Power master brakes
- Thread starter butch2000
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Apparently these Turbo 6's will make enough torque that they can overcome the braking pressure put on the rear drums (with vacuum brakes) therefore allowing most cars to push through the lights at only a few lbs of boost. Some people put the longer shoes on the rear helping their cars performance.....
There are of course, more than one application for braking power. I think we can all agree on that.
I also think we can agree that the less force one needs to apply to the brake pedal to get the brakes to do what you want (not locking up!! Locking the brakes and skidding to a halt is HARDLY the most efficient way to come to a stop). Coming to a stop and doing it as efficiently and effortlessly as possible is the goal, AND. for many of the drag racers that can't afford the huge $$$ that go with well operating trans brakes, there the needed ability to hold solidly on the line against the foot brake.
I also think we can agree that the less force one needs to apply to the brake pedal to get the brakes to do what you want (not locking up!! Locking the brakes and skidding to a halt is HARDLY the most efficient way to come to a stop). Coming to a stop and doing it as efficiently and effortlessly as possible is the goal, AND. for many of the drag racers that can't afford the huge $$$ that go with well operating trans brakes, there the needed ability to hold solidly on the line against the foot brake.
Dave I do agree hydroboost is complex when doing a change-over, but stopping power is the mechanical function of many items in the brake system including tires, and using a different manner of powered assist does not give better stopping.
I respectfully disagree. The type of power assist directly translates to the pressure you can put on the calipers or shoes.
They can do that no matter what system you use.
They will at some point.... yes..... There is a difference in launching a car at 3 psi vs launching a car at 13 psi no? Most threads I see with people with vacuum conversions wanting to hold more boost are complaining they can't hold any boost or just a couple psi boost before it pushes through the lights.
Two checkballs, no issues with that anymore. I don't even have the long shoes. I blow the tires off at more than 10psi. Taller would probably help that I suppose.
As stated earlier, depends on the type, and amount of pressure that can be applied to the brakes. There are many variables.
It's been proven beyond the shadow of a doubt, that, for example that a rear shoe brake will impart a far superior holding force on the line than will a disk brake setup. HOWEVER, when it comes to actual stopping power, the disk brake is far far superior.
With some minor modifications, the rear shoe setup can easilly hold in excess of 15# of boost on the line, even with a relatively tight converter. Even my tired old setup can still easilly hold in excess if 15# agianst the foot brake.
Hopefully Scot wont object, but after driving his car, it has the most phenominal braking performance I've ever seen. Only light to moderate pedal pressure can produce stopping power from a roll that is nothing short of scary!!! And really hit the brakes and it feels like it wants to rip your eyeballs out!!
But will it hold good boost on the line?? Not really, IMHO. Not more than a few pounds. But his car is not built for drag racing, it's made for handling.
My car was not made for handling. It has seen nothing but drag racing for 25 years, and as such I needed solid and dependable line holding force. Hence, I've kept the Powermaster system.
What the hell does the type of power assist have to do with holding boost at the line?
Once the pedal is pressed, the power assist job is done.
At that point it is a MECHANICAL problem, and has nothing to do with the type of assist.
I really try to avoid pissing contests based upon opinions rather than facts or personal experience, so I will just bow out of this thread, and let you spread your beliefs.
I do have a BSME in mechanical engineering, but I have learned to overcome that handicap in the real world.
Nick, with all due respect......you are off-base here
There are many documents out there that state the HB puts more pressure at the calipers than vacuum..... I'm not suggesting everything on the net is fact...... just that I've yet to find an article quoting actual braking pressures that state that a vaccum assisted system puts more pressure at the wheels.
Oh..... I too have a BSME degree.
IMHO, it depends.
What is the PM doing.... or not doing?
If it is a simple fix...say under $150, I'd fix it.
If you aren't concerned about holding lots of boost on the footbrake at the track..... or you don't race your car...... or you have a trans brake...... and you want the least effort to get away from the PM system.......I'd consider vacuum conversion. Vacuum conversion is fairly straightforward with not a whole lot of work.
If you have a few skills.... and aren't scared to tackle a poor-boy HB conversion.... you can convert a car for under $200 with new hoses. I think I have less than $150 in my conversion. There are several good how-to threads on here for this conversion.
I think it is easy to hold up to 15 psi with bone stock calipers/drums/pads/shoes/wheel cylinders with a HB conversion. I think most struggle to build 2-3 psi with the same stock braking components and the vacuum conversion...... if you are into some drag racing.
Don't race.....want to drive with little or no worries.... go vacuum.
turbofabricator
Well-Known Member
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I'm gonna side with Nick on this. Pressure at the M/C is approximately 1750 Psi on a stock PM system. Then it goes through the combination valve and is reduced to the rear wheels to about 750psi. How would hydoboost do anything to change/improve on that. Years ago there was a jumper valve kit that bypassed the combination valvee and sent the full 1700+ psi to the rear wheel cylinders. Flip a switchand you had enough pressure to France tire aluminum drums. Still easy enough to do today. Grainger carries everything to do it. If you need info on how to plumb it in let me know and ill post the info.
