What is the best crank ventilation method

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dscott
Posts: 16
Joined: Wed Oct 07, 2015 2:59 pm

What is the best crank ventilation method

Post by dscott »

So I just built a 2387 with fuel injection. Runs great. Currently I'm venting both valve covers and the filler to a bugpack oil breather. After driving it hard for a few hours I have oil sprayed all around the breather and engine. I'm looking into venting it differently. I want to use a oil breather can with baffling. Install check valves. What is the best breather configuration? Should I Vent valve cover cylinders 1/2 only and oil filler to breather can with a check valve in both hoses? So don't vent cylinders 3/4, just keep it sealed? I'm trying to fix this messy oil problem so I'm going to be changing a few other things as well. I was running valvoline vr1 20-50 which I found out is to heavy and could have caused some of the oil spray. Thinking of changing to a 5w-30. Also this engine is in a sandrail so the engine leans more forward than in a bug and I had the oil topped to the top line on dip sick, so Im considering running less oil down to the half way point to prevent crank whip. Any other suggestions I can try I'm willing to do. I also did a leak down test to make sure I'm not leaking past my rings and that checked back ok. So i'm guessing it's just positive crank case pressure from crank whip and movement of the pistons. How are you venting your crank case on a big engine? Do you have oil mess?
JWP
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Joined: Mon Jun 11, 2012 3:00 pm

Re: What is the best crank ventilation method

Post by JWP »

I think what Frank posted in the other thread is probably about the best way. I have an idea I'm going to try first to see if I can make it work. Else I'll probably be doing the dual Krank Vents like he showed. IMO, the biggest challenge with a bigger engine is there the possibility for more pressure to relieve when compared to a meek and mild 1600. I really suspect the Krank Vents are up to the task as they are designed for bikes turning in excess of 10k rpms.
dscott
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Joined: Wed Oct 07, 2015 2:59 pm

Re: What is the best crank ventilation method

Post by dscott »

Well I vented valve cover 1/2 and the oil filler to a oil separator with baffles with two of these http://m.ebay.com/itm/UPR-12MM-Non-Retu ... 4195976020
Check valves instead of the krank vent. Krank vents are expensive. I haven't had a chance to really drive it hard for a good amount of time, but when I do, I will post back for the results.
dscott
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Joined: Wed Oct 07, 2015 2:59 pm

Re: What is the best crank ventilation method

Post by dscott »

I ran a test today with it setup the way I stated above, with a vacuum gauge hooked up to oil dip stick and saw no vacuum in the crankcase at any rpm. It was at zero with a small spike to about 1 psi at high rev. I was really hoping to achieve some vacuum. Any ideas how to create a small amount of vacuum without a vacuum pump? I know I always have the option of running a hose to the air cleaner but I did not want the chance of getting any oil into the heads. I have a o2 sensor in the exhaust for air fuel ratio so did not want to run a hose to the exhaust either.
JWP
Posts: 171
Joined: Mon Jun 11, 2012 3:00 pm

Re: What is the best crank ventilation method

Post by JWP »

My guess is the quality of the check valves. I'd be curious to see what the numbers were just venting to the atmosphere without the check valves. As for 3/4 side if you can vent from the top of the valve cover you should be good. In Frank's write up on the other thread he did note having to put a catch tank in line to catch any oil/water vapor.

The setup I'm going to experiment with I hope will be under 100 bucks to assemble.
The short list is;
Vacuum pump from early 2000s VW for brake booster vacuum, also found on mid 2000s volvos. Local yards have these for about 10-15 bucks
Adjustable vacuum switch which will turn the vacuum pump on below a preset amount of manifold vacuum this is about 30 on ebay
Appropriate vacuum hose from oil filler and valve covers
PVC from hardware store to be used as a catch tank/vacuum chamber.

The thought is the vacuum switch would only run the vacuum pump above some percentage of throttle based on manifold vacuum and this value is adjustable.
The reason is these pumps aren't meant to be 100% duty cycle so expecting them to run non-stop will result in me swapping out the pumps frequently
My car is going to be used for weekend cruises and track days, if it works the way I planned it, I can set it to run the pump at a higher manifold vacuum on track days and a more mild setting for the remainder of the time.

