spoonplugger1 wrote:
Crankcase press is measured in " inches of mercury". It should be well under 5 psi.
With the CRD it's measured in quarts of oil.
| LOST JEEPS http://www.lostjeeps.com/forum/phpBB3/ |
|
| What is acceptable crankcase pressure? http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=8744 |
Page 1 of 1 |
| Author: | Goglio704 [ Sat May 20, 2006 7:37 pm ] |
| Post subject: | What is acceptable crankcase pressure? |
How much pressure (or vacuum for that matter) can you have in a crankcase before seals fail. I think I'm too far south to have trouble with an open vent freezing in the winter, but there is a lot of water vapor in the air from the crank vent. I can see where it could be trouble up north in the winter. A pressure relief valve would a good safety measure, but what pressure should it relieve at? I'm thinking something less than 5 PSI, like maybe 2. Opinions? |
|
| Author: | RFCRD [ Sat May 20, 2006 7:45 pm ] |
| Post subject: | Re: What is acceptable crankcase pressure? |
Goglio704 wrote: How much pressure (or vacuum for that matter) can you have in a crankcase before seals fail. I think I'm too far south to have trouble with an open vent freezing in the winter, but there is a lot of water vapor in the air from the crank vent. I can see where it could be trouble up north in the winter. A pressure relief valve would a good safety measure, but what pressure should it relieve at? I'm thinking something less than 5 PSI, like maybe 2. Opinions?
I recall reading that the relief valve on the Provent is something like 1 or 2. |
|
| Author: | spoonplugger1 [ Sun May 21, 2006 12:29 pm ] |
| Post subject: | |
Crankcase press is measured in " inches of mercury". It should be well under 5 psi. |
|
| Author: | RFCRD [ Sun May 21, 2006 1:04 pm ] |
| Post subject: | |
spoonplugger1 wrote: Crankcase press is measured in " inches of mercury". It should be well under 5 psi.
With the CRD it's measured in quarts of oil.
|
|
| Author: | Goglio704 [ Sun May 21, 2006 2:12 pm ] |
| Post subject: | |
spoonplugger1 wrote: Crankcase press is measured in " inches of mercury". It should be well under 5 psi.
O.K. I'll buy that. Any idea how many inches of mercury? To convert from inches of mercury to: atmospheres, multiply by .03342. feet of water, multiply by 1.133. kgs/sq. cm, multiply by .03453. kgs/sq. meter, multiply by 345.3. pounds/sq. ft., multiply by 70.73. pounds/sq. in., multiply by .4912. |
|
| Author: | spoonplugger1 [ Sun May 21, 2006 4:06 pm ] |
| Post subject: | |
E mail the factory, I doubt DC will know. Haven't seen a manual for the engine out yet over here. Wasn't listed with Detroit Diesel last I looked. |
|
| Author: | Goglio704 [ Sun May 21, 2006 10:00 pm ] |
| Post subject: | |
Might email VM, but I was really just looking for a rule of thumb. Rope seals being a thing of the past, everybody seals a crankcase about the same way now - spring loaded lip seal. I wouldn't think the acceptable pressure would be much different from one make to another. |
|
| Author: | Jeger [ Thu Jun 01, 2006 4:54 pm ] |
| Post subject: | Crank Case Pressure |
I have been pondering this same issue myself. The Mann Provent release valve cracks at 50 mbar if I remember correctly which is about 0.725 PSI I think. So it is definantly a low pressure system. I should have a release valve coming that is set at 40mbar or .58 PSI. I am not sure if that is too low or not but for someone that is running an open vent and wants a release valve in case their vent should freeze up it might just work. |
|
| Author: | gmctd [ Mon Sep 24, 2007 3:48 pm ] |
| Post subject: | |
The CCV system limits crankcase VACUUM to ~4-6"H2O - that's right: inches of water 27"H2O ("water) = 2"HG ("mercury) = 1psi So it's little more than a baby's breath Keeping the crankcase a few inches below Barometric pressure prevents oil leaks as the mainseals wear, and also from any gasketed or RTV'ed joints - any greater vacuum level would cause reverse leaks, bad in any conditions but worse in dusty conditons, or in wet conditions - |
|
| Author: | Jeger [ Tue Sep 25, 2007 8:29 am ] |
| Post subject: | |
I havnt put a gauge on it but my CCV hose has stuff coming out of it...not getting sucked back in. Im sure the turbo pulls a vacuum but if you unhook it the vent side has positive pressure. You are saying the CCV system (in stock form?) Puts the crankcase under vacuum? By doing the EHM are we undoing something important by not keeping the crankcase under vacuum? Questions questions.... |
|
| Author: | gmctd [ Tue Sep 25, 2007 12:13 pm ] |
| Post subject: | |
