Electrical Vacuum Pump Conversion Project - Page 4 - PeachParts Mercedes-Benz Forum

Smoker · #46 12-21-2013, 01:51 PM

Quote:

Originally Posted by mach4

But you're running a manual transmission if I recall correctly.

It is starting to look like the transmission vacuum bleed is going to put it over the limit for what the VW/Audi vacuum pump can handle.

I'd considered the VCV when I was planning the conversion and my assumption was that the amount of bleed was quite small and wouldn't be an issue. Guess that's the problem with making certain assumptions. My reasoning was based on the relative sizes of the vacuum hose servicing the brakes vs the size of the vacuum hose servicing the rest of the vehicle.

It turns out to be true that exhaust port on the pump is actually smaller than the ID of the nylon vacuum lines

This whole project is beginning to look more and more unworkable. The good news is that I've only got $20 and a few hours into it to this point.

That's why it's going on my 240 with stick, but, I'm still going to make a pvc pipe vac res. I don't expect the pump to run all that much.

OM617YOTA · #47 12-21-2013, 01:55 PM

Quote:

Originally Posted by pgringo

with the car idling and no brakes applied, it goes off & on about every second or half second.

edit: the vac switch i used had ebay heading of: Adjustable Universal Vacuum switch 6-22 inHG lockup 700r4 2004r 350c

Mine does that too sometimes. There is no range on my vacuum switch, it's just on or off at a set point. You may not have as much of a vacuum bleed as you're thinking.

Shortly in the works is an adjustable vacuum switch like Mach4 has.

Mach-

Indeed I do have a manual trans.

Smoker · #48 12-21-2013, 03:23 PM

Quote:

Originally Posted by OM617YOTA

Mine does that too sometimes. There is no range on my vacuum switch, it's just on or off at a set point. You may not have as much of a vacuum bleed as you're thinking.

Shortly in the works is an adjustable vacuum switch like Mach4 has.

Mach-

Indeed I do have a manual trans.

I bought two switches, one adjustable, one not, but didn't get a round tuitt today as I didn't have the PVC stuff I thought I did.....I used to have a bunch of pipe and end caps from building confetti canons (stage productions), but either used it all or lost it

. I can store quite a bit of vac in a pvc pipe based vac canister, and since all I need is brakes and shutdown don't expect I'll be using much.

OM617YOTA · #49 12-21-2013, 03:41 PM

My system goes:

VP -> Check valve -> Vacuum switch -> Vacuum reservoir and various loads

When the VP shuts off, it will "bounce" quickly three or four times, I can hear the relay click and the VP actuates very briefly. Can't be good for the relay or the VP, and I'm confident that a vacuum switch with turn-on and turn-off points separated by at least a small amount would fix this.

Here's the relay I went with:

http://www.pickercomponents.com/pdf/Relays/PC795-80-Amp-NO-60-Amp-NC-240-Amp-Switching-Mini-125C-Automotive-Relay.pdf

Diesel911 · #50 12-21-2013, 04:40 PM

Quote:

Originally Posted by OM617YOTA

I have the EXACT same pump on my conversion. It handles all the vacuum requirements for the whole vehicle, and works just fine without heating up beyond design limits.

Not arguing but what are the design limits on the Vacuum Pump you used?

I got the impression that on the Turbo Gassers that the Vacuum Pump came from that during some point that Intake Manifold Vacuum was also availiable.
Meaning that the Electric Vacuum Pump is there to make up where the Minifold Pressure leaves off.

mach4 · #51 12-21-2013, 04:41 PM

Quote:

Originally Posted by OM617YOTA

My system goes:

VP -> Check valve -> Vacuum switch -> Vacuum reservoir and various loads

When the VP shuts off, it will "bounce" quickly three or four times, I can hear the relay click and the VP actuates very briefly. Can't be good for the relay or the VP, and I'm confident that a vacuum switch with turn-on and turn-off points separated by at least a small amount would fix this.

Yes, that definitely sounds like a hysteresis issue. I don't see any issue with your setup. That's precisely what I had in mind for mine.

Diesel911 · #52 12-21-2013, 04:51 PM

Quote:

Originally Posted by pgringo

I have the same vw vac pump I set up with a vac switch (22hg adjustable off eBay) and relay. With a Volvo 240 vac reservoir (fits perfect between firewalls next to master cylinder). It works great except I have a 300sd so the trans has a constant vac bleed. I was pizzed!

It is experimental and you don't really know until your as you are doing try it.
It could be that the Pump running all the time if that is what actually happens is not an issue.

mach4 · #53 12-21-2013, 04:57 PM

I just hooked up power to the VP to check the noise levels and it is really not objectionable at all. I'd say it is very similar to a Bosch fuel pump in the way it sounds. Looks like the mounting design works well.

Diesel911 · #54 12-21-2013, 05:06 PM

Quote:

Originally Posted by pgringo

Because of the trans bleed, the vac pump only cycles off for a couple of seconds at a time. It'll probably burn up in no time.

I guess we will be finding out if that is true or not.

But, there is other ways to go.

The Vacuum Pump in the Picture is a double diaphragm electric one made for an Electric Vehicle.
A diaphram pump should not get as hot even if it runs all the time.

