From one of the drawings, it looks like it pulls air from the valve covers down into the exhaust? Won't that possibly cause cat failure? Or would the connection be past the cats?

 

Most installs I've seen on domestics put it ahead of the where the cats would have been.

 

DO NOT install those venturi tubes on a car with a full exhaust.

Problem A: It isn't going to be creating enough vaccuum when you still have the backpressure of the exhaust.

Problem B: Even with a check valve, it can still cause a nasty ballon/burst to the valve cover if/when it backfires.

The check valves do a good good of curtailing backfiring, but it's still possible. Problem is installing those upstream of any restriction. They are meant to be installed right after the header collector.....inches away from no exhaust system at all (race car)

That stuff you found Gee has been around for years and years. Unless you are running a straight exhaust with no muffler, a tail pipe that ends up being about 1 foot from your collectors, etc.... I wouldn't even bother.

Don't even think about putting something like that up ahead of a CAT.... you would just pump exhaust gases into your cranks case...

Sorry to be the bearer of bad news, maybe I can save you a few $$

 

I think that is why Dennis made the comments, which he did.

 

I understand where you are coming from, however with the currant exhaust systems on the Nisson, back pressure is not a problem with the currant cam timing. Velocity will over ride any back pressure from the exhaust. 3 lbs of vacuum should be plenty at upper rpm's.
Currant system are pulling over 7 lbs of vacuum, and is needed with the low tension rings run in drag racing. Any backfire stock right now can cause just as many problems as this setup. I'm sure that this will work fine for the currant stock setups and PVC filter setup. Time will tell

 

Dave-B,

If this is the case why are the guys who have installed this mod experiencing little to no oil in the filter bowl under normal driving, but significant amounts, meaning a lot more than none, at WOT or very spirited driving?

As a reference point on my 03.5 G35 I noticed oil all around the center bolts under the plastic washers Crawford provides w/his plenum...it was pretty bad. I would hate to think I would have run 13.9's in the 1/4 mi if my engine wasn't retarding power b/c massive blow by was coming into the intake manifold and mixing with the fuel turning it to $hit.

 

I still believe the ingestion of oil through the intake manifold is very minor and I think the placement of these catch cans are causing increased oil production. I couldn't explain to you why because I don't fully understand why the engineers do what they do sometimes and I'm pretty most everyone doing this mod doesn't fully understand the engineering behind the VQ35 emission system.

Consider this, if our cars were consuming significant amounts of oil we'd be bitch-ing. I don't know about your VQs, but mine have never consumed oil over 5000 mile oil changes and I rarely read about a VQ35 with oil consumption problems. I drive my VQs damn hard too. I also rarely hear about VQs blowing smoke at WOT, and I'd think if we were really burning significant amounts of oil at WOT, wouldn't we'd be seeing smoke at WOT and on roadrace situations?

Other things to consider are:

1) The oil gets smeared along the runner. It's not like huge oil droplets are going to lifted off runner walls and be sucked into the combustion chamber. The air is going to roll and pull the oil across surface. Not pull it off.

2) Even if a little oil finally makes it's way down into combustion, it's going to get vaporized on one cycle. Seeing that at 5000-6500rpms, there 80+ cycles happening every second, therefore I doubt one droplet of oil would cause a timing/performance drop.

These are simply my opinions. That's all.

 

I hear ya, but I am just recalling how dirty my Crawford would get w/oil on my old Sedan...I used Snowmobile trailer concave washers with adhered rubber gaskets to better seal the upper bolts on my crawford install for my coupe and so far no oil blow by...but...even if this $hit is lining our intakes it can't be good for air flow...IE, the opposite of a good port and polish ya know...so if anything you are providing a more slippery surfacr for better air flow at the least I would think.

I also can't see how simply placing a catch can would increase oil production, but I am no mechanic as I am quick to point out. It does seem like a nice little proactive tool though in preventing BS build ups and blow bys in our engines.

 

I couldn't tell you why either. Also, I don't think it's a "bad" mod at all. I won't be doing it, but I don't see how it can hurt.

 

Just finished my install and found a few drops of oil already after a 100 km highway round trip to work and back. No high sped runs, just normal driving.

This mod works like a hot damn!

 

Wow, can't believe my little mod. would stir up so much discusstion.

Here is a very basic description of how a PCV system operates and why it's needed. From reading the posts here, I think a lot of people are forgetting that the simple little PCV valve has a spring loaded pintle that meters the flow of blow-by gases back into the manifold to be burned. This action is controlled by vacuum and varies with engine load.

"PCV - what does it stand for? Positive Crankcase Ventilation. Let's pick that apart a word at a time and see just what this little piece of hardware does. Let's start with the word Crankcase. The crankcase of an internal combustion engine is that portion of the engine that contains the crankshaft (no duh), the connecting rods, the under side of the pistons. It is also connected via passages in the casting of the engine block to the upper engine, the valve train, the camshaft and the timing gears and chain. The most critical part of the above components regarding the PCV is the pistons. Fuel and air enter the combustion chamber on the top side of the piston where the fuel burns and forces the piston down. That motion is converted into rotary motion of the crankshaft via the connecting rods and the crankshaft. That is what drives your car.

