Yeah, it is just a solenoid controlled vacuum valve. Most ECUs have the capability to control such a solenoid based on an RPM window. You could even control it with an aftermarket RPM switch if your ECU could not...but it seems like you are good to go.

Yes these relays can be RPM programmed to do different things, AC, fans, switches, etc.

Mark, the flapper is a butterfly actuated by a vacuum pot, activated by a solenoid valve. Vacuum supplied by a reservoir. A solenoid connected direct to the butterfly arm should work fine.

Do you have examples of the resonance butterfly being controlled directly by some solenoid? I would like to see that as it would save people from installing a bunch of vacuum lines, valves, reservoirs, etc.

Mark, here are some photos where the black plastic intake is a 1995 993 and the alum intake is about an 89 or 90 964. In the closer pictures of the 964 you can see the flap butterfly. Unfortunately I tossed this 964 part when I built a simplified replacement which is essentially a couple tubes, throttlebody, and your good to go. If you integrate a "flap" it was nothing other than a butterfly. Though this 964 part was magnesium it weighed quite a bit. Anyhow it's probably not difficult to find a used one.


Here is a description of the flap operation as written by Steve Wong:

Post from Steve Wong 5-25-2007

Checking Resonance Flap for Operation:

When the ignition is switched on, the resonance flap is closed by vacuum action. When the ignition is switched off, the resonance flap is opened (rest position). The opening and closing noise is audible in the engine compartment.

4. Resonance Flap

The DME control unit activates a vacuum-controlled diaphram valve which either opens or closes the resonance flap.
The resonance flap is closed between 3,000 prm and 5,000 rpm and at throttle opening angle of > 60 degrees.
Due to the ignition sequence, the intake system is alternatively supplied by both tanks. Due to the firing order, air is drawn in an alternating manner from both intake system tanks. If resonances occur, the intake frequency of one row of cylinders matches the natural frequency of the pressure vibrations in the respective tank. The natural frequency is determined by the geometry of the intake pipes, the resonance pipe and the tanks. A crucial factor, however, is the total length of the pipe from the actual intake cylinder to the next cylinder being supplied, the distribution in intake and the resonance pipe lengths as well as the depth of the tank in the direction of flow. In the no-current state, the resonance flap is open. As soon as the ignition is switched on, however, it is triggered and closed. If the DME control unit detects that the engine is being started, the resonance flap is opened again.


Pin 1 from the DME unit is used to control the resonance valve.





http://forums.pelicanparts.com/uploa...1614057205.jpg

http://forums.pelicanparts.com/uploa...1614057205.jpg

http://forums.pelicanparts.com/uploa...1614057205.jpg

http://forums.pelicanparts.com/uploa...1614057205.jpg

http://forums.pelicanparts.com/uploa...1614057205.jpg

http://forums.pelicanparts.com/uploa...1614057205.jpg

http://forums.pelicanparts.com/uploa...1614057205.jpg

Also note that the flapper in the 964 plastic intake setup is open when the solenoid is not activated (no vacuum) while the 1995 993 flapper is closed when the solenoid is not activated (no vacuum).

Well, it could be the other way around but I am 99% sure I have that right.

Thanks for the pics Jim, the intake I'm being given the center parts/TB were destroyed in the top end fire, so it's good to see what you did.

This is taken form another forum but shows a dyno from working and non working flap on 964 (plastic intakes). As you can see it makes a pretty big difference on the top end power.

http://forums.pelicanparts.com/uploa...1614113649.jpg

john

FYI a small 12V servo motor with actuating arm on a custom bracket mount can drive the resonance valve on the 964/993 intakes rather than the vacuum pod. This can easily be triggered by most EFI systems using an I/O pin.

I suspect the Porsche Factory chose to use the vacuum system because it was less prone to failure than a 12v servo motor strong enough to move the flapper and able to deal with being activated for long periods of time. A solenoid is much less likely to fail.

I'd like to see a servo motor setup that works and is reliable. Has anyone seen such a setup? All of the systems I have seen with a resonance flapper use a vacuum system. As I said, it would sure make things simpler...

Scott - you are correct on the 993 plastic intake, resonance flap is spring loaded closed.

All others - have a 993 plastic intake with resonance flap and throttle body tube with throttle if anyone is interested.

I saw similar results on my motor as the dyno with res flap closed beyond 5.5k.

So basically it looks like the flap opens at 5500rpm and stays open to my redline. That's easy enough to do.

First I have to get the two fire damaged intake halves I'm getting, to see if they're useable, before I can start fabricating. They're in Texas so I do have to wait a few weeks for the fellow to recover from the cold snap.

In the meantime I just sent my ECU in for an update cable install, this will allow me to update the software via download to current 2021 spec (system is a 2012), better datalogging and a few other feature details.
Totally worth it as it's only costing $125, which was about the cost of chipping the previous systems once.

Dang, my buddy can't find the intake so I'm back to square one.

I shipped my ECU off to get the data logger daughter board and cable installed. More Importantly this allows me to download and update the software when new versions come out. Only cost $125 plus the shipping for this upgrade.

Check with JoeMag to see how much his 993 intake setup would cost you.

Thanks Scott I didn't even see that.

JoeMag I'll send you a PM.

My pleasure!

I stumbled across 'Adapt Motorsport' from Australia... they have 964 manifold stuff like billet 2 bolt adapters, developing a DBW throttle body etc. Aussie $ is pretty much on par with the loonie to boot.

adaptmotorsport.com

Ross

Thanks, I'm capable of this in-house.

I just made a deal on two 964 aluminum intake halves, so I should have them before this Friday.
A member on 914world suggested a reversion flapper out of a Nissan that looks promising.

http://www.914world.com/bbs2/uploads...14480547.1.jpg

J Series Honda V6 have an electronic cable actuated resonance flap.