Exhaust crankcase breather set-up - Scrapyard hunt?
Discussion
I want to make up a crankcase evacuation set-up for my car. A couple of companies make kits but they are in America and I don't want to wait a couple of weeks for delivery for what is essentially a metal pipe and a one way valve.
I'll need a one way valve that can handle exhaust heat. The plan will be to get to the local scrappy and have a look around but just asking on here incase people have a good idea what car I could find something suitable on. Or alternatively if there is a UK seller for these that Google hasn't been able to dredge up.
I'll need a one way valve that can handle exhaust heat. The plan will be to get to the local scrappy and have a look around but just asking on here incase people have a good idea what car I could find something suitable on. Or alternatively if there is a UK seller for these that Google hasn't been able to dredge up.
I used to have an MV6 3.0 Omega that had pretty much exactly that set up. Other v6 Vxs of a similar age may have the same thing, it was 1996 IIRC.
Beware with the Check valve though, I went through one just after getting the car, so check it works first.
Oh, and obviously don't use heater hose.
Beware with the Check valve though, I went through one just after getting the car, so check it works first.
Oh, and obviously don't use heater hose.
Edited by E-bmw on Wednesday 10th May 10:17
Thanks for the reply. Was it one of these? https://www.worldcarparts.co.uk/valve-secondary-ve...
E-bmw said:
I used to have an MV6 3.0 Omega that had pretty much exactly that set up. Other v6 Vxs of a similar age may have the same thing, it was 1996 IIRC.
It seems far more common to use intake vacuum and burn the breather gases. Didn't the exhaust extraction system cause problems with emissions? Do you know what pressure the valve needs to open at? The basic construction looks very simple and I imagine you could fabricate your own by welding a suitably shaped spigot into the exhaust and putting a one way valve somewhere in the line. I suspect the valve is attached directly to the spigot in that system you showed to prevent hot exhaust gases from entering the rest of the breather system i.e. the valve is exposed to that heat to avoid the hose/pipe from having to be exposed, which means you'd need a suitable rated valve. I've seen a few all-metal sprung flap valves in that sort of size which might do the trick. Judging by the pictures, that one you showed uses some sort of sprung poppet valve.
I'm still skeptical that this approach will actually add significant suction to your breather catch tank (i.e. compared to the conventional dead loss vent to atmosphere) under power, and also suspect that it's going to make emissions problems even worse if you need to be road legal, but the hardware looks simple enough to make if that's something you want to try.
I'm still skeptical that this approach will actually add significant suction to your breather catch tank (i.e. compared to the conventional dead loss vent to atmosphere) under power, and also suspect that it's going to make emissions problems even worse if you need to be road legal, but the hardware looks simple enough to make if that's something you want to try.
Escy said:
There might be some confusion, the system on the Omega is probably air injection for better emissions on cold starts rather than a crankcase breather but it'll work for what I want if I can find one so it's a good shout.
Well that makes sense from my recollection (10+ years ago) but if it helps, go for it!I did assume at the time thast it was to drag air into the exhaust to help in burning unburnt fuel, but was never sure.
GreenV8S said:
I'm still skeptical that this approach will actually add significant suction to your breather catch tank (i.e. compared to the conventional dead loss vent to atmosphere) under power, and also suspect that it's going to make emissions problems even worse if you need to be road legal, but the hardware looks simple enough to make if that's something you want to try.
There are a few reasons for wanting to do it, it's going on a mid engine car where there isn't much ventilation so venting to atmosphere isn't ideal, especially if there was a leak into the cabin. Plus a small vacuum is better than none at all. I can always disconnect the pipe if it's an emissions problem.The drawback i'm aware of is back pressure in the exhaust, people say they are no good on systems with silencers. They are typically used on drag cars with open headers in the US. I read about a tuner running one on a 800bhp Skyline on a 3.5" exhuast, it was working perfectly until they did a top speed run and the back pressure in the exhaust built up and then there is no where for the blowby to go, it shot the dipstick out and made a mess so it's something to be aware of.
I think my exhaust is perfectly suited to trying it. It's 3.5", there is a separate screamer pipe which effectively makes it bigger still and I'm going to place it after the backbox right at the end of the system. Being mid engine it's a short run to the catch can which is handy.
Escy said:
Yes, use the flow from the exhaust gas to draw a vacuum.
I don't know about flow rates but the standard breather pipe isn't that big. I expect it'll have to be quite small to draw a decent vacuum.
Any particular reason you don't want to flow it into the intake pre or post throttle body? It's been a few years since I've worked on a 2.7T but I'm sure as standard the PCV system is recirculated and burnt not dumped to atmosphere, certainly not run through the exhaust.I don't know about flow rates but the standard breather pipe isn't that big. I expect it'll have to be quite small to draw a decent vacuum.
Even with a catch tank I have a horrible feeling this is going to smoke and leave the back of your car covered in oil residue.
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