Has anyone with a C5 Stock LS1 Magnuson Blower who has experienced Knock tried venting the Crank through the Oil filler and plugging the manifold port (elliminate the PVC)?

Yes I know that this is illegal, and yes I know that you can now smell it.

I have been running with and without the PVC connected and logging with EFI-Live.

During acceloration:
With the PVC I hear slight knock and the logger reports 1 to 4 degrees.
With out, I hear nothing and have 0 knock.

Has anyone else experienced this?

 

was it a pre ignition sound? where does it occur-what rpms? boost pressure? ive been looking for a similar sound ,maybe your on to something. ive been told by magnuson that its the by-pass valve at between 1 lb vacuum-1lb boost, caused by the valve being 1/2 closed ,1/2 open. so far i have not solved it. let me know what you find out.

 

First of all my C5 is running great so these comments are only to investigate making a good situation better. :thumbs:

I have an automatic (A4) so the commanded A/F and timing is manipulated to reduce the torque on the transmission when shifting and deaccelorating. I can see knock after the throttle is released. This makes tuning the A4 more problematic.

When I am at WOT (not for long) there was audable rattle or detonation at about 5200 RPM which is immediately stopped by the knock retard (or the police). Without the PVC connected I have yet to hear this. On the Dyno they were not hearing or recording this and the PVC was connected.

Under part throttle and accelorating I hear what sounds like preignition, it is almost subjective, but without the PVC connected I dont notice it anymore, the autotap confirms a reduced amount of knock without the PVC. If you vent the crank out the filler hole select recyled air in the cockpit as the fresh air will pickup these fumes.

The noise at low RPM is a mechanical sound that happens when the engine is hot and at transition between neutral and first or reverse. I would raise the RPM but this makes holding at stopped harder with the A4. At higher RPM you could be dragged into the car infront.

The last time my car was on the dyno we recorded the AF at 10.8 which is contrary to the comanded value of 11.7. I plan to install a wide band to confirm this and look for a more optimum tuning.

Once again the car is running just fine as is. :lolg: I dont expect the fun factor to get any better and I dont know how it could. I just have the inclination to play with it! :rofl: I cant tell you how pleased I am with the performance of this Blower.

 

would you be able to vent the breather down below the engine compartment? like a draft tube from the old days. im going to give this a try id like to see if it eliminates the knock sound i have.