30 replies to this topic

[Swift_General]

Nice idea. I also initially thought there may be an issue with emmisions, but thinking about it the test is initially conducted only at tick over when clearly the pressure in the inlet manifold will be much lower than at the exhaust. Just be mindful thought that if your car is '72 onwards the above, catch tanks and the like may fall foul of C&U regs.

 
Run catch tanks in all my performance cars, all sailed through MOT's. Including the VTA ones I've had on the Evos.

Not something that would get tested on an MOT.

Relevant legislation:

"The engine shall be equipped with means sufficient to ensure that, while the engine is running, any vapours or gases in the engine crank case, or in any other part of the engine to which vapours or gases may pass from that case, are prevented, so far as is reasonably practicable, from escaping into the atmosphere otherwise than through the combustion chamber of the engine."

Not something that will concern many I'm sure, but worth a mention.

[Trissy B]

Hi, without wanting to hijack the thread - i do have a question: I've noticed in articles over the years and most recently an article in the new mini world by Tim Mundy.. he has recommended using the small K&N/Pipercross filters on top of the normal breather canisters. Seemingly the only reason he gives for this is that they look nice..

 

However, from reading this thread, positive crankcase pressure seems quite important and allowing the engine to just breath into the air at normal atmospheric pressure is'nt good enough..

 

Have i got the right end of the stick?

[Steve220]

If you stick a filter on it, it will get full of oil and gunk very quickly. For my MPTi I will be running it to vent under the car behind the front subframe.

[Ethel]

Hi, without wanting to hijack the thread - i do have a question: I've noticed in articles over the years and most recently an article in the new mini world by Tim Mundy.. he has recommended using the small K&N/Pipercross filters on top of the normal breather canisters. Seemingly the only reason he gives for this is that they look nice..

 

However, from reading this thread, positive crankcase pressure seems quite important and allowing the engine to just breath into the air at normal atmospheric pressure is'nt good enough..

 

Have i got the right end of the stick?

Yes.

 

It wouldn't be allowed on current production cars because of hydrocarbon air pollution. The original Mini system is adequate to keep the crankcase pressure slightly under atmospheric, reducing leaks and also being kind to your oil by evacuating the nasty fumes and letting fresh air in through the filler cap. 90's Min's with charcoal canisters under the wing go a stage further in controlling the hydrocarbon fumes in the fuel system.

[Dusky]

Those k&n breather filters are more "cloggers" instead of filters. Absolute rubbish imho.

[panky]

I always thought the little filters were to filter the air entering the rocker box as the crankcase breathers draw out the fumes. But if you do fit them to the crankcase breathers. instead of piping them to the manifold, then yes they would clog up in no time

[Trissy B]

On rocker box breathers.. surely the oil cap is a breather so an additional one is pointless.. unless you have a solid cap of course.

[panky]

Indeed, that's why I fitted one when I went for a polished alloy rocker box with a nice shiny chrome cap

[Orange-Phantom]

On this topic what's well worth a read is David Vizard's Yellow Bible!

 

https://images-na.ss...04,203,200_.jpg

 

Page 425 is where you want to start.  He also details his "Evacusump" crankcase pressure reducing system on page 427 which is well worth reading.

 

It's a bit ironic reading some of the comments above that the engine on the front cover of David Vizards book has 3 K&N filters on it!

[Trissy B]

It's a bit ironic reading some of the comments above that the engine on the front cover of David Vizards book has 3 K&N filters on it!

 

HA! quite. Will have a good read up i think thanks.

[Dusky]

It's a bit ironic reading some of the comments above that the engine on the front cover of David Vizards book has 3 K&N filters on it!

 
HA! quite. Will have a good read up i think thanks.

Then again, it also has 200£ HT leads and is a full race engine, hardly comparable with anything road going

[Orange-Phantom]

Actually there is a whole section in David Vizard's book about using K&N breathers for crank case ventilation for road cars.  It's on page 425 for your reference.  He then goes on to talk about dealing with crankcase pressure on race engines to which he refers to "evacupan" and " "evacusump" systems.

