Gen 3 Motor Issues - Piston Soak - Blowby Pressure

So as most of us know the main issue with the 2010 prius is the piston rings which causes a lot of secondary issues. Whether that issue is solely from "low friction piston rings" or a combination of that and 10k oil changes we will never know. The damage to most cars is probably already done. I think its safe to say now that most of us agree to do a 5000 mile synthetic oil intervals at max to prevent further clogging/damage. I have also swapped to Pennzoil Ultra Platinum Full Synthetic although i doubt it will make a measurable difference in oil evaporation which goes into the intake to be burned through the PCV valve but hey every bit helps.
So the way the PCV system works is you have two pcv ports. The port on the valve cover is the breather port and the secondary port at the bottom is the exhaust port which is connected behind the throttle body on the intake manifold with a check valve inbetween. So at throttle conditions less than wide open the intake manifold will have a vacuum to a varying degree where idle should have the strongest vacuum being pulled as the throttle valve should be closed the most. The pcv valve controls the flow through the bottom port so at cruise with the throttle valve somewhat closed it pulls a vaccum and the valve allows it to pull that vaccum on the crankcase. This vacuum giving a small benefit in mpg from the pressure reduction and the secondary benefit is it sucks out the blow by vapors that enter the crankcase through the piston rings on compression stroke and effectively keeps the oil a bit cleaner and if the pressure differential is off the upper port allows air to flow in or out. Its a tuned flow as the pcv valve only allows so much flow into the intake manifold and the upper breather port has been reduced in size internally to tune flow further. The blow by gases are comprised of water, unburnt gasoline, and burnt exhaust. So this is why you get a lot of brown goo in your catch cans as its not just oil its a lot of blow by filled with other liquids as well. Also the pcv valve is a check valve so it only allows one way flow etc... At wide open throttle there is no intake vacuum and the crankcase pressure from the high amount of RPM from the pistons and blow by then close off the lower pcv port and that excess pressure goes out the top breather port into the intake before the throttle body. I'm sure many prius mostly see the former condition and not much racing. But also these are atkinson cycle engines with EGR valves and they like to keep the throttle valve mostly open to reduce pumping losses so I wonder if that effects the vacuum the car pulls on the crankcase versus a normal engine without all of that.
Anyways, I just wanted to type that to catch people up. I see a lot of threads and it is clearly some people don't understand how the pcv valve works.
NOW to my thread:
My 2010 was having egr issues like 15,000 miles ago. I saw the gasket masters video where they unplug the electrical connector on the car to diagnose if the egr system on your car is clogged. If it is clogged the car will instantly start to run better with it unplugged. I ran the car like that with p0403 temporarily until i cleaned the egr system, and the i decided to just leave it unplugged. If I ever need to go cel free i can plug it back in. But i somewhat dread having to do that cleaning process multiple times more. After I got the egr pinging issue fixed I tried to figure out the oil consumption issue. This car would consume probably half a quart in 400 miles on the interstate if i let the car use cruise control through the mountains, but if I didn't use the cruise and kept the RPMs below 3000 RPM the oil consumption stays around a quart every 6500 miles. So this points me to piston rings. I then verified it as well as when you take off the oil cap you get a nice flow of air which is well above normal so the car has a lot of blow by lol. I also tried 0w-40 vs 0w-20 and the oil consumption was the same with both.
So what I am going to try on this car is:
1. Drill out the tapered upper pcv intake port to its full size to get rid of its taper and get the maximum port size out of it.
2. Install a large straight fitting in place of the pcv valve down low to get the maximum port size out of it.
3. I will probably use 5/8" heater hose to connect these to a vent to atmosphere catch can. Using the shortest distance possible for each hose for the least restriction.
4. Dissassemble and remove spark plugs and intake manifold. Drain oil. Remove oil filter. Do a piston soak and valve soak and clean with e85, which i have found to be the magic fluid for cleaning carbs, fuel systems, fuel varnish of any age or level of stick, engine oil pan sludge (this stuff being related to the ls400 i just got running a week ago that sat for 13 years with oil and gas in it).
1st round piston soak: I will do it for 24 hours and clean the intake valves and port since its easy.
2nd round piston soak: Maybe 3000 miles later I will note oil consumption and see if it got any better and do the second piston soak for say a week straight instead. Baked on carbon is a bit more challenging for solvents than other things.
Hoping that this will help free up the rings and reduce the massive amount of crankcase pressure the car gets at higher RPMs to reduce oil consumption. The pressure just overwhelms the rings. Also, the thinking on the EGR delete and routing the PCV system outside of the intake is i will get less carbon build up on the rings going forward.
*A lot of the startup pinging is from the car sucking in oily blowby liquid that pools up in the bottom of the intake manifold will be gone. The design is just a bad design. The intake pools up oil in the direct air stream allowing turbulent air to kick up the oil to be picked up and brought into the cylinders. These are high compression cars so that will make the engine knock pretty hard. A better design would've been like every other car where the oil pools up in the intake at say the back or bottom of the manifold outside of the direct air stream.
Disclaimer:
1. If you have smog checks the car will fail from the PCV needing to be a closed system. If you route the catch can back to the intake BEFORE the MAF you will be a closed system. If you live outside of the united states in a country without emissions requirements you should be good to go!
2. Any CEL code at all will fail a car on emissions testing in the united states so be aware of that.
*Technically i guess you could connect the intake and exhaust ports of the pcv system into the intake system after the maf to avoid destroying the maf sensor. You just have to realize points after the maf are for already accounted air so if you pull one port from after the maf the other one will also need to return air after the maf.

