Racor water separator? - PeachParts Mercedes-Benz Forum

Sooty Taillight · #1 06-01-2004, 08:27 AM

I have wondered what would happen if I got some water in my tank and it made it all the way to the firing chamber?

Hydro-lock!

I'm not aware any such filtration such as a Racor, water sepatation device, is installed in our Benz's?

It is not uncommon, or impossible, to pick up water either by condensation in our tanks or even at fill up at the station.

I know that in the marine enviroment, all diesels use water separators and I have emptied water from many over the years.

Anybody have a comment about this subject?

leathermang · #2 06-01-2004, 08:51 AM

I think your mental image of the amount of fuel injected into the engine for each power stroke may be a little optimistic...
Once the water hits that portion the system the engine is going to stop turning over....
Only an open injector combined with an electrically powered fuel pump would might allow water to get into the bore in the amounts you visualize....and that would still be tricky through the injector pump....

SoyDriver Matt · #3 06-01-2004, 09:10 AM

I don't think it would hydolock, but it could blow thet tip off an injector as it expanded into steam during ignition! Not as much risk in the non-marine environment, better storage normaly, many more gallons consumed in a hurry on an average boat followed by extented non-use off season leading to condensation in the tanks.

P.E.Haiges · #4 06-01-2004, 09:36 AM

SoyDriver,

And why doesn't the fuel expanding blow the tip off an injector during ignition? The fuel expanding is much more of a violent explosion than a little water turning into steam and injectors with stand these explosions for many years and hundreds of thousands of miles.

P E H

SoyDriver Matt · #5 06-01-2004, 10:08 AM

I thought that water has a huge increase in expansion as it flashes into steam compared to normal fuel combustion that can damage things in there, but I'm going on second hand info. Anybody know for sure?

coachgeo · #6 06-01-2004, 10:14 AM

my understanding is water in the amounts you can get from NOT having submerged your engine under water hurts the IP not the engine. Thus, water seperating filters protect not the engine. They protect the IP.

Now if you submerge your engine, that's a different story.

R Leo · #7 06-01-2004, 10:31 AM

Other than the obvious 'no run' situation caused by a lot of water in the tank, another other big problem with excessive moisture is caviation inside the IP.

Water has a significantly different vapor pressure than distillate oil. It will not behave well in the IP and over the long haul you will definitely experience some erosion issues. However, if this were a consistent problem, I suspect that other negelcted things will kill the engine long before the IP died.

TimFreeh · #8 06-01-2004, 10:39 AM

Soydriver

Think about your post - if it were true we could all fuel our cars from the nearest water hose.....

Ask any fireman - Water does not burn.

It is however a very destructive oxidizer and will cause IP damage if allowed into the pump.

P.E.Haiges · #9 06-01-2004, 10:42 AM

Soy,

The water might not even turn into steam, Since it is being injected into the cylinder that has a pressure of about 300PSI = about 600*F, the water would not turn into steam until the water reached about 800*F.

This is because the boiling point of water increases about 2 *F for each 1 pound increase in PSI the water is subjected to. I calculated this as ~800*F because 300PSI X 2 =600*F plus 212*F boiling point at standard pressure.

If the cylinder did not fire, eventually the pressure and temperature in the cylinder would decrease as the piston went down in the cylinder and the water might or might not turn into steam depending on how hot the cylinder is.

If the cylinder did fire, the water would turn to steam but that would be part of the combustion process and is why sometimes water injection is used to increase the power of an engine.

But water injection mixed in with the fuel would not lead to more power because it would the decrease the amount of fuel injected.

P E H

dabenz · #10 06-01-2004, 11:25 AM

PEH, you know water boils at 212F at sea level at normal atmospheric pressure of 14.7psi. Another way to think of this is the pressure cooker on the stove. If you keep adding heat then the pressure keeps going up, meaning one follows the other (assuming you boiled water for 10min to evacuate the air before sealing the lid). Now go back to the car and put a bit of water in the fuel. Assume 300psi outside the tip. Water boils at 417F at 300psi, and steam at this temp/pressure needs 81.7 times the volume of liquid water, using the same mass of water. The tip isn't going to cool off much during the cylinder's cycle, say to 350F. Uh oh, here comes an injector cycle. Say 1500psi in the injector line. Yes, the fuel expands but the fuel expansion is insignificant compared to water. The water will flash to steam a little bit before crack pressure, which represents the fuel expansion under normal conditions. The rest of the water will flash immediately after the crack. But not all the water is at the tip. The expanding steam behind a glob of fuel accelerates the glob and creates an impact on the tip that the tip wasn't designed for. Yes, the fuel will stay liquid even after the crack, but in very small pieces AFTER the tip. And we aren't even talking about water erosion, which makes the pieces even weaker.

SoyDriver Matt · #11 06-01-2004, 01:30 PM

"I thought that water has a huge increase in expansion as it flashes into steam compared to normal fuel combustion"

For Tim, I'm pretty sure water doesn't burn either, and for sure don't plan on filling up at any water fountains anytime soon. But any water in the fuel will, as the fuel is burning, expand significantly. Perhaps I should have written "water/fuel in a low enough ratio to allow combustion still will have a huge...etc. etc." Didn't mean to confuse you about my perceptions of waters burnabilty

Hatterasguy · #12 06-01-2004, 02:14 PM

Boats tend to sit so water accumulates more. Also some marine diesel is questionable at best. Frankly if your getting enough water in your car to make you want to install a Racor you need to switch stations and tell the owners they have a water problem.

TimFreeh · #13 06-01-2004, 02:59 PM

Matt

Got it, I did not understand your point but I do now.

I also don't plan on introducing water into my fuel system - I have heard about water injection on gas engine vehicles, I'm not exactly sure what the water does but I have never heard of Diesels benefitting from water injection.

rwthomas1 · #14 06-01-2004, 05:04 PM

In the spirit of belt&suspenders type of theory an additional filter can only be a good thing. While the MB filters certainly are up to the task under ordinary situations there are reasons one may want to add an additional filter. In very cold climates an aftermarket heater filter may help keep the fuel from gelling. If you travel in areas where dirty or contaminated fuel is common an additional filter may be a good idea. RT

Sooty Taillight · #15 06-01-2004, 06:08 PM

Wow! I asked for some comments and I got some! Thank You....

The reason I posted such a question is because I have, and my brother has also, gotten bad gasoline contaminated with water in it, in the past, and had caused my engine to run extremely poorly. Also, I had a "Hydro-Lock situation occur with a 4 cylinder Perkins 4107 marine diesel engine once.

When I opened my fuel tank cap to fill up recently, there was a lot of condensation present on the cap and that concirned me. I thought about installing a Racor, just for preventative measures.

I know that any amont of water introduced into a diesel fuel supply system is a no no, and I have wondered might it be worth installing such a filter.

While it is not obviously a common, or wide spread problem in autos, it just seems for me at least, to install a Racor, pease of mind!

Thank You