PSI inflection point should look more like 2500/1000 PSI.

But given the slope of the curve after the booster is maxed out, the average user might only be able to develop ~300 PSI with the 2" bore or ~400 PSI with the 1.75" bore. Someone with much more strength might be able to get 1.5x that reasonably.

 

[Steel City 06]

@mrblaine
In your experience, what sort of brake line PSI correlates with lockup of the tires? (I’m sure it’s dependent on a lot of factors.)

Do you happen to know the brake pedal lever ratio on a TJ?

A complete new Hydromax retrofit assembly is about $1124, including the hydroboost booster, electric booster, master cylinder, flow switch/relay, pedal rod, and associated parts.

That’s not much over a Vanco hydroboost kit, though the power steering pump alters that cost.

The big issue is that 1.75” minimum bore. With power, I’d be concerned the pedal travel will be quite short, and since the hydroboost certainly has the power to push that cylinder, could make the brake pedal very sensitive.

And if both power steering and electric power were lost, that’s a 3x reduction in manual brake line pressure over a factory 1.00” master cylinder. I would suspect that losing both power steering and electric power would be improbable, but not impossible.

 

[mrblaine]

@mrblaine
In your experience, what sort of brake line PSI correlates with lockup of the tires? (I’m sure it’s dependent on a lot of factors.)

More than a few factors plus the difficulty in even being able to monitor and then record that value.

Do you happen to know the brake pedal lever ratio on a TJ?

It is about 8-1. I can get the exact ratio if it matters.

A complete new Hydromax retrofit assembly is about $1124, including the hydroboost booster, electric booster, master cylinder, flow switch/relay, pedal rod, and associated parts.

That’s not much over a Vanco hydroboost kit, though the power steering pump alters that cost.

The big issue is that 1.75” minimum bore. With power, I’d be concerned the pedal travel will be quite short, and since the hydroboost certainly has the power to push that cylinder, could make the brake pedal very sensitive.

And if both power steering and electric power were lost, that’s a 3x reduction in manual brake line pressure over a factory 1.00” master cylinder. I would suspect that losing both power steering and electric power would be improbable, but not impossible.

That 3x pedal force is an astoundingly monstrous change in effort given that only a slight increase in bore size will ruin the effectiveness of the brakes.

 

[Steel City 06]

Thanks. That pedal ratio is more than I expected.

I pulled open the Brake Buddy Stealth yesterday to see what powered it. It is powered by a Hongba linear actuator, with a 100mm travel, 150N max load, and 50 mm/s travel. (It’s possible the stall load is higher.)

Assuming it is mounted as low as possible on the brake pedal bar, I’ll assume there’s about a 7.5 pedal ratio.

Thus, given a full application, the actuator can apply 253 lbs to the booster. That’s only 650 PSI of brake line pressure on Hydromax electric brakes even with the smaller 1.75” bore. So I doubt that would be sufficient for flat towing.

Edit: based on a competitor’s equivalent actuator, I think the stall load is about 75 lbs on the actuator, and 35 lbs is the rated load.

 

[Steel City 06]

So yet another option I have come across is the existence of “active” brake vacuum boosters.

In addition to being able to be actuated by the pedal rod, the vacuum booster also has a small electric solenoid valve that vents atmospheric pressure to the booster when the solenoid is energized, allowing it to engage with no pedal input whatsoever. These were primarily used on advanced ABS systems prior to the development of fully electronic stability control. I think in some cases they were also used as a means of early AEB actuation.

I have learned that a lot of 2008+ Fords, including the 2008 Explorer Sport Trac, were equipped with these boosters. According to Cardone, most of these are dual diaphragm, and have various diaphragm sizes.

If one could build a simple controller to actuate that valve, that could be a very simple way to autonomously engage the brakes for the purposes of flat towing or even as a temporary supplemental holding brake. It would be far simpler than a flat tow braking kit, and possibly far more effective and reliable. I suspect one could easily drive it with an Arduino plus an Arduino motor shield for very little cost, and make it capable of doing anything you program it to do.

 

[hongmihn]

So yet another option I have come across is the existence of “active” brake vacuum boosters.

In addition to being able to be actuated by the pedal rod, the vacuum booster also has a small electric solenoid valve that vents atmospheric pressure to the booster when the solenoid is energized, allowing it to engage with no pedal input whatsoever. These were primarily used on advanced ABS systems prior to the development of fully electronic stability control. I think in some cases they were also used as a means of early AEB actuation.

I have learned that a lot of 2008+ Fords, including the 2008 Explorer Sport Trac, were equipped with these boosters. According to Cardone, most of these are dual diaphragm, and have various diaphragm sizes.

