TheSamba.com :: View topic - Routing for an Auto with Carbs and EFI Dist

Tue May 03, 2016 8:14 pm

I recently fitted my 73 squareback with the dual weber 34 ICT kit due to having an incomplete FI system. I've had the same kit on my bus for the last 6 years and absolutely love it. The problem i'm having is that the square is an auto, so I'm trying to figure out how to run the vacuum lines for the modulator on the transmission.

The ICT's come with vacuum ports on the carb itself, but not the manifold. I was going to use these vacuum ports as a balance tube between the two carbs and the vacuum advance on the distributor (Still an EFI dist). Then I was going to tap the manifolds and run a balance tube from both manifolds to the vacuum modulator on the transmission. Is this the proper way? or can I use the vacuum ports on the carbs and forget about tapping the manifolds?

Picture as a reference to show the vacuum port I'm discussing

Thanks in advance!

Tue May 03, 2016 10:38 pm

I think the stock balance pipes and connections are larger diameter than those on your carbs.

Wed May 04, 2016 3:23 am

Dubbin68 wrote: I recently fitted my 73 squareback with the dual weber 34 ICT kit due to having an incomplete FI system. I've had the same kit on my bus for the last 6 years and absolutely love it. The problem i'm having is that the square is an auto, so I'm trying to figure out how to run the vacuum lines for the modulator on the transmission.

The ICT's come with vacuum ports on the carb itself, but not the manifold. I was going to use these vacuum ports as a balance tube between the two carbs and the vacuum advance on the distributor (Still an EFI dist). Then I was going to tap the manifolds and run a balance tube from both manifolds to the vacuum modulator on the transmission. Is this the proper way? or can I use the vacuum ports on the carbs and forget about tapping the manifolds?

Thanks in advance!

The carb ports are too small for a balance tube. You really only need 1 port of the carbs for vac advance (1 carb only). Drill and tap the manifolds for either a 3/8ths pipe thread, or 1/4 inch at a minimum. If you go 1/4 inch pipe, drill and tap both ends, and "T" the sides together then in the middle add a reducing "T" for the vacuum modulator. The idea here is to get as much vacuum as you can for the trans to shift correctly. You still might need to adjust the modulator valve too, so keep that in mind. I only say that as the FI set up uses the entire plenum to get a vacuum signature, and you don't have that with carbs.
I hope this helps.

Wed May 04, 2016 4:18 am

Here is a look at what I did on a 70 I owned in the past with Dell 36's.

http://www.thesamba.com/vw/forum/viewtopic.php?t=5...;start=260

This was my solution with parts found at the local Lowes. It is a bit of a pain with the space constraints. I did both sides, ran a hose between them with a tee and got the best signal I could from a dual carb setup.

Wed May 04, 2016 4:43 pm

Thank you all! This helps clear things up nicely. I'll be drilling/tapping both manifolds with a 1/4 inch fitting. Also, I wasn't planning on running the kick down switch because I figured the vacuum signal from the manifolds would be enough and also because I haven't really come up with a good way to mount it. Think I'll be alright without running a kickdown switch?

Wed May 04, 2016 4:54 pm

Dubbin68 wrote: Thank you all! This helps clear things up nicely. I'll be drilling/tapping both manifolds with a 1/4 inch fitting. Also, I wasn't planning on running the kick down switch because I figured the vacuum signal from the manifolds would be enough and also because I haven't really come up with a good way to mount it. Think I'll be alright without running a kickdown switch?

No...the kick down switch is required. The vacuum and the kick down switch have nothing to do with each other.

The vacuum feeds a modulator valve that varies main fluid pressure in the valve body coming from the pump to aid proper shifting under load.

The kick down switch operates an electronic solenoid that actually performs your downshifts for you. This is not like a lot of watercooled american car transmissions where your downshift is a vacuum function.
Ray

Wed May 04, 2016 5:01 pm

raygreenwood wrote: Dubbin68 wrote: Thank you all! This helps clear things up nicely. I'll be drilling/tapping both manifolds with a 1/4 inch fitting. Also, I wasn't planning on running the kick down switch because I figured the vacuum signal from the manifolds would be enough and also because I haven't really come up with a good way to mount it. Think I'll be alright without running a kickdown switch?

No...the kick down switch is required. The vacuum and the kick down switch have nothing to do with each other.

The vacuum feeds a modulator valve that varies main fluid pressure in the valve body coming from the pump to aid proper shifting under load.

The kick down switch operates an electronic solenoid that actually performs your downshifts for you. This is not like a lot of watercooled american car transmissions where your downshift is a vacuum function.
Ray

Well it's not really required...
My kickdown switch was broken when I got my car, and it was over a year until I got one. The transmission will downshift quite well when you romp on the gas (or at least mine will). On the rare occasions when it won't, you can just move the lever to 2.

It's nice to have, but it's not absolutely necessary. You can certainly enjoy your car while you decide how you want to mount it.

Wed May 04, 2016 6:52 pm

This is how I activate my kick down. All you need is a normally open blade switch, make up a bracket to mount it, then an arm to hit the blade. The holes for the switch hold down screws are slotted so I can adjust the switch. I also tweak the blade a little. Also, since I am a little over protective, and am pulling power from the coil wire, I have an inline fuse feeding the switch.

Wed May 04, 2016 7:25 pm

Multi69s wrote: Also, since I am a little over protective, and am pulling power from the coil wire, I have an inline fuse feeding the switch.