Just want to throw this out there. I have 87 S10 wheel cylinders and shoes on my car as well a hydra-boost. In my driveway, with foot brake, I can hold 14# of boost like nothing and no tire spin. With hydra-boost, 90% of the turbo regal owners issues are related to vacuum. If you bullet proof your vacuum and maintain your brake system, then you are set!!
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An overlooked reason for building boost or not, is an item your car has that ANY car needs to build boost at the line, and that is the proper converter loose enough, which you DO have.
I have built MANY TR race cars over 25 years, and this "not building boost at the line because of my ****** brake assist" is complete bull shit.
If your combination is NOT compatible and proper, your launch will suffer the most.
I have worked on lots of record setting turbo Buicks with various brake systems, and all of them work when the combination is proper.
The guys with one car they built put out their bull shit opinion that so-and-so is the BEST because they think it works for them, and that is the BEST?
Yes, I do get fed up with "experts" telling everyone how to build a race car when they have only opinions with no actual track experience to measure different methods and parts.
No wonder so many experienced and knowledgable tech guys no longer choose to post as some arrogant ass-clown with "internet" keyboard knowledge can do it better.
Nick Micale said:An overlooked reason for building boost or not, is an item your car has that ANY car needs to build boost at the line, and that is the proper converter loose enough, which you DO have.
I have built MANY TR race cars over 25 years, and this "not building boost at the line because of my ****** brake assist" is complete bull shit.
If your combination is NOT compatible and proper, your launch will suffer the most.
I have worked on lots of record setting turbo Buicks with various brake systems, and all of them work when the combination is proper.
The guys with one car they built put out their bull shit opinion that so-and-so is the BEST because they think it works for them, and that is the BEST?
Yes, I do get fed up with "experts" telling everyone how to build a race car when they have only opinions with no actual track experience to measure different methods and parts.
No wonder so many experienced and knowledgable tech guys no longer choose to post as some arrogant ass-clown with "internet" keyboard knowledge can do it better.
I was partial a sleep when I posted this. I have vacuum booster brakes and not htdra-boost. Duh!!! Or maybe it was a good dream!!!
An overlooked reason for building boost or not, is an item your car has that ANY car needs to build boost at the line, and that is the proper converter loose enough, which you DO have.
I have built MANY TR race cars over 25 years, and this "not building boost at the line because of my ****** brake assist" is complete bull shit.
If your combination is NOT compatible and proper, your launch will suffer the most.
I have worked on lots of record setting turbo Buicks with various brake systems, and all of them work when the combination is proper.
The guys with one car they built put out their bull shit opinion that so-and-so is the BEST because they think it works for them, and that is the BEST?
Yes, I do get fed up with "experts" telling everyone how to build a race car when they have only opinions with no actual track experience to measure different methods and parts.
No wonder so many experienced and knowledgable tech guys no longer choose to post as some arrogant ass-clown with "internet" keyboard knowledge can do it better.
Somehow I thing that tyrade was pointed at me, and possibly a few others, so I'll refrain from adding any expertese in such matters.
I'm pretty sure I was at the top of the list. I tried to offer a contradicting opinion with the utmost respect. Apparently, the respect is one sided.
To the OP, do what you want..... Read a lot of posts on here and pick which one you want after reading about them all.
Dave I do agree hydroboost is complex when doing a change-over, but stopping power is the mechanical function of many items in the brake system including tires, and using a different manner of powered assist does not give better stopping.
Reliability of the different assist systems is another matter!
Here is a page that says otherwise:
http://www.classicperform.com/PDFs/BoosterBrakePressureChart.pdf
The effects of a vacuum booster on brake pressure
The brake pressure that comes out of the master cylinder is a result of "manual brake pressure" and "boosted brake pressure". "Manual pressure" is the pressure generated by pushing on the brake pedal with out any extra force from the booster. "Boosted brake pressure" is the pressure created by the extra force the booster sends to the master cylinder. In the case of a vacuum booster, this boost is "free pressure". The engine vacuum pulls 1 or more diaphragms that act on the master cylinder. The larger the diaphragms area the more "free pressure" the booster can provide. For example: A driver applies 100 pounds of force on the brake pedal. The car has a pedal ratio of 7:1 and a 1" bore master cylinder. The car will make 891psi of brake pressure. If the same car were to add a 9" single diaphragm vacuum booster the brake pressure would increase by 899psi with a total brake pressure of 1790psi. The 899psi increase is "free pressure".
There are a few other variables here that the don't mention to keep it simple so most won't loose the point...... but the pedal ratio on our cars could differ from this example.... could be higher....could be lower.... I don't know. They also don't tell you what manifold vacuum these results were obtained with. The higher the vacuum, the higher the "boosted pressure" would be. A sizeable portion of the cars on here have larger than stock cams... and hence will pull less vacuum than a stock cammed motor..... and this would mean less braking force at the tires....when running vaccum brakes.
