V7 SLR Posted April 9, 2003 Share Posted April 9, 2003 Anyone point me in the right direction please? I've looked around and cannot find a one-way check valve with the characteristics I need. I wish to allow air into my cam cover, which under normal circumstances produces a vacuum. On occasions it may produce a positive pressure so I wish to install a one-way valve to allow air in, but to prevent it from venting outward. The characteristics I need include: 1. Mountable horizontally. This means it cannot have *just* a disc or flap, but needs a spring to hold the disc/flap closed. 2. Very low pressure opening force. Typical ones I've seen are 0.35bar. This is way too high. The spring, as mentioned above, contributes to the opening force therefore I need a very "gentle" spring. 3. It is required to pass air only but will have occasional deposits of oil or petrol passing through, so needs to NOT react and degrade from such contamination. I thought of inserting a spring into one of the disc valves found in DT, to allow it to be used horizontally, but I doubt I could find a suitably "gentle" spring so as to not increase its opening pressure beyond what I need. A perfect vacuum referenced to atmospheric pressure can only result in a max of a 1 bar opening force. The vacuum in my cam cover will be anything but perfect, so the opening pressure of those I've seen (0.35bar) is too high. If it were made from a lovely piece of anodized alloy too... *thumbup* 😬 Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours Link to comment Share on other sites More sharing options...
Bill Shurvinton Posted April 9, 2003 Share Posted April 9, 2003 Sniff.....I know a man who can. Contact me at the home email. Bill Link to comment Share on other sites More sharing options...
V7 SLR Posted April 9, 2003 Author Share Posted April 9, 2003 Ooh, thanks Bill but I appear to only have your work email addy (Nokia). Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours Link to comment Share on other sites More sharing options...
V7 SLR Posted April 10, 2003 Author Share Posted April 10, 2003 I've not managed to get in touch with Bill, however I have identified some aluminium airhose type valves which look like they might do the job. Can any engineery-type of person check and validate this please? rswww.com In the quick search, enter 3847650. It's for compressed air installations. Observations: 1. Will it do the job I want, i.e. is it suitable for venting clean filtered air into the cam area of my head?, I'm particularly worried about the fact that it'll be working in an area where there is the potential for oil and petrol to contaminatethe valve. I'm not bothered if this results in it requiring a clean, but not to have to replace it. 2. The cracking pressure is very low (perfect). Something like 0.05 bar. 3. It's ally construction (read: looks hardy enough for an engine bay), but is rated only to 150 degrees C. Is that enough? How hot can the cam cover get? 4. Which one out of the two? Options are: Inside diameter (thread) Outside (A/F) Length 1/8 inch 0.55 inch 1.67 inches 1/4 inch 0.67 inch 2.13 inches The smaller would suit I'm sure, but I'm not very good with imperial measurements. Anyone with one of the new Julian Thompson cam covers know what type of thread is on the air spigots? Will the fact that 1/8 inch inside diameter is so restrictive that it can only let in a small amount of air and mean this will have an insignificant effect to the vacuum inside the cam cover? Also, bear in mind this is just a bit of fun... to solve a problem that's causing me no grief at all. It's one of those "if it ain't broke, have a go at fixing it anyway" type situations. Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours Link to comment Share on other sites More sharing options...
Rob Walker Posted April 10, 2003 Share Posted April 10, 2003 Nig, If your running with the gold scavenge pump then I think your wasting your time as there is only a negative pressure within the engine unless your piston rings are shagged and you are getting blow by. Link to comment Share on other sites More sharing options...
V7 SLR Posted April 10, 2003 Author Share Posted April 10, 2003 Piston rings are not shagged and I'm getting a vacuum in the cam-area of the head. It's common for all dry sumped engines to run in a vacuum for some reason. I wish to use this vacuum to assist with head-drainage. I need (read: would like) a valve for this to prevent occasions where oil may spit outward from the head. Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours Link to comment Share on other sites More sharing options...
max_torque Posted April 10, 2003 Share Posted April 10, 2003 what you need is an Audi part as fitted to 2.7 v6 and i think th e4.2 v8, basically it's a 3" diameter saucer shaped black plastic thing that has inside it a diaphram and a spring with 3 tappings. 1 to crankcase, 1 to air box (preferably post filter, or you could just stick a little filter straight on this pipe) and 1 that is left vented to the atmospere. It basically uses the diaphram and spring to move an orrifce to maintain an inwards (into crankcase) airflow that keeps crankcase pressure at around -10 to -15kpa. (in a std audi application the plenum has a tapping to the plenum to provide the suck via a PCV valve,but you can use your dry sump pump to pull a vacuum) unfortuantely for pose value it looks pretty dull! Link to comment Share on other sites More sharing options...
V7 SLR Posted April 10, 2003 Author Share Posted April 10, 2003 OK. Thanks. I'll have a look at this too. Please remember that I'm doing this for fun, as I said above. I am glorying in a teeny tiny minor engineering challenge. 😬 For "proper" engineering I bow completely to the experts. Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours Link to comment Share on other sites More sharing options...
Rob Walker Posted April 10, 2003 Share Posted April 10, 2003 I am well aware that there is a vacuum created when running sealed but why would oil be blown out of the head ???????????. I run with a 1.5mm restrictor in one of the cam cover vents the small amount of air that is drawn in is also filtered. This allows air in whilst running but more importantly allows air in on shut down to prevent the seals from being distorted when the oil pressure has fallen away. Link to comment Share on other sites More sharing options...
V7 SLR Posted April 10, 2003 Author Share Posted April 10, 2003 Ok, I see what you're getting at now. I agree that it should always be patially evacuated but I wasn't 100% certain that it would be at all times. I couldn't think of an occasion where there would be any net positive pressure, but my inability to imagine a senario doesn't mean there isn't one. If you're saying it is always negative, then you're right and I don't need a a valve. Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours Link to comment Share on other sites More sharing options...
Peter Carmichael Posted April 10, 2003 Share Posted April 10, 2003 Have run with the breather caps not positively attached and they don't blow off. Pressure is always negative. Formula one use spring loaded valves so partial vacuum maintained. Link to comment Share on other sites More sharing options...
Rob Walker Posted April 11, 2003 Share Posted April 11, 2003 Nig Like I said I don`t see the need for the valve. Just make sure you filter the air being sucked in. I found that running with the cam vent fully open resulted in an increase in oil consumption a greater amount of oil mist being blown out of the vent on top of the swirl tower. IMHO the restrictor is the why to go. 1.5mm seems about right. Edited by - Rob walker on 11 Apr 2003 09:14:22 Link to comment Share on other sites More sharing options...
V7 SLR Posted April 11, 2003 Author Share Posted April 11, 2003 Righty-ho . The spigot supplied with the cam cover has a very small hole. I was actually wondering whether it was too small to effect much difference. However, as I forgot to bring it to work with me today I can't say exactly how small it is. I can guarantee it is no larger than 1.5mm though. I'm intending to connect the spigot, via a short piece of hose, to the backplate of my airbox. The air in there passes through my brand air filter so it should be fine. Thanks guys. You've saved me about 20 quid for a valve. I'll keep a note of the oil consumption. Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now