Apparently I have time on my hands because I thought about replacing the Double Throttle Valve.

As you may or may not know, getting a working version of these is near impossible. And even if you could get one, would you? All it does is keep the throttle plates closed during warm up so you can't over rev the engine on a frozen day.

What I discovered is the under normal circumstance, the default is OPEN and only when the car is warming up does the water thermo wax valve allow vacuum to pull the actuator in, . . .. Running the car with this valve broken doesn't really do anything as long as you don't high rev on cold day prior to warming up. . .. . But as you know, the failure is the ruptured diaphragm which causes loss of vacuum on that line and raises the overall vacuum level in the car during warm up.. . .Vacuum leak,

The spring action does come from the DTV so removing it just lets the plates in the intake just flop around. . . .So you gotta keep it in place or you have to wire the plates open or remove them.

For $29.99 I saw an EGR valve for a jetta 1.9 diesel and thought what the F. . . .

Aftermarket Products Fitment Type: Direct Replacement Manufacturer Part Number: EGV1079

I then removed the Linear Vacuum Actuator and lined it up. . . . . .I then thought why can't I also use the diaphragm for the EGR valve which is also no longer available.. . .Apparently the EGR only opens up in 5th gear so blanking it off may be the better solution. .. . .I need a broken Rx7 EGR to experiment with. . . Anybody got one?

But back to the Double Throttle Valve. . Below are the pics. . . . I gotta bend a piece of sheet metal next and line it up. . . It's slightly large, but not impossible. There is enough room if you get creative with your bracket. .. . .And for 30 bucks, it's cheap enough to go through the exercise and not care if I fail.

Anybody got better ideas or comments let me have it,


Stock Jetta EGR valve

After Removal

original lower bracket removed and pushed out of the way. . . .Looks like I could enlarge that lower hole on the actuator. . . .. .i could probably use the upper hole if I make the bracket right but the upper hole is a little large for the pin and may get sloppy.. .

EGR Diaphragm removed to see if it might work for the no longer available EGR valve on the 86 Rx7 S4 . . .

comparison in size. . . Looks I could get it to fit with the right sheet metal bracket.

 

Finally got the motivation to bang this out.

Notice the final location of actuator relative to intake lever.

During the install, you have to make sure the actuator plunger slightly pushes on the intake plate lever in a neutral state

What I like about this pneumatic actuator is the that you can rotate the lever relative to the base.. . .This allows you to position the outlet of the vacuum line underneath everything.

What I don't like about my design is the lock nuts on the 10-32 screws. They are too close to the intake plastic and could possibly rub. I will most likely use a low rise nut on the back side of the screw to get away from the intake plastic some more. .. . ..If I bend the bracket slightly I could get more clearance.

The hole in the actuator lever is not a perfect size for the intake plate lever/pin. . .It is slightly bigger that the shoulder on that screw. . . .Just slightly.. See the side pic. . .. It's functional.. . . .Always have the lever pushing on it and it's not a big thing.

I had to stack up washers to get the offset I needed.. . .Kinda cheapo solution.

The bracket you make only needs to be a single plate. . . . I tired to make a bent one with an offset and it came out cruddy cause I didn't have a sheet metal brake.

Thankfully, for ease of install, all you need to make is a single piece of aluminum sheet metal as the bracket.

Actuation happens at around 10" vacuum. . Maybe less.

 

 

Very cool! You get 2 thumbs up from this guy.

 

The Actuator by itself, no bracket, can be bought for $ 18.00 on Amazon, So once you set it up, it's pretty cheap. They probably sold millions of those engines in Europe.

labwork EGR Valve Actuator Exhaust Gas Recirculation Valve 038131501E Replacement for VW ALH TDI 1.9L Diesel Turbo 1998-2003

 

Just a note, the vacuum leak should not matter too much, as there is a delay valve that barely lets any air through (I still capped the line tho). I really like your installation!

 

Photo showing interaction with Cork Sport intake.. . . mounting flange clears better with the aluminum intake.

