NITROUS OXIDE ( nos / n2o ) advice forum

I am going to fit an oil catch can to my TVR Chimaera 450.
At the moment the idea is to have twin flame traps on the rocker covers with 19mm hose to a twin inlet tank.

The tank will be alumnium, at least 1 litre capacity, baffled, have a sight tube, a filter/breather to atmos and a drain plug.

Any thoughts?

In the streetlegal dragracing events in which I participate an oil catch can is mandatory because of the bikers who compete there aswell.
I have a simple diy catch can which consists of a powersteering canister from a Toyota Starlet and a few sturdy hoses which don`t collapse under vacuüm.
Keeps the oily gunk out of the intake manifold. The Map sensor also stays clean.
All from the scrapyard. Total cost 10 Euro.





Paul.

Cheers Paul, I like your penny pinching style.
I will bodge something similar up and test it for a while before getting a nice shiny ally tank made up.

Problem I`ve always had with catch cans is stripping the oil out of the air. I`m looking for one for the GTO, engine breathers into the can, oil removed and the vent going back to the intake side of the car.

Would be interesing to see what you come up with, small aircraft seem to have some nicely designed ones?.

The idea is to reduce the velocity of the vapour in the vent line by letting it breathe into a larger area, ie the catch can. If the low velocity vapour can then pass through a coalescing filter mesh the microscopic oil particles will gather on the mesh as the vapour passes slowly through it. Eventually they will find each other and start to form heavier droplets that will seep under their own weight against the low velocity vapour flow and drop into the catch tank while the less oily vapours exit the catch tank vent for re breathing if required. Thats the basic theory I think. I'm sure I could build one if I had the time and the space in my engine bay. Until that time arrives I'll stick with my twin 40mm bore X 50mm long mesh breathers that dont let anything drip out

I'm sure there must be a formula to calculate the area's of the relevant pipes and vents based on engine size and blow by? But as I dont know this I just fitted two of the biggest vents I could and it seems to have paid off.

But then my car is race only and my main concern is not having oil seeping out onto my engine

If I were to make a catch tank system for my car. The first thing I would be designing is a system where the vent pipes all rise gently to the point where they enter the catch tank. This would aid natural oil drain back to the engine. A lot of the systems I've seen on cars have awful dips and low bends that just act as oil traps that fill with oil. This means the discharge vapour has to force it way past an obstruction which never clears??

There seems to be two good methods of catch cans in basic terms.

1. A vented catch can using small ish rocker cover filters.

E.G.

http://www.youtube.com/watch?v=Qa8unh6UeFU

That cars going to be running around 40/45psi of boost so it will be built quiet "loose" so there's going to be a fair amount of blow by. As you can see the catch can breaths a bit when the motors really being pushed!



2. A vacuum catch can using either a vacuum pump or a slash cut pipe in the exhaust.

This type of venting can leave the crank case in a slight vacuum which can give small HP gains but can be tricky to get just right & it needs a one way valve incase of engine backfires!


HTH

Bill

Perry has it right and the only things to add are;
1) the catch can should be filled with some kind of gauze for the oil droplets to collect on.
2) The outlet area MUST be bigger than the total inlet area

So the tank should ideally be higher than the rocker covers then?
That makes it more difficult. Most I have seen on TVRs are on the inner wing or near the radiator.
Now i have switched to Megasquirt the dizzy has been removed and replaced with a 'stubby' so i do have a fair size void i could exploit.
This is a pic before the megasquirt but you can see the space the removed dizzy provides....



I cant wait to get home now to measure and design something.
Cheers guys i think i am almost there on this one.

You don't need the can to be higher than the rockers but it must have a fairly big outlet to let the 'cleaned' gases escape, the bigger the outlet the better. The best cans have the inlet pipe going in the top and extending down inside then the scouring pad and outlet at the top. This way the stuff going in drops to the bottom before the gases escape and the scourer catches anything that didnt drop.

I have a catch can that has bigger pipes than the 1/2" outlet from the engine This works fine and is down low in the engine bay so I can drain it into a bucket from underneath.

The only issue I have is getting the mayonnaise out - it catches on the pan scourer I have in there. If you don't run LPG then you wont get as much water in there as I do!

I need to make a catch can for the other car but need a smoke removal as at full throttle it smokes out the inlet in a solid stream but doesnt contain much gunk!

Del!!
As long as the vent pipe to the catch can does not have any obvious oil traps you can put it where ever you want.
If the pipe from the breather can do a gentle curve up and over and down to the catch tank this will be fine. If the vent pipe has a smooth arc any residual oil vapour that condenses will either drain back to the engine or get over the hump and fall into the catch tank.

1) Is what i meant by.....ie the catch can. If the low velocity vapour can then pass through a coalescing filter mesh the microscopic oil particles will gather on the mesh as the vapour passes slowly through it. Eventually they will find each other and start to form heavier droplets that will seep under their own weight against the low velocity vapour flow and drop into the catch tank

2) Is the thing that a lot of folk miss some times. Especially the bloke who fitted this system to my Fiat Turbo. It has a fancy carbon fibre looking catch can with a K&N outlet filter. The filter breather is always dripping oil. Mainly because the can is hollow and the lines are a bit smaller than the main breather pipe from the engine. So the oil vapour is doing what it should do and is gathering at the area of lowest velocity. Thats where the 15mm bore outlet line expands into the 50mm diameter K&N filter body...

I bet the previous owner of the Fiat was impressed with the look of the system. Shame it doesnt work