so we have an intake plenum so that if you measure the vac with a mechanical gauge it will show a constant reading. so its not a pulse. if you have individual intake runners maybe you'd get an unsteady reading (a pulse)

 

So if you use a 35lph vac pump to effectively drain the catch can, how much pressure will that create in the return line and will that then inadvertently effect crankcase pressure, or will it make a difference also if the return line is above or below sump oil level?
All speculation until somebody tries it with data to back up the findings.

 

Brake boosters don't operate on vacuum pulses.

As ViciousLSD said, the vacuum at the intake is relatively steady. Not only is it a blend of four cylinders after a large volume of air (think about all the piping and intercooler), we have a literal air pump (turbo) also pulling a vacuum and buffering any impulses from the cylinders. You won't see the same vacuum pulses that you'd get from a tiny single-cylinder engine without a turbo and with 1/100th of the intake air volume.

 

The turbocharger does not buffer vacuum pulses. It creates its own vacuum as it is literally sucking in air.

The plenum is actually what buffers vacuum pulses by giving the engine a large volume of air to draw from, the plenum generally holds more air than a single can consume on the intake stroke.

The vacuum the cylinders create is only measurable POST throttle body, just like an NA engine. Vacuum reference in the plenum is fairly constant (same reason why the PCV nipple is attached to all 4 runners), just like how when you're in boost the boost gauge doesn't fluctuate much. But each runner is where you would find vacuum or (when in boost) pressure pulses if you were to put a map sensor on each runner near the head.

I can't believe this catch can thing is such a huge conversation still, even getting into vacuum pump talk. The build in my sig didn't even use oil at 550whp in track. I'd add MAYBE 1/2 a quart of oil through a day of doing 4 25 minute sessions. I had the stock PCV valve and line, and a 10an line off the driver front of the valve cover with a catch can, then recirculated to the turbo inlet.

I think a big part may be the ER oil pump gear. Keeping oil from gathering in the head with sustained high rpm, where it just gets shoved out the valve cover breathers.

 

The catch can is a patch job for when your build is not as healthy as others. *IF* one is "unlucky" like the G&G dude then its good to know there's a solution

 

How does a lower volume oil pump reduce the amount of oil getting trapped in the head?

 

By pumping less oil to the head? Kinda the same idea of it keeping more oil in the pan to prevent starvation. Which is the same principle your external regulator operates on. You just have a high flow regulator instead of slowing down the pump.

 

Thats only true if the regulator is overrun and pressure increases. ER gear helps reducing the load on the regulator which does drop oil in the head. But the external regulator on the infinity pan has better pressure control so its less of an issue.

 

Most gauges are damped and give an average reading. Otherwise they would be unreadable.

I don't have this problem so at this time I will not test this. But all you need is a pump off a lawn mower a container and some tubing.

Hook up pump on the general area that the vacuum brake booster is drawing from. The pump lines one in a container of water the other aimed toward the ground. See if the pump moves water. If so you have just invented a self draining catch can.

Mitsuatb

 

what about the other thing...boost

 

I agree with you, catch cans can be required by race rules but I don't see why a healthy engine needs one. But popular wisdom seems to treat them as a performance mod. I see it as a bandaid. Modern engines with PCV & EGR can make the use of a catch can more problematic if it is not plumbed in a way that avoids issues with PCV & EGR systems.

I am running IE oil pan Cosworth crank scraper and OEM windage tray and max 21psi boost. I have 80 - 90 psi oil pressure depending on air temp running down the highway at 75mph about 3500 rpm. 90,000 miles on Mobil 1 10W-30 every 3000. It does not burn any oil between changes.

Not yet sure as to what it will do on a track.

 

A drag racer is always in boost, not true in a RR. Every time BOV blows the butter fly is closed. That and valve events create vacuum pulses. The boost gauge is damped also. The existence of a plenum on the intake is to try and reduce the pluses in pressure. Only one intake valve pair is open during each revolution. So you have a centrifugal pump with inertia running against an intemitiant valve or butterfly opening. This will create pressure variations no way to avoid it.

Mitsuatb

 

I mean the booster can NOT take boost so it has a check valve. Surely you want to add a check valve on your "vacuum pump" idea. unless theyre used on turbo'd lawnmowers
or you can just use that check valve for a gravity-oil-return

 

A impluse vacuum fuel pump can't use a check valve because unlike the Vacuum brake booster one side is not vented to atmosphere. It uses only one line and has no vent because it is pumping volatile fluids. The impluse travels up and down the single tube. I think its construction and internal return spring will handle 30 psi if not it would need a pressure limiting valve but a one way check valve will not work.

Mitsuatb

 

Now I want a turbo lawnmower.