[maartenvandorst]

After replacing the stock T25 turbo on my NG900 with a TD04 from a 9-3 Viggen/9-5 Aero, the turbo intakepipe didn't fit anymore. The intakeside on T5 turbo's differs from T7 turbo's. An Aero spec T7 intakepipe was fitted, but it seemed to be restrictive at higher powerlevels. Most tuners replace it with a bigger one. These pipes are quite expensive, so I decided to build my own pipe connecting airbox and turbo.

The crankcase ventilation line was not connected to the new intake, but a small filter is fitted, as you can see on the picture.

This setup works fine, but Julian mentioned the following issue: The bigger of the hoses exiting the cam cover (the one that has the filter on) is used to evacuate crankcase gases during high load/full throttle. The vacuum in the intake where this hose would normally terminate is supposed to greatly assist the evacuation of the gases (basically sucking them from the cam cover). Since the engine lost this suction and is tuned for more boost, I am wondering if crankcase pressure could get excessive and if it might cause a problem in the long term.

 

[California Saab Tuner]

I've been told by many people this is not a problem. Many of them running in excess of 2 bar of boost on daily drivers. (Yes, Chrysler turbo boys are nuts)

The real reason for the recirculating one is for emmissions. You get a lot of oil fumes, and crankcase fumes coming through there. Much like in So Cal there are gas tank cap tests to make sure your gas tank isn't poluting the air with fumes, they check your PCV tube and make sure the system is functioning.

It should be fine as long as there is a filter like you show, to prevent debris from entering the engine. Though it couldn't hurt to adapt a recirc. tube if you feel you want to. I just don't believe it to be necessary.

Dubbya~

 

[mark e]

I'd agree with Adrian here and add that if you do decide to reconnect the vent to the intake, make sure you fit a check valve to avoid trying to blow oil out under boost.