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[Webby the Bear]

This is a strange one. Am watching this with interest.

Re breathers I always remember that the big 'Y' pipe goes on the outside pipes. The left middle (as you look at engine) is the pipe on left hand of breather box and the right one for the right middle (if that makes sense lol)

Chris, re your experiment on your amended breather box. How does it work that you increased oil consumption? I just cant work out why increasing the diameter of a small pipe would see increased consumption  Presumably it was being burned in the c. chamber?  Therefore you'd have had blue smoke? Just trying to understand for my own learning 

[blackviper90210]

Might do

What mileage is on the car, and how many miles is it doing each week

Mileage is currently 134k
Cover approx 300miles a week.

[05omegav6]

Any trace of oil on the bellhousing where it meets the sump

[VXL V6]

Does it consume more oil when you utilise the full rev range - as in motorway runs with the throttle halfway or more?

[blackviper90210]

Ref oil on the bell housing, I couldn't say at this time as not looked. I did have a major oil leak due to both cam covers leaking when I bought her, so not sure if that will give a false indication??

Regarding consumption of oil, again, not sure tbh. I use the M42 every day to work so can be doing 70 one day or 25 the next. I usually go through a 5 litre can in about 6-8 weeks on average. 

[chrisgixer]

This is a strange one. Am watching this with interest.

Re breathers I always remember that the big 'Y' pipe goes on the outside pipes. The left middle (as you look at engine) is the pipe on left hand of breather box and the right one for the right middle (if that makes sense lol)

Chris, re your experiment on your amended breather box. How does it work that you increased oil consumption? I just cant work out why increasing the diameter of a small pipe would see increased consumption  Presumably it was being burned in the c. chamber?  Therefore you'd have had blue smoke? Just trying to understand for my own learning 

Ok so pipes on the back of plenum.
Two y shaped pipes go to the big nipple on the breather box by cylinder 5, this is unrestricted.
The bigger of the two middle pipes, iirc, goes to the small nipple ion the breather box behind cylinder 5.

It's this small nipple that has the restriction of a 0.5mm hole, or whatever size it is. That whole limits the amount of vapour that the plenum vacuum can pull from the crank case, presumably just enough to hold it a few psi just below atmospheric pressure. Make it bigger, and the plenum pulls more vacuum and hence more vapour. This is necessary to stop blow by combustion gasses pressurising the crank case.

Vapour removed equals oil removed from the crank case and burnt via combustion of the engine.

I haven't fully understood why the unrestricted y shape breather outlet doesn't remove even more oil, but I presume that set of pipe work goes to different holes in the plenum with a different vac rate. Probably pre throttle.

What I have understood though, is don't opps about with it

[Webby the Bear]

This is a strange one. Am watching this with interest.

Re breathers I always remember that the big 'Y' pipe goes on the outside pipes. The left middle (as you look at engine) is the pipe on left hand of breather box and the right one for the right middle (if that makes sense lol)

Chris, re your experiment on your amended breather box. How does it work that you increased oil consumption? I just cant work out why increasing the diameter of a small pipe would see increased consumption  Presumably it was being burned in the c. chamber?  Therefore you'd have had blue smoke? Just trying to understand for my own learning 

Ok so pipes on the back of plenum.
Two y shaped pipes go to the big nipple on the breather box by cylinder 5, this is unrestricted.
The bigger of the two middle pipes, iirc, goes to the small nipple ion the breather box behind cylinder 5.

It's this small nipple that has the restriction of a 0.5mm hole, or whatever size it is. That whole limits the amount of vapour that the plenum vacuum can pull from the crank case, presumably just enough to hold it a few psi just below atmospheric pressure. Make it bigger, and the plenum pulls more vacuum and hence more vapour. This is necessary to stop blow by combustion gasses pressurising the crank case.

Vapour removed equals oil removed from the crank case and burnt via combustion of the engine.

I haven't fully understood why the unrestricted y shape breather outlet doesn't remove even more oil, but I presume that set of pipe work goes to different holes in the plenum with a different vac rate. Probably pre throttle.

What I have understood though, is don't opps about with it

 

That does make perfect sense mate. Is the nipple on the right of the breather box a bigger diameter? I thought they were the same roughly. Either way I was just pondering if this scenario could happen if Viper had got the two pipes the wrong way round.....? 

[chrisgixer]

Dunno, but summats not right somewhere. Maybe one of the y pipes on the inside nipple...?

[blackviper90210]

Just been and checked the pipes on the back of the plenum. They are in the correct position.

I need to take the plenum off anyway and change the HBV, so might find something amiss then. Not holding my breath though, lol.

[blackviper90210]

Evening all,

Done a few long distance runs recently and it seems to lose oil quicker than just the usual trips to and from work.
Just noticed the one of the bag pipes going to the TB is split quite badly. Could this be a possible cause to the loss of oil?

[chrisgixer]

Doubt it, but it won't do the fuel trims any good. Air leaks are baaaad.

[terry paget]

I am fascinated by Chris's experiment with the drilled out small breather, but it makes sense. As on the 4 cylinder engine, there is one breather ahead of the throttle and one behind it. At idle, with the throttle closed, i.e. no vacuum ahead of the throttle but hard vacuum behind it, the small breather sucks out the crankcase gases. To avoid it sucking out too much it sucks through a small hole. With throttle open there is less vacuum behind the throttle, but a little vacuum ahead of the throttle and downstream of the air filter, so larger pipes and a larger hole in the breather box (on the V6) are needed to suck out crankcase gases. On the 4 cylinder the rocker cover replaces the breather box.

By drilling out the small breather box pipe Chris allowed idling hard vacuum to suck lots of crankcase gases out of the engine, including some oil spray. This caused excessive oil consumption.

[allen25]

Evening all,

Done a few long distance runs recently and it seems to lose oil quicker than just the usual trips to and from work.
Just noticed the one of the bag pipes going to the TB is split quite badly. Could this be a possible cause to the loss of oil?

Have you sorted the problem yet? I'm local to you as you know and thanks for the loudspeaker. If I can help you find the problem, I'm happy to try.

[allen25]

Sorry, typed in the wrong place, but happy to help if needed.