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My hose running from the intake manifold to the brake booster just crumbled on me the other day, but trying to find a replacement is nearly impossible. I finally found an import store here in El Paso that had some 12mm hose, but it is not wire reinforced like the old one. Will I experience a problem with that or will I be alright?

Dave in El Paso
 

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Good luck!

I recently purchased a 50' roll of vacuum hose on e-bay. It isn't wire reinforced either, but the rubber is much harder than heater hose or fuel line in order to keep it rigid. It has worked fine for me, and should for you.
 

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Be carefull of the hose you buy. The vacuume can cause the hose to "suck" in and pinch. That will reduce braking effectiveness. No brakes=:( (Brakes are one of my obsessions... if you have not read my article "Give Me a Brake" , go to www.tgsi.com/brakes.html

As is almost always the standard answer for this kind of stuff... call the Opel GT Source. The will have the correct hose
 

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it seems like hydrolic hose will work if you can find the right size, my napa and auto zone make custom hydrolic hoses.
 

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funny that I see this thread now.

I've noticed that there's a vacuum leak somewhere on my car, and upon inspection of the braided brake hose, it looks rather beat-up.

I'll have to look up getting a replacement soon...
 

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The brake booster hose I use is 15/32 ID Anti-Smog hose. It is the correct size & is made for that purpose. A good parts store should have this. I just bought(well it was given to me) some more last week for one of my other GTs I want to get on the road this summer. Having alot of friends in the automotive parts, paint, & service fields has its advantages.

Tom C
 

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suck

man, how much vacuum does it produce?! That's got to have some serious vac to collapes the hose. Actually, while on the subj: Bob (TGSI) - Since your a brake guy, is it better to tap 2 vac ports (1 on each manifold) on the intake manifolds of a dual carb setup, or is it overkill?

-kyle
 

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First question.: On decelleration (which is when you are braking), the vacuum will exceed 20PSI. Every time a cylinder goes through the intake stroke, it tries to pull in 500cc fuel/air mixture. But since the throttle butterfly is closed, it tries to pull it in from anything the manifold is connected to... including the brake booster. So what you have is 4 cylinders "sucking" on the line as hard as they can.

Second question... an interesting question indeed. Some of the answer depends on what cam you are running. A really wild cam will produce less manifold vacuum at low RPM because of valve overlap. (Exhaust valve is still open, so if the throttle is closed, it pulls back in from the exhaust). Also, if you are running dual side-drafts, then you only have two cylinders "sucking" on the brake booster instead of four. So, "on paper", the answer is yes. However, when I was first raced my car in F-Production and still had the brake booster, I didn't have any problem with a single line. The cam was not really wild. (restricted valve size and only 40DCOE carbs) so, if you have a "moderate" cam and 40DCOEs, then I think you're ok.

On the other hand, it would be really easy to drill and tap the second manifold and "T" the two vacuum ports together. If you stayed with only one check valve, this would in effect create a "cross-over tube", and I don't think that's what you want... fuel/air mixture in a rubber hose doesn't sound too good. So, put a check valve in each leg. However, if you want to experiment, then fabricating a metal cross-over tube might be an interesting performance experiment. (I have not tried this because the rules don't allow it.)

As I said, an interesting question.

Hey, Rally Bob!!! any comments? Have you tried this?... (maybe we can coax him back once in a while)
 

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Um, to show off my Engineering degree, vacuum can't exceed 14.7 psia, unless you are willing to submerge the car under water first! The absolute absence of atmosphere results in a "vacuum" equal to current atmospheric pressure. So to get 20 psi of vacuum, you would need to have the car under (20-14.7 times 0.4326 psi/foot) 2.29 feet of water. Less if it were the ocean. Salt water weighs more, and has a higher "gradient" (pressure per depth). Don't try this at home.

And even 14.7 psi will EASILY cause a normal heater hose (used incorrectly in lieu of a proper reinforced vacuum or hydraulic hose) to collapse. They are designed to withstand 15 psi (or more) of internal pressure, but NOT to handle vacuum (external pressure).