Right - Diesel guys, incl engineers, don't like to say the word "vacuum" - they prefer the word "depression" - a Diesel engine that is developing significant levels of vacuum in the intake is not running efficiently - usually resulting from a dirty air filter, or stuff blocking the intake path - even a convoluted ducting system, resulting from design constraints in modern vehicles. The CCV system is a Crankcase Depression Regulation system - by creating a very slight vacuum in the crankcase - a "depression" - just a little below Barometric pressure, engine oil cannot easily pass thru a seal because atmospheric pressure is pushing against the other side of the seal, trying to equalize the pressure - the slight pressure helps to compress the seal, thus forming a better seal - if that vacuum level increases, Baro pressure will force dust, dirt, silt, water, etc, thru the seals into the engine - not good, in any event - really bad, in an off-road vehicle. The turbo compressor inlet develops varying levels of vacuum depending on rpm and air flow, and air filter condition, and ducting path - the CCV system is designed to compensate for each vehicle configuration and regulate that varying vacuum source, such that the crankcase "depression" is within the design specs of the seals - usually 4-6"H2O @ 2000rpm. Your engine is classified as a light-duty Diesel, which means it must comply with light-duty vehicle emissions standards - EGR, CCV, EVAP, Etc - all that stuff, most of which is detrimental to engine function, but is good for your lungs, and your descendants lungs. The CCV system is a good thing, as blowby and normal hot-oil vapors are combusted along with that light oil we know as Diesel fuel - however, it is definitely not good for a turbocharged Diesel with a charge-air cooler - intercooler in streetese - as the vapors cool and collect inside the ducting and heat exchanger - wotta mess! - requires the 'cooler be removed, drained, and cleaned, even moreso as the engine wears and blowby vapors increase. The Provent and similar systems maintain the integrity of the CCV system if the cannister is drained and the filter changed regularly - wotta hassle, right? - until compared with pulling and cleaning the 'cooler and ducting - the Provent system is defeated when the filter becomes black and saturated, as the slight vacuum is blocked and cannot evacuate the vapors That area on the cam-case cover is not a good position for a CCV port, as the vapor-level is increased due to cam rotation and camlobe action - a better location would be the oil-filler tube, which has a little better isolation from valve-train splash There is another method, guaranteed to fail emissions testing, but serves the same function without the mess - install a reverse pitot-type tube into the downpipe back towards the soot-trap - develops the required vacuum, the vapors are burned-off in the soot trap, no drip, no mess - but, you must first measure exhaust backpressure levels in the exhaust system to ensure that the crankcase is never pressurized - the old gasser (patooie!) A.I.R. systems employed low-pressure backfire valves for just such function - Diesels don't backfire, but a similar valve would block any normal backpressure Yes, the EHM defeats the CCV system - the medium-duty Diesels use that system with larger mesh buffer-filter, but like your dog, will leave a 'mark' everywhere - the Cummins crank seal has an integral teflon sleeve, intended for dripless +200kmi service |
|
| Author: | flash7210 [ Mon Oct 01, 2007 8:18 am ] |
| Post subject: | |
Just a thought... This engine has a vacuum pump right? Why not use the vacuum pump to pull negative pressure on the crankcase? Drag racers use a similar setup by adding a belt driven vac pump and and a catch can thing to trap any oil. |
|
| Author: | gmctd [ Mon Oct 01, 2007 9:14 am ] |
| Post subject: | |
Good thought - the vacuum pump usually consists of a dry sliding-vane pump with carbon\bakelite vanes - crankcase fumes and oil would soon disable the system - besides, the compressor makes more than enough vacuum to do the job - only requires 4-6"H20 - (27"H2O = 2"HG) - the vacuum pump makes ~26"HG vacuum The Provent and the Racor systems are suitable oil-removal elements if they are maintained, meaning replace the element as it becomes saturated - the Racor has a filter-minder valve for indicator - this Provent has the valve, but without the external indicator - creates a service problem Iirc, the racers use ~15"HG for a dozen or so full-throttle 1/4 mile trips twice a week - the system is designed to reduce windage at high rpm - our system is to prevent seal leakage for several hundred thousand miles while removing and burning crankcase vapors |
|
| Page 1 of 1 | All times are UTC - 5 hours [ DST ] |
| Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group http://www.phpbb.com/ |
|