Admittedly this is a niche question.

I've been running my modified SC for 18 months and over 10k miles, and through it all I've been routing my PCV/ Crankcase vent house/ blowby gasses out into the environment. I tried an oil catch can with a breather, but it was just messy, so I ported the gasses into the air, minus the catch can.

But now I've recently rerouted the blowby gasses into my pre-boosted, post-MAF air intake, as was the intended design of the manufacturer.

My reason not to like this is that it sends the nasty blow by back through the intake, and it may very marginally may raise air intake temps.

But since doing so I've experienced more eratic idle at startup- specifically, upon starting I idle right at 880RPM's, not the usual 1,200 RPM's, which then settles into 880.

I can't sort out why this minor change in blowby would impact idle at startup.

Could it be that this minor add'l air being added after the MAF is alterning the AFR such that not enough fuel is being added to the chamber? Maybe fouled plugs? Any thoughts?
CATTMAN

 

IMO,rough idle could be a dirty MAF sensor.CHEAP and easy,clean it and then try it again!
Also you could pull a plug and check them....but seriously start with the MAF.
Let me know!

Stacy

 

Well, if it is a dirty MAF, it's got to be due to the blowby being recirculated through the intake. Even thought it's re-entering the cycle after the MAF, some of it must be fouling the MAF. Wierd. I'll pull it out and clean it and post results.
CATTMAN

 

all the samples of cars with SC i saw had oil catch cans - it is not anything specific for Porsche.
imho if previous vent out solution worked well - why to change it? your MAF also could get oil on it if it ws in the vented gas.

 

John,
Sitting here thinking and because you must have pulled the intake out(pre charger) to run the crankcase vent tube,I bet you have an air leak.Air leaking by after the MAF and you will get a rough idle as well as mess your AF ratios up when on throttle.Using you boost/vacuum gauge check the vacuum at idle and report back.

Stacy

 

Stacy,
I believe that I do indeed have a boost leak. I need someone to ride shotgun with me tomorrow and keep an eye on the gauge while I punch it WOT to redline. As far as I can tell, I am getting only about 4psi, and I used to get 6.1psi.

I'll retrace everything, but honestly, I can't find the leak. Though there obviously is one. I'll begin the dissection of the intake again tonight, ugh!
CATTMAN

 

You won't see it and unless the hose is completely 'off' or maybe folded under!
I am guessing that BECAUSE you are not seeing full boost and have a rough idle....the leak is most likely after the charger BUT check all the connecting hoses!

Good-luck

 

Not sure of differences from 996 to 997 however, like others have said most run closed loop system including me feeding the crankcase air back "After" the MAF metered airflow going into the comp. At idle there should be no bypass via BOV and will not see any boost press. I would suggest checking with a Durametric to see voltages at MAF, O2's etc or maybe disconnecting the MAF to see if idle is better. As I recall mine (996) idles at 750 to 800 sorry can not be more specific for a few days as my SC is going back on now. Here is some excel spec sheets of my tune before my IMS problem. Hope this helps.

http://www.webbspot.com/Porsche/fvdvideo.html

 

I am sure it's a boost leak, so I'll check and tighten things down again tomorrow, as well as clean my MAF for good measure. I made no big changes so it should be simple, although it will certainly shred my hands again, there's no room back there, LOL!
CATTMAN

 

Hi Carter,
I am sorry to learn that you will not be installing the SC, I was looking forward to watching your progress. As for selling your kit, I would encourage you to list it on the for sale forums on this site, rather than here in this informational thread. The for sale forum is a very healthy and active one- I've bought and sold there, very smoothly, several times.
Good luck!
CATTMAN