Vacuum Design

[fullthrottle]

Wanting to know if anyone has experienced slightly different vacuum setups from the factory install that has simplified the setup, but also improved performance.

My factory setup (was)....
- Vac pump on alternator
- two small vacuum reservoirs seperated.
- factory brake booster and clutch booster
- vac operated transfer

Ideally wanting to improve breaking as it's been repowered with a 1HDT. My thoughts are...

- Vac pump straight off the timing gears of the 1HDT.
- single, much larger capacity vac reservoir
- dual diaphragm brake booster
- single, larger vac reservoir supplying vac to break and clutch booster, as well as the transfer.

I do wonder though, for safety reasons if the brake booster should have it's own reservoir. Yet they all run off the same pump anyway.

 

[JuanJ]

Hello,

You can use a Terrain Tamer brake booster.

Regarding the setup, you can use a 2004-2006 HDJ78/79 as a guide.






Juan

 

[jblueridge]

I added a 3rd vac reservoir and it helped a lot with the dual diaphragm booster.

I have sometimes wondered how the vacuum is “transmitted” through the hoses and pipes.
When the booster uses a big chunk of vacuum, how much of a split second is needed to replenish it from a reservoir? Would a big reservoir and big hoses do the same job as 3 reservoirs?
Seems like it would be similar to a positive pressure system using 15psi.

 

[Hulsty]

Have you checked for leaks? Both my MWB cruisers had vac leaks and wouldnt hold vacuum once switched off, i'd start there.

 

[jblueridge]

Have you checked for leaks?

Very good point. My BJ74 had a crushed/cracked hard line leaking. I ran a new tube and left the damaged one in place at the back of the engine bay.

 

[fullthrottle]

LoL, I'm not sure how this thread turned into looking for a vacuum leak.

I'm just redesigning the vacuum system from the original BJ73 to a better, simpler solution with the 1HDT transplant.

 

[Chamba]

We're blokes. We mostly hear what we think the question is, not what the actual question is.

We're also not that bright, so we need pictures.

 

[fullthrottle]

And I thought only I had that problem, well so the wife sometimes tells me

The perks of being over 50 and male...
- I can walk into the garage for a specific job. Completely forget what I was going there for, but get something completely unrelated done.

 

[RHINO]

since your main concern is brakes, why not just run an electric brake booster?

 

[Chamba]

Or hydraulic off the power steering pump. Those are great from what I know of them. Mate of mine has one on a 56 Belair and swears it stops like a modem car..... granted he's got a Corvette front end in it, which couldn't hurt.

 

[AirheadNut]

Or hydraulic off the power steering pump. Those are great from what I know of them. Mate of mine has one on a 56 Belair and swears it stops like a modem car..... granted he's got a Corvette front end in it, which couldn't hurt.

The hydroboost systems are great. My Mercedes 300GD had a GM hydroboost with stock brakes (disc front/drum rear) and 37" tires and it stopped amazingly well.

 

[Hulsty]

LoL, I'm not sure how this thread turned into looking for a vacuum leak.

I'm just redesigning the vacuum system from the original BJ73 to a better, simpler solution with the 1HDT transplant.

You asked about improving performance? Leaks = Bad performance. Dont need to overcomplicate things, connect it up and go. Are you running out of vacuum now? Additional reservoirs wont improve performance unless your running out of vacuum due to depletion, ie quick repeated stops can deplete vacuum if the tank is to small.

They likely have seperate reservoirs and check valves so that the operation of ones does not impact the other, ie pushing the clutch while braking does not drastically change the braking pressure.

If your wanting to improve braking performance, do a search, pretty simple solution, 80 series dual diaphram booster, HSJ75 calipers and bored out master cylinder to suit.

 

[fullthrottle]

Another query....So because my 1HDT engine has been transplanted into a BJ73, I don't really have a good reference for the vacuum hose connections off the pump. From what I can work out the pump has two suction tubes.

In a factory vehicle, the small one seems to route to a solenoid, which then goes to the Air-Con, idle-up actuator, correct? (hose circled in red) I seem to be getting that mixed up with the PCS actuator. Maybe the same thing.
The other larger tube goes via a non return valve and into the vacuum reservoir, which then goes to the brake booster, correct?

Note: my injection pump has had the ASCD removed.

 

[jblueridge]

That is the general scheme on my 13BT BJ74.

 

[DrRock]

You asked about improving performance? Leaks = Bad performance. Dont need to overcomplicate things, connect it up and go. Are you running out of vacuum now? Additional reservoirs wont improve performance unless your running out of vacuum due to depletion, ie quick repeated stops can deplete vacuum if the tank is to small.

They likely have seperate reservoirs and check valves so that the operation of ones does not impact the other, ie pushing the clutch while braking does not drastically change the braking pressure.

If your wanting to improve braking performance, do a search, pretty simple solution, 80 series dual diaphram booster, HSJ75 calipers and bored out master cylinder to suit.

On my Ute I went with the 80 series booster as the original was pretty old and crusty with evidence of a master cylinder leak from days gone past. The new booster, coupled with proper adjustment of the LSPV, transformed the braking system. I also baselined my engine first and confirmed my vacuum was within factory spec as well. I also run factory pads up front and shoes in the rear and bled my braking system every year.