My current PCV
Safety Car
Joined: Jul 2005
Posts: 4,275
Likes: 4
From: Vancouver WA
Originally Posted by QuickSilver2002
Yes, I have actually tried that and I still have part of it on my car. It has to be hooked up after the mufflers on a car with a full exhaust. There cannot be any backpressure for the venturi to work. I routed alum lines up into the engine bay (boy was that a PITA). You can actually see the line in the pic in the first post.
It only works at WOT and high RPM and the air that it moves is pretty minimal. It also pushes a little exhaust back upstream in non WOT conditions (it has check valves but they let a little air move between pulses at low RPM). This is not an issue if you are just venting, but it is the reason I don't have it hooked up right now. I might try it again at some point, but my current thought is that it is not worth it.
I actually have the ability to data log crankcase pressure with my setup, so I plan to do several different experiments once I get some other tuning issues worked out (I’m in the process of switching to SD and removing the MAF right now).
It only works at WOT and high RPM and the air that it moves is pretty minimal. It also pushes a little exhaust back upstream in non WOT conditions (it has check valves but they let a little air move between pulses at low RPM). This is not an issue if you are just venting, but it is the reason I don't have it hooked up right now. I might try it again at some point, but my current thought is that it is not worth it.
I actually have the ability to data log crankcase pressure with my setup, so I plan to do several different experiments once I get some other tuning issues worked out (I’m in the process of switching to SD and removing the MAF right now).
Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 2,931
Likes: 2
From: Tx
Originally Posted by QuickSilver2002
I'll post a data log within the next week or so. It will show Kpa in the crankcase.
Anyway, I logged the crankcase pressure today. Here is a quick graph of what it is basically doing.
Note: Atmospheric on the CC pressure sensor was 102 Kpa. The gridline at 101.5 kap is just below atmospheric for that sensor.
Click on thumbnail to see full size.
It looks like it is hitting about .25psi of pressure in the CC. I did make one change to the system while hooking it up. The solenoid that dumps to atmosphere now opens at about .5 psi.
I’ll be making some full pulls to redline soon. I seem to also be having a little belt slipage. I'll be throwing on a new belt tomorrow (think this one is more than a year old).
Last edited by QuickSilver2002; Sep 16, 2005 at 12:13 AM.
Melting Slicks
Joined: Jan 2003
Posts: 3,251
Likes: 4
Originally Posted by QuickSilver2002
Note: Atmospheric on the CC pressure sensor was 102 Kpa. The gridline at 101.5 kap is just below atmospheric for that sensor.
What I see is the baseline is 102kpa and on decel and cruise you have about 90kpa (vacuum) and at WOT you have about 105kpa(positive pressure). If that's correct the system is a failure. You are generating vacuum at rest and pressure at WOT. This is contrary to the desired objective to gain vacuum at WOT to seal the rings, et al. Thanks for posting the results, I wish I had that equiptment to dink around with, to offer a better option. Under cruise conditions, I don't believe GM intened the engine to be in a constatnt state of vacuum. This will probably wear out the seals quickly.
Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 2,931
Likes: 2
From: Tx
Originally Posted by IM QUIKR
QS,
What I see is the baseline is 102kpa and on decel and cruise you have about 90kpa (vacuum) and at WOT you have about 105kpa(positive pressure). If that's correct the system is a failure. You are generating vacuum at rest and pressure at WOT. This is contrary to the desired objective to gain vacuum at WOT to seal the rings, et al. Thanks for posting the results, I wish I had that equiptment to dink around with, to offer a better option. Under cruise conditions, I don't believe GM intened the engine to be in a constatnt state of vacuum. This will probably wear out the seals quickly.
What I see is the baseline is 102kpa and on decel and cruise you have about 90kpa (vacuum) and at WOT you have about 105kpa(positive pressure). If that's correct the system is a failure. You are generating vacuum at rest and pressure at WOT. This is contrary to the desired objective to gain vacuum at WOT to seal the rings, et al. Thanks for posting the results, I wish I had that equiptment to dink around with, to offer a better option. Under cruise conditions, I don't believe GM intened the engine to be in a constatnt state of vacuum. This will probably wear out the seals quickly.
It is also hard to compare this with other setups, since nobody really knows what the CC pressure is with those other setups.
Drifting
Joined: Sep 2004
Posts: 1,727
Likes: 19
From: Carson City, NV
Could you guys comment on my setup (see link). I have a 1998 N/A engine with a few mods. I used a different check valve than the stock one. I removed the OEM PCV and replaced it with a heavy duty PCV from www.mcmaster.com part # 7775K52 "viton". I installed it close to the intake between the catch can and intake port.
My PCV Setup
Thanks for any feedback you might have. I've noticed a little erratic idle occasionally since installing this. Wondering if this has anything to do with it.
Cheers
John
My PCV Setup
Thanks for any feedback you might have. I've noticed a little erratic idle occasionally since installing this. Wondering if this has anything to do with it.
Cheers
John
Melting Slicks
Joined: Jan 2003
Posts: 3,251
Likes: 4
Originally Posted by Cscokd
Thanks for any feedback you might have. I've noticed a little erratic idle occasionally since installing this. Wondering if this has anything to do with it.
