Printable Version | Subscribe | Add to Favourites
New Topic New Poll New Reply
Author: Subject: Duratec Crankcase Pressure
ChrisJ15

posted on 28/1/18 at 03:38 PM Reply With Quote
Duratec Crankcase Pressure

I just ran up the Duratec in my Sylva J15 and it belched out clouds of smoke which it generally does when its been left for a while.
I noticed a hissing sound of air going into the catch tank so took the oil filler off the cam cover and ran it again and there's a huge amount of air that gets pushed out. You can feel each pulse of the engine.
There is a breather from the top of the cam cover and the one on the inlet side of the engine into a small catch tank. There isnt any oil in the catch tank.
Is this normal or do I have a problem? There cant be too much wrong with it because it got 196bhp on the dyno at Northampton Motorsport and it would smoke on startup then.
Probably worth adding the donor had only done 8k and there's no breather/filter on the catch tank.

[Edited on 28/1/18 by ChrisJ15]

View User's Profile View All Posts By User U2U Member
dave r

posted on 28/1/18 at 05:18 PM Reply With Quote
Only time mine did that it had cracks in the piston around the ring slots
Mine is similar power and on standard internals, seem to pull ok, just blew the top off my catch pot and steamed a bit
Do a leakdown check and compression check to see if they are all the same.





I'd love to give my imaginary friend a great big hug,

but this jacket makes it impossible.

View User's Profile View All Posts By User U2U Member
anthony1

posted on 28/1/18 at 06:28 PM Reply With Quote
EGR Valve......???

On my zetec engine there is a breather from the cam cover and one from a box on the side of the engine. The box arrangement had a valve fitted , in between the box and the pipe which I routed to the catch tank along with the other from the cam cover. I think if the duratec has a similar arrangement if the valve is left in place it will cause an excess build up of crankcase pressure......worth checking this out.
View User's Profile View All Posts By User U2U Member
ChrisJ15

posted on 28/1/18 at 06:47 PM Reply With Quote
I do vaguely remember seeing something about removing this valve.
Trouble is I started the build 7 years ago and cant remember if I did this or not!
I wonder if there's a way of finding out if I did do this or not as it's pretty well buried now?
I guess if there's no valve I should be able to blow down the pipe into the engine??
I was also wondering about fitting one of those filters on the catch tank to vent the pressure but dont know if the Duratec is designed to have positive pressure in the crank or not?

[Edited on 28/1/18 by ChrisJ15]

View User's Profile View All Posts By User U2U Member
peter030371

posted on 28/1/18 at 09:29 PM Reply With Quote
I read about removing the egr valve when I built mine. Unsure what to do I took it apart and checked what it did. It works by letting pressure out the crankcase but stopping higher pressure in the inlet manifold (presumably from the exhaust gas recirculating which we don't have) from pressurising the crankcase. I couldn't work out why it would be a problem on my build so cleaned it up and refitted it.

So far it seems to run fine.

View User's Profile View All Posts By User U2U Member
snapper

posted on 29/1/18 at 06:48 AM Reply With Quote
The crank case pressure valve is acticated by negative pressure in the inlet manifold, if you vent to a catch tank you won’t get the negative pressure to pull the valve open, crank case pressure builds up ang goes up the oil drains into the cam cover this then goes to the catch tank and without a filter on the catch tank the pressure has no where to go hence the chuffing out of the oil filler.
Remove crank case valve and fit catch tank breather.





I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)

View User's Profile View All Posts By User U2U Member
peter030371

posted on 29/1/18 at 12:20 PM Reply With Quote
Just had a read of this http://www.burtonpower.com/tuning-guides/tuning-guide-pages/engine-breather-system.html

When I striped my PCV (sorry I called it an egr before, my bad) I found it required very little pressure difference across it to open....so I left it in. However I do have a filter on my catch tank but I have not felt any air coming out of it when revved whilst stationary and I have felt for it. Whilst on the move, on track, I have no idea if I get much crankcase pressurisation as I can't reach the filter to see whilst driving

So far my catch tank has caught no oil to see in the sight tube which is still perfectly clean and also the engine has zero oil leaks from anywhere (wish I could say the same for the Type 9!).

View User's Profile View All Posts By User U2U Member
Angel Acevedo

posted on 29/1/18 at 02:57 PM Reply With Quote
If you feel pulses, I´ll put my money on a cylinder leaking into the crankcase.
If it were more than one, it would be harder to detect "pulses"
I also think compression test is in order.





Beware of what you wish.. for it may come true....

View User's Profile E-Mail User Visit User's Homepage View All Posts By User U2U Member
snapper

posted on 29/1/18 at 07:25 PM Reply With Quote
Pretty obvious next step, bypass the pcv
I have rebuilt an engine because of exactly this issue, just needed bigger breather pipes and a properly vented catch tank





I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)

View User's Profile View All Posts By User U2U Member

New Topic New Poll New Reply


go to top






Website design and SEO by Studio Montage

All content © 2001-16 LocostBuilders. Reproduction prohibited
Opinions expressed in public posts are those of the author and do not necessarily represent
the views of other users or any member of the LocostBuilders team.
Running XMB 1.8 Partagium [© 2002 XMB Group] on Apache under CentOS Linux
Founded, built and operated by ChrisW.