 

Here is a great video by David Vizard on tuning the A-Series engine.

 

 

For your reference 4:27 is where you want to watch from when he talks about filtration.  He goes into great detail on K&N filters, he recommends them highly and guess what!  Without question he actually does know what he talking about!

Edited by Orange-Phantom, 18 January 2017 - 10:40 PM.

[Dusky]

Actually there is a whole section in David Vizard's book about using K&N breathers for crank case ventilation for road cars.  It's on page 425 for your reference.  He then goes on to talk about dealing with crankcase pressure on race engines to which he refers to "evacupan" and " "evacusump" systems.
 
Here is a great video by David Vizard on tuning the A-Series engine.
 

 
For your reference 4:27 is where you want to watch from when he talks about filtration.  He goes into great detail on K&N filters, he recommends them highly and guess what!  Without question he actually does know what he talking about!

4:27 he talks about air filters for the carb -.-
In his books he also makes a very good point on why you want a pcv system.
"It has been found that of the crankcase pressure can be reduced below the atmospheric pressure, the amount of oil that can go past the rings is greatly reduced" and everything below that.

Edited by Dusky, 19 January 2017 - 08:07 AM.

[jt19]

Reducing the crankcase pressure is a good thing, not just to help stop oil leaks, it also reduces the energy loss through windedge. Inside the crank case air is constantly being forced from underneath the two outside pistons to the underside of the inside pistons and back. It is surprising how much energy is lost through this reciprocating air movement at high engine speeds. The effect is exacerbated by having a free flowing air filter. With little resistance to flow the vacuum in the inlet manifold is only marginally lower than atmospheric and fails to do a good job of evacuating the sump gasses.
 
What I did to remedy this problem was to obtain a couple of non-return valves the type you used to find on the vacuum pipe that goes from the inlet manifold to the servo brake unit on some cars. Next I welded a short piece of 10mm pipe onto the exhaust pipe just past the last "Y" joint at about 30^o​ so that it acts like a venturi and creates a vacuum in the smaller pipe when the gas flow is sufficiently high enough. I then connected silicone pipe from their to a "Y" connector that connected vacuum hose from the inlet manifold and another pipe to the top of the catch can (or ideally a knockout pot). I then fitted the non return valve, One between the "Y" connector and the inlet manifold so that gasses can only go into the manifold and the another in the pipe from the "Y" connector to the exhaust pipe so as gasses can only go towards the exhaust.
 
The idea is at low engine speeds the vacuum in the manifold is high and so this evacuates the sump. at higher engine speeds the exhaust creates an even higher vacuum and takes over. You have to make sure that oil cap has no vent (I sealed mine up) and the dip stick has an "O" ring type seal. And under no circumstances do you want to make the mistake that I made and put the manifold non-return valve in the wrong way round. When first testing it when I reached a certain speed a big white cloud came out of my exhaust pipe. With valve the wrong way round the exhaust drew fuel air mixture out of the manifold producing the white cloud that followed me. Luckily I realized what was happening and pulled over quickly before it ignited like a JATO rocket or propelled my exhaust pipe like a sidewinder missile.
 

Would this system work on a turbo mini?

I've currently got my transfer housing breather going into my rover box. Timing cover breather also to rocker box, then rocker box to MED catch tank under the wing. Then I have one of thoughs oil breather filters on the catch tank.

Thanks
Josh

[Ethel]

In theory, yes. The exhaust connection would be down stream of the turbo of course, and the lambda sensor if you have one.

 

That's the valve BL put on the turbo Metty, the metal pipe's for the brake servo.

 

It also had one of these red jobbies

That transferred the sucking duty from the inlet manifold to the  oulet from the air filter when it was making boost.

 

You only want 1 or 2 psi below atmospheric, so you might well need a restrictor on the line to the manifold. The carb's throttle disc does that job on a normally aspirated SU.