However, I would not expect the Daiphram Pump to have the longivity of a Rotary Vane or Piston Type Vacuum Pump.

There is also Electric Pistion Vacuum Pumps.

Diesel911 · #55 12-21-2013, 05:13 PM

Quote:

Originally Posted by Jooseppi Luna

It also seems to bust the myth that the original VP runs selectively.

Maybe not. The Piston on the Stock Vacuum Pump moves a lot of Volume in one stroke in a short period of time. That could give it some time to have the Roller off of the Timer Cam for many revolutions of the Timer. Especially if the Engine is turning 3500 rpms.
That means the timer is turning 1750 rpms. So if the Vacuum Pump does not touch the Timer even for a few seconds over many years that saves a lot of wear and tear on the Vacuum Pump.

Diesel911 · #56 12-21-2013, 05:20 PM

Quote:

Originally Posted by 4x4_Welder

I thought that was already busted by testing and math?
The Ford Superdutys use an electric vacuum pump, does it have a switch built in?

Images Search Goolge for a Ford Super Duty electric vacuum pump.
The electric vacuum pump they are showing is for the cruise control and accessories; not for the Brake Booster.

OM617YOTA · #57 12-21-2013, 10:31 PM

Quote:

Originally Posted by mach4

Yes, that definitely sounds like a hysteresis issue. I don't see any issue with your setup. That's precisely what I had in mind for mine.

Thank you sir! I'll get an adjustable switch on the way.

Quote:

Originally Posted by mach4

I just hooked up power to the VP to check the noise levels and it is really not objectionable at all. I'd say it is very similar to a Bosch fuel pump in the way it sounds. Looks like the mounting design works well.

That's awesome. I definitely need to change the mounting for mine - it is very audible, even above the diesel clatter. People outside the vehicle look at it funny.

mach4 · #58 12-23-2013, 12:32 AM

Quote:

Originally Posted by OM617YOTA

I definitely need to change the mounting for mine - it is very audible, even above the diesel clatter. People outside the vehicle look at it funny.

If you decide to emulate my bracket as opposed to cutting out the stock mount and adapting that, here are some close up pictures and commentary.

It turns out that the barrel of the motor portion of the pump is exactly 2" which means that a 2" hole saw will provide the perfect hole for it do drop through. It's a fairly snug fit and you'll need to clearance the top plate just a bit to allow the motor to fit flush with the plate. I also clearanced the lower bracket just to prevent any metal to metal contact of the pump that could possibly transmit some unwanted vibration. To secure the VP to the top plate, I used the two screws that hold the motor case to the body (yellow arrows). The best shock mount would be the type shown below, but since I didn't have any, I made do with rubber washers like you see. I didn't have access to a brake, so I just did the vice-and-hammer trick to get the 90 degree fender mount. (Note: this is just mock up at this point, so I'm not yet using nylock nuts)

I used a triangular configuration only in order to clear my high pressure P/S hose.

Hope that helps if you go this direction.

mach4 · #59 12-30-2013, 06:57 PM

I've decided to continue with the project just to see if it's feasible. It's more of a proof of concept than a real solution at this point. My current thinking is to use two vacuum pumps, one dedicated to servicing the brake booster and the other for climate, shutoff and locks. I'm going to attempt to use an Arduino micro-controller to control and monitor the pumps and vacuum. (I say "attempt" because I've no experience with electronics or device programming so this will be a fun learning exercise)

I've done the research and determined that a GM 1 bar MAP sensor provides a linear reading between zero and full vacuum. It's a 5 volt device so it's perfect as an analog vacuum input for the Arduino.

My working plan is to use a potentiometer to allow adjustment of the set point for vacuum. I've got two choices - either two potentiometers to provide a low set value (turn on) and a high set value (turn off) or alternately two potentiometers, one to set the turn on point and the second to control the amount of hysteresis. (Or I may go dirt simple and hard code the on and off points in software and forget the pots)

I'll include code that will monitor the run time of the pump and if it runs continuously for some pre-determined amount of time (10 minutes??) it will turn off and turn on a LED in the dash. I'll also have an LED to show that the pump is running (... more likely one RGB LED that will glow green for pump running, blue for pump running over 5 minutes and red for pump emergency shutdown).

I've got enough control pins available to duplicate the circuit (and code) for the second pump.

I think I can control the pumps with MOSFETs and avoid the need to have external mechanical relays, but that's under investigation. (Even thought about the possibility of using PWM to slow down the motor as it neared the upper set point)

I had hoped to take advantage of the 1/2 price sale at the junk yard to pick up the second vacuum pump for $10 but couldn't find any, so for now I'll try running with one. My biggest concern is getting another leak in one of the vacuum pods, but if I know the pump is exceeding it's duty cycle I can turn off the climate and be OK until I get it fixed.

I'll continue to update as the project continues.... or not.

OM617YOTA · #60 12-30-2013, 08:13 PM

Mach-

Awesome, thank you for the pics of your setup. Love how your whole conversion is so clean and well thought out. Looks factory, and I'm sure the Mercedes gods would heartily approve of your work.

As I've posted, I'm in the components industry. If you need help sourcing let me know.