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Old 12-08-2019, 11:20 PM
Join Date: May 2009
Location: New Jersey
Posts: 15
docnabimmer is on a distinguished road
Oh, its an M54 with the M56 valve cover mod but my co sumption for worse because of a bad diaphragm(CVV).The plastic cover breaks without a replacememt membrane available other than the Russian membrane.Over at e46fanatics,. There is however a Paraklas updated cover that u can use the Russian membrane with and user e46sulev cover and membrane that will be available soon.These fixed the excessive vacuum that some M56 cover mods have encountered.
I couldn't wait and decided to do the Bave39 MoD first.
Thank you CN90.I assume you have no codes developing after the mod with NO Oil consumption.
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Old 12-09-2019, 04:57 AM
Join Date: Nov 2019
Location: Pa
Posts: 3
2004325ciLover is on a distinguished road
I did the mod Friday but on cold start an throwing lean codes. My long term fuel trims are high and idle. Under load they normalize which indicates a vacuum leak. Anyone else experience this?
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Old 12-09-2019, 05:01 AM
Join Date: Nov 2019
Location: Pa
Posts: 3
2004325ciLover is on a distinguished road
Originally Posted by Xelo View Post
Hello again,

I am planning to do this modification also (including a catch can) but after days of studying I've stumbled upon one issue that has not been adressed (or addressed too little).

There are 2 versions for any PCV system: open and closed.
Open ones are venting the blowby gases to atmosphere, closed ones (as in this case for the M54s) are venting the "filtered" air back into the engine through the intake manifold.

Now comes problem #1: this "filtered" air is not measured .

MAF measures air coming through the intake manifold, but the one coming back from the valve cover through this modification is routed back into the IM AFTER the MAF (through distribution cover) - so there is a surplus of air going to the cylinders, although the ECU has measured less and O2 sensors will measure more.

This will cause crazy fuel trims.

Any schematic of closed PCV system on the net is described as having a venting hose coming from the air filter (so metered air) which allows the crankcase to breath.

See examples below:

Returning to the case of M54 engines: OE system does not have a supplementary/aditional valve cover breather as I remember. The only port of the VC is the one going to the CCV.

So this raises so many questions:
1) Why does the OE M54 CCV system does not have a breather allowing the crankcase to draw air from the intake
2) Would this breather be a good idea as it still allows vacuum but also protect engine seals ?
3) Where would the best connection for a breather be ? I have heard a case where the guy connected a hose from the vacuum F connector in the intake boot to the oil dipstick. If so, would this need a non-return valve (for the improbable case oil from the crankcase/oil pan would come up and flood the intake) ?

My take on this:

You're right. I did this and my ltfts are crazy high at idle because of the massive amount of unmetered air from the crank case.

I did however just drive 350 miles on the mod and got some awesome gas mileage (30.2 mpgs). Ltfts may be wacky at idle but she sure runs good. If oil consumption is down, I'll consider it a win.
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ccv, oil separator, pcv, vacuum, ventilation

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