xr4tic

I noticed recently that I was running lean by ~12% at idle, and I thought it had to with my MAF issues.

Then a thought hit me, what if it's sucking air in through my crankcase breather?

So I disconnected the PCV valve running to the intake manifold, and sure enough, I'm only lean by about 2% now at idle.

It's also interesting to see smoke rolling out of the crankcase breather at idle.

This is the PCV valve I'm talking about, it's only open under vacuum.
<img src="http://www.wideopenwest.com/~xr4tic/audi_crank_breather_lo.jpg">

So I was thinking of going to a closed-type system, and run a hose going to the intake before the turbo, but that would still be considered unmetered air in my configuration (blow-thru MAF)

I could possibly install the other PCV valve (the one that goes pre-turbo) and hope it limits the amount of air that gets sucked in under vacuum conditions.

I'm thinking worst-case scenario, is that my emissions at idle will be bad, but I'm wondering if it would have any long term effect on ring-wear due to lack of vacuum at idle and cruise.

Any thoughts?

CharlieGSanD

but its is still in the Parts gatehring stage

ill let you know if i get any results

SMOKINA4TURBO

I been running a tube right out of the block, no PCV...hrmmm can I just throw a check valve on there? Yea I wonder if its been sucking in unmetered air.

So whats your thaught on picking up a S4 oil cooler vs. going external and having a couple lines made? My cars oil temps are always pretty cool anyways and since I drag a bit too if I go external the oil will always be really cold during runs.

I also hate waiting for oil temps to rise and I think with a big external it would take days. Hrmm.

Good thaughts on the PCV valve.

xr4tic

it would stop the air from being sucked in under vacuum, but I would think it might hamper the ability for the crankcase to breathe under boost, and it would have to be a big check valve.

Now that I think about it, that might be the ideal setup.

Something like this:
<img src="http://pictureposter.audiworld.com/12130/pcv.jpg">



I don't know if I'd ever go with an external oil cooler. Here in Michigan, during the winter it takes forever to heat the oil up. Probably even longer with an external setup.

You could probably do both. Run the internal and a small external (with oil thermostat). You wouldn't have temps any lower than you usually see, but any long periods of time spent under WOT, where the oil will usually get a lot hotter, the external should help keep it at the same temp as normal.

If the S4 unit costs as much as a small external setup, I'd add a small external setup to the stock unit.

Mike O.

Aren't you going to have oil all over the MAF that way?

WYSIWYG

i have that big check valve

SMOKINA4TURBO

Doesnt seem ideal.

Why not like right out of the crancase port on the block a tube, check valve and then catch can?

You can see in the picture the rippled tube is coming off the crancase. Just throw a big check valve that will allow oil to pass and then the catch can.

markbradford

Oil temps stay pegged at 180, unless on the track, where it will get up to 200-205 max (Road AMerica)

Vic995

Once the O2 sensor heats-up, shouldn't the idle run in closed-loop mixture control mode?

xr4tic

theoretically, vacuum increases the ring seal.

Since most of the time is spent at idle and PT, not WOT, then having less ring sealing may cause funky ring wear, or increase the chance of polluting the oil.

It's all speculation of course, but it shouldn't be hard to do, and I don't see a reason not to do it.