Cheers
John
Cheers
John
I know it sounds simple but did you make sure that the check valve allows air flows into the intake? Then I would make sure there are no vacuum leaks and recommend an IDLE RELEARN.
Did you cap the valve cover port on the pass. side front? Hard to tell fron=m the diargram. Do you have a fresh air source? The engine is expecting a specific amount of air coming from the PCV.
Drifting
Joined: Sep 2004
Posts: 1,727
Likes: 19
From: Carson City, NV
Originally Posted by IM QUIKR
[IMG]
I know it sounds simple but did you make sure that the check valve allows air flows into the intake?
yes....arrow points toward the intake
Then I would make sure there are no vacuum leaks and recommend an IDLE RELEARN.
didn't do this yet...will do a search for instructions
Did you cap the valve cover port on the pass. side front? Hard to tell from the diargram.
no...didn't touch this
Do you have a fresh air source? The engine is expecting a specific amount of air coming from the PCV.
didn't touch the air source going to the passenger side valve cover
I know it sounds simple but did you make sure that the check valve allows air flows into the intake?
yes....arrow points toward the intake
Then I would make sure there are no vacuum leaks and recommend an IDLE RELEARN.
didn't do this yet...will do a search for instructions
Did you cap the valve cover port on the pass. side front? Hard to tell from the diargram.
no...didn't touch this
Do you have a fresh air source? The engine is expecting a specific amount of air coming from the PCV.
didn't touch the air source going to the passenger side valve cover
Thanks for the suggestions. Let me know if I missed something. QuickSilver2002, my appologies for hijacking this thread.
John
Last edited by Cscokd; Sep 19, 2005 at 12:33 AM.
Melting Slicks
Joined: Jan 2003
Posts: 3,251
Likes: 4
Originally Posted by Cscokd
Thanks for the suggestions. Let me know if I missed something.
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Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 2,931
Likes: 2
From: Tx
Make sure your fresh air source is hooked up in front of the TB, so the air can still be metered by the MAF.
I also agree that you should probably put the stock PCV valve in place. Without it, you have too much flow from the crankcase at idle and the idle air trims are probably maxed out. You have to remember that air from the PCV inlet bypasses the TB and confuses the IAC control.
If you want a vacuum on the crankcase at idle, you have to put some type of flow restrictor on the fresh air side.
I also agree that you should probably put the stock PCV valve in place. Without it, you have too much flow from the crankcase at idle and the idle air trims are probably maxed out. You have to remember that air from the PCV inlet bypasses the TB and confuses the IAC control.
If you want a vacuum on the crankcase at idle, you have to put some type of flow restrictor on the fresh air side.
Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 2,931
Likes: 2
From: Tx
Cscokd,
Make sure your fresh air source is hooked up in front of the TB, so the air can still be metered by the MAF.
I also agree that you should probably put the stock PCV valve in place. Without it, you have too much flow from the crankcase at idle and the idle air trims are probably maxed out. You have to remember that air from the PCV inlet bypasses the TB and confuses the IAC control.
If you want a vacuum on the crankcase at idle, you have to put some type of flow restrictor on the fresh air side.
Make sure your fresh air source is hooked up in front of the TB, so the air can still be metered by the MAF.
I also agree that you should probably put the stock PCV valve in place. Without it, you have too much flow from the crankcase at idle and the idle air trims are probably maxed out. You have to remember that air from the PCV inlet bypasses the TB and confuses the IAC control.
If you want a vacuum on the crankcase at idle, you have to put some type of flow restrictor on the fresh air side.
Drifting
Joined: Sep 2004
Posts: 1,727
Likes: 19
From: Carson City, NV
Thanks for the advice you two...my car is N/A and not SC or TC...I'll change back to the stock PCV and try it for a while. Since I did not touch the stock hose from the TB to the passenger side valve cover at the oil fill pipe, I should be ok there right? Do you think I should do an idle re-learn procedure on it? Seems since I installed my LGLTs my idle has been irratic at times.
John
John
Melting Slicks
Joined: Jan 2003
Posts: 3,251
Likes: 4
Well now, since you have installed LTs you really should have a professional tune to help with the idle and get the most performance from the headers. Changing exhaust headers can make the computer think you're running lean so the idle will be effected. Put her on a dyno and get her tuned. You're gonna love it.
Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 2,931
Likes: 2
From: Tx
Disregard the results I posted above.
I kept thinking about my old results and realized that something was totally different now. The car previously hissed as I shut it down and lately there has been silence. I realized that I had lost most of my vacuum on the crankcase. After further investigation (including a compression test….) I found that I had a big open port in the side of my catch can (#2) where the plug fell out (duh!!!!).
I just ran a quick log again and the results were totally different. It runs at about 75kpa at cruise. It then holds a vacuum under boost until about 7psi and then it goes to about 103kpa. I’m still working on the SD tune in that area, so I have not pushed it to redline.