Gil at OGTS sells the fancy braided cloth OEM-type (ATE to be precise) vacuum hose for $36, and the reinforced rubber hose for $16.50.

And I won't even BEGIN to pretend I know the answer to the second question. Bob....????
 

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Message from Beyond...

This just came in on my crystal ball....

In response to the issues about the vacuum booster hose....

I *think* Bob at TGSI meant that at closed throttle, full deceleration, the engine would see 20 inches/HG, not psi. Big difference!

In regards to the shared vacuum ports on an individual-runner intake:

Yes, it's beneficial, especially for the street. Smoother idle quality, much better vacuum for the brakes. Less chance of the car stalling when the brakes are pushed hard too, which is a common side effect of having a big cam and a single vacuum source for the power brakes. Low-end torque also increases, which I've seen in back-to-back comparisons. As Bob @ TGSI commented, it's not legal for his racing class, simply because there is a performance advantage to doing it.
 

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What you say is correct... now, I'll show off my degree... and then my PHK. At sea level atmospheric pressure is 14.7 PSI (1 atmosphere). Also known as absolute pressure. However, vacuum guages are designed to read zero when are exposed to 1 atmosphere or 14.7 psi.. It is only when the pressure is above or below 1 atmosphere that there is a change in pressure. To actually cause a vacuum of 14.7 psi we would have to have an absolute zero vacuum. Even in deep space there is not an absolute zero vacuum.

Now the PHK. Indeed, I mispoke when using "pounds" The Scale on engine vacuum gages is : inches Hg (inches of mercury) So, when I said 20 pounds, I really should have said 20 inches of mercury.

Now the real world. Every time a piston does an intake stroke it tries to pull a successively stronger vacuum in the intake tract. Following 4 or five intake strokes like this something must leak... crank case "air" pulled up past the rings, "air" down through the valve guides, and some through the carb butterfly. One of the first tell tale signs that piston ring seal or valve guides are starting to go bad is when a car smokes when decelerating

Another effect of this in the real world... we use Total Seal piston rings in all our race engines. They seal so well that they will pull "air/oil" in through stock Opel exhaust valve guides during decelleration. So, since we don't want the oil being pulled in, we cut the top of the exhaust valve guide to accept a proper valve seal.

"Dualing degrees" asside, kwilford and I both agree. Engine vacuum could collapse cheap hose just like sucking a thick milkshake through a thin paper straw. When it comes to something your life depends on... your brakes... buy the good stuff from the OGTS.
:D
 

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Well, at least great "Bob" minds think alike! Since I was actually quoting another "Bob". I just happen to have a link to the other side....
 

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Manifold pressure

Yes, you corrected yourself before I could respond (inches of mercury, but I knew what you meant) I understand the basic manifold pressure concept. (and your description was very good)When you fly T-34's near their max MP of 65" it can get very sensitive to sudden changes. Which could mean if you broke it, you bought it.

So if I have cylinder #3 tapped, I should tap cylinder #1 to offset the piston strokes? ....If I recall 1 and 4 are moving in the same direction when 2 and 3 are moving in the opposite direction...correct? Or is it 1 and 3 and 2 and 4....hmmm


-kyle
 

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number one and number 4 piston moves the same direction at the same time......same with number 2 and 3 just opposite of cylinders one and four
 

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Which one to tap? This continues to be an interesting question. With dual side drafts, what you have is 4 individual runners. So, maybe the answer is to tap all four. That would give you a true "cross over" and get the brake booster back on all 4 cylinders and give you a true "cross over" (with the performance advantage of a cross over).

Doing just 2 then this might produce bizzare stuff. One pair of cylinders would have a cross over, but the other pair would not.

So, I think having thought this through, either do a cross over between all four... or do 2 with a check valve in each one. (With check valves in each of the two legs, you would not have a cross over between the two )
 
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