I should know this, but how exactly does this work? I think I should be to find a vacuum port (upstream of the carb) where the vacuum will increase as the throttle is opened. I know the intake manifold sees the deepest vacuum at idle. Seems like I should be able to find more suction when the thing is floored. maybe the one in this photo is designed like a waste gate ( opens with an increase in pressure) ?
It appears they are using the vacuum reservoir of the brake booster to hold them open during acceleration. At WOT, you have no vacuum. IMO, I would go with electric actuated.
I’m guessing the power brakes work well at any throttle. Don’t have the knowledge to explain why though.
Yeah the booster looks like a reliable source of vacuum. My Lincoln is currently 6 Volt, so looking for something that doesn’t use a 12V solenoid.
Well, the booster has a check valve that holds vacuum in the reservoir when vacuum drops off under acceleration. That is to make sure you have enough boost to stop in emergencies like your engine dying, etc. It will work and since you are 6 volt, it might be the best option. Is the solenoid valve available in 6 volts? You would need that, as well.
Vacuum ***isted power brakes work at any RPM or throttle opening because the 90 degree plastic fitting where the vacuum hose connects is a one way check valve. At WOT when manifold vacuum drops, the check valve keeps the ac***ulated vacuum inside the booster and ready for a brake application. @rockable types faster than I do!
Thanks. I can probably find a find a six volt solenoid. I will may go with a 6/12 battery for starting in 12V. That’s next on my list of questions I should already know the answer.
I've got it in my head that a vacuum brake booster should have its own dedicated supply of manifold vacuum with a check valve inline to the booster. No other vacuum accessories should be connected to that vacuum line. I'd find another source of vacuum somewhere else on the carb or intake manifold and probably plumb in a vacuum reservoir as well. Actually it looks like a good place to use a 12v linear actuator and a DPDT switch. https://www.amazon.com/Electric-Hig...&hvlocphy=&hvtargid=pla-4584345024930371&th=1 Or a push/pull choke cable, like shown above.
Why not just use electric operators with an open/close two position dashboard switch? That's what I did years ago and it still works just fine. Sometimes you might want to hear that rumble while you're sitting still. Cutouts are good for maximum horsepower but they are even better for the sound at any throttle position.
Pontiac had an optional muffler for the GTO that did the same thing. Under a high speed blast with low vacuum they would go open.
They are usually set up so that when you apply vacuum (often electronically switched) they go quiet. A lot of the OEM systems that are not electronic control and go loud under full throttle are just a spring loaded flap that opens under high flow
Brake boosters work on balanced vacuum. Equal vacuum is normally maintained on both sides of the booster diaphragm. ***ist is provided by admitting air at atmospheric pressure on the pedal side of the diaphragm.
You don't need a cutout, manual, electric or vacuum, if you build it without mufflers. You're welcome.
I tried that on my coupe. It’s incredibly loud to go down the highway. Something you can get tired of really quick
Actually it was just a spring-loaded ****erfly within the muffler that would open under higher flow conditions. Has nothing to do with low vacuum although that's a coincidental condition when you floorboard it...
How does Nope, it actually had vacuume line run to it. Option did not last long before it was gone. Melted the diaphragms and lines. Then it got a pop off valve type thing. That quickly died too but about 200 of those were produced.
Having had cutouts on a couple rides I have kinda outgrown it. Kudos to you guys keeping the roar alive though. Being able to quiet the car at any speed is a nice feature. I would never do another system that I couldn't regulate from inside the car. Late model front engine vettes had a cut out switch that opened 2 more pipes in the back (they have 4) and byp*** the resonators so it sounded throaty. I installed a switch on a buddy's so he could run them loud all of the time or quiet it for funeral processions or sneaking into work late.
The VOE Pontiac system used a rod with a "floating" valve that was spring loaded (shut) and a 4" vacuum actuator would pull it open via manual control via the driver. Even at WOT with no engine vacuum, the vacuum canister under the front fender was "charged" enough it could pull and hold the mufflers open. I am building 12 more right now. The AVATAR shows a set I built and polished in 2008 or so. I also was able to create a vacuum operated engine cutout setup for my father in law's 32 . I'll find images and share them. They work pretty sweetly.
Pontiac did have some that were vacuum, complete with vacuum pull pod on the front of each muffler. Used to have a schematic of the vacuum hose routing to the mufflers in my younger days, don't know what I ever did with it though.... ...
Could you use something like this? No electronics or vacuum, and same result. I'm a fan of a well-tuned single mode exhaust, but if you want an on-the-fly changeable cutout, something with less stuff to fail seems like the best bet. https://www.holley.com/products/exhaust/cut_outs_and_multi_mode_kits/parts/5424
This is surprisingly quiet. Well, maybe "not loud" as opposed to quiet, but it's very tolerable at speed. I think the bends in the pipe baffle it just enough. And, it's small displacement, so that helps too.
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