Moving my cruise control servo

[flienlow]

Okay, call me anal, but I have searched everywhere for the infamous PVC check valve. Shucks auto supply (several stores), autozone, and Napa. No one in my area has any that will work. Shucks has one by "HELP" brand that could work, except it's sized 1/8" X 1/4" and all the other tubing is 3/16". I could use an inducer, but that is hacking a little to much for me. After some googling I ran accross this and think this is the way to go.

https://www.usplastic.com/catalog/product.a...duct%5Fid=15641

 

[ionbeam]

When I did my install I used more than one vacuum line size. 'Course I have a lot of different sizes in my garage from years of wrenching. My selection of Tees and 90° elbows was simplified by using various sizes of vacuum hose to accommodate the most commonly available fittings.

By the numbers, the check valve you found should work fine. Only thing that may be a problem is that the valves are lab grade and not automotive rugged and perhaps not automotive temperature stable either.

This is what I used, I purchased this exact check valve from Autozone though this link is to Napa. BTW, should anyone need a 3 port vacuum check valve, Napa carries them -- here.

 

[flienlow]

I saw both of those. the first is the 1/8X1/4. Imaging that would work great, except if having a huge vaccum reservoir is a concern, why would you want go to such a small diameter of hose? Not to mention having to obtain all the different fittings to patch it together with. I also saw the second, but that doesnt fit your aforementioned diagram which I have now adopted as law

I saw both of those. the first is the 1/8X1/4. Imaging that would work great, except if having a huge vaccum reservoir is a concern, why would you want go to such a small diameter of hose? Not to mention having to obtain all the different fittings to patch it together with. I also saw the second, but that doesnt fit your aforementioned diagram which I have now adopted as law

:huh: how did I get a double reply there?

 

[ionbeam]

having a huge vaccum reservoir is a concern, why would you want go to such a small diameter of hose?

Flow is so low that hose diameter really isn't an issue at 1/8" dia and larger . The vacuum 'reservoir' is more like a pressure buffer than a tank full of vacuum :blink:

Beyond this point thar be dragons...

The tendency is to see the AVCC vacuum system as either at full vacuum or vacuum depleted with the trusty ol' reservoir rushing in to make up for the depletion. The AVCC vacuum system actually has fluctuating vacuum levels around some nominal value. The other part of the equation are the fluctuating vacuum levels in the throttle bodies. At idle and light engine loads the throttle bodies will have a high vacuum (~220-250mm Hg), at higher engine loads the vacuum level becomes less (e.g. 60-110mm Hg). When the vacuum level in the throttle body moves closer to atmosphere (pressure is higher than that of the AVCC vacuum system) the vacuum check valve will close and the Reservoir becomes the vacuum source for the AVCC until 1) the throttle bodies vacuum level returns back to the same pressure level as the reservoir or 2) the reservoir vacuum becomes reduced to that of the throttle body at which point the check valve will open again. The reservoir is the buffer between the varying displacement of the AVCC vacuum diaphragm and the varying vacuum levels in the throttle bodies.

Earlier today I also had a double text entry. The new Forum software is such a joker :lol:

Edited to add: The AVCC is a CAR cruise control. The vacuum system of larger auto engines behaves much more civilly than a small, high revving motorcycle engine.

 

[flienlow]

Makes sense thanks. The only thing I am missing now is 4 check valves and a sick pack, and this thing is getting installed!!

 

[radman]

having a huge vaccum reservoir is a concern, why would you want go to such a small diameter of hose?

Flow is so low that hose diameter really isn't an issue at 1/8" dia and larger . The vacuum 'reservoir' is more like a pressure buffer than a tank full of vacuum :blink:

Beyond this point thar be dragons...

The tendency is to see the AVCC vacuum system as either at full vacuum or vacuum depleted with the trusty ol' reservoir rushing in to make up for the depletion. The AVCC vacuum system actually has fluctuating vacuum levels around some nominal value. The other part of the equation are the fluctuating vacuum levels in the throttle bodies. At idle and light engine loads the throttle bodies will have a high vacuum (~220-250mm Hg), at higher engine loads the vacuum level becomes less (e.g. 60-110mm Hg). When the vacuum level in the throttle body moves closer to atmosphere (pressure is higher than that of the AVCC vacuum system) the vacuum check valve will close and the Reservoir becomes the vacuum source for the AVCC until 1) the throttle bodies vacuum level returns back to the same pressure level as the reservoir or 2) the reservoir vacuum becomes reduced to that of the throttle body at which point the check valve will open again. The reservoir is the buffer between the varying displacement of the AVCC vacuum diaphragm and the varying vacuum levels in the throttle bodies.

Earlier today I also had a double text entry. The new Forum software is such a joker :lol:

Edited to add: The AVCC is a CAR cruise control. The vacuum system of larger auto engines behaves much more civilly than a small, high revving motorcycle engine.

Thats a beautiful description of vacumn/cruise dynamics. Though I can understand and work with everything you wrote, I can never express myself as eloquently, or as clearly, something that bugs the **** out of me and puts me at a loss here and elsewhere when trying to convey ideas. Well done.

Makes sense thanks. The only thing I am missing now is 4 check valves and a sick pack, and this thing is getting installed!!

Mine and many others operate perfectly with but one vacumn line, one check valve. It greatly simplifies the install.

 

[ionbeam]

and a sick pack

And this would be used in the event the CC doesn't work first try? :rofl:

Thats a beautiful description

:blush:

 

[flienlow]

yeah, Let's hope I dont need it!