Catch Tank Design

Road-race engines and ancillaries - general discussion
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fingers99
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Catch Tank Design

Post by fingers99 »

I've just bought a Volvo V70 T5 estate.
It has a few mods by the previous owner, chipped, adjustable boost, tweaked intercooler, etc. but he has fitted a tiny little catch tank -- maybe 500ml -- which I don't believe is up to the job. I'm not sure that the relatively small bore single breather tube is really up to it either but currently I just want to address the capacity/design issue. Later I can see where I can take a second breather from.

As I see it:

1. There's plenty of space for me to custom design and fit a bigger catch tank.
2. Ease of draining is something I need to look at (if they're not easy to empty, they don't get emptied), so I thought a simple tap connected to a tube running down the side of the engine bay, so I can simply drain direct into a catch tray.
3. Some form of sight glass so it never gets more than half full.
4. This is a road car, so what goes to the catch tank is going to be moisture and blow-by products. It's important for engine health that these do not enter the inlet manifold, but under UK rules, they cannot vent directly to atmosphere.
5. I hear Cusco (probably amongst others) make catch tanks with some mechanism for condensing blow-by, but I've never seen one, have no idea of the design, and I'd sooner make something to use the available space anyway.

I thought of a relatively deep tank, divided in two parts. The divider has holes which progressively get smaller toward the top, the inlet side is filled with stainless steel wool (or ASDA stainless pan scourers, if they still have them in the £1 section!).
The outlet side has the tap at the bottom but no filling.

Ideas and comments would be very welcome. Thanks.
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Guy Croft
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Re: Catch Tank Design

Post by Guy Croft »

CATCH-TANK

SOME KIND & INFORMED MEMBER PLEASE RESPOND

I AM RUSHED OFF MY FEET AT WORK

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tmvolumex
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Re: Catch Tank Design

Post by tmvolumex »

I like to keep things simple so I use a Teflon bottle / tank available from a laboratory supply company. I have used it for more than 15 years on my Volumex Montecarlo / Scorpion.
Its clear and remains clear even after 15 years, so its easy to see the moisture in the tank. Here in California, it only collects water in winter, in the summer very little water accumulates.
I doubt if the behavior will be the same if you are in the UK. In the UK you will need to empty it year round. Picture in Guys 2nd book, page 220.

2 literTeflon tank (100 dollars US), couple of fittings at the top and your done.
Dont be temped to try the much cheaper polypropylene bottles but they dont last, they get brittle, turn brown etc.
In a turbo car, with all the heat in the engine compartment dont even try a poly tank.
Tom
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fingers99
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Re: Catch Tank Design

Post by fingers99 »

I was thinking more of an aluminium one (it's nice to hammerform, weld and so on) and I can fabricate it to really fit the engine compartment neatly.

But I'll take a peek at Guy's book when it comes.

Thanks!
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tmvolumex
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Re: Catch Tank Design

Post by tmvolumex »

Yes, a custom formed, aluminum tank looks very trick. Its a lot easier to clean a clear, Teflon, breather tank, which has a screw top is 5 inches in diameter, that is the same diameter as the 5 inch diameter tank.
What winds up in the tank is an emulsion of oil vapor and water vapor. Not a solid or a liquid, smelly stinky stuff, that will not fully drain out of a .250 inch diameter bottom drain.
Put in a half inch diameter drain in your custom aluminum tank and you have a chance of getting most of it out.
Remote blowby tanks are much cooler than the, on engine, blowby systems, consequently a lot of oil mist and water condense out, creating slime in the remote tank.
Tom
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tmvolumex
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Re: Catch Tank Design

Post by tmvolumex »

Whoa, its been 15 years since I priced my Teflon tank. Its not 100 US dollars its more like 300 US dollars !
Sorry about that.
Tom
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parrish
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Re: Catch Tank Design

Post by parrish »

Firstly use a cheap plastic see through bottle and see what amount of residue you are catching.
In my experience sometimes best just to route the tube to under chassis level and forget.
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Steve
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fingers99
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Re: Catch Tank Design

Post by fingers99 »

For purposes of the MOT, I've just -- this week -- put the drain bung back into the itsy bitsy teeny weeny catch tank the last owner fitted (he'd removed the plug, so, while the tank wasn't filling up, it was venting directly to atmosphere, which -- according to the regs -- is an automatic MOT failure here).

If I get a chance (in between working on my new MR2 turbo and setting up a new company) I'll take a peek tomorrow. Not a lot of miles in the meantime, but a fair few short trips.
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fingers99
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Re: Catch Tank Design

Post by fingers99 »

Well, I looked.
The blow by has not even reached the bottom of the sight tube, so the tiny tank has virtually nothing in it.

This is a good sign (as regards engine health) but short trips around town don't really permit the use of much boost (and you'd expect blow by to increase with boost, were it going to).

I'll try and be harder on the loud pedal at the weekend!
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