I mentioned that the combustion takes place in the combustion chamber. Ideally all the combustion gases which are in the combustion chamber stay there until they are exhausted via the tail pipe, however as engines get older (and even in brand new engines) some of the combustion gasses get past the sealing hardware on the pistons, the piston rings. As the engines age, the clearances between the rings and the cylinder walls increases and more of the combustion gasses escape into the crankcase. These combustion gasses contain acids and other harmful by-products of combustion which used to escape from the crankcase via a breather tube which exited into the environment. All that garbage going into the atmosphere makes smog and other breathing problems in our environment. In addition, the moisture in those gasses also caused sludge to build up in the engine, so the PCV system also helps reduce the sludge build up. So the engineers decided to capture all that stuff from the crankcase and ventilate it in a way that it becomes less harmful. Notice I said less harmful, not pristine. Notice also that we have covered the second word, Ventilation.

What's so positive about Positive Crankcase Ventilation?

It is called positive since there is a positive force that removes the combustion vapors from the crankcase. That force is vacuum - just like the vacuum that sucks the dirt out of your rugs and furniture only this vacuum is derived from the engine, not from a Hoover. Vacuum derived from the engine is a rather sensitive resource, that is you don't want to steal any vacuum from the intake manifold when the engine is idling. However, when the engine is running at highway speed the engine can afford to allow a "vacuum leak" to occur via the PCV Valve. It is a metered flow of air, controlled by a needle valve inside the PCV Valve. When the engine is at idle and vacuum is high the force of the vacuum overcomes the force of a spring inside the PCV Valve and it is closed down to allow a flow of about three cubic feet per minute. When the throttle is opened and the intake manifold vacuum is reduced (closer to atmospheric) then the spring in the PCV Valve forces the valve to open allowing up to six cubic feet per minute of flow to occur."

I'm no expert, but I do have a BSME degree and work on all of my own cars. Just wanted to share a little postive knowledge and a simple mod. that's been used by many racers (one form or another) and myself with very good results. By the way, the clear plastic canister and filter have not been degraded by engine oil at all, I use Mobil 1 5W-30.

FWIW and enjoy,

djl

 

holly ****!!!! I can't believe you would take the time to give such good, detailed information! Thanks - even though I think the floodgates are open now (no I don’t mean PCV flood gates, I mean debate).

I'm certainly not debating one way or another, but I do appreciate this type of info! It's what brought me to this forum originally.

 

I don't want to argue with you, but read what you wrote. Velocity overcomes backpressure? Backpressure doesn't have a damn thing to do with cam timing, it has to do with a muffler or other restriction blocking the flow of exhaust. Increasing the power output of the car means buring more air/fuel. I think you meant volume. The only thin I could see increasing the velocity of the exhaust gasses would be if you had some high over-lap cams with a SC on the motor, and you might be "blowing through the hole".

As far as exhaust flow goes, the more exhaust the engine is pumping out, the more backpressure will be there given the same restriction (muffler).

To make this work effectivly, you are going to have to run no exhaust system at all, straight out a collector, which is why the venturi tubes are meant to be mounted in a collector.

Current systems? The G35 doesn't use an exhaust scavaging PCV system that I know of. A backfire with an exhaust venturi will cause the valve cover, or whatever else it's hooked up to, to ballon, and/or crack/be destroyed. I know this from experiance, when a honda all motor race car had a backfire, and blew the valve cover right off the motor. When I say race car, I mean tube frame, glass front end, etc..

It's your money and time, but I wouldn't waste it on this type of thing. You might NEED something like this if you were running low tension rings, but then again, it'd be an all out drag car, and this wouldn't even be a question if it would work or not.


Bottom line, sperating the crankcase vapors from re-entering the intake will produce gains in the form of increased timing, because the octane rating won't be taking a hit.

2 ways I see of doing this. Add breathers (LARGE) in several different spots on the valve cover, so the crank case gasses can escape on their own. NOT EMMISIONS LEGAL

Build a catch can that seperates the oil vapor from the crankcase gases, install it inline, and have fun.

 

i just hit Home Depot and Advance Auto Parts.

Now, I have my oil catcher. Great idea, and thanks for the parts list!!!

 

Cracker

Let's not generalize, When I write about or post about something, I'm talking about the VQ and my car in general. When you spend the time I have understanding what Nissan has done with there cam timing in the rev-up engines, you would know where I was coming from. The factory exhaust system is very free flowing and in fact most header installs show nothing or a loss of drivability, This is one special little engine that is tuned very well from the factory with many well figured out items that work well with each other. Many very sharp people have spent many hours trying to make HP gains. This is not a Ford or Chevy engine we are talking about here. Its a very tech **** engine. Its been a challenge for me just trying to figure out what and how the camshafts work and the brilliant design behind the design.
There is no bottled neck design in the factory setup exhaust. There should be plenty of velocity to pull vacuum from. The future looks great when you want to race a lawn mower.