Electrical Vacuum Pump Conversion Project - Page 8 - PeachParts Mercedes-Benz Forum

yvairguy · #**106** 01-27-2014, 07:04 PM

I was thinking about this the other day, could you make a plate to go over the original mounting area for the OEM vacuum pump, but bring the "power" out through a shaft and have it drive something like a vacuum pump from a early 7.3 ford diesel? then maybe still use the electric for low vacuum, like at idle, if needed?

other than that, i would guess maybe going to a serpentine belt setup so you can stack all the stuff close together

mach4 · #**107** 01-27-2014, 08:57 PM

Quote:

Originally Posted by Dan Stokes

A couple of questions:
1) Is there a vacuum switch on a VW to turn it off and on? Mine won't need to run very often as it only needs enough slurp to shut the engine off but I'd like it to not run if not needed.

2) Which wire is ground? I got the pigtail and a little wire from the harness so I can make a plug-in connection but I don't know which wire is which.

No vacuum switch on the VW pump. It is controlled by the ECU, which is why I was headed down the path of using a microcontroller to turn it on and off. If your's is only used for shutoff, that pump is kind of overkill. I'd just hook it directly to a momentary switch (and a relay) and use a pin-hole in the vacuum line to bleed off vacuum so you can restart right away.

The Red/Green-stripe wire is the positive and the Brown/Green-stripe wire is ground.

mach4 · #**108** 01-27-2014, 09:01 PM

Quote:

Originally Posted by yvairguy

I was thinking about this the other day, could you make a plate to go over the original mounting area for the OEM vacuum pump, but bring the "power" out through a shaft and have it drive something like a vacuum pump from a early 7.3 ford diesel? then maybe still use the electric for low vacuum, like at idle, if needed?

other than that, i would guess maybe going to a serpentine belt setup so you can stack all the stuff close together

That would be beyond my engineering capabilities. Even the serpentine belt idea would require more than I'd be willing to put into it.

At first look, the electrical pump seemed elegant and interesting, but alas, the design of the VCV for the auto trans, just makes it impractical. For manual transmission cars, I think it is a real excellent option.

yvairguy · #**109** 01-27-2014, 09:27 PM

Quote:

Originally Posted by mach4

That would be beyond my engineering capabilities. Even the serpentine belt idea would require more than I'd be willing to put into it.

At first look, the electrical pump seemed elegant and interesting, but alas, the design of the VCV for the auto trans, just makes it impractical. For manual transmission cars, I think it is a real excellent option.

I wish i could pick up a CHEAP parts car with a running motor, it would be interesting to play with some of these ideas on a car i don't have to drive several times a week, if not everyday, of course any good parts car would probably be nicer than the car i now have LOL.

The Gears · #**110** 01-27-2014, 09:57 PM

I like the idea of the blanking plate with bearing holding a shaft picking up power from the center of the dual cam drive. What is in the center? Can the dual cam wheel be removed without everything falling apart behind it? I think the dual cam wheel has to be removed to allow a flat plate to mount and use the original gasket and bolts.
VW has a engine driven rotary vane vacuum pump that could be mounted to the blanking plate. Some machining would be required. On second thought a bearing would not be required as the VW pump has a bearing at it's base. I think. There has to be a way to solve this problem, after all we have, on this board, a collection of the best automotive minds in the world.
I have my hat of to mack4 for the work he has done on this problem.
I purchased a Volvo Vacuum pump and a switch only to see the BUSTED sign.
Hart broken but not out of the game.

The Gears · #**111** 01-28-2014, 08:18 PM

Problem is the VW rotary vane vacuum pump run the opposite direction to the 617 engine. Oh well.

mach4 · #**112** 01-28-2014, 09:02 PM

There are combination alternator/vac pump units that would probably be relatively easy to setup.

ROLLGUY · #**113** 01-29-2014, 12:51 AM

Quote:

Originally Posted by mach4

There are combination alternator/vac pump units that would probably be relatively easy to setup.

Yes, that is what my '85 Mitsubishi 2.3 turbodiesel pickup uses.

yvairguy · #**114** 01-29-2014, 01:20 AM

hmmmm that sounds interesting, now can we build the alternator large enough to have an on board welder and the room to add a york compressor for on board air..... i so just need a unimog

The Gears · #**115** 01-29-2014, 06:10 PM

Question for Mach4. Is the VCB bleed so great that the pump would run constant at half or full throttle or close to it? You mentioned an average of around 8Hg. Would a reservoir help?
The Alternator mounted pump sounds great till the problem of getting oil to and draining back to the engine base has to be considered.
Is there any place that a venturi could operate. Would a minimal restriction in the intake ahead of the turbo charger be possible?

