Mark's Catch Tank

[Doug_RS2]

Originally posted by Greg_S
, the other comes up from side of the block.

That is the connection I'm not sure about.

[audiman]

Breather venting to atmos is NOT a testable item!! It will be ok. I would do it myself, but the car has done too many miles and breathes heavier than most younger models!!!

[S2central.net]

Tom - I know you are an MOT man so obviously I can't teach you to suck eggs, but my old Coupe failed on this six years ago purely on a visual inspection. The guy spotted the breather and marked it down straight away. MOTs in Northern Ireland are much more strict and formal than here in the mainland - its done by government test centres - not local garages. I actually prefer that system as it avoids Joe Public getting screwed over by unscrupulous garages who see the MOT as a money printing machine !

Just my 2 cents !


Paul

[bigtoe]

You guys need to read a few David Vizard books, he developed a system he called evacusump which i have used on quite a few engines.He shows it on turbo'd Pinto's pushing 500+BHP so it should work on your Audi's.

What you need is a catch tank with a drain, a mid mounted inlet and a top mounted outlet.

The drain goes back to the sump.
You need to vent from the cam/rocker cover and from the block to the midmounted inlet on the tank.
The tank needs to have internal baffles so the oil condences on them and falls to the base of the tank and only vapour is left.From the top outlet you need a 1 way valve and then a hose down to a pipe you weld into the exhaust down pipe just before it mates to the system. This pipe needs to be cut in such a way that the exhaust gasses passing round it create a vacume within it, so it needs to be blind to the turbo side but open to the exhaust system.The One way valve is to stop blow back into the tank which would intern pressurise the engine.

What this system does is to create a negative pressure within the engine,it had the effect of making lumpy idling rally engines tick over like they had a standard cam installed. MPG increases, oil uses decreases and best of all BHP increases. I saw an 11BHP gain on a 1600CC rally engine and 17BHP on a 2.1L engine.The rolling road tech couldn't believe it as i had only had the 2.1L tuned 5 days earlier and he swore it wasn't the same lump.We took the breather off and the BHP gain disapeared.

Things to remember:

The engine needs to be air tight.
The catch tank can be an issue, some have in and out at the top, as long as the oil falls to the base it should be ok.
The hose to the down pipe needs to be pretty special to withstand the heat.

I have run a few cars thru MOT's with this system, all passed very easy.

It may be worth looking at.

[S2central.net]

Hmmmmm Intersting...

David Vizard - was one of the hot writers at CCC about ten years ago ?

I'd personally be very reluctant to connect the outket into the exhaust system - just doesn't smell right to me - why not just vent the vapour to atmosphere ?

Also - correct me if I'm wrong but our wonderful S2 engines don't vent at the cam cover as far as I can remember... they just vent from one side of the crankcase. The cam cover could easily be modded to do that if it was necessary though.

I do think a properly designed air/oil separator and catch/drain tank is a worthwhile mod - especially on chipped cars where the increased boost is bound to increase blow-by effects which potentially puts more oil vapour into the intake system (yuch) and could potentially cause detonation in extreme cases.

Anbody out there with contacts in the fabrication industry willing to help ? If we get these properly designed and tested it could be yet another group purchase potential.


Paul

[SteveH]

Paul,

The 3B motor has a breather on the back of the rocker cover, unlike the ABY which doesn't have one fitted. The breather is situated right under the HT leads so it isn't that easy to see. I've seen one 3B without the breather on the rocker cover, that was Zorro's S2 at Combe. As you say, it would be pretty easy to add one if you needed to.

[S2central.net]

Wishing I had my head under the bonnet as I type this...

Are you sure the pipe you are referring to, isn't just the connection onto the transfer pipe (inside the cam cover) which connects to the hose from the MAF into the turbo (allowing blow-by gasses and oil vapour to be re-circulated).

I must work out the full mysteries of the PCV (positive crankcase ventilation) on these wonderful cars of ours. The complications of having an engine that produces negative pressure in the crankcase (when cruising) and positive pressure (when accelerating) is the reason for the various check valves etc on the standard breather system. What does the standard system do when the crankcase is under +ve pressure ---> surely the gasses cant be vented to the MAF pipe as it is always under vacuum ?

****** it - I'm just gonna have to take it apart and try to work it all out properly. Can't get my head round it sitting at a desk


Paul

[SteveH]

Hi Paul,

Yes, I'm sure m8
The layout is completely different on the 3B. The pipe that runs through the cam cover on the ABY isn't fitted to the 3B motor. Instead, there's a pipe that runs under the inlet pressure pipe down the side of the rocker cover.

HTH
Steve

[bigtoe]

David Vizard has got to be one of the greatest engine builders of all time, its been around 20 years since he was a writer for CCC but he is still active and recently met with some of the guys from one of the owners clubs im a member of in london. He has now moved back to the US.

I'd personally be very reluctant to connect the outlet into the exhaust system - just doesn't smell right to me - why not just vent the vapour to atmosphere ?

I suggest if you can you read some of the articles regarding this sytem, it for me is one of the best mods available.
How do you know its not right till you try it?


Regarging only venting from the block, this would actually be better as your catching the fumes etc at source, not when they have travelled up thru the engine.

Regarding the catchtank, I had a look at one of mine earlier.It has in and out at the top with a divider going half way down the tank so all fumes have to fall before they rise to exit the tank, it seens to work ok. I would say internal baffles would be a little better though.

[S2central.net]

OK a little bit of lunchtime surfing has taught me a few things about PCV. Its been around a lot longer than I realised. Think I've worked it out now

I'll make up a drawing or two later to capture my thoughts and a proposed tweak to the 'evacusump' post which I'll try and explain below...

