Dual Actuator Vanos

[David Ferguson]

So it sounds to me like as you are changing the cam profiles, you need to also reduce the mechanical range the VANOS is allowed to move. Is there some way to fit a pin, or machine a spacer/stop to reduce the operating range?

[Herrubermensch]

So it sounds to me like as you are changing the cam profiles, you need to also reduce the mechanical range the VANOS is allowed to move. Is there some way to fit a pin, or machine a spacer/stop to reduce the operating range?

Should not be a problem now. Different vanos unit, helical gear inserts to the correct depth but not beyond, no binding at any point in rotation. I absolutely will be using the M1 to manage maximum retard and advance. With the functioning mechanicals, that should suffice.

--Peter

[AndrewD]

... the bank 1 vanos seemed to allow the helical gear to go too deeply into the exhaust cam, allowing the cam gear to rotate beyond its factory rotation range, then stick and refuse to move. Piston to valve contact, resulting in smashed valve and cracked block and damaged pistons, all within 1:52 of startup.

Nasty.

I absolutely will be using the M1 to manage maximum retard and advance.

You can set the range of normal operation with the ECU but the extremes are still governed by the mechanical limits. During cranking (no oil pressure) the position is normally governed by lock pins (retarded inlet, advanced exhaust) that are released by oil pressure when the solenoids are actuated. You need to ensure the cams have been returned to the position required by the lock pin before the engine stops otherwise the exhaust cam could be retarded to the mechanical stop by camshaft torque during cranking. No matter what you do with the ECU the mechanical limits must be safe.

Unfortunately from what you described this early generation vanos system can suffer from a mechanical failure that effectively moves the mechanical limit, which results in catastrophic engine damage.

[Herrubermensch]

Correct, Andrew. Interestingly, the vanos unit covers provide a hard stop for the helical gears in one direction (essentially, assembly position). One learns this if one tries to set the timing with the covers off, as putting the covers on pushes the helical gears in a bit and changes the timing. So in one direction, there is a mechanical stop. And it is my belief that there is supposed to be a mechanical stop in the other direction as well, but with the machining done to the vanos gears (or some other defect), that stop was eliminated. In any event, none of this should be the case with my current build, so your prior statement--that however the M1 moves the cams, it should not pose any risk of valve-to-piston contact--should apply to this build. I am just a bit spooked by the whole experience, causing me to obsess about getting vanos control down pat!

Thanks for your help.

--Peter