 

The dealers list this part but after ordering they let me know that it is not available! Then issue a refund, waste of time.
Even tried Japan, but I am not getting anywhere in my search.

So, I just ordered the egr valve and will install it as in this thread, Thanks!
I like the fact that 10" of vacuum will close the #2 secondary throttle valves closed as per the workshop manual!
I will be using my 1988 GXL as a grocery getter, so the drivability when cold is important to me.

Speaking of cold, I drove my car through 20 New England winters with the stock tires and never got stuck. Thanks to the manual transmission. Slipping the clutch is a necessary requirement to learn.
Yes, you can drive this car in the snow, watch out for the ice though!

 

What a blast from the (admittedly not that far away) past! Just to clarify for future readers, there is no drivability downside to not having a functional double throttle, it only prevents you from applying full power when cold (or, well, at least I don't consider that within driveability).

 

During the installation there are two things to note:

1) Make sure the plunger when it is in neutral position/without vacuum, is slightly pushing up against the vane pin.

Because

2) The vane control pin is slightly smaller in diameter than the hole in the plunger/actuator. . . .This causes the vane to have the ability to flap around ever so slightly .. i.e. the pin is sloppy in the hole.

It's hard to notice in the pics but I improved this by putting a small brass tube over the pin to increase the overall diameter . .Hobby shop tube material was used. I used some calipers to find the OD of the pin, and the ID of the hole in the plunger, and then I slipped a short piece of tube in between them.. . Then I used a retaining clip to hold it together as seen in the pics.

Finally, when it is working correctly, you will notice a reduction in power when the vane is closed while the car is cold. . .. . Makes sense right? That's the purpose.

But I never noticed how much it made a difference.. . . .Sometimes I want to get out in traffic right away and then realize I've got 15hp less.

At idle in the driveway it takes about 7 to 10 minutes before the Thermowax valve releases the pressure through the line, the actuator pushes forward, and the vane is open.

The secret is all in the plate you need to make. . .. It took me 3 times before I could get one I liked.

 

Thanks for the tips!
This is the only part left to complete my throttle body rebuild.
It's nice to know how it all works, nothing to be afraid of now!

 

I received the EGR valve and removed the diaphragm, thought about the concerns over the stock attachment bracket pin.

Here is my fix:

reusing the new EGR pin

I filed off the peened back of the pin, next I have to do the same to the stock bracket and remove the existing pin.
This will be neater and look better then stacked washers.

Then I have to decide whether to use a tap and die or try peening it to the bracket. Not much meat for threads on the pin.
What do you think? 
Perhaps a dab of JB weld?

With the longer pin I will have more clearance for the attachment screws, just need to make a thicker plate.

 

Here is a picture of the new bracket:



After removing the pin from the stock bracket (filed it flush and hammered it out with a nail punch), I measured the pin that I wanted to swap in, it was .172" which is 11/64ths. The hole was .156" or 10/64ths, so I carefully widened the hole using a 11/64ths drill in a hand drill.

It turned out that I needed to use a small vise to press the pin into the hole, got a good friction attachment between the pin and the stock bracket. Amazingly, the new pin is flush with the bracket! Looks like they were designed that way. My luck doesn't run so well so I am waiting for the other shoe to drop.

Notice that the pin now allows for a much taller screw head, like my nice shiny SS Hex head bolt!

Now to fabricate the bracket to attach the diaphragm with. It appears that the longer pin helps also for making the new bracket. The bracket I am using from the EGR valve, it lines up with the original bracket, but it is 7/8ths of an inch off. A simple adaptor plate will do the job.

Since at rest the fully extended arm if 7/8ths longer, how much spring pressure is needed to hold the throttle plates fully open?

Where is the sweet spot? A little or a lot of pressure? I can split the distance remining and slot the bracket holes.
The goal is to meet the specs for the amount of vacuum needed to fully close the #2 secondary throttle valves. It's like 10" of vacuum.
Too much spring pressure will need a higher vacuum to close the valves. Too late to prevent a lean A/F mixture. (Hesitation)
Too little Spring pressure will cause the plates close under 10" of vacuum. Leading into a richer A/F mixture. (What does a too rich mix do to performance?)

