Join Date: Sep 1999
Location: Southeast Iowa
Thanked 0 Times in 0 Posts
Re: so whats the deal with \"hydro boost\" brakes?
[img]/wwwthreads_images/icons/smile.gif[/img] Here is the scoop:[img]/wwwthreads_images/icons/crazy.gif[/img] "Hydro-Boost" means that the brake ASSIST is derived from hydraulic pressure rather than atmospheric pressure. In most power brake systems, intake manifold vacuum evacuates both sides of the diaphram of a vacuum pot and holds the diaphram "suspended". When you press the pedal, a valve opens and lets atmospheric pressure into the rear chamber and that pressure pushes the diaphram forward and helps you set the brakes. Using the suspended system makes the action of the vacuum booster very quick and it's a simple mechanism. There are, however, some disadvantages: FIRST of all, the amount of PUSH that can be generated is the diameter of the diaphram TIMES ATMOSPHERIC PRESURE....(about 14.7 PSI). That's ALL you would have to work with AT SEA LEVEL.....14.7 PSI; at 7,000 feet it would be a LOT less. SECOND of all, what if you have a diesel? There IS no intake manifold vacuum on a diesel[img]/wwwthreads_images/icons/crazy.gif[/img], so you're screwed completely.[img]/wwwthreads_images/icons/frown.gif[/img] THIRD, as you pedal the brake, and the vacuum that is behind the diaphram is broken, the intake vacuum must restore it and that lets the engine go THAT MUCH FASTER, just when you needed engine braking, you have the opposite.[img]/wwwthreads_images/icons/crazy.gif[/img] FINALLY, if you had enourmous tires and needed a crapload of braking effort, you could only get it by increasing the diaphram diameter; and soon it would be so big that the hood could not close; OR....use dual diaphrams like GM did. Today's modern cars have such low cruise vacuum to get the mileage up that control vacuum for heaters and so forth is too low to work, so the dual diaphram setup was the fix for the brakes and an electric vacuum pump for the controls.[img]/wwwthreads_images/icons/tongue.gif[/img] HYDRO-BOOST uses the power steering system as a fluid power source and the pump pressure is used to help you push that brake pedal down. That system is independent of engine vacuum, and the power needed to crank that power steering pump and boost those brakes actually HELPS the engine braking effect as well, so it's a win-win. The hydro-boost is capable of one heck of a lot of boost since it isn't limited by altitude, engine vacuum, and diaphram diameter.[img]/wwwthreads_images/icons/crazy.gif[/img]
A moonguy-operated Jeep Skunkworks in the "Heartland" building the Ultimate SNOJEEP.