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Engine Breather Pipe

modified good idea or bad?

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#1 MartinS

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Posted 14 April 2012 - 10:23 AM

The pipe that comes off the top of the engine has always been a pain for me. When it went into a catch tank, that filled up really fast with the emulsified oil mix and went everywhere, so it was changed into breathing through a filter and positioned at the end of a 70cm pipe near the r h wheel arch. This then spread a fine mist of oil all over that area which wasnt good, so following the example of another vxer, I extended the pipe to about 1.5 metres and it now exits down through the middle of the diffuser. Is this ok?
I had just assumed it was, but have since been told to think about the following and that the pipe may now be too long?!-

Re the length of pipe, I have kept the pipe as short as possible to minimize pressure drop. The engine is already pressurized enough imho. What you’ve done seems a good idea so I’ll wait to see what happens to your engine

Positive crankcase pressure is bad. It contributes to contaminating the oil quicker. If you put your hand over the oil filler while it is idling, what you are feeling is the blowby. Now imagine that at 7k rpm and all going down a small dia pipe to atmosphere, the longer the pipe the greater the resistance!! Apparently blowby goes up exponentially with revs so double the revs and you more than double the blowby.

Am I not thinking enough, or is that person thinking too much?

Martin s

#2 Ormes

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Posted 14 April 2012 - 11:55 AM

I extended the pipe to about 1.5 metres and it now exits down through the middle of the diffuser. Is this ok?

Not sure the affect it will have on your engine, but is spraying a fine mist of oil over the road behind you a good idea :D Granted its probably only a drop a month :)

#3 leevx2.2

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Posted 14 April 2012 - 11:58 AM

All us S/C boys suffer from this someone has come up of the idear of a secound breather pipe which is coming out of the top of oil filler cap . I have done this mod and hopefully it will work I will let you no or for the sake of butchering a cap have a go yourself I just cut a hole all the way through and put a 19 mm 90degree bend coming out the top of cap and connected a pipe to this . Hopefully it will work have ago Martin

#4 Sutol

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Posted 14 April 2012 - 12:02 PM

Martin's quoting me btw, the other thing i forgot to mention to him is that resistance goes up by the power of 2 to flow rate ie double the flow rate and you quadruple the pressure drop.

#5 Sutol

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Posted 14 April 2012 - 12:06 PM

All us S/C boys suffer from this someone has come up of the idear of a secound breather pipe which is coming out of the top of oil filler cap .
I have done this mod and hopefully it will work I will let you no or for the sake of butchering a cap have a go yourself I just cut a hole all the way through and put a 19 mm 90degree bend coming out the top of cap and connected a pipe to this .
Hopefully it will work have ago Martin

Lee I will be interested to see how you get on with that mod.

#6 The Batman

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Posted 14 April 2012 - 12:07 PM

yup as lee said although sticky made me mine and it looks alot less chav that lees :lol:

#7 leevx2.2

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Posted 14 April 2012 - 12:12 PM


All us S/C boys suffer from this someone has come up of the idear of a secound breather pipe which is coming out of the top of oil filler cap .
I have done this mod and hopefully it will work I will let you no or for the sake of butchering a cap have a go yourself I just cut a hole all the way through and put a 19 mm 90degree bend coming out the top of cap and connected a pipe to this .
Hopefully it will work have ago Martin

Lee I will be interested to see how you get on with that mod.

If you fancy one doing Chris I got the bits in the gararage and could nock you one up and post it to you.
I was thinking the other day on a z20 let and lots of other engines they have a breather from rocker to sump I wonder if this would help us aswell . ? Only one way of finding out if this breather doesn't work I will be looking at dong this to

#8 leevx2.2

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    Turbo's are for girls and throttle bodies are too slow

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Posted 14 April 2012 - 12:13 PM

yup as lee said although sticky made me mine and it looks alot less chav that lees :lol:

Had to change that the boot wouldn't close lol

#9 The Batman

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Posted 14 April 2012 - 12:15 PM

Surprised you didn't hole-cut a hole in the bootlid :P have it coming out the top like a v8 air filter :lol:

#10 leevx2.2

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Posted 14 April 2012 - 12:18 PM

Surprised you didn't hole-cut a hole in the bootlid :P have it coming out the top like a v8 air filter :lol:

Sounds like thats what you would of done Chav boy lol

#11 The Batman

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Posted 14 April 2012 - 12:19 PM

:lol: that says it, you are actually more of a chav than me as my filter will be hidden :P will buy you a burbery hat ;)

Edited by joe_589, 14 April 2012 - 12:19 PM.


#12 JG

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Posted 14 April 2012 - 12:28 PM

What is the purpose of a second vent? If its because the original one isn't big enough, wouldn't it neater to weld in a large pipe exit as a replacement of the current one?

#13 Sutol

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Posted 14 April 2012 - 12:29 PM



All us S/C boys suffer from this someone has come up of the idear of a secound breather pipe which is coming out of the top of oil filler cap .
I have done this mod and hopefully it will work I will let you no or for the sake of butchering a cap have a go yourself I just cut a hole all the way through and put a 19 mm 90degree bend coming out the top of cap and connected a pipe to this .
Hopefully it will work have ago Martin

Lee I will be interested to see how you get on with that mod.

If you fancy one doing Chris I got the bits in the gararage and could nock you one up and post it to you.
I was thinking the other day on a z20 let and lots of other engines they have a breather from rocker to sump I wonder if this would help us aswell . ? Only one way of finding out if this breather doesn't work I will be looking at dong this to

Lee that's very kind of you but i think the answer lies in trying to replicate how the engine was before SCing ie venting into the air intake which will keep the engine under a negative pressure. Perhaps something on the lines of this could do it

http://www.gzmotorsp...cuum-pumps.html

#14 The Batman

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Posted 14 April 2012 - 12:39 PM

What is the purpose of a second vent?

If its because the original one isn't big enough, wouldn't it neater to weld in a large pipe exit as a replacement of the current one?


Yes and yes :)

But lee has a plastic cam cover

#15 Sticky

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Posted 14 April 2012 - 12:43 PM

What is the purpose of a second vent?

If its because the original one isn't big enough, wouldn't it neater to weld in a large pipe exit as a replacement of the current one?


I have a plastic cam cover (as do Lee and Joe) so enlarging the original vent doesn't work.

#16 leevx2.2

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Posted 14 April 2012 - 12:44 PM


What is the purpose of a second vent?

If its because the original one isn't big enough, wouldn't it neater to weld in a large pipe exit as a replacement of the current one?


Yes and yes :)

But lee has a plastic cam cover

I was at Homebase earlier a water but downpipe connector would work on my plastic cam cover if this cap vent helps I will adapt my cam cover

#17 JG

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Posted 14 April 2012 - 12:44 PM

I'm still not entirely sure i understand why it needs to be bigger, Is it to reduce flow rate?

#18 Sutol

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Posted 14 April 2012 - 12:46 PM

I'm still not entirely sure i understand why it needs to be bigger, Is it to reduce flow rate?

resistance overall

#19 vocky

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Posted 14 April 2012 - 12:46 PM

Joe will be able to reconnect his original engine breather system ........ once he fits the LSJ ecu ;)

#20 JG

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Posted 14 April 2012 - 12:48 PM


I'm still not entirely sure i understand why it needs to be bigger, Is it to reduce flow rate?

resistance overall


but that still doesn't make much sense to me. its open, there is no resistance.





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