This is me with my CDO, it's like OCD but the letters are in the correct order!

 

With the longer pin it is now possible to attach the new bracket to the stock one with a bolt. The top holes align!

Here is a picture of the alignment:



I will do an initial test fit; I can pivot the bracket about 1/8th of an inch before it contacts the TPS. This will reduce the angle of the arm a little.

So, I don't have to make a bracket after all! Just see if I can use the second hole in the new bracket for a two bolt attachment so it will stay in place.

Once I secure it in place I will apply vacuum and see how much is needed to fully close the #2 secondary throttle plates.
If it isn't 200 I can slot the holes to move it in or out as necessary to match specs.

This seems to be working out just fine.

 

Hi everyone
I received the 5mm tap for the stock bracket, now to proceed with the installation of the new diaphragm.


Tapping the stock bracket, 11/64ths drill bit, oil on the tap.



5mm hex bolt fit. I do like the smooth sides of this bolt.




Initial bracket attachment.




Initial fitting, the top hole and the one beneath it are too high for proper alignment.
I needed to drill another hole lower on the new bracket.




Initial arm angle, not pleased with this, need to try bending the new bracket a bit.




Cut line to trim the excess material from the bracket.
I needed to make a new attachment hole in the arm!
The point that I selected allowed a 4mm deflection of the arm for some spring pressure when the plates are fully open.
See below, it looks like 1mm or 2mmn deflection is what is needed!




Adjusted arm angle, not perfect but good enough. Notice that the pin is coming undone!
I have not arrived at a solution about the loose pin attachment, perhaps JB Weld will do the trick?
Any suggestions?




Final fitment, I needed to make another attachment hole for the pin, this new hole position has 4mm of arm deflection.
The stock diaphragm arm has about 1/2mm deflection and 8mm of travel to contact the bracket stop.
I beveled both sides of the hole, makes pushing it on or off the pin easier.




air horn clearance of the attachment bolt, it's a bit long, I think I will shorten it some.




Fully closed throttle plates at 260mm of vacuum.

This is 30% higher vacuum then the FSM specs!
This will cause the plates to close later then they should, resulting in some hesitation when the secondaries are opened while the engine coolant is below 140 degrees.
So, I have to reduce the spring pressure to allow the plates to open sooner.
To do this I will slot the pin attachment hole I made in the arm towards the diaphragm a mm at a time.
Then recheck the fully closed vacuum reading and repeat as necessary.

And yes, the diaphragm must hold vacuum, no leaks!

I am also going to order two more new diaphragms at $14 each to have as spares.
To add to the longevity of the diaphragm's membrane, I will add a few drops of silicon oil to both sides to coat it.

What do you think of my install?

 

The pin came loose, I don't have the skill to peen it in place.

Looks like I have to bring it to a welding shop to firmly attach it to the bracket.

I moved the mounting hole on the arm to 0 deflection (arm fully extended, no spring pressure on the pin).

The #2 secondary throttle plates now do not fully open! Also, it still requires more then 200mm of vacuum to close the plates. The spring tension is higher in this piece.
I will have to set it so the valves just about fully open and be happy with where they close too. (fully closes at around 250mm of vacuum, 25% higher than spec.)

What would happen if I drilled out the vacuum nipple on the manifold a bit? Would this increase the overall vacuum pull?

 

The bracket needs to be remade to get the proper throw and angle. . . I had to make 3 of them before I got it right.

Sucks about the pin. . Old cars

 

Thanks, the throw as I measure on my 88 throttle is about 8mm from stop to stop.

I need the reduce the 90 degree angle for the left to right arm angle.

My concern is how to reduce the spring tension so that it matches the tension of the stock spring.

My initial fix is to add a low-tension spring over the diaphragm arm to overcome the internal spring, (when adjusted to a setting that is too low to fully open the plates) to allow the #2 secondary throttle plates to FULLY open.

What do you think of my fix?