![]() 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. 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. ![]() 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. The Hydromax can usually be found in a 1.75” bore, and can also sometimes be found in a 2.00” bore. 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. ![]() 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. 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. On the other hand, if you were to try a Bosch Hydromax, that could potentially work. 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. ![]() 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. 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. It would be far simpler than a flat tow braking kit, and possibly far more effective and reliable. 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. According to Cardone, most of these are dual diaphragm, and have various diaphragm sizes. I have learned that a lot of 2008+ Fords, including the 2008 Explorer Sport Trac, were equipped with these boosters. I think in some cases they were also used as a means of early AEB actuation. These were primarily used on advanced ABS systems prior to the development of fully electronic stability control. 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. So yet another option I have come across is the existence of “active” brake vacuum boosters. Just a normal install plus maybe three or so wires. Plus the Hydromax is not much more difficult to install than a normal hydroboost. Run it off the PS pump when the engine is running, and use the motor for toad and emergency braking. 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. 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.īut one thing I am still considering as a possibility is the Hydromax unit. A couple of tees, a pair of check valves, power, ground, and turn-on wiring and it would be done. Plumbing and doing the basic wiring would be super easy. 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. That ZF unit apparently is the brain for the entire traction control system, not just the brakes. Yeah the more I looked into it the worse it gets.
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