Something else to consider on all of this is that converting to dry sump really reduces the need to have crank case evacuation in the terms we are discussing here.
The cost of going dry sump is about 2.5 the times of 2 Krank Vents and all the stuff to make them work. If you can buy used parts to make your dry sump system then the cost differences goes way down.
dscott
Posts: 16
Joined: Wed Oct 07, 2015 2:59 pm

Re: What is the best crank ventilation method

Post by dscott »

Was I supposed to be able to produce crankcase vacuum while using inline check valves even though my vent hoses only went to an oil seperator not to the air cleaners or any vacuum source. I guess what I'm saying is if I vented my filler vent to the air cleaner that would pull air from the crankcase and the check valves would prevent air from going back in which would create vacuum in the crankcase. If I was to route the 1/2" hose from filler to air cleaner would that cause to much vacuum requiring me to install line restrictor?
Last edited by dscott on Wed Oct 14, 2015 11:27 am, edited 1 time in total.
JWP
Posts: 171
Joined: Mon Jun 11, 2012 3:00 pm

Re: What is the best crank ventilation method

Post by JWP »

Frank claimed he was pulling liquid oil with the Krank Vents and adding the second one reduced the vacuum per hose that it no longer did that. Frank also had hoses going to the air cleaner but this was after a breather. I'm not sure if it was vented or not. I would be curious to know what the behavior is without the check valves you have. This would be a good testament to their operation. If you see anything over the 1psi that you noted in your test then they are doing their job.

Which leads me to believe venting your oil filler to the air cleaner would probably get the extra vacuum you need. Researching OPP on this topic it seems to be that 3-5 Hg" is about all that is needed, beyond that the returns diminish rather quickly.

One thing I don't see mentioned is do you have a sand seal on the crank pulley? If not you won't likely ever pull much vacuum without some serous volume
dscott
Posts: 16
Joined: Wed Oct 07, 2015 2:59 pm

Re: What is the best crank ventilation method

Post by dscott »

Yeah it is sand sealed. Very fresh built engine by me. I will test it more this evening to see if the check valves are doing anything.
JWP
Posts: 171
Joined: Mon Jun 11, 2012 3:00 pm

Re: What is the best crank ventilation method

Post by JWP »

Cool, i'm curious to see the results. Those check valves are a lot more affordable. If the remaining vacuum can come from the air cleaner that's a huge win.
dscott
Posts: 16
Joined: Wed Oct 07, 2015 2:59 pm

Re: What is the best crank ventilation method

Post by dscott »

So I finished testing crankcase pressure and it is the same results with both check valves on or off. At idle it is 0 pressure and when revving high and holding the rev it only spikes almost 1 psi but then it goes right back to 0 while still revving. So bassically as long as it is venting no pressure builds up. I plugged both vent hoses with my fingers and crankcase pressure started to rise. I also tried routing one vent hose into the velocity stack while the other hose was through the check valve and connected to breather and saw no difference either. So at the moment Im puzzled as how the krank vents are supposedly creating vacuum. What's weird is it shouldn't take much to create vacuum because I was able to suck with my mouth on one hose and create crankcase vacuum.
JWP
Posts: 171
Joined: Mon Jun 11, 2012 3:00 pm

Re: What is the best crank ventilation method

Post by JWP »

I think the reason the Krank Vents work is their tolerances are very tight. I think this is one of those situations where you get what you pay for and that's why Krank Vents cost so much.

Another user on the other thread mentioned using some check valves, however the tolerances in them leave a gap between 2"hg and 1 psi.
I expect the Krank Vent has a tolerance within the ranges you are working with and that's why they went to the trouble (expense) to file a patent.

I get that they are expensive and it looks like you can kinda cheat their pricing if you get one for a bike instead of the "universal" one.
The good news is you are close to 0 psi with your current setup. I wish I could speak to the Krank Vents more, however I don't have them and for the same reason you don't....$$$. So it may be a good idea to get in touch with Frank and see if he can help assure you the Krank Vents are worth the investment.


My plan will cost me as much as one Krank Vent or pretty close, but should I fail I still have use for the parts on another vehicle I'm working on.
dscott
Posts: 16
Joined: Wed Oct 07, 2015 2:59 pm

Re: What is the best crank ventilation method

Post by dscott »

I've considered setting up an exhaust evacuation system. I've seen some tests done and that seems to work. What do you think?
JWP
Posts: 171
Joined: Mon Jun 11, 2012 3:00 pm

Re: What is the best crank ventilation method

Post by JWP »

They seem to work well, but I've read the NAPA check valve is far superior to the one that comes in the Moroso kit. It's for a mid 80s GM car of some sort. They were used for air injection systems.

I considered this for mine, but with the setup I have I don't know if there is room. On a rail you are essentially limitless.
dscott
Posts: 16
Joined: Wed Oct 07, 2015 2:59 pm

Re: What is the best crank ventilation method

Post by dscott »

I'm interested in information on that Napa check valve. I'm going to research and see what I can find. I think this is the route I'm going to take.
Steve Arndt
Posts: 7420
Joined: Sat Mar 10, 2001 12:01 am

Re: What is the best crank ventilation method

Post by Steve Arndt »

Pinto EGR or air injection valve is the robust replacement for the Moroso check valve. I still plan on hooking the pan e vac up just haven't yet. I made a video...
Last edited by Steve Arndt on Thu Oct 15, 2015 10:04 am, edited 1 time in total.
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