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xctasy":1t5m441e said:
xctasy":1t5m441e said:Go to a library, and get this book if you can.
http://www.amazon.co.uk/Tuning-British-Leylands-Series-Engine/dp/0854297324
Tuning British Leyland's 'A' Series Engine Hardcover – Aug 1989
The problem with your high rpm air fuel ratio swing is blow by.
The way to fix it is to remove it by an evacusump system, two 5/8" PCV valves to the intake manifold from the rocker cover.
And then two anti back fire valves flowing in excess of 18 cfm each from the lower turbo manifold flange to a dedicated rocker cover catch can.
David Vizard described on in pages 398 and 399 of his second edition of modifying BMCs A series engine, and discussed Turbo applications specfically. Diagrams 15.2a, and 15.2 nail the sysyem down.
Its also covered in
How-to-Modify-Ford-s-o-h-c-Engines-David-Vizard
http://www.scribd.com/doc/26804743/How-to-Modify-Ford-s-o-h-c-Engines-David-Vizard#scribd
page 79 -85 Chapter 5 "Exhaust Manifold & Exhaust System"
and page 115
"This practice is relatively new and, as far as I know, it originated in the U.S.A.
A Pressure-balanced lubrication system is a means of reducing the air pressure in the crankcase so the rings and valve seals have fewer tendencies to pass oil up into the combustion chambers. With air pressure reduced in the crankcase, the reverse tends to happen.
The higher pressure gases in the ports and combustion chambers tend to come down by the rings or seals and end up in the crankcase. Now at first this may seem to be the wrong way of doing things but it does have several advantages......"
"......This brings us to crankcase ventilation. On very high-rpm turbocharged engines, ventilation of the crankcase becomes super-important. Unless there is space for plenty of air to move in and out of the crankcase, the engine is likely to blow an oil mist out, covering the engine’ compartment with oil. It will also drop oil on the track and your fellow competitors will not thank you for this"
Fig 8_3, page 115 with just one 18 cfm PCV.
In the A series 2ND Edition book, DV said that blow by from valves and pistons collectively defines remaining engine life. An Evacusump system should pull 1.85 to 2.65 inches of Hg suction at operating temperature. When the figure drops below that, it only has 15 to 30 minutes more operation time at full load.
Fig from Page 135
There are smaller 100 and 150 models, but the 200 is easier to find and has simple hose barbs to attach to the engine which makes installation easier. I'm trying to find a source for the smaller 150s so I can make a fitting - I think it's better suited to normal passenger vehicles. The 200 is clearly designed for bigger trucks. Still worth considering though - it's exactly the right idea for top-notch PCV in a boosted environment.
powerband":3uwjwfnn said:
Changing to side exit exhaust and crankcase venting with separator and suck from there. I think the sucking should be from the crankcase to promote down flow of the oil in the valve area ,maybe a vent in the cover would be ok?il separator placed at the top of the engine bay is going to offer the best performance. The suction point wants to be a place of high vacuum, which on a forced induction car is going to be pre-blower/turbo. You need a good way to clean the PCV air so that you're not blasting the blower/turbo with dirty oil. A traditional catch can will address that, but on a car with high blowby you can overwhelm the catch can - a friend of mine used to fill his on a boosted 300ZX after ever autocross run. The advantage of that Mann Provent is the replaceable filter does a better job that any baffling, so you can return the separated oil to the sump. It's really a good design.thesameguy":3rlmvow7 said:If I can find it I will post it, but I read some information about PCV design, and the forces in play that you have to deal with. You need the suction point to be sufficiently higher than the vent so that you're only sucking air and not oil, but you need to keep it short enough that the contents don't cool down and coagulate, and you need adequate baffling so that air goes back into the intake but not oil.
The problem with exhaust drafts is that the suction is coming from below the engine, and that creates the ready potential to start siphoning oil out of the sump. A air
On an OHV engine I'm not sure you really need to suck from the head like you would an engine with a timing belt. You are addressing blowby, and assuming you have good suction on the crankcase there won't be any gains from a second top port. I think a better approach would be a filtered vent on the valve cover so PCV on the crankcase can draw fresh air through the valve cover, down the oil drain holes, and out the block. Pipe that into a good catch can or the Provent, then into the intake. My 8v Saab and my Ford 2.3t both draw PCV across the air filter to ensure any particles still hanging in the air don't get back into the engine and that seems like a good idea. My Volvo and 16v Saab both dump the PCV right before the turbo, which seems like a less good idea.
DannyG":edgn1dj7 said:
:thanks: