V8 catch can question

[user-23911]

Personally I use those see through plastic carburettor type fuel filters as catch cans.
Not because I need one but because they're see through and I can see that they're not filling up with oil.

One in each hose.
So long as you can see that they don't collect oil, you know the engine is still good.
If there's a sudden change.......you've broken it again.
If the oil filler cap starts dribbling.......it's broken.
Same with the rear main seal.
When the dipstick gets pushed out.........it's very broken.

Done all of the above....more than once.I even got to the stage where the missus wouldn't go in the car anymore due to the stink of oil.
Still got the car though, not the missus.



Swapped her for a newer model.

[ptuomov]

My personal preference is to not use a PCV valve. Instead, I have only a 2mm calibrated orifice and a check valve feeding the plenum between intake ports and the throttle plates. With boost in the manifold, you don't want it to get to the crankcase. I think my way is simpler. Car factories have used both the calibrated orifice and PCV valve, so it's not really "my way" and both are factory-level solutions.

The BMW separators like this #2855427 work very well, if you have one of them in each hose:



From those, you can run the oil discharge either to the turbo oil sump which I assume is actively evacuated, the main oil sump with a check valve in the line, or to a clear bottle. The gas outlet port should go to a Gatorade bottle at least initially and then maybe in the long run to the compressor inlet. If the engine is working well, the stuff that collects in that Gatorade bottle is about as toxic as what they sell in it at the store!

In terms of from where to vent out the crankcase gas, I think that it's important to have the manifold vacuum pick up from the rear of the engine (say back of the valve covers) and the compressor inlet pick up from the front of the engine (say block valley front). This is because with the throttle closed and manifold vacuum, the car is likely to be not accelerating. With the throttle open, the car is unlikely to be decelerating. The oil will then slosh away from the pickup point, or at least unlikely to be sloshing towards the pickup point.

The other thing that I think makes sense for a V8 is connecting the valve covers with an interconnect. This will reduce the likelihood of vacuum in one valve cover and pressure in the crankcase, which may hurt oil drain. V8 in a 1g turn has the oil drain passages of one bank approximately horizontal from the perspective of combined gravity and cornering forces. By connecting the valve covers with an interconnect, this possibility of oil "plugs" in the drain passages (however unlikely) is reduced.

Finally, inside the crankcase, you in my opinion should make sure that the piston pumping pulses don't directly blow into the oil drain passages of either bank.

[Caprimaniac]

The BMW separators like this #2855427 work very well, if you have one of them in each hose:

Great tip there; what size in/ outlet (for gases/ air) on that separator? I Wonder about putting on separators on my V8, and always prefer OE against shiny alu aftermarket....

Also; would a separator work With wacum (pump or those header-drawn wacum setups w/ valves)?


BTW I think Your idea of connecting the valve covers for road racing/ turning racing seems like a good idea (up to the point where you drain one side completely....). Has filled the Catch can many a time at the track.

[ptuomov]

Great tip there; what size in/ outlet (for gases/ air) on that separator? I Wonder about putting on separators on my V8, and always prefer OE against shiny alu aftermarket....

Also, would the separator work with vacuum (pump or those header-drawn vacuum setups w/ valves)?

3/4 inch gas inlet and outlet, so I figured one of them on each side should work well. So far they are working well.

I don't see any reason why a vacuum pump or header evac system wouldn't pull from the separator outlet, especially if the oil drain has a check valve or goes to a sealed catch can.

[maca]

Thanks for the post and pic you put up.
I will Google them and have a read and go from there☺
I built this engine several years ago and it has had a fair bit of punishment with me, the wife and my oldest son all drag racing it. I may freshen it up next year as it wont cop such a flogging now as i have just built another car for the wife and kids. One thing that has been a big learning curve in the last build was cam selection. This older engine when fitted with the supercharger made 8 psi with a decent sized cam. Where as the new engine i have just built with a baby cam makes 15 psi with the same supercharger and also made more hp. The main difference between the cams is lobe separation.
I cant wait to get this turbo going on the old girl and have some fun

[Belgian1979]

I wonder if there is a necessity to connect a pcv system to manifold vacuum. For instance in an engine with an airfilter/airbox, where there is always a certain amount of lower pressure than atmospherical pressure would it make sence to connect there ?
Reason I ask is that I have witnessed a situation where under decel/high vacuum the engine tends to pull a lot of air. I know that the pintle is supposed to shut off the PCV line, but it needs to be tuned, which is the difficult part.