If one could build a simple controller to actuate that valve, that could be a very simple way to autonomously engage the brakes for the purposes of flat towing or even as a temporary supplemental holding brake. It would be far simpler than a flat tow braking kit, and possibly far more effective and reliable. I suspect one could easily drive it with an Arduino plus an Arduino motor shield for very little cost, and make it capable of doing anything you program it to do.

as you said i think ibooster is not so bad.
some guy here was saying negative words with JUST two variables of stroke, bore size again and agian, but there will be much more things , we could't know, such as stroke, leverage of a brake pedal, stroke, caliber diameter, foot pressure of hitting a pedal, average displacement of a piston and so on.
i am also leaning toward to "ibooster is effective!" and got ibooster gen2 which can make maximally 1700 psi with 26mm bored piston.
will soon replace my hydro booster on GM 1ton full sizetruck with ibooster gen2 then tell you what i will find.
if no reply here in future, take a look at my insta @ich_bin_hahn

 

[mrblaine]

as you said i think ibooster is not so bad.
some guy here was saying negative words with JUST two variables of stroke, bore size again and agian, but there will be much more things , we could't know, such as stroke, leverage of a brake pedal, stroke, caliber diameter, foot pressure of hitting a pedal, average displacement of a piston and so on.
i am also leaning toward to "ibooster is effective!" and got ibooster gen2 which can make maximally 1700 psi with 26mm bored piston.
will soon replace my hydro booster on GM 1ton full sizetruck with ibooster gen2 then tell you what i will find.
if no reply here in future, take a look at my insta @ich_bin_hahn

If those two numbers are correct, psi and piston bore, and you get it working properly, the pedal will go just about to the floor because the master can't move enough fluid. Pressure is fine, volume isn't.
Info I find shows the truck has a 37mm bore which is 1.67 square inches of piston area.
ibooster has 26mm bore which is .82 square inches of piston area or less than half of what is needed.

Good luck and if you report your findings honestly, then we will both know the same thing.

 

[hongmihn]

If those two numbers are correct, psi and piston bore, and you get it working properly, the pedal will go just about to the floor because the master can't move enough fluid. Pressure is fine, volume isn't.
Info I find shows the truck has a 37mm bore which is 1.67 square inches of piston area.
ibooster has 26mm bore which is .82 square inches of piston area or less than half of what is needed.

Good luck and if you report your findings honestly, then we will both know the same thing.

thanks for info. i tried to find volumetric info of ibooster. some guy mesaured cylinder capacity is about 15cm^3. what i found info about master cylinder of my truck is 1.25inch bored and 1.1inch stroke , which is about 17cm^3 more larger than ibooster cylinder.
i think, considering experiential stroke of brake pedal for full-lock this 2cm^3 diffrence might be able to be corved by changing some leverage between a pedal and a input shaft of ibooster.

anyway, i will try it! and tell you my honest result. it will be so interesting.

 

[mrblaine]

thanks for info. i tried to find volumetric info of ibooster. some guy mesaured cylinder capacity is about 15cm^3. what i found info about master cylinder of my truck is 1.25inch bored and 1.1inch stroke , which is about 17cm^3 more larger than ibooster cylinder.
i think, considering experiential stroke of brake pedal for full-lock this 2cm^3 diffrence might be able to be corved by changing some leverage between a pedal and a input shaft of ibooster.

anyway, i will try it! and tell you my honest result. it will be so interesting.

The 1.25" bore is 50% larger than the 26mm. That will net a 50% increase in pedal stroke for the same volume at a 50% increase in pressure at the caliper piston.

 

[Steel City 06]

Personally I wouldn't try it. Without adequate displacement, you physically won't be able to compress the calipers far enough to effectively brake, no matter how much pressure the booster is normally capable of.

It's like trying to use an air compressor as a leaf blower - sure it has plenty enough pressure, but the sheer volume of air is just completely insufficient to do any work.

On the other hand, if you were to try a Bosch Hydromax, that could potentially work. Since the bore is excessively large, you would always have more than enough displacement, and with either hydraulic or electric boost, you would still have some braking capacity. The big risk there is that if you lose both hydraulic and electric supply, you will have a very hard time stopping the car due to the massively increased surface area.

Neither of those options are probably a "good idea" but I think using a significantly undersized piston is going to prove to be downright dangerous in all conditions, whereas an oversized one will be dangerous in only a rare circumstance.

