Electrical Vacuum Pump Conversion Project - Page 2 - PeachParts Mercedes-Benz Forum

Smoker · #1 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.

Diesel911 · #2 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.

yvairguy · #3 12-20-2013, 09:04 PM

now time to add hydrostatic brakes

Mölyapina · #4 12-20-2013, 11:37 PM

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

Diesel911 · #5 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.

4x4_Welder · #6 12-21-2013, 12:24 AM

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?

mach4 · #7 12-21-2013, 01:26 AM

Quote:

Originally Posted by 4x4_Welder

I thought that was already busted by testing and math?

Yup, sure was.

Mölyapina · #8 12-21-2013, 08:54 AM

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?

Yup, by Stretch... but here's one more nail in the coffin.

Diesel911 · #9 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.

Stretch · #10 12-21-2013, 04:26 AM

Does anyone have the specifications for these pumps?

(Flow rate - electrical power consumption - dimensions - noise produced - I don't know what else => anything else on the box perhaps {except quality checked by tester #3...})

yvairguy · #11 12-21-2013, 04:32 AM

Going at it backwards need to know how Mercedes calculated the required vacuum then find a pump that can equal that.

Stretch · #12 12-21-2013, 04:38 AM

Quote:

Originally Posted by yvairguy

Going at it backwards need to know how Mercedes calculated the required vacuum then find a pump that can equal that.

I've attempted to make a stab at that data here =>

More than you are likely to ever want to know about OM61X piston vacuum pumps

for the piston vacuum pumps fitted to OM617s - it is all my garden shed reverse engineering though...

...if anyone actually has the official specifications that must exist somewhere (Pierburg?) I'd love to see them

OM617YOTA · #13 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

mach4 · #14 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.

OM617YOTA · #15 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.