There was a typo / brain fart in an earlier post when I was banging on about pressure changes at cruise or on boost.
- Its only the pressure in the inlet manifold which changes from vacuum to pressure. The crankcase is *always* pressurised (in varying levels) by nature of fractional blow-by of combustive gasses past the piston rings. As engine load increases, then so does blow-by effect and the need to vent the crankcase and prevent oil being pushed past seals etc - not to mention restriction on the movement of pistons in such a pressurised environment.

The PCV valve plumbed into the pipe between the crankcase vent and the recirculation pipework regulates the amount of pressure that is released into the MAF hose. Interestingly that MAF hose is the only point on the S2 engine which is always under vacuum and in so doing sucks the vented crankcase fumes, oil vapour and other crap back round the system for another chance to burn off ... and another... and another until the engine stops.

Got me to agreeing that the evacusump idea actually makes damn good sense but I didn't like the idea of exhaust gas via some sort of adapter being used as the source of vacuum on that system. I propose an electrically powered vacuum pump to pull the vented gas out of the top of catch/drain tank !!!

The catch/drain tank needs the following -

- one input from the crankcase (directly I presume)
- one input from the cam cover (if available)
- one output at the bottom for oil to return directly to the sump (below oil level or this line will be pressurised also
- one output at the top for breathing/venting assisted by a vacuum source

Upsides are as follows -

1. You can blank off the PCV port on the MAF hose so that your S2 engine breathes sweet clean air all the time

2. Any leaks in the PCV system are not linked to the intake system - this eliminates the possibility of air leaks in this area

3. A blocked PCV valve fitted on standard cars has the potential to reduce performance and increase oil usage. The standard PCV valve would be removed on such a modified breather system.

Downside is that you need to plumb in a vacuum pump and I dunno much vacuum is 'enough'. Maybe its not really necessary as at high loads the pressure in the crankcase is surely going to be enough to expel blow-by gasses directly to atmosphere...

Anybody else think I'm onto something or out to lunch ?

Where's the proper engineers when you need one - not an electronics guy ?


Paul



Sorry for the long post !

[S2central.net]

@BigToe - It was Dave Walker that I was thinking of - He is my generation.
CCC was a great mag in its day - you just don't get tech articles like that in the drossy rags of today.

There's more articles on 'TnA' than 'PCV' in any copy of Max Power I ever flicked thru. Dross. Bloody kids these days... Rant... Ramble...

Thanks for your thoughts on this from Mr Vizard - couldn't have got this far on the subject without the 'evacusump' stirring a few brain cells

Cheers,

Paul

[bigtoe]

I regard Dave Walker pretty much up there with David Vizard. Both have inspired me to mod engines in weird and wonderful ways with usually good gains in power.

I feel your looking to deap into the vacuum side of things.Drawing vacuum from the exhaust is proportional to revs which in some weird way is proportional the the pressure build up in the engine.The lower the revs, the lower the vacuum and the lower the pressure in the engine.All you need to do is to make sure you DON'T draw oil into the system.This is where a good catch tank comes in.

On a side note i can't believe you guys are recirculating fumes back thru the induction side of your engines, i know thats how they come from the manufacturers but it is FAR from ideal.The last engine build cost me upwards of 2.5k and there is NO WAY i would feed the engine with ****** air.

If I find time i will have a look thru the hundreds of old CCC mags to see if an article was ever written on the "EvacUSump" system.If I find it i will try and scan it and just post the bits you need.Unfortunately i lent my books out a while ago and they have beem lost, if anyone has the tuning A series engines book it is in there.

[martinjs]

i was going to set mine up as pauls just suggested, if you look at diagram 103-87 under engine section on etka the 3b system is the lower setup, so the pipe which connects to the rear of the cam cover needs blanking and another pipe fitted to feed straight to the catch tank, and the pipe which feeds to the maf/turbo hose is to be fed to the catch tank also, didnt know where to feed the catch tank ventilation pipe though?
so the flame trap and solenoid (is this the pcv thing your on about paul does this release vapours from the fuel tank?)
will all remain?
will be tapping into the sump plug as marks done for the return.

confusing or what!

[S2central.net]

@Martin - your post isn't very clear mate but you might have a few mistakes (or too much beer or caffiene)

You want to blank off the pipe that goes into the MAF.

If the 3B has a vent from the camcase (instead of a transfer pipe like the ABY) then you'll need that to enter the catch tank as I suggested. This would be alongside the pipe coming direct from the crankcase.

Also - the PCV valve is NOT the solenoid based one you mention, but its reminded me of a correction I need to make to the design for this. The PCV valve is embedded in one of the pipes en route from the crankcase pipe.

The EVAP solenoid is used to occassionaly vent fumes from the Fuel tank via the carbon canister treatment into the inlet manifold so they are burnt off to prevent pressure build up in the tank.

Suggest it might be a nice trick to rejig the EVAP solenoid such that it vented these treated fuel fumes into one of the hoses going into the catch can. Hold on - that doesn't work cos the crankcase pipe will always be pressurised - so you'd need to vent on the OUTLET side of the catch tank - possibly assisted by vacuum as discussed.


Paul

[Doug_RS2]

I'm getting more confused by all this.

ABYers - I know we disconnect the 90degree rubber connection on the back of the rocker cover and connect that to one of the inlets of the catch tank.

I don't know how to plumb in the connection from the crankcase - I wouldn't know what to do with the rest of the plumbing that is connected in the pic :confused: :confused: :confused: