Reviving an old idea - Catch Can for the LS

mholhut

mholhut

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I gave this some thought back in my days with LLSOC and we tossed it around there with nothing evolving. Seems like a popular accessory for preventative maintenance if not some performance gains so I thought I'd bring it up. By any means, I'm no expert and I'm going to use some laymans terms, so if you have some input, please chime in.

oil_catch_can.jpg


The LS vents compression gasess from the cylinder heads back into the intake tract. I think this is called Positive Crankcase Ventilation (PCV). This venting is hot oil filled air that gets reingested into the motor. There's some obvious detriments to performance with this... oil buildup in the intake and the fact that your car is reingesting hot air.

If you don't already know, a catch can or con can (short for condensation can) is a canister that separates the oil from the venting gas before returning it to the intake. By placing the catch can out of the engine bay where air can cool it, the hot gas condenses against the cooler can and causes the oil to condense in the container where it can be drained later. Think of as the opposite of a cold bottle of beer on a hot/humid day.

There are two places where the heads vent into the intake. On the driver's side of the car, it vents from the valve cover to the intake snorkel just after the MAF sensor. On the passenger's side, it vents from the valve cover to just before the TB.

So, a few things to discuss:
  • Would each vent from the valve covers require their own catch can or could they be "T'd" together to one can?
  • If you were to construct one, it would have to be made out of somthing that could withstand the temperature of the hot PCV gas.
  • Would the catch can require an air filter-type vent or should it be a closed system?
  • Would this be a worthwhile endeavor if you could make one for $50 in parts?


Any ideas?
 
I'll take a crack at this, since we used to use these on the capris and triumphs that I used to roadrace. We used the very scientific terminology "windage vapor and blowby recovery can"

mholhut said:
  • Would each vent from the valve covers require their own catch can or could they be "T'd" together to one can?
Click to expand...
only if you can keep the condesing can close enough to both sources to keep the vapor from condesing in the hoses. Otherwise the vapor will start to deposit itself on the inner wall of you hoses and might potentially block off the hose
mholhut said:
  • If you were to construct one, it would have to be made out of somthing that could withstand the temperature of the hot PCV gas.
Click to expand...
Well, It would have to handle a 300-350 degrees or so remember the vapor is not all that much higher than the oil in the motor. I would think that a good quality thermoset plastic tank would be able to take the heat and the vacuum
mholhut said:
  • Would the catch can require an air filter-type vent or should it be a closed system?
Click to expand...
It should be a closed system, otherwise the pcm might have issues with unmetered air entering the intake. As an additional gain, any vacuum that you could maintain in the system helps the piston rings and valve stem seals work improving chamber sealing and compression. Also the vacuum created by the system would reduce the frothing and windage of the oil, which inturn would reduce the vapor that gets formed in the first place.
Drag racers use a system that is tapped into the exhaust (no cats obviously) and the hot exhaust flow creates a huge vacuum in the crankcase. No pressure reduces the frothing and windage to nearly nothing so very little vapor is sucked out of the crankcase.
mholhut said:
  • Would this be a worthwhile ndeavor if you could make one for $50 in parts?
Click to expand...
I would be very interested. The system would need to make a pretty good amount of vacuum and the rest of the pcv system would have to revised. but it is a good idea.
 
mholhut said:
I gave this some thought back in my days with LLSOC and we tossed it around there with nothing evolving. Seems like a popular accessory for preventative maintenance if not some performance gains so I thought I'd bring it up. By any means, I'm no expert and I'm going to use some laymans terms, so if you have some input, please chime in.

oil_catch_can.jpg


The LS vents compression gasess from the cylinder heads back into the intake tract. I think this is called Positive Crankcase Ventilation (PCV). This venting is hot oil filled air that gets reingested into the motor. There's some obvious detriments to performance with this... oil buildup in the intake and the fact that your car is reingesting hot air.

If you don't already know, a catch can or con can (short for condensation can) is a canister that separates the oil from the venting gas before returning it to the intake. By placing the catch can out of the engine bay where air can cool it, the hot gas condenses against the cooler can and causes the oil to condense in the container where it can be drained later. Think of as the opposite of a cold bottle of beer on a hot/humid day.

There are two places where the heads vent into the intake. On the driver's side of the car, it vents from the valve cover to the intake snorkel just after the MAF sensor. On the passenger's side, it vents from the valve cover to just before the TB.

So, a few things to discuss:
  • Would each vent from the valve covers require their own catch can or could they be "T'd" together to one can?
  • If you were to construct one, it would have to be made out of somthing that could withstand the temperature of the hot PCV gas.
  • Would the catch can require an air filter-type vent or should it be a closed system?
  • Would this be a worthwhile endeavor if you could make one for $50 in parts?


Any ideas?
Click to expand...

I kinda made one of PVC for my SHO... every oil changed I drain the water/oil from the can. I had few failed designs, but this last one seems to work good. I know Paul has a vacuum valve on his to seal at certian vacuum and open at idle, mine is close until I drain it.

I can get pictures if you like. I have considerabally reduced the oil ingested into the surge tank on the 3.4L V8.
 
JES_LS said:
I would be very interested. The system would need to make a pretty good amount of vacuum and the rest of the pcv system would have to revised. but it is a good idea.
Click to expand...

Like I said, I'm no expert... but what are the other parts of the PCV system that would need revisions? Seems like this mod for other vehicles is a simple interuption of the vent hoses between the valve cover and the intake.
 
Mac98SHO said:
I kinda made one of PVC for my SHO... every oil changed I drain the water/oil from the can. I had few failed designs, but this last one seems to work good. I know Paul has a vacuum valve on his to seal at certian vacuum and open at idle, mine is close until I drain it.

