fireant

I've had this smoking on downshift while hard braking/turning problem and I was worried about blowby. I did a compression test and it was all 200-205s (D16A6 with thinner head gasket). This oiling problem was around before I put the new gasket on BTW. I also went through a new PCV, but no help, so I decided to try an inline catch can.

This weekend was my first time to track the car with a new catch can. It is a sealed canister between the PCV valve and the PCV inlet on the manifold.

Everything starts off fine, but within a few laps my old oil burning problem starts. After the session I look at the window on the catch can and its filled to the brim (1/2 quart) with oil.

When I pulled the hose off the inlet to the IM, it was drooling oil. I plugged up that vac inlet and routed the hose coming from the catch can into a plastic soda bottle. I taped the hose securely in the bottle, then punched some holes in the neck for air to escape.

I finish the track day without any more oiling issues. Not a drop, and the car felt stronger.

So what is going on with this IM sucking up so much oil when I downshift and burning it off as soon as I get back on the throttle? Is this a common thing on A6s that requires bypassing the PCV system? The motor is otherwise healthy with perfect compression and leakdown tests, and new stem seals... just tons of vacuum.

For now I have gutted the spring-valve out of my PCV and put a little filter on the catch can instead of the hose-to-bottle thing. I know its not putting suction on the crank case, but there's definitely a free path for air to escape.

Kaan

iTrader: (3)

I had a Moroso catch can... in my old A6 motors i would tap between cylinder 1 and 2, take the sensor out between cylinder 3 and 4... and i'd also take out the PCV and run it to the can too. Its common.

If thats your first track day with it, plan on getting a new O2 sensor too they like to eat them.

fireant

Its my third track day out. The car is really fast, even on non-R tires. I'll check my O2 sensor, its about 2 yrs old now.

Kaan

iTrader: (3)

oh you'll know... when the check engine light comes on. just be aware and keep one in the box incase it happens. On my CRX the rev limiter/fuel cut stops kicking in when the light comes on... so you might over rev it a bit. just FYI.

JOE BD-0

D16A6 Road Racers... do you use a PCV?
No, the pcv hole is plugged w/freezeplug. There is a hose to a catch can from the stock valve cover hole. Not much oil comes out from there on my car, only a little. The motor is NASA H4 100% legal. I've seen a b series race car try to vent to a catch can from the pcv hole and the valve cover hole at the same time and it filled up two water bottles very very quickly......good luck

fireant

Thanks Joe. It held up for the last part of the day fine. For the next event I will bring a spare pcv valve incase the now-gutted one is a problem, or I can just put a rubber cap on it and try using the valve cover only.

So with the crank-case only venting through the valve cover, are there any oiling issues? I mean all the excess air pressure goes up through the oil passages to escape right? So the oil drooling down has air coming up... no problems?

Lo-Buck EF

i also vent off the valve cover (on my b-series tho). alot of drag guys figured out that venting the back of the block with high boost would fill the catch can in one pass. but when they vent just off the valve cover, the crank case pressure is where it needs to be but the can doesn't fill up. its almost like using the engine as a baffle because it has to build pressure to push oil all the way up to the valve cover

fireant

Makes sense. Do most H4 folks do this?

JOE BD-0

For the record...I don't think I would bet on a rubber cap, especially at the race track. My freezeplug cap (approx 1") is made of metal (brass?), and was seated in the pcv hole nicely with the hammer and some hondabond. No oiling issues or problems have been reported thus far from guys using this method on several West Coast H4 engines assembled by the "b"uilder....good luck

CW-ITR

iTrader: (11)

Sorry for digging this post up. Can you or someone with the same set-up post pictures of the mod? Thanks.

Tyson

this is a freeze plug.

place at the back of the block, in place of the black breather box.

Crx Jimmy

A baffled pan would probably help in this case as well.

dirty19

iTrader: (1)

Im surprised Jimmy C "Slammed 93 hatch" hasn"t chimmed in......
I know he has used the D series for a while now.

FormulaIntegra

Probably cuz he sold all his D stuff to me, including the engines. He said he's stepping up to H2, but I'm not sure what engine he's running now. Even the built D16Z6 engine he had still had the PCV valve, and he told me he just routed that and the valve cover vent to a catch can. I'm running them both to a 1 qt. Dasani bottle that fits nicely in the stock airbox hole in the front, passenger corner of the engine bay, just behind the headlight. Last race weekend, I had about a half a cup of oil in the bottom of the bottle, but no worse than that.

fireant

Just an update on my setup:

Currently the valve cover vent is just like stock, connected to the intake pipe.

The black box is in place, with a gutted pcv valve that goes to a catch can with a filter.

The PCV inlet on the intake manifold is capped with a rubber vacuum cap.

I had no oiling issues at all at the last track day, and the car is running strong and idling well.

The only difference I really noticed is an increase in brake boost, due to sealing up a vacuum 'leak' in the manifold.

FormulaIntegra

So, this discussion got me wondering a bit more about crankcase pressure, and in doing some research, have come up with a question: Which is better: sealing off the PCV breather system and letting the pressure force it's way back up to the valve breather hose, or letting it naturally breathe through the PCV tube?

