Performance Overflow Valve - Page 2 - PeachParts Mercedes-Benz Forum

Phillytwotank · #16 11-04-2014, 09:57 PM

Right on. Sounds pretty cool. I'd try one.

greazzer · #17 11-05-2014, 06:41 AM

Fuel pressure relief valve adjustment

Some related info on the most recent commentary

volker407 · #18 11-05-2014, 11:14 AM

Quote:

Originally Posted by Phillytwotank

Did you have any measurements of fuel pressure with this vs. a normal 27mm spring?

I did some pretesting with the valve a while ago.
My stock fuel pressure with OM617 Turbo engine was ~15psi. With the valve from Greazzer it did not fall below ~36psi....!

Gruß
Volker

Diesel911 · #19 11-05-2014, 08:34 PM

More than 1.5 Years ago Funola was selling an Overflow/Pressure Relief Valve that was Adjustable.

oldsinner111 · #20 11-06-2014, 06:49 AM

I hope you have one next month,I'm on a fixed income,and can't afford this month.

Peterac · #21 11-06-2014, 06:54 AM

Hi Greazzer,

I'll take one.

Peter

OM617YOTA · #22 12-03-2014, 09:33 AM

Quote:

Originally Posted by greazzer

As a follow-up to more questions I received:

Yes, it works also on OM603 and OM606 engines. It works on N/A as well, but I suggest its application with turbo engines.

The spring is stainless spring steel, calculated for the Mercedes engines and fatigue tested.

With the spring (actually rebuilt valve) a turbo engine will get more fuel/power without modding the pump on a bench. (It works on a NA engine as well, but as I indicated, the most gains are felt on a turbo engine).

What was involved in the fatigue testing? I'm envisioning hooking up to a jig with a cam or actuator to compress the spring a couple million times while measuring the spring pressure and length at regular intervals.

I'm in the market for a replacement, found my oem(?) spring in two separate pieces.......

rocky raccoon · #23 12-03-2014, 09:58 AM

quantified the effect on fuel economy?

OM616 · #24 12-03-2014, 12:44 PM

Quote:

Originally Posted by volker407

I did some pretesting with the valve a while ago.
My stock fuel pressure with OM617 Turbo engine was ~15psi. With the valve from Greazzer it did not fall below ~36psi....!

Gruß
Volker

At that pressure with the stock pump spring, how much by pass fuel are you seeing?

OM617YOTA · #25 12-03-2014, 01:12 PM

The lift pump is a positive displacement pump, it will bypass exactly the same volume of fuel that it did at 15psi, just maintain a higher pressure in the fuel gallery of the IP.

Cloudsurfer · #26 12-03-2014, 01:59 PM

What about for OM606 Turbo engines?

greazzer · #27 12-03-2014, 04:26 PM

Quote:

Originally Posted by Cloudsurfer

What about for OM606 Turbo engines?

Yes Sir.

volker407 · #28 12-03-2014, 05:06 PM

Quote:

Originally Posted by OM617YOTA

What was involved in the fatigue testing? I'm envisioning hooking up to a jig with a cam or actuator to compress the spring a couple million times while measuring the spring pressure and length at regular intervals.

I'm in the market for a replacement, found my oem(?) spring in two separate pieces.......

The company that manufactures the spring did the testing you describe after calculating the specification.

Still your original spring or any other spring is not to blame after 30 years of hard work

and several billion cycles ....

Gruß
Volker

Cloudsurfer · #29 12-04-2014, 02:11 AM

Quote:

Originally Posted by greazzer

Yes Sir.

Have to say I'm certainly interested then

OM616 · #30 12-04-2014, 11:17 AM

Quote:

Originally Posted by OM617YOTA

The lift pump is a positive displacement pump, it will bypass exactly the same volume of fuel that it did at 15psi, just maintain a higher pressure in the fuel gallery of the IP.

Yes it is a positive displacement pump, BUT, it is the piston return spring that generates the pressure, the cam only moves the piston back, compressing the spring, (actually when the piston goes back, it transfers the fuel on the outboard side of the piston to the inboard side of the piston), and the spring tries to move the piston back (drawing in fuel on the outboard side, and pushes against the fuel creating pressure on the inboard side. If the fuel is able to flow freely then no pressure. If you dead head the pump output line then the fuel pressure will be what ever the pump spring tension is.

As I recall, the pump on a NA will generate just above 15 psi dead headed, and a dead headed turbo pump will generate just over 30psi. I installed a stronger pump spring in my pumps and am running 30/36 psi with a good amount of bypass fuel.