Electrical Vacuum Pump Conversion Project - Page 6 - PeachParts Mercedes-Benz Forum

OM617YOTA · #76 01-07-2014, 03:48 PM

My vacuum reservoir is a chunk of PVC pipe with a cap on one end, an adapter to an NPT threaded fitting on the other end, and an NPT threaded fitting to hose barb adapter. The NPT hose barb adapter came from the landscaping section, whole thing cost less than five bucks.

funola · #77 01-07-2014, 05:39 PM

A really easy tempporary improvised vacuum reservoir is a gallon glass wine jug with a rubber tapered stopper. Drill a hole in the stopper and use the metal tubing from telescoping antenna sections (use a drill to spin it in). Barbs on fittings or clamps are not needed when dealing with vacuum.

funola · #78 01-07-2014, 05:43 PM

mach4, do you know about the mod to get rid of the VCV? It is not needed for the tranny to shift properly and may eliminate a potential vacuum leak source.

mach4 · #79 01-07-2014, 05:48 PM

Here's the test bed ready to be installed in the car. Can't install it yet as I want to install a diode across the solenoid and I don't have that yet.

If I decide to actually run this in production, I'll move the components off the breadboard onto a soldered proto-board and clean up the wiring to eliminate unneeded wires and create a cleaner mount for the LEDs and put them on a connector to facilitate removing the cluster.

mach4 · #80 01-07-2014, 05:50 PM

Quote:

Originally Posted by funola

mach4, do you know about the mod to get rid of the VCV? It is not needed for the tranny to shift properly and may eliminate a potential vacuum leak source.

You mean the one where you install a 5-speed manual?

If not, I'm listening....

funola · #81 01-07-2014, 05:53 PM

Quote:

Originally Posted by mach4

You mean the one where you install a 5-speed manual?

If not, I'm listening....

http://www.peachparts.com/shopforum/diesel-discussion/158216-its-critical-how-you-set-your-transmissions-vacuum-system-your-diesel-mbz-15.html

Skip this if you have a 5 spd manual.

Diesel911 · #82 01-07-2014, 09:02 PM

Quote:

Originally Posted by mach4

Of course.... but what would be the fun of that

I stated earlier in the thread that this isn't being done as a "solution", but rather a learning project and a proof of concept. Learning is always best when working on a real project...and boy have I learned a lot.

Indeed.

Diesel911 · #83 01-07-2014, 09:05 PM

Quote:

Originally Posted by BillGrissom

I also don't think the fairly small volume of the transmission modulator requires more flow than the pump can deliver. I suspect the flow restriction of the VCV is the main limiter in how fast vaccuum is applied to the modulator. Before adding a reservoir, try a simple test. Disconnect the tube to the modulator and turn on the vacuum pump. Measure the vacuum pump outlet pressure vs the VCV outlet at various "throttle" positions. If the pump keeps up, even at wide-open-"throttle", a reservoir wouldn't help much. 1985 cars got a "vacuum amplifier" (blue moon) to account for the VCV restriction (and to process a boost signal).

The Vacuum is limited by the restricted Fitting before it even gets to the VCV.

mach4 · #84 01-11-2014, 05:13 PM

Well it now appears that as long as there is a VCV required for proper transmission shifting, the use of an electrical vacuum pump to replace the engine driven pump on an automatic 617 is not a viable option.

With a setup consisting of just the vacuum pump, a check valve and a small reservoir (7 fl oz), the pump pulled 22" in about 5 seconds and with the pump off, held with no discernible leak-down.

I then hooked up the electrical vacuum pump in a test that isolated the VCV system as shown below. With the VCV in the circuit, the pressure went to 12" and held. There was enough leakage that it could not get above 12". Activating the throttle linkage showed the pressure dropping to 1" as it should, obviously dumping all vacuum above the 1" level.

So this is definitive confirmation that the VCV does constantly bleed all vacuum above it's set point (12" at idle and 1" at full throttle") and behind the restrictor. The restrictor ensures that the amount of vacuum leaking does not overwhelm the engine driven pump, which clearly has significant excess capacity and is designed to run constantly, but would be a serious problem for a relatively undersized electrical pump. Note: I took my pressure readings upstream of the restrictor, so at no time was the electric pump able to pull more than 12". Translated, that means that the brakes would never have more than 12" available for boost.

My conclusion: The use of an electrical vacuum pump would be a solution for a manual transmission vehicle, and should someone desire to use a microcomputer controlled system to control the pump, that would also work, though probably overkill as a simple pressure switch and relay would do the job.

It was a fun project with an unfortunate ending... unless of course there is a way to modulate the transmission without vacuum, then maybe it would work.

