Purpose, Function, and Possible Elimination of CDR Valve

[Sharecropper]

I am considering supercharging my new P400 engine and was wondering what would happen when I completely remove my CDR valce and piping. In thinking about this, I began pondering what happens to the valve when adding a turbo or supercharger, as the additional boost/intake pressure would obviously traverse into the valve and either increase crankcase pressure or add stress to the valve diaphram.

Because our OEM 6.2 engines are naturally aspirated, which means there is a vacuum inside the intake when the pistons draw air into the engine for combustion, does this mean this NA engine vacuum is supposed to suck air past the valve to prevent pressure build-up inside the crankcase from blow-by? Or, does the valve control pressure inside the crankcase and allow excess pressure to escape into the combustion air as needed? If the CDR valve was completely eliminated, couldn't a vented oil fill cap serve the same purpose?

It seems to me that changing the static air inside the intake from suction to pressure may actually defeat the purpose of the CDR valve completely. Regardless, my CDR valve will have to be eliminated when the supercharger goes on. Just wondering what to do about venting the crankcase afterwards.

Thanks in advance for comments.

 

[WWRD99]

I am considering supercharging my new P400 engine and was wondering what would happen when I completely remove my CDR valce and piping. In thinking about this, I began pondering what happens to the valve when adding a turbo or supercharger, as the additional boost/intake pressure would obviously traverse into the valve and either increase crankcase pressure or add stress to the valve diaphram. Because our OEM 6.2 engines are naturally aspirated, which means there is a vacuum inside the intake when the pistons draw air into the engine for combustion, does this mean this NA engine vacuum is supposed to suck air past the valve to prevent pressure build-up inside the crankcase from blow-by? Or, does the valve control pressure inside the crankcase and allow excess pressure to escape into the combustion air as needed? If the CDR valve was completely eliminated, couldn't a vented oil fill cap serve the same purpose? It seems to me that changing the static air inside the intake from suction to pressure may actually defeat the purpose of the CDR valve completely. Regardless, my CDR valve will have to be eliminated when the supercharger goes on. Just wondering what to do about venting the crankcase afterwards.

Thanks in advance for comments.

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Being the supercharger is built for that engine Eaton should have the answer for that....catch can or whatever setup can be used...sometimes a different valve covers with screw in connections to hook lines to....do they make a crank pulley to fit it as well to drive the pulley? looks like a blast!! Do you need vacuum for anything else to run on?? can get an electric pump to get that if you need it too.

 

[Sharecropper]

Being the supercharger is built for that engine Eaton should have the answer for that....catch can or whatever setup can be used...sometimes a different valve covers with screw in connections to hook lines to....do they make a crank pulley to fit it as well to drive the pulley? looks like a blast!! Do you need vacuum for anything else to run on?? can get an electric pump to get that if you need it too.

I am just now exchanging emails with the fellow at Bullet in Austrailia. I have concluded that the CDR valve will have to be removed in its entirety. I have no problem with this, just need to know what to do about crankcase venting. Don't need vacuum anymore, changing the TH400 to 700R4. I've documented all this in my rebuild thread. Not sure about how to drive the supercharger. I'm currently driving my Sanden AC compressor off a custom crank pulley. If I need to, I will have another custom crank pulley produced to drive both the AC compressor as well as the SC. Uncharted waters here, I'm having to figure things out as I go. There is a possibility that none of this will work, but I will still try to.

 

[Keith_J]

The CDR keeps the crankcase at a very slight vacuum AND induce fresh air flow through the crankcase to keep blow by humidity from spoiling the oil. Fresh air enters the crankcase through the oil filler cap. Also engine crankshaft seals can weep with excessive crankcase pressure.

On turbo engines, it also deals with compressor/turbine leakage. Any crankcase pressure would cause slobber or wet stacking. This is where oil leaks from the CHRA into the intake and or exhaust. There are only dynamic labrynith seals on modern turbos, usually a single piston ring seal. Boost pressure and exhaust drive pressure leaks past these seals, draining to the crankcase with the oil return.

For a supercharger, just reroute the CDR to between the air filter and supercharger inlet.

 

[Keith_J]

Factory specification for crankcase vacuum is 5 inches of water at 2000 RPM. A dirty air filter could restrict air flow, causing this vacuum at lower RPM. No throttle in a diesel intake so air flow is engine speed dependent. When the air filter clogs, the CDR prevents excessive vacuum in the crankcase which could cause seal damage.

This system is analogous to Positive Crankcase Ventilation systems on gasoline engines.

 

[Sharecropper]

The CDR keeps the crankcase at a very slight vacuum AND induce fresh air flow through the crankcase to keep blow by humidity from spoiling the oil. Fresh air enters the crankcase through the oil filler cap. Also engine crankshaft seals can weep with excessive crankcase pressure.

On turbo engines, it also deals with compressor/turbine leakage. Any crankcase pressure would cause slobber or wet stacking. This is where oil leaks from the CHRA into the intake and or exhaust. There are only dynamic labrynith seals on modern turbos, usually a single piston ring seal. Boost pressure and exhaust drive pressure leaks past these seals, draining to the crankcase with the oil return.