 

[mrblaine]

Personally I wouldn't try it. Without adequate displacement, you physically won't be able to compress the calipers far enough to effectively brake, no matter how much pressure the booster is normally capable of.

It's like trying to use an air compressor as a leaf blower - sure it has plenty enough pressure, but the sheer volume of air is just completely insufficient to do any work.

On the other hand, if you were to try a Bosch Hydromax, that could potentially work. Since the bore is excessively large, you would always have more than enough displacement, and with either hydraulic or electric boost, you would still have some braking capacity. The big risk there is that if you lose both hydraulic and electric supply, you will have a very hard time stopping the car due to the massively increased surface area.

Neither of those options are probably a "good idea" but I think using a significantly undersized piston is going to prove to be downright dangerous in all conditions, whereas an oversized one will be dangerous in only a rare circumstance.

I'd disagree that too much can work. That all depends on what pressure it can develop. I've messed with a lot of hydro-boost and larger masters. Even only as large as this 50% increase, the pedal with HB is still high and hard.

What pressure is the Bosch capable of and what size is the bore?

 

[Steel City 06]

I'd disagree that too much can work. That all depends on what pressure it can develop. I've messed with a lot of hydro-boost and larger masters. Even only as large as this 50% increase, the pedal with HB is still high and hard.

What pressure is the Bosch capable of and what size is the bore?

The Hydromax can usually be found in a 1.75” bore, and can also sometimes be found in a 2.00” bore. This is obviously way oversized for the application, but depending upon the actual pressure requirements it could be made to work, albeit with stupidly low pedal travel.

In normal operation (hydroboost mode), it can provide up to 1900 psi at 320 lbs input (pedal force multiplied by pedal ratio), up to a maximum pressure of 2200 psi at 500 lbs input.

In emergency operation, using the electric motor to back up the hydroboost following a loss of hydraulic supply, it can provide 800 psi at 320 lbs input, or up to 900 psi at 500 lbs input.

The electric mode is designed to operate solely if hydraulic supply is lost, as might happen if the engine were to cut out, the power steering pump were to give up the ghost, or a line were to burst. It also operates when the engine is off and braking is demanded.

In the highly unlikely (but not impossible) event that both hydraulics and the electric backup are lost, that would be the absolute worst case scenario, as the user might only be able to generate 3-400 psi max.

Here is a brief introduction to the Hydromax:
http://1999southwind.com/DOWNLOAD/Bosch HydroMax Booster Manual.pdf
I believe those pressures are based on a 2.00” bore. It’s possible the 1.75” bore may be capable of proportionally (to area) higher pressures, but I have no way to verify that.

 

[mrblaine]

The Hydromax can usually be found in a 1.75” bore, and can also sometimes be found in a 2.00” bore. This is obviously way oversized for the application, but depending upon the actual pressure requirements it could be made to work, albeit with stupidly low pedal travel.

I don't think you quite have a firm grasp on what stupidly low pedal travel is yet. With hydroboost and a 1.25" bore master, from free height to full lock up is about 1- 1 1/2" of pedal travel depending on how much free play has been adjusted into the pedal push rod into the hydroboost and how well adjusted the push rod length into the master is.

If you could use the 1.75 version, that is still twice as much piston area as the 1.25" bore master which is 50% larger than the stock 1". Pedal travel to full lock up is at least stupidly low.

In normal operation (hydroboost mode), it can provide up to 1900 psi at 320 lbs input (pedal force multiplied by pedal ratio), up to a maximum pressure of 2200 psi at 500 lbs input.

In emergency operation, using the electric motor to back up the hydroboost following a loss of hydraulic supply, it can provide 800 psi at 320 lbs input, or up to 900 psi at 500 lbs input.

The electric mode is designed to operate solely if hydraulic supply is lost, as might happen if the engine were to cut out, the power steering pump were to give up the ghost, or a line were to burst. It also operates when the engine is off and braking is demanded.

In the highly unlikely (but not impossible) event that both hydraulics and the electric backup are lost, that would be the absolute worst case scenario, as the user might only be able to generate 3-400 psi max.

Here is a brief introduction to the Hydromax:
http://1999southwind.com/DOWNLOAD/Bosch HydroMax Booster Manual.pdf
I believe those pressures are based on a 2.00” bore. It’s possible the 1.75” bore may be capable of proportionally (to area) higher pressures, but I have no way to verify that.

I can tell you that even the larger GM D52 caliper will not do much at 800 psi. We've tested that trying to solve a front brake issue with the larger Dodge master swap so many tout as an upgrade. At 1.25", the most we could generate with both feet on the pedal was 800 psi measured at the caliper.