I can get pictures if you like. I have considerabally reduced the oil ingested into the surge tank on the 3.4L V8.
Click to expand...

Ahhhh Mac, I forgot you were here ;)

Yeah, I like Paul's design with the thin-walled aluminum tube... I was just surfing at v8sho.com and rediscovered that thread. I'm just worried about the frequency at which liquid accumulates and how often it would need to be drained.

Are there any benefits to the thought that the PCV air can be cooled sufficently to reduce intake temps, or am I barking up the wrong tree with my thinking?

And then, what are the possible negative aspects of doing this... any way to botch the car up bad other than having the gas condense in the tube leading to the catch can?
 
mholhut said:
Like I said, I'm no expert... but what are the other parts of the PCV system that would need revisions? Seems like this mod for other vehicles is a simple interuption of the vent hoses between the valve cover and the intake.
Click to expand...
Well the PCV valve itself would need be gutted or altered so it was open to the intake less, letting the system build more vacuum than normal.
Also the other idea of only building vacuum to a certain level would be important as well.
What is the peak vacuum on the other SHO's system?
 
Well, the cooling of the gases with pvc over metal I would have to measure temps and get back to you. I get about 1/4 to a half a cup of oil/water my last oil change, I will let you know when I change my oil here soon. I also plan to change plugs this winter, so the intake will get cleaned.

I can say this, I had different design last year, which fail due to light materials, but when my cams were welded I had very light oil less than normal for (15k mile since plug change) in the intake. I have since attributed that accumulation to my design flaw.

I will snap some photos, I will also be remaking it this winter to better fit in the fender(my proto type design if you will needs refinment), where the silencer once was. I have also check the hoses repeatedly, and they still remain clear.
 
Cripe, I couldn't tell ya what the peak vacuum on the SHO would be. Mac, can you drop Nimz a line with that question?

From what I understand, only the 2000-2002 V6 LS has a PCV valve... none is listed for the 2000-2002 V8 on either Fastpartsnetwork.com, autozone, etc. I'm not sure about the '03+ LS's and I don't know if the absence of one helps or hurts.
 
Mac98SHO said:
I will snap some photos, I will also be remaking it this winter to better fit in the fender(my proto type design if you will needs refinment), where the silencer once was. I have also check the hoses repeatedly, and they still remain clear.
Click to expand...

There's another issue... what are you using for hoses that withstand those temps and that vacuum?
 
sorry, I have a v6 so I was paying much attention to what the V8 has.

I'll have to research the V8 a little more.
 
mholhut said:
Cripe, I couldn't tell ya what the peak vacuum on the SHO would be. Mac, can you drop Nimz a line with that question?

From what I understand, only the 2000-2002 V6 LS has a PCV valve... none is listed for the 2000-2002 V8 on either Fastpartsnetwork.com, autozone, etc. I'm not sure about the '03+ LS's and I don't know if the absence of one helps or hurts.
Click to expand...

Yes, will send email him this morning at work.

mholhut said:
There's another issue... what are you using for hoses that withstand those temps and that vacuum?
Click to expand...

Fuel Line (5/8 I think)- I will post pictures tonight. I actually have the PCV closed off and am just using the Valve cover vents. There is possitve pressure at idle.
 
Mac98SHO said:
Fuel Line (5/8 I think)- I will post pictures tonight. I actually have the PCV closed off and am just using the Valve cover vents. There is possitve pressure at idle.
Click to expand...

Was there alway positive pressure or just after you blocked off the pcv?

you might want to consider adding a two port vacuum reservoir with a check valves to maintain some vaccum at idle. Like one from a cruise control unit, maybe.
 
Yes, but more so with the pcv blocked. It is a closed loop syem so at idle the intake pulls air thru can. Will post a picture here few minutes.


JES_LS said:
you might want to consider adding a two port vacuum reservoir with a check valves to maintain some vaccum at idle. Like one from a cruise control unit, maybe.
Click to expand...

Not sure I follow here, but to just let you know... cruise is electronic on this car. Last time I checked at least it was. :D
 
I meant a vacuum reservoir off of another car to use as a way to maintain continuous negative pressure in the crankcase, I was just thinking of how some of the older cruise controls used a good medium sized ball shaped chamber to hold some vacuum at all times.
 
Gotcha on the reservoir.

But I not sure why you would want to maintian vacuum on the crankcase. Since the orignal design (OEM) allows the PCV to breath at idle, and closes at set vacuum on the intake. The way I am thinking (could be off) the crankcase is alway at positvie pressure it just bleeds thru the valve cover vent back into the intake.

All my little condensation can is meant to do limit or remove the oil blow back into my intake. On the 3.4L V8 there is set o secondairies that will get gummed up overtime and need to be cleaned. I just trying to prolong time between teardown and cleaning and maintian airflow without degradation(sp?)

Seems to be working so far....... Had this or a simalar setup for over year now. I once was just venting to atmoshoere, but smell was annoying.
 
Well there are a couple of reasons.
1. If you continuously pull a vacuum on the crankcase, the piston rings and valve stem seals will seal better allowing less blowby and other contamination of the crankcase oil.
2. Oil foaming and windage will be reduced also reducing overall oil vapor in the crankcase.
3. The pcv is open at idle, allowing the crankcase positive venting to the atmosphere, which in later cars like ours translates to the intake.

I have had the same issues of buildup in the intakes of several fords. I have converted a couple to constant vacuum systems in an effort to reduce the buildup. The real issue is what to do with the vapor, that is where the condenser can would come in.
condensing, and possibly filtering the oil for recycling.
 
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