Diesel911 · #**116** 01-29-2014, 07:10 PM

Quote:

Originally Posted by The Gears

Question for Mach4. Is the VCB bleed so great that the pump would run constant at half or full throttle or close to it? You mentioned an average of around 8Hg. Would a reservoir help?
The Alternator mounted pump sounds great till the problem of getting oil to and draining back to the engine base has to be considered.
Is there any place that a venturi could operate. Would a minimal restriction in the intake ahead of the turbo charger be possible?

On the Turbo Diesel 300Dsthe space behind the Alternator is restricted.

OM617YOTA · #**117** 01-29-2014, 08:41 PM

Quote:

Originally Posted by mach4

What I was hoping would happen is that the VCV would only "take 12 inches" and then "close off" - it doesn't, it bleeds it off excess vacuum continually, at the max rate allowed by the orifice (restrictor). That fact makes an electrical vacuum pump, or any pump that cannot run continually a non-solution.

I was re-reading this thread a bit. Could you put in a smaller restrictor that wouldn't bleed down vacuum so fast, and still have the transmission shift well?

mach4 · #**118** 01-29-2014, 09:42 PM

Quote:

Originally Posted by The Gears

Question for Mach4. Is the VCB bleed so great that the pump would run constant at half or full throttle or close to it? You mentioned an average of around 8Hg. Would a reservoir help?
The Alternator mounted pump sounds great till the problem of getting oil to and draining back to the engine base has to be considered.
Is there any place that a venturi could operate. Would a minimal restriction in the intake ahead of the turbo charger be possible?

Exactly how much the pump would run is unknown, but it is my assessment, based on the testing, that it would be beyond what would be prudent. My initial hypothesis was that the VCV was essentially a steady-state device, meaning that if there were no throttle change (I know there is no throttle on a diesel, but it's a convenient proxy-word to describe changing position of the rack due to pedal movement) there would be no vacuum consumed. Alas, such is not the case as it continually bleeds vacuum to hold the level indicated by the VCV at any particular position. The VCV sits between a vacuum source of 22" nominal and between 12 and 1" on the transmission side. It bleeds the difference between those two levels almost instantly and replenishes the vacuum at a rate which is controlled by the restrictor upstream of the VCV. Adding a reservoir to the system would not change the usage, thus would not change the time the pump ran, rather would only change the amount of time the pump would run at any one time between the low set point and the high set point of the vacuum switch, microcontroller or whatever else might be controlling the pump.

Quote:

Originally Posted by OM617YOTA

I was re-reading this thread a bit. Could you put in a smaller restrictor that wouldn't bleed down vacuum so fast, and still have the transmission shift well?

The restrictor is sized for vacuum replenishemt not bleed. I pondered for some time the feasibility of creating a sub-system that would somehow maintain a lower vacuum level that would feed the VCV. I envisioned a vacuum pump zone of 18-22" inches, a VCV feeder zone of 12 -14" and a transmission zone of 0-12" as determined by the VCV. The complexity quickly became problematic as I would need the microcontroller to control the pump in one zone and some kind of a switchover valve in another zone.

I even thought of creating some kind of a VCV replacement, as well as doing a quick search for a manual modulator that would allow eliminating the VCV altogether. Again, too complex.

Dan Stokes · #**119** 01-30-2014, 10:53 AM

I think I made a significant find for this conversion. There's a company called EV parts that offers a vacuum switch designed for this type of application. I found them online and they're EV as in Electric Vehicle Parts. Inc. - they specialize in bits for EV builders. The woman on the phone said that they have these built with the right parameters for automotive use. You'll need to run the pump thru a relay but that's not a big deal.

EDIT: I just double checked and the vacuum setting is adjustable but comes from the factory at 18-22"Hg. As I understand it, this means that the pump will switch on at 18" and off at 22". I'll crank mine down a little as I don't need that much just for shut-off.

The bottom line is you fork over about $40 (with shipping) and you get a device that will switch the pump off and on as needed to maintain a pre-set vacuum level.

Mine's on the way

Dan

mach4 · #**120** 01-30-2014, 12:02 PM

You mean this one which was referenced in the original post in this thread?