[user-23911]

This older engine when fitted with the supercharger made 8 psi with a decent sized cam. Where as the new engine i have just built with a baby cam makes 15 psi with the same supercharger and also made more hp. The main difference between the cams is lobe separation.
I cant wait to get this turbo going on the old girl and have some fun

Boost is just a measure of intake restriction.
More flow = less boost.

It's normal for a smaller cam to make more boost but it makes less power per pound of boost.
It's also normal when fitting a bigger cam for the boost to drop but for the power to increase.

So don't be too concerned about boost numbers.

I wonder if there is a necessity to connect a pcv system to manifold vacuum. For instance in an engine with an airfilter/airbox, where there is always a certain amount of lower pressure than atmospherical pressure would it make sence to connect there ?
Reason I ask is that I have witnessed a situation where under decel/high vacuum the engine tends to pull a lot of air. I know that the pintle is supposed to shut off the PCV line, but it needs to be tuned, which is the difficult part.

Your PCV system is effectively sealed.
If you're using a MAF then the MAF measures total airflow.
There's 2 breather hoses, one to the intake manifold, the other to the pre turbo pipe.
At low load there's intake manifold vac.
Under boost , the PCV valve to the intake manifold should completely close and seal (it probably won''t)
The pre turbo pipe will have a vac when under boost.
That way you've always got suction on the crankcase.
If you've got an engine problem, it shows up by blowing the oil out of the breather pipe into the turbo.
But the same happens with the wrong PCV valve when you hit boost.

[maca]

Boost is just a measure of intake restriction.
More flow = less boost.

It's normal for a smaller cam to make more boost but it makes less power per pound of boost.
It's also normal when fitting a bigger cam for the boost to drop but for the power to increase.

So don't be too concerned about boost numbers

Ahh i understand. makes perfect sence now. You mentioned
Under boost , the PCV valve to the intake manifold should completely close and seal (it probably won''t)

I was going to hook my (one way) factory pcv back up to the carby so its venting the crankcase all the time except under boost. Are the pcv valves unlikely to close under boost when hooked to the carb?

[user-23911]

Are the pcv valves unlikely to close under boost when hooked to the carb?

The PCV valve goes between the intake manifold and the crankcase.
Easy to test by blowing through them once removed.

Air duster / compressor.

[n2xlr8n]

My personal preference is to not use a PCV valve. Instead, I have only a 2mm calibrated orifice and a check valve feeding the plenum between intake ports and the throttle plates. With boost in the manifold, you don't want it to get to the crankcase. I think my way is simpler. Car factories have used both the calibrated orifice and PCV valve, so it's not really "my way" and both are factory-level solutions.

The BMW separators like this #2855427 work very well, if you have one of them in each hose:



From those, you can run the oil discharge either to the turbo oil sump which I assume is actively evacuated, the main oil sump with a check valve in the line, or to a clear bottle. The gas outlet port should go to a Gatorade bottle at least initially and then maybe in the long run to the compressor inlet. If the engine is working well, the stuff that collects in that Gatorade bottle is about as toxic as what they sell in it at the store!

In terms of from where to vent out the crankcase gas, I think that it's important to have the manifold vacuum pick up from the rear of the engine (say back of the valve covers) and the compressor inlet pick up from the front of the engine (say block valley front). This is because with the throttle closed and manifold vacuum, the car is likely to be not accelerating. With the throttle open, the car is unlikely to be decelerating. The oil will then slosh away from the pickup point, or at least unlikely to be sloshing towards the pickup point.

The other thing that I think makes sense for a V8 is connecting the valve covers with an interconnect. This will reduce the likelihood of vacuum in one valve cover and pressure in the crankcase, which may hurt oil drain. V8 in a 1g turn has the oil drain passages of one bank approximately horizontal from the perspective of combined gravity and cornering forces. By connecting the valve covers with an interconnect, this possibility of oil "plugs" in the drain passages (however unlikely) is reduced.

Finally, inside the crankcase, you in my opinion should make sure that the piston pumping pulses don't directly blow into the oil drain passages of either bank.

Excellent post- Thank you.

Now to wrap my head around implementing this on Ford 2.3 Lima turbo.....