355 Capristo bypass valve slow to close

I'm not sure if this is normal or not. On start up after sitting for a few days, I would imagine it would take a while for the engine vacuum to charge up the vacuum canister. The vacuum would also have to operate the secondary air valve with the car being cold.
When you say it's ok on startup after you have driven the car multiple times a day, I wonder if there is still sufficient vacuum in the vacuum canister from the previous drives? If the check valves are good on the vacuum system, then there may still be some residual pressure.

The behaviour when you "get on it" seems to confuse the issue. Surely should be plenty of vacuum during a drive. Maybe the bypass valve gets sticky when the temperatures go up?

I'm not sure of the internals inside these actuators. How do they get such a large range of mechanical movement from such a small capsule diaphragm? Also, are there helper springs in particular directions? Is it easier to open a valve than to close it (or vice versa).

When you installed the capristo bypass valve, did you have to mechanically pull/push on the actuator rod to make the linkages line up. I know in my Lotus Workshop Manual, there was a warning about not pulling on the actuator rod of the turbo wastegate with tools, but to activate it using a vacuum pump. I'm wondering if there is some physical damage to the capsule diaphragm. Capristo may hit you with this question, too, if they respond.

 

My mistake. I forgot that the capsule and valve are installed as one and no adjustment should be required. I know some folks try to adjust the linkages on the OEM valve to stop it rattling.

I believe the only things maintaining the vacuum in the "bean can" vacuum tank are cheap plastic non return valves on the vacuum hoses. Do you know if these were changed when the hoses were changed?

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I still don't understand why the problem should occur after high rpms.

 

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Apologies for the semi-thread hijack. Maybe it’ll be helpful though.

I’ve got a problem with my Capristo exhaust + Capristo valve and remote. With the remote set to valve open (default) it closes as soon as the throttle is sufficiently depressed - nearly the opposite of how it’s supposed to work. It sounds loud at idle and hitting the gas hard will essentially mute it.

I’ve tried recently disconnecting the vacuum hose and the valve stays open while sounding glorious at all RPMs, as expected.

Any thoughts about what would be telling the valve to close when the vacuum is hooked up and actually using anything but a slightly cracked throttle?

PS - I actually think the stock exhaust valve might have exhibited the same behavior. I was new to the car and just thought the stock exhaust was timid and robbed the engine of its proper sound but come to mind I think the original valve might have been performing identically. Is this a computer fault or something mis-wired?

 

Seems unlikely that someone would tamper with the solenoid valve wiring. Are the hoses going to the right ports on the solenoid valve?

For reference, the standard Ferrari solenoid valve looks like this with power coming in on the green/black wire:

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The ECU provides an earth when the valve needs to be opened.
Did your kit come with a Capristo solenoid valve?

Make sure you have the hoses hooked up to the appropriate ports on the solenoid valve.

 

There is a way to measure vacuum using a gauge. It is measured in psi and it takes 8-10 psi to open the stock bypass valve. The Capristo valve has reverse logic where vacuum closes it and no-vacuum opens it. Using a hand pump to operate the valve is a good first step. You can also use a hand pump to check the vacuum integrity of the system and that would be a good second step.

 

Indeed it appears the hose is connected to the original solenoid and the Capristo solenoid was overlooked by the shop. I've reached out to them to get it addressed. Thanks for the nudge!

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Aha! Easy fix. Let us know how you go with the proper (Capristo) solenoid.

 

if you have changed to the solenoid valve to the capristo one and plumbed it up correctly, it should work properly. Make sure you keep the bottom connection free as per the diagram above in Qavion's post.

 

No further troubleshooting is required. A Capristo solenoid valve must be fitted. The Capristo solenoid valve operates in the opposite sense to the OEM valve. This is the way it was designed (to match the Capristo exhaust bypass valve).

The Capristo solenoid valve is normally open allowing engine vacuum to close the Capristo exhaust bypass valve. When the Motronic ECU determines the exhaust bypass valve should be open (high engine load/rpms), it electrically energises the Capristo solenoid valve, closing the solenoid valve, shutting off the vacuum and opening the Capristo exhaust bypass valve. Loss of vacuum or power will open the Capristo valve (for safety).

 

Sorry, my mistake, I was getting you and Ivan mixed up.

If stored vacuum can hold the valve closed for 15 minutes after shutdown, it seems as though your vacuum system is good.

Have you tried contacting Capristo with your symptoms? Have they had any previous reports of, say, sticky solenoid valves?

 

An earth provided by the Motronic ECU on the blue/yellow wire. You should have 12 volts on the other pin (with the ignition on). i.e. on the green/black wire.


If there is voltage, you might want to do continuity checks between the Motronic ECU and the solenoid plug.

 

Sorry, I didn't realise you had a 95 car. The wire colours on the solenoid plug are different. Yellow is the power, blue/red is the earth from the ECU.
The exhaust bypass valve is controlled by the left hand ECU pin 21.

Your ohmmeter leads probably won't be long enough to stretch across the car between the LH ECU and the solenoid plug, so you will need a long piece of wire (say 4~6 feet). Set up the meter something like this:

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The resistance should be very low (depending on how good your connections are). You may need a piece of lockwire or fuse wire to insert into the plug socket/s. The multimeter probes may be too thick to insert into the connector sockets.

If the resistance checks are ok, on the 2.7 Motronic car, you have the option of swapping over the Motronic ECUs. This will tell you if the LH Motronic ECU is causing the problem or not.

 

As a preliminary step, you might want to check the resistance of your test leads with all the extensions and bits of wire attached to your leads. Any additional resistance during the actual resistance check of the car's wiring will be the resistance of the blue/red wire.

Note that there is one inline connector between the solenoid plug and the Left ECU plug. A corroded or bent pin on this inline connector might cause a high resistance. I believe the inline connector is located close to the ECU (not 100% sure).

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The parts diagram above appears to show the RH ECU. The LH ECU should be a mirror version of that.

If you don't have wires and crocodile clips and such to do wiring checks, maybe it would be best to jump straight to the ECU swap. Be very careful not to bend pins on the ECUs. Also inspect that inline connector.