Ferrari 412 - Failed Inspection. High HC and CO Values

In my case the WURs were adjusted within the lower value of the spec (but WITHIN spec) - the "clue" was that it started and ran great when cold, but got progressively worse as it warmed up.

Incredible how just a few 1/10 of a BAR can make such a diffference - WCP spec is 2.7 to 3.1 BAR - and them at 3.1 BAR and ran terrible, once they were adjusted to 2.6 BAR the engine pulls incredibly, leaving skid marks. Ideally I would like to bring it down to 2.5 BAR.

Has anyone done the "adjustable" modification on the WURs?

 

I have seen a few WUR with adjustment screws installed. Not somthing I would do personally. But is has been done. It honestly looks like a rather simple mod to install. I think there are a few Porsche guys who have done it and they give directions how to do it an a few different Porsche sites.

 

I have done the adjustment screws several times. It does work pretty well and is a popular solution in Porsches 911SC for a WUR that misbehaves at cold start up.

Drill a hole on top of the pin, thread it for a small bolt.
Install a bolt, and a counter hold nut to the hole
Drive the WUR pin down with a firm knock
Turn the ignition on with car cold, counter hold the nut, turn the screw in the tightening direction while monitoring the WUR pressure until you get the fuel pressure you want.

 

It's ugly and not very usefull as it adjust cold start pressure, not the regulat control pressure. Well it does marginally affect control pressure if you lower the cold pressure to the point the bimetalic strip hits the mexican hat even when hot, but that's crude and horrendous in terms if polution.

First thing fist: fix the regular control pressure by knocking the reound cylinder that holds the inlet and outlet ports, then adjust the cold pressure by knocking the small round pin. If you knock too much, no issue just open the wur and knock the two cylinders from the inside.

 

Here is how to adjust it properly : https://www.ferrarichat.com/forum/threads/what-did-you-do-to-your-365-gt4-2-2-400-412-today.488990/page-9#post-148136419

 

So if I punch the "small" pin, I increase WCP, and the "large" disc, CCP? In both cases: IN = higher pressure, yes?

 

It works in opposite direction: if you knock the small pin it lowers the cold control pressure, whereas if you knock the large barel it increases the hot control pressure.

 

Got it - is there any "trick" to pull the cast iron barrel out without having to take it apart?

 

You have to take it appart nut as this is not involving disasembling the vacuum chamber this is not a tedious process. As you can see in the photos, my mechanic used a large socket in order to "push out" the barrel.