I think I’m convinced that a nice check valve would be worth it. I hate paying $100 for the krankvent valve, but it would be worth it if it really worked. I think the vacuum will hold most all the time if I only vent when slight pressure forms.
Anyone ever had one of those KrankVent valves in their hands. I would like to ask a few questions about how it flows…. I basically need a check valve that has very low cracking pressure and can flow a lot of air if it needs to.
If anyone knows of a source for a cheap vacuum regulator that would also be great.
I kept thinking about my old results and realized that something was totally different now. The car previously hissed as I shut it down and lately there has been silence. I realized that I had lost most of my vacuum on the crankcase. After further investigation (including a compression test….) I found that I had a big open port in the side of my catch can (#2) where the plug fell out (duh!!!!).
I just ran a quick log again and the results were totally different. It runs at about 75kpa at cruise. It then holds a vacuum under boost until about 7psi and then it goes to about 103kpa. I’m still working on the SD tune in that area, so I have not pushed it to redline.
I think I’m convinced that a nice check valve would be worth it. I hate paying $100 for the krankvent valve, but it would be worth it if it really worked. I think the vacuum will hold most all the time if I only vent when slight pressure forms.
Anyone ever had one of those KrankVent valves in their hands. I would like to ask a few questions about how it flows…. I basically need a check valve that has very low cracking pressure and can flow a lot of air if it needs to.
If anyone knows of a source for a cheap vacuum regulator that would also be great.
Last edited by QuickSilver2002; Oct 5, 2005 at 12:17 PM.
Safety Car
Joined: Aug 2004
Posts: 4,067
Likes: 62
From: Houston Texas
A very good piece QS 2002, it has been very informative. I was reading this article about a dual krank vent valve set up, if you will read it and tell me what you think.
http://www.stealth316.com/2-krankvents.htm
On a side note, I am buying a c6 and going with a s/c with about 6psi. Would it not work well if I were to simply leave the stock PCV and run a hose off the valve cover through a one way by pass valve to a small breather. I believe this would maintain vaccum at idle and releave crank case pressure under boost. Thanks for your time.
http://www.stealth316.com/2-krankvents.htm
On a side note, I am buying a c6 and going with a s/c with about 6psi. Would it not work well if I were to simply leave the stock PCV and run a hose off the valve cover through a one way by pass valve to a small breather. I believe this would maintain vaccum at idle and releave crank case pressure under boost. Thanks for your time.
Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 2,931
Likes: 2
From: Tx
Quick update.
I got the ET Performance KrankVent valves in the mail today. The cost was high, but it does seem to be a really good valve. I'm amazed how low the cracking pressure is and it also seems to flow a decent amount of air.
I replaced the solenoid on catch can #2 with it. The results are very good so far.
I made a few quick pulls tonight and it held a vacuum up to about 8psi and then it just went to atmospheric. This is better than I expected with the current setup (the restrictor inlet side is a known vacuum leak once in boost).
I've got a few more tweaks to make and should have a final design by the end of the week.
The best part of this is the added low end tq the motor has. The throttle is very crisp. I drop it to 3rd at about 80 and I loose all traction if I nail it all the way (that is with only about 6psi or so @4900 rpms). It pulls so dam hard by 6k that everything feels like it is starting to blur.
I can’t wait to get it on a dyno for the final tune and to see how much power she is making. I'm hoping to do that next weekend.
I got the ET Performance KrankVent valves in the mail today. The cost was high, but it does seem to be a really good valve. I'm amazed how low the cracking pressure is and it also seems to flow a decent amount of air.
I replaced the solenoid on catch can #2 with it. The results are very good so far.
I made a few quick pulls tonight and it held a vacuum up to about 8psi and then it just went to atmospheric. This is better than I expected with the current setup (the restrictor inlet side is a known vacuum leak once in boost).
I've got a few more tweaks to make and should have a final design by the end of the week.
The best part of this is the added low end tq the motor has. The throttle is very crisp. I drop it to 3rd at about 80 and I loose all traction if I nail it all the way (that is with only about 6psi or so @4900 rpms). It pulls so dam hard by 6k that everything feels like it is starting to blur.
I can’t wait to get it on a dyno for the final tune and to see how much power she is making. I'm hoping to do that next weekend.
Safety Car
Joined: Aug 2004
Posts: 4,067
Likes: 62
From: Houston Texas
Thats great news, did you run both valves the same way that they illustrated on the web site? Or did you completely remove you PCV and put the smaller valve in place of it? I think I am going to try runing the valve with the PCV, and with the large valve, run it off the back of both valve covers to a T and then to a vented catch can. From what they said on there site, this should work well.
Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 2,931
Likes: 2
From: Tx
Originally Posted by vertC6
Thats great news, did you run both valves the same way that they illustrated on the web site? Or did you completely remove you PCV and put the smaller valve in place of it? I think I am going to try runing the valve with the PCV, and with the large valve, run it off the back of both valve covers to a T and then to a vented catch can. From what they said on there site, this should work well.
The original design of the valve was for big v twin engines and the concept as described on their website will not work on a v8. The valve is however an amazing check valve with extremely low cracking pressure and it works great as a one way venting valve.
