markwild

When I rallied minis, the crankcase had pressure release filters (in fact it had two, which fed back into the induction system).

I enhanced these when I modified the engine, by replacing them with K+N filters. I also added an extra two, by drilling holes into the block in strategic places. This was necessary, as the crankcase pressure became so high at revs, that oil was FORCED back through the oil filler cap and the dip stick would launch from the tube it rested in like a rocket

Several users on here seem to be suffering from minor oil leaks, possibly due to a similar problem -

Does anyone know if the Impreza has (or anyone has made it) similar breathers ?

Mark



[Edited by markwild - 10/21/2003 7:45:42 PM]

Jolly Green Monster

iTrader: (4)

The Impreza engines have a crank case breather and two cam cover breathers which feed back into the induction..

The oil leaks are due to worn seals.. imho..

JGM

Jolly Green Monster

iTrader: (4)

plus if you remove the oil filler cap.. and put your hand over it you will feel blowing air from it.. rev the engine and that blowing air turns into a suck.. therefore there is no pressure within the crank case at high rpm..

JGM

markwild

JGM,

I'm sure you're right about the seals, BUT - mine have been fine until I've fitted the dawes (and hence increased power) and now I'm getting a slight leak and hot oil smell (though I've not proved its a seal/gasket yet) and Skoosh has had a similar prob. since fitting a scooby ECU (thus increasing power)..

When I ran my mini, it was an A series engine, originally designed for 50 odd hp - I only needed the breathers once I broke 100hp, at 120 they were a MUST !

I just wondered if the mega hp amongst scoobynet had done anything with the breathers, or whether its just a matter of making sure that the gaskets and seals are tip-top.....

Cheers,

Mark

dowser

If you raise boost then most likely you'll start to get noticeable oil vapour flowing through the breathers. I used to clean my intercooler with petrol every 2 months to flush it out, boost control pipes or Dawes as well. I then fitted a catch tank to the crank breather only, and this stopped it.

With the new engine I'll take a bit more care of the whole breather system, but confess to not fully understanding it until I can see what everything does and where it goes! I'm a little concerned because the vapour which was coming out is now staying in engine.....at least, more of it is....I've only had to empty catch tank once in 10 months...and even then it only had a couple of mls in it.

Richard

Jolly Green Monster

iTrader: (4)

Dowser,

I too get next to nothing in my catch can, but used to get lots in intercooler and running our of pipework where it enters air intake.

I think the longer pipework allows the oil vapur to become oil again and run back down the pipes, or sucked back down when engine crank case is in vacum state etc..

JGM

markwild

catch can ? Where can such a device be purchased good sirs ? (although I'm fairly sure mine is not this, as it actually smokes under the bonnet V. occassionally (Twice in 3 weeks))

JGM, I think the A-series used to show pressure at the oil filler cap, as it was on top of the rocker case, not under the cylinders on the block, like the prez's

Mark

dowser

JGM,

Yep - it would normally be sucked back into the inlet on boost by the turbo. Fitting the catch can means this vacuum, at the crank side of can, is largely reduced & is no longer drawing the same amount of vapour into the catch can.

So where's this vapour going? If it's staying in engine, I'd guess the oil lost whatever value it had as it was forced past the piston with extreme violence....I'd prefer it out than in I guess it's not too bad given 6k km oil change intervals, but best practice would still be to eject it if possible.

What part does the PCV valve thingy connected to the inlet manifold play in this role? Andy.F and Bob Rawle posted good info on these systems a while back, but the link's at home. I need to review it and see if I understand now, lol

Edited to add: Mark - I bought a Cusco catch can. It's very shiny and looks lovely, but I'd still use an old plastic bottle if I was doing it again. Especially given that the pipework diameter in the kit wasn't exactly right, and there is still a large chunk of my finger down by the crank breather somewhere as a result. Cusco also charges "like a wounded bull" Got mine from JW Racing.

Richard

[Edited by dowser - 10/23/2003 7:11:42 AM]