 

Low 200s. I'll have to go look at the dash for the specific number.

 

Yup already visited the egr issues so i agree. Thanks. Yes the engine can suck drops of liquid upwards a couple inches. Its more about how the tumbling turbulent air actually whips the liquid slightly and can pull drops upwards. I don't have that issue but sometimes we all get that early morning start up knock once a year or so.

 

P0403 is not a misfire code.

 

This isn't an EGR thread so reply to me in one of the other ones though. Thanks!

 

Its about 6" so in relative terms its a couple inches in my book. I get that its not exactly 2". Yup the code is from an intentionally unplugged egr connector. I cleaned the system and then left it unplugged. But the conditions you named off is when vaccum is the highest.
*I was trying to copy and paste a pressure and velocity equation, but the higher the pressure differential the more velocity you get.

 

Okay second highest. I agree that the high rpm will create more vacuum than idle the moment the throttle body is closed again. But, there is zero vacuum at wide open throttle. Its definitely not a modest vacuum though. Take the lower pcv hose off and let it suck on your arm. It for sure has a lot of vacuum. And its not across the throttle plate its called manifold pressure for a reason. The whole manifold will have a vacuum lol. But it is like a 6hp shop vac or something comparable. My comparison is how i have cleaned the intake valves on the ls400 and was able to lift droplets out with my vacuum easier by creating a more turbulent air path. The reduction in pressure helps lift them and evaporate them as well.
So the belows that robots use use a vacuum seal cup to pick things up. This is another comparison to how hard the intake manifold vacuums at idle. Also, 2010's have a nice amount of blow by so that also increases the pressure differential further.
It makes sense though it ties in to the massive eliminate that start up knock catch can thread.

The manufacturers do actually tune the cars to get a lot of vacuum on the crankcase though. Their goal is to decrease the pressure in the crankcase so there is less pressure differential between the upper piston and lower piston to reduce pumping losses and make up for blow by the added into the system as well etc... And then they tune that vacuum to work the best from idle closed throttle body and up. The vacuum benefit of the system going away as you get into the high rpms and the throttle body is open more and not creating as much vacuum...

 

Isn't it wild? The thinking here for me is: can I take away the tiny pcv valve which helps a lot at low rpms, to add some more pressure relief for the crankcase up top in the higher rpms through larger breathing hoses? Will it balance out to a net positive or a net negative increase in oil consumption or will there be no change? Don't know yet but i plan to test it as its all reversible pretty easily.

 

Ah yes i see what you mean. But you can put a vacuum port anywhere on the intake manifold and as long as it is behind the throttle body it will pull a vacuum. So my ls400 has a port on the back for the acis itb actuators, a port on the back for the brake booster, a port in the middle for the power steering idle up valve connections, and a connection for the pcv valve. I know they all have a vacuum but yeah i'm not entirely sure on the difference between them as there could some variance in available vacuum at each location like its inverse which is a pipe with pressure and it has varying diameters. I will say that and Manifold pressure itself is actually a measure of the vacuum pressure between the throttle and the cylinders which is the principle map sensors work off of. So... I still say since the intake valves are doing the sucking it is possible.

 

Yes and no. I'm trying to say the pressure differential is between the intake valves and the manifold forward to every where else. But I say plausible. I use a vacuum to dry things and it pulls liquid up but yeah we aren't sure on the size of the drops so we will leave it as: Maybe? Not proven.

 

BUT I have to stop you there. Thats 100% wrong. There is no vaccum when the throttle body is open at high load. This is one of the reason why drag racers and others dont use pcv valves anymore as there's no vacuum at wide open throttle to take advantage of. It its greatest at closed throttle and diminshes to almost zero as the valve goes completely open. So its not something to be relied on for reducing oiling pressure as you get closer to wot.