19 replies to this topic

[Spider]

Your Mini should have a CCV Crankcase Breather arrangement. When I can get Imgur working again, I'll post a diagram.

 

This is the complete diagram, however, it's pipe no. 7 here that is of concern

 

 

That pipe connects here on the Carb;-

 

 

 

 

[Lplus]

Okay I had a good look this evening - yep the pipe into the air filter is a dummy - like a chump I’ve been attaching it to a blank off hole! The pipe on the cab that the breather pipe should attach to was blanked off. I un-blanked it and connected the breather pipe as it should be. Of course the engine then would not run - stalls / won’t tick over and lumpy without revs. I re-blank the carb pipe and it runs fine as before. For some reason the garage that fitted the stage 1 kit deliberately blanked off the carb pipe and tuned the engine in that state - and it runs absolutely fine. I am only pursuing this because of the oil leak issue. So … does any of this make sense and why would the garage do this ( very reputable and not doubting their wisdom).

Yes it makes sense.  The positive crankcase breather system does draw air in through the oil filler cap vent and circulates it through the engine and into the carb.  This extra air will weaken the mixture at idle and just above, so it isn't surprising an engine tuned to run without the extra air will misfire at idle if the air flow is introduced.  Provided there are no other breathers or air holes into the engine than the one from the rear cover plate to the carb ,and the oil filler cap is undamaged, the extra air should be restricted enough that you can richen the tickover mixture to enable the car to run correctly.  That's how they were supposed to be run.  The dipstick should have a tapered rubber seal to stop air getting in that way.

 

Why the garage would do this, I'm not sure, though presumably they considered the extra air and fumes would "reduce the extra power"  Which it would on a pure race engine....

 

Connecting the breather to the air filter tends to block the filter with oil in the long run.

[Spider]

Why the garage would do this, I'm not sure,,,,,

 

999 times out of 1000 it's done out of ignorance. A lack of understanding and a 'I know better' attitude as to just how the system works and why it's beneficial.
 

[Richard e]

Thanks all. The garage races minis… so probably squeezing a bhp out of it. Decided not to plumb into the carb - to avoid messing with the settings- instead I drilled the tube into the air filter so at least the breather system can breathe. I expect I’ll need to change the air filter more regularly but don’t do the miles for this to be an issue. I added an o ring to the dipstick and rigged a way to hold it down snug. One test drive later and running / performance unchanged = fine and no leak of oil - so that will do me.

[Cooperman]

Well done.