I'm not concerned with where the blow-by pressure goes, as that appears to be strictly an emissions argument, and not really a concern for a dedicated track car. Way back when internal combustion engines were new, designers relied on engine seals to restrict positive crankcase pressure, and over time, the blow-by gasses would simply work their way through (osmosize, if you will) those seals. As power became greater, so did the pressure, and a breather tube was required to maintain the integrity of the oil seals. When the issue of emissions standards became evident, it was determined that this breather tube was a major source of hydrocarbon emissions, and a major contributor to smog, hence the PCV system.

I've heard some say plug the system up with a freeze plug and let the positive pressure force it's way up through the oil journals into the valve cover, but do you risk damaging your crankcase oil seals by doing this? Is there any gain horsepower-wise by restricting the PCV breather?

Others (and this is how my car is set up) vent both the valve cover and PCV tube (with or without the valve...I haven't figured out how to remove the valve from the housing yet, so my valve is still there and functioning) to some form of a catch can. I would tend to think allowing those pressurized gasses to escape from the crankcase would be beneficial to you're crankcase seals, as well as reducing the back pressure against the underside of the pistons. In theory, would it be most beneficial to have an actual vacuum in the crankcase?

Anyone have any concrete evidence as to which way is better, power-wise, durability and longevity-wise, or otherwise, for a dedicated track-only car? Is it one of those trade off/compromise things (i.e.: more power with the system sealed, but you'll be replacing crank seals more often, etc)?

At some point, I'm thinking I'm planning on getting rid of my charcoal canister and all the related components, because it's a great place for a remote oil filter relocation, or maybe for a better catch can. I'm just wondering what all needs to be routed where when I do that, but I think there's already some posts on that front.

fireant

The charcoal canister you speak of is for something different. It captures the expansion gasses from your fuel tank, as it can expand with temperatures just like the air in your tires. It "stores" this vapor, and when you turn on the car for a brief moment the purge-cut solenoid is opened. This electronic valve opens a vacuum line that sucks open the valve on top of the purge canister, allowing the hose going to the manifold to suck out all the vapors. The point of this complexity is to keep the electronic solenoid removed from the area of the fuel vapor. There's not a real advantage to removing it besides making the engine bay tidy... I guess the hose that feeds from the tank into the canister should be vented and filtered.

Depending on the PCV valve you have, gutting it is a matter of hitting it with a small dremel bit to get rid of the lip inside where the spring-loaded bit closes, turning it into a right-angle hose fitting.

There are lots of theories and ways to do your PCV system, and some of the info is from FI folks who are dealing with something entirely different.

The way I see it is the oil goes down from the head to the pan, so forcing air upwards through there is not as good...but its probably not a real factor on an NA motor. Honestly I think if I just changed to a 'tighter' pcv valve, I could run my motor as stock...but I dont have any idea what or how much tighter I should be looking for. I do know that my manifold was seriously pulling hard on that PCV port enough to keep a brand new stock PCV valve stuck open almost always.

solo-x

My ST D16z6 didn't need any modification to the stock PCV system and I had no oil problems with it. My DSP ITR on the other hand.... I was using the stock PCV system and kept getting massive amounts of oil smoke after a long decel or a hard autocross run. So I put a catch can setup in that bypassed the stock black box and used a large, baffled catch can, but still utilized a PCV system. The extra ability to evacuate oil vapor from the crank case became an even GREATER issue. At the last autocross the car was dumping so much oil into the exhaust the engine almost wouldn't run after I finished a run. The ECU got confused and started dumping more fuel, etc. It was _bad_. I gave up and punted, zip tying a gatorade bottle to the brake lines near the ABS motor and dumping the hose off the PCV valve on the catch can into the bottle. (I heard you like catch cans....) I capped everything else pcv related and enjoyed no longer fogging the paddock with oil smoke.

vinuneuro

Sounds like leaky valve seals.

solo-x

Please read my entire post before "fixing" something that isn't broken.

sackdz

solo, are you saying that your larger, baffled catch can was not separating oil from the vapor? And it was worse than the stock setup?>

solo-x

I was still routing the catch can to the IM through a pcv valve. The first 2-3 runs had no problem, but each run after that would gradually have more and more oil getting into the engine. Turns out, the oil vapors were condensing in the hose to the IM, and once it started forming droplets, they would run down the hose, into the IM, and then smoke like crazy. I've since routed the hose to a seperate bottle and blocked of the IM. The 2nd bottle has no oil in it since doing this as there is no vacuum to draw the oil vapor out before it can condense in the catch can.

It was worse with the external catch can because a) it could move more vapor b) the hose to the IM was downhill.

Tyson

moral of using a catch can, separate it completely from the intake.

fireant

I'm about to get ****-retentive about this...

I have my crankcase breathing into a vented catch can (with the IM port sealed off), but I still have my valve cover breather connected to the air intake tube, like stock.

Would that create any upward vacuum on the crankcase/valve cover? If so, I should probably just put a filter on the valve cover breather, rendering the whole crankcase/valve side of things 'neutral' from both ends air-wise.

Tyson

since the title of the thread is "D16A6 Road Racers... do you use a PCV?", the answer is, "NO, you eliminate the PCV by plugging the airbox opening at the back of the block that would lead to the PCV and vent the valve cover to a vented catch can and plug the remaining holes in the intake tube and manifold."

but you keep asking questions not following the above answer.

to answer your last question, why wouldnt you follow the right way to vent your engine in the first place?

i've asked you this question before, its not the first time youve asked about catch cans, venting, etc. but you still refuse to do it the right way.

just vent it all to a vented catch can. done. its totally reversible if you need to pass smog or whatnot.