For a supercharger, just reroute the CDR to between the air filter and supercharger inlet.

Thanks for your reply. I’m still struggling to understand exactly what the valve is supposed to do. Is it to keep positive pressure in the crankcase or negative? Is the valve set at 5 LBS? is the valve similar to a thermostat but opens upon pressure instead of temperature? So the negative pressure in the NA intake sucks the valve open and creates ventilation inside the crankcase?

 

[NDT]

Maybe start a new thread on belt drive supercharging a 4 cycle diesel. I have never heard of this.

 

[Recovry4x4]

I have a remote concern to contemplate. Is the snout of the 6.2 crank sufficient enough to drive a supercharger? I no nothing about the P400 engine.

 

[chevymike]

CDR creates a negative pressure situation. If it was positive, it would blow oil out of the seals.

 

[Sharecropper]

Maybe start a new thread on belt drive supercharging a 4 cycle diesel. I have never heard of this.

I will update my rebuild thread in the CUCV Hotrodding forum pertaining to the possible supercharger. This thread relates to the function of the CDR valve.

 

[Sharecropper]

I have a remote concern to contemplate. Is the snout of the 6.2 crank sufficient enough to drive a supercharger? I no nothing about the P400 engine.

No issues related to the strength of a P400. It’s like a 6.5 diesel on steroids. Developed by GEP to power the new upfit HMMWVs but then GEP lost the military contract. So a few of these engines were released to the public. I was fortunate to have acquired one a couple years ago. Forged crankshaft, forged connecting rods featuring cracked cap technology, forged pistons with ceramic top, hardened valve seats, improved coolant passages, improved oiling, and a massive cast iron girdle on the bottom end. You can read about it in my rebuild thread.

 

[Sharecropper]

CDR creates a negative pressure situation. If it was positive, it would blow oil out of the seals.

Thanks Mike for your reply. So do you think it will be OK to re-plumb the CDR hose to upstream from the supercharger, downstream from the filter?

 

[Keith_J]

The CDR uses the air filter restriction induced vacuum to induce a 5 inches of water vacuum in the crankcase. This is less than 0.20 PSI vacuum. Tiny. The real purpose of this vacuum is to draw air into the oil fill cap(there is a filter in there, hence its shape) to keep blow by gases clear in the engine.

Yes, you should keep the CDR regardless of induction system . And you must plumb it between the air filter and the supercharger.

As far as the crank supporting a supercharger belt, it should be fine with a cog belt drive. Especially with a single serpentine drive system, necessary for space.

Turbocharging is still more effective, using the 50 % of the waste energy to drive the intake and only sacrificing 5 hp to back pressure . Supercharger will draw at least 25 hp. And unlike gasoline engines, the lack of a throttle plate means that parasitic load is nearly constant and you will suffer at part throttle conditions since there is far more air than needed, diluting the combustion temperature. This additionally decreases efficiency.

A simple free floating turbo (Banks) uses the exhaust gas temperature to regulate boost. The most advanced turbos (variable geometry turbine) sense load, road speed, temperature, altitude and engine RPM to maximize efficiency while minimizing emissions.

 

[Sharecropper]

The CDR uses the air filter restriction induced vacuum to induce a 5 inches of water vacuum in the crankcase. This is less than 0.20 PSI vacuum. Tiny. The real purpose of this vacuum is to draw air into the oil fill cap(there is a filter in there, hence its shape) to keep blow by gases clear in the engine.

Yes, you should keep the CDR regardless of induction system . And you must plumb it between the air filter and the supercharger.

As far as the crank supporting a supercharger belt, it should be fine with a cog belt drive. Especially with a single serpentine drive system, necessary for space.

Turbocharging is still more effective, using the 50 % of the waste energy to drive the intake and only sacrificing 5 hp to back pressure . Supercharger will draw at least 25 hp. And unlike gasoline engines, the lack of a throttle plate means that parasitic load is nearly constant and you will suffer at part throttle conditions since there is far more air than needed, diluting the combustion temperature. This additionally decreases efficiency.

A simple free floating turbo (Banks) uses the exhaust gas temperature to regulate boost. The most advanced turbos (variable geometry turbine) sense load, road speed, temperature, altitude and engine RPM to maximize efficiency while minimizing emissions.

Thanks for your reply. I believe I now understand how it works.

 

[Rutjes]

There is a difference between N/A and turbo CDRs. In your case I think you'd need to find one for a turbo'd engine.

Member Swfb is having his engine supercharged. Maybe he can fill you in on how they are going to plumb his CDR. The guy who does it, does it for a living.

 

[Sharecropper]

There is a difference between N/A and turbo CDRs. In your case I think you'd need to find one for a turbo'd engine.

Member Swfb is having his engine supercharged. Maybe he can fill you in on how they are going to plumb his CDR. The guy who does it, does it for a living.

Thanks! I’ll see if I can track him down.