That's a good idea, and not overprotective at all. VW did the same thing. :wink:

Wed May 04, 2016 8:01 pm

I'm happy to fab something up to hold the kickdown switch. So, if I'm understanding it correctly, the switch should be activated when at full throttle, correct? Then all I would have to do is fab a mount up to engage the switch when the throttle is fully opened?

Wed May 04, 2016 8:06 pm

VW had a fancy system where you had to press harder on the pedal after it was wide open to engage the kick down. But for us mere mortals, set it so the switch clicks at wide open, or just a touch before.

Wed May 04, 2016 8:16 pm

Multi69s wrote: VW had a fancy system where you had to press harder on the pedal after it was wide open to engage the kick down. But for us mere mortals, set it so the switch clicks at wide open, or just a touch before.

Great. Thanks for clearing that up. I should have the engine and transmission back in the car hopefully by tomorrow if my governor seal shows up,but then it's time to rebuild the brake system before I can test all of this out. I'll just be happy to have the car running again after it sat for nearly 25years!

Thu May 05, 2016 10:07 am

Multi69s wrote: VW had a fancy system where you had to press harder on the pedal after it was wide open to engage the kick down. But for us mere mortals, set it so the switch clicks at wide open, or just a touch before.

Yes....the crossbar mounted microswitch timed a little lower in throtttle opening is actually much better than the factory system on EFI cars (under the pedal with WOT+)
On the EFI cars...and this was especially true with the 411 and 412 which have the exact same part # of pedal and switch....the problem with having to have the pedal all the way at WOT...especially on wet pavement with stock tires and engine is at medium rpms..... its very easy to be rounding a curve and have the system kick down from 3rd to 2nd or even 2nd to 1st....with the engine now revving at max torque peak from WOT....and have the rear end pass the front as you get wheel spin.
There is a reason they warn about this in the owners manual.

The factory under pedal switch just affords poor control.

And yes...as Donnie Strickland mentioned...it will eventually shift due to fluid pressure.
But....while that is great on a long ramp when you have plenty of running room to get up to rpm to generate fluid pressure to get the valve body to shift....its not great when you need quick passing from steady state driving.

The stockish engine just does not build torque and rpm that quickly.

I solved the problem on my automatic car by extending the button with a rubber bumper glued on of about 3/16" thick. Much more controllable.

The point I was getting at is that these are two separate systems. The solenoid allows you to shift down when you require it...not having to wait until the engine is wrapped out.

The other issue you will find...is that unless you are meticulous in both rebuilding of your now 40+ year old transmission...or at least do the due diligence and adjust the main pressure using the driving test in the brown Bentley.....which is probably about 3% of all owners.....you are likely driving around on a transmission that is most probably down a bit in fluid pressure from normal wear....and having to wait for the fluid pressure to build for a shift point to pass a truck on the highway with a 60hp engine....can be downright dangerous.

Yes....you can always shift manually....but thats kind of clunky with the type 3 shifter.

Its too simple as as Multi69 noted...to just hook it up so everything functions.

What I was also referring to earlier is that many American cars used an actual vacuum solenoid back in the 70s/80s on carbed v6s and v8s. It was highly annoying with age when vacuum lines or the diaphragm crapped out....and quick downshifts disappeared....and you were left wrangling the column mounted selector lever to downshift....or wait floor it and wait for rpm to bring you up to a screaming level to have hydraulic downshift. Ray

Thu May 05, 2016 10:45 am

raygreenwood wrote: The factory under pedal switch just affords poor control.
Ray, what years of Type 3 had an under pedal mounted switch? My 71's switch is on the IAD:

Thu May 05, 2016 10:56 am

A few more pics/diagrams (FI and carb):

Thu May 05, 2016 10:58 am

The purpose of the dual pivot/spring setup was to let you floor it (to the point of initial added spring pressure so your foot knows when to stop) without down shifting. Then, if you needed even more power, press the pedal to compress the spring, and it will force a downshift. The gap shown is to let the throttle close JUST before you start to compress the spring, to avoid forcing downshifts any time you want full throttle.

Thu May 05, 2016 11:15 am

KTPhil wrote: The purpose of the dual pivot/spring setup was to let you floor it (to the point of initial added spring pressure so your foot knows when to stop) without down shifting.

That's right. I'm not sure what "under pedal" system Ray is referencing -- perhaps that was for the Type 4?

Here's a better photo of the setup on my FI car:

With this setup, there is nothing under the pedal. It works perfectly to let you know when you're about to activate the kickdown, and I have never accidentally downshifted. There is also no warning in the owner's manual.

Thu May 05, 2016 12:09 pm

Thats odd. My orange 1973 type 3 fastback with auto had it under the pedal just like my first 411. I wonder if it was some kind of dealer hack?
I had a 1968 type 3 FB with the switch on the left side of the plenum just like in your picture.

Either way....the micro switch itself is the same part from the dealer.

The warning about rear wheel skidding under load during kick down was in at least one of the manuals.....either the combined type 1,2, 3, 4 manual.....and was def in the type 4 speciific manual. I will have to look. Its the same risk either way.

Point is that not everytime you need to downshift....do you require the engine to be at WOT or absolute max rpms.

Being able to adjust this to not be absolute WOT for downshifts is good.

I will see if I still have one of pedals with the switch and post a picture in case someone else ha the same verison in their square or FB. Ray

Thu May 05, 2016 12:27 pm

It's definitely factory; the IAD is cast to allow mounting of the switch, and the owner's manual shows it:

Maybe yours was a 73 only, or 72-73?