Ferrari 412. Uneven banks. Trying to diagnose the problem.

The references are engraved on the top.

Image Unavailable, Please Login

 

You'll need to be careful looking at photos of 412s as some may have been "converted" for US importation (and adopted to "quasi-Lambda" operation - at least at one time ). Your photos in this post are probably a 412 that was converted for the US as the not-connected-to-anything lower port (and the upper port being connected upstream of the throttle plate) is something that might be done if they didn't want to buy proper "with Lambda" WURs:

Stock 400i/412 WUR:
Upper port connected to vacuum (downstream of throttle plate)
Lower port connected to atmosphere (upstream of throttle plate)
Hard acceleration = lessens upper chamber vacuum = opens WUR valve more = lowers control pressure = adds enrichment

"With Lambda" WUR:
Upper port connected to atmosphere (upstream of throttle plate)
No lower port present (the lower chamber is a sealed anechoic chamber)
Atmospheric pressure drop (like going to a higher elevation) = lowers the upper chamber pressure = closes the WUR valve more = raises the control pressure = removes enrichment (as required for a lower atmospheric pressure)
This type of WUR does nothing for acceleration/deceleration

Cheesy way to convert a stock 400i/412 WUR to "with Lambda" operation:
Upper port connected to atmosphere (upstream of throttle plate)
Lower port connected to atmosphere (just left open or connected upstream of the throttle plate)
In this configuration, it will also do nothing for acceleration/deceleration (which it should for "with Lambda operation"), but it will do nothing to compensate for atmospheric pressure changes

Do your WURs have a lower port present, and are they connected to anything -- or are the lower ports just left open to atmosphere?

 

Thanks Steve for the detailed history of environmental hacks!

Second 412 photo has what looks like a frequency valve next to the k-jet distributor. First one has an unknown item on top of the timing chest. So none of these engine bays do look untouched.

I would revert to the stock setup, maybe a bit more work but the WUR WOT enrichment makes the k-jet much more responsive. No point in keeping such modifications considering these are not required where you live.

 

Yes, that's totally mucked up - and wrong for either without Lambda or with Lambda . If the added Frequency Valve has been removed, you should revert back to the stock arrangement as shown in the 412 SPC:

Image Unavailable, Please Login

Upper WUR port connected to vacuum (downstream of throttle plate)
Lower WUR port connected to atmosphere (upstream of throttle plate)

Are you confirming that the rest of the system has been put back to stock? No added Frequency Valve, no added ECU , and no O2 sensor(s) in the exhaust?

 

Yes, that pretty much confirms that it once was converted to "(quasi) with Lambda" at one time -- and whoever unconverted it didn't really know what had been changed and how to undo it correctly. No question that you'll have to retweak the idle mixtures as the control pressure at idle will now be some other (more correct) value.

 

I am away from my car and documents, but your vaccuum amplifying valve seems also quite dodgy in terms of plumbing, this green highlighted hose could play havoc with your right bank when idling if it is connected to the lower WUR chamber. Blue one is easy to re-route properly (to top WUR vent).

Image Unavailable, Please Login

 

Vacuum amplifying valve is for the transmission, that requires vacuum for the modulator (part throttle shift management)

 

The deformation is normal, but one of the hole did not line up just like what I experienced with mine :

Yours:

Image Unavailable, Please Login

Mine :
Image Unavailable, Please Login
Image Unavailable, Please Login

We used two different gasket brand, same problem. Our Ferrari k-jet looks like different than the one used on German cars...

Have you checked the wur pressure, as this faulty passage goes to the WUR.

 

I left a lengthy post in the other thread.