New Capristo 355 Exhaust Valve

I recently purchased the new Capristo Exhaust Valve for the 355. I bought it from Nick's Forza Ferrari http://www.nicksforzaferrari.com/forzaferrariwebsite1_002.htm Took a couple weeks for delivery, but he should be stocking them now. If you are not familiar, this is a direct replacement for the factory oem Pierburg valve. It's operation is slightly different, as it's resting state (engine off) is with the valve open, where on the factory unit it would be closed. When vacuum is applied, it closes, and when removed, opens. This is the opposite of how vacuum is applied to the factory valve, so in order to do this, a replacement Pierburg solenoid is substituted for one of the factory solenoids in order to reverse the vacuum direction.

Below is a photo of the plumbing difference. Note the two vacuum lines to the left solenoid are moved to the new Pierburg solenoid mounted above. Also, the Amp Junior Timer electrical connector is also removed from the factory solenoid and plugged into the Pierburg solenoid. Note the red vacuum line would normally be plugged into the bottom vacuum line on the factory solenoid. And the black vacuum line that runs to the Exhaust Valve would normally be fitted to the upper connection on the factory solenoid.

Note this photo came from Capristo. On a North American 355, you cannot mount the solenoid in that location, as a catalytic converter ECU resides there. I ended up simply wire tying mine to some cables slightly to the left and above in this picture. If I can find a better spot, I will mount it to something in the future. I was thinking I could even mount it to one of the cat ECU mounting bolts.
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Here are a few photos to compare the two valves. Note that the Capristo exhaust valve is apparently of their own design, and also uses an unknown maker vacuum bellows. The factory oem valve and bellows are both marked "Pierburg". Pierburg I hear also makes these exhaust valves for BMW M3's (E46 series).

Notice the Capristo valve has the vacuum line attachment on the top of the bellows. This created a slight problem, as the factory hose would not reach. Had to source a longer piece of hose, keeping in mind it is pretty hot around there, so needs to be heat resistant.

Notice also that the valve has a spring at each end, keeping it under a bit of tension laterally. I assume this is to prevent the valve from rattling like the factory unit.

So, how's it work? Very nicely. What I notice immediately, is that it opens a bit sooner. My factory valve opened at around 3500 to 3700 rpm, though the WSM states it should open around 4000 rpm. This Capristo valve seems to open around 3000 rpm...perhaps even a bit sooner...it is hard to tell, as I do not hear the transition as clearly as the factory valve, which almost "popped" open rather suddenly, this is much smoother and linear.
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Here is a picture of the end of the valve, with the spring. There is a spring on each end or side of the valve.
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Along with opening slightly sooner, I noticed the Capristo valve appears to open more willingly at part throttle. The factory system is supposed to only open at wide open throttle, or at least at "spirited" throttle openings, now it will open pretty readily if I dip into the throttle, without having to punch it.

I am satisfied with the minor improvements. There is also the safety advantage that if this were to fail, it will fail in the "open" mode, rather than closed like the factory unit. Granted, if it is closed, when it should be open, it should trip a "check engine" light, and you should hear the difference, but is nice insurance, against burned exhaust valves in the heads. More importantly, this has the potential to be more durable, and remain "rattle free" during it's life. Time will tell, and I will be the "f-chat beta tester"!

 

I believe the list is $999. Talk to Nick, he might be able to offer a discount off that.

 

BTW, the Capristo valve is considerably less expensive than the factory valve, which sells for anywhere from $1200 to $1800, depending on where you source it.

 

The valve opens, based on a signal to the solenoid from the Motronic ECU. The only way it can trip a CE light is if the valve is open when the ECU thinks it should be closed, and vice versa. It confirms this through the temperature probe off the Y pipe to the ECU. I can only surmise that the reason the Capristo valve opens faster, is it is simply responding faster. Remember, it is only opening and closing based on the signal from the Motronic ECU. It also seems to have slightly less resistance to opening and closing force...so requires less vacuum to operate. Again, I am only guessing. But the bottom line, is the Capristo valve should not trip a CE light, because it is only open and closed when signaled by the Motronic ECU, there is no way around that.


The reason wiring the factory valve open sets off the CE light on a Motronic 5.2 F355 (1996 to 1999) is because now it is always open, and yet the Motronic ECU is sending a signal at idle (for example) and the thermo probe is hot, telling the ECU the valve is open when it shouldn't be. Got it?

 

Actually, that answer is not correct.

Those rpm specs are not specified in the 5.2 Motronic section, but only mentioned that specific rpms exist. It would be interesting to confirm they are the same. In the 5.2 section it goes on to say for USA cars only: It will also open under very high throttle opening (ie high load), accelerating over 100 mph, or constant over 150 mph.

 

Hey JM3, no problem, but we must have different copies or something. What you printed was in the "2.7" section of my WSM (though formatted differently), and slightly different stuff written in the "5.2" section, though with a reference to rpm settings. If I could figure out how to copy and past from a pdf, I would...