OM617YOTA · #85 01-11-2014, 05:25 PM

Dang! You put a lot of work into that!

funola · #86 01-11-2014, 05:32 PM

Quote:

Originally Posted by mach4

Well it now appears that as long as there is a VCV required for proper transmission shifting, the use of an electrical vacuum pump to replace the engine driven pump on an automatic 617 is not a viable option.

With a setup consisting of just the vacuum pump, a check valve and a small reservoir (7 fl oz), the pump pulled 22" in about 5 seconds and with the pump off, held with no discernible leak-down.

I then hooked up the electrical vacuum pump in a test that isolated the VCV system as shown below. With the VCV in the circuit, the pressure went to 12" and held. There was enough leakage that it could not get above 12". Activating the throttle linkage showed the pressure dropping to 1" as it should, obviously dumping all vacuum above the 1" level.

So this is definitive confirmation that the VCV does constantly bleed all vacuum above it's set point (12" at idle and 1" at full throttle") and behind the restrictor. The restrictor ensures that the amount of vacuum leaking does not overwhelm the engine driven pump, which clearly has significant excess capacity and is designed to run constantly, but would be a serious problem for a relatively undersized electrical pump. Note: I took my pressure readings upstream of the restrictor, so at no time was the electric pump able to pull more than 12". Translated, that means that the brakes would never have more than 12" available for boost.

My conclusion: The use of an electrical vacuum pump would be a solution for a manual transmission vehicle, and should someone desire to use a microcomputer controlled system to control the pump, that would also work, though probably overkill as a simple pressure switch and relay would do the job.

It was a fun project with an unfortunate ending... unless of course there is a way to modulate the transmission without vacuum, then maybe it would work.

Don't give up just yet. VCV is not needed for proper transmission shifting and can be eliminted. Did you look at the thread link I posted? Brian Carlton gave a good step by step description on eliminating it.

mach4 · #87 01-11-2014, 05:34 PM

Quote:

Originally Posted by OM617YOTA

Dang! You put a lot of work into that!

Yea, but learned a ton!

Diesel911 · #88 01-11-2014, 05:49 PM

Quote:

Originally Posted by mach4

Well it now appears that as long as there is a VCV required for proper transmission shifting, the use of an electrical vacuum pump to replace the engine driven pump on an automatic 617 is not a viable option.

With a setup consisting of just the vacuum pump, a check valve and a small reservoir (7 fl oz), the pump pulled 22" in about 5 seconds and with the pump off, held with no discernible leak-down.

I then hooked up the electrical vacuum pump in a test that isolated the VCV system as shown below. With the VCV in the circuit, the pressure went to 12" and held. There was enough leakage that it could not get above 12". Activating the throttle linkage showed the pressure dropping to 1" as it should, obviously dumping all vacuum above the 1" level.

So this is definitive confirmation that the VCV does constantly bleed all vacuum above it's set point (12" at idle and 1" at full throttle") and behind the restrictor. The restrictor ensures that the amount of vacuum leaking does not overwhelm the engine driven pump, which clearly has significant excess capacity and is designed to run constantly, but would be a serious problem for a relatively undersized electrical pump. Note: I took my pressure readings upstream of the restrictor, so at no time was the electric pump able to pull more than 12". Translated, that means that the brakes would never have more than 12" available for boost.

My conclusion: The use of an electrical vacuum pump would be a solution for a manual transmission vehicle, and should someone desire to use a microcomputer controlled system to control the pump, that would also work, though probably overkill as a simple pressure switch and relay would do the job.

It was a fun project with an unfortunate ending... unless of course there is a way to modulate the transmission without vacuum, then maybe it would work.

????There must be something else going on as I drove around with the Vacuum Pump in the below thread and I have an Automatic Transmission and everthing operated norally with the exception that I worried that the Vacuum Pump was getting too hot (and I had no Resivoir or Check Valve Check Valve on the Vacuum Pump).
The Vacuum Pump ran all of the time as I had no Vacuum Shutoff in the circuit.

http://www.peachparts.com/shopforum/diesel-discussion/296397-electric-vacuum-brake-booster-pump-tested.html

mach4 · #89 01-11-2014, 07:48 PM

Quote:

Originally Posted by funola

Don't give up just yet. VCV is not needed for proper transmission shifting and can be eliminted. Did you look at the thread link I posted? Brian Carlton gave a good step by step description on eliminating it.

I read the entire thread and didn't see anything about removing the VCV. He did talk about removing the 3/2 and egr stuff but never the VCV... at least that I saw. Can you reference a specific post?

ROLLGUY · #90 01-11-2014, 07:59 PM

Quote:

Originally Posted by mach4

I read the entire thread and didn't see anything about removing the VCV. He did talk about removing the 3/2 and egr stuff but never the VCV... at least that I saw. Can you reference a specific post?

After reading the same post, I would have the same question. I did not read anywhere about a VCV delete....rich