jackal2513

hi chaps,

in the service schedule it says:

resonance flap and varioram: check operation

&

throttle linkage: check for smooth movement and full throttle opening


anyone know how I achieve these ?


thanks in advance

NineMeister

The throttle is easy, just get someone to floor it (with engine switched off!) and reach over the engine to feel if there is any movement left in the throttle linkage. Be careful though as the movement of the linkage can nip your fingers.

The resonance flap and varioram function has to be tested with either the Porsche "hammer" or a system tester & the engine switched on but not running. There is a function in both of these to test ecu outputs and provided you have vacuum stored in the engine's vac reservoir, a functioning system will operate the solenoids and allow the vacuum to the actuators. If you don't have a system tester, you can test the solenoid and vacuum functions by rigging a 12V supply direct to the solenoids (behind the heater blower on the manifold) with the engine turned off.

Fly911

Colin, I have a '95 with a non VRAM, what happens if the resonanse flap stays open all the time? Will i lose power/torque in the mid range?

Bill Verburg

They cycle when the ign. is turned to run. You should be able to hear them.

I posted the operational modes here

On non v-ram 993 the resonance flap has 3 modes too

0-3500 open
3500- 5520 and more than 60* throttle open closed
5520 -6640 closed

NineMeister

The open state of the resonance flap increases power from 5600 to redline. If the flap remains open below this rpm you will be significantly losing out on mid range torque. I'll see if I have a dyno plot on my laptop and post the overlapping curves tomorrow.

CalvinC4S

96-98 Varioram

Both actuators cycle?

right is flap valve and left is tube sliders, right?

1pcarnut

With a helper in the car, watch the varioram arms on the intake manifold and they will cycle when the ignition is turned on. Don't need to start, just turn on the ignition, so long as there is a little vacuum left.

epj993

You'll also want to periodically check the vacuum. Here's what the shop manual has to say ("special tool 9160/1" is a vacuum gauge that displays in bar):

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 flag is opened (rest position). The opening and closing noise is audible in the engine compartment.


Fuel System - Checking Vacuum System For Leakage:

General
If there are leakages in the vacuum system, the variable induction system may not operate correctly and there may be a reduction in engine power output.

Leakage Test
1. Run engine until operating temperature (70...90 degrees C oil temperature) is reached.

2. Remove vacuum hose from solenoid valve (fresh air/engine air) switchover flap. Attach special tool 9160/1 to open end of hose (on vehicles not equipped with a switchover flap, the plugged hose end is under the intake system). (This is up front on the left, attached to the heater blower box)

3. Start engine. Hold engine speed at 2500 rpm for about 10 sec. to build up vacuum.

4. Turn off ignition.

5. Test function of slide valve actuator. A second persion is needed for this work. Turn on ignition. As you turn the ignition on, the second person must observe the movements of the two levers on the intake pipe. If the levers are moved as the ignition is switched on, the slide valves and vacuum capsules will operate correctly. If the levers do not move, the vacuum system, the vacuum capsules or the slide valves may be faulty.

6. Pressure maintenance test on vacuum system. The ignition is still switched on. After the completion of items 3 and 5, the vacuum in the vacuum system must still be at least 0.64 bar. The pressure drop over about 3 minutes must be no more than 0.02 bar. If the pressure drop is higher, the entire system must be checked for mechanical faults.

7. After the test has been completed, reconnect vacuum hose to solenoid valve.

NineMeister

Dyno plot of nonVarioram 993 engine on Motec as promised. What I have demonstrated on this test is the differenec in the resulting power curves when the operating state of the resonance flap is reversed, hence the red curve is the correct version with flap closed to 5600rpm & open to 7000rpm; the blue curve is the wrong version with flap open to 5600 and closed to 7000rpm. Hence if your flap was set permanently open, you would get the best power above 5600 but lose a lot of bottom end torque from 3500 to 5500rpm.

DanL993

WELL DONE to all. I don't need this service yet but copied it all (including that great dyno analysis) and will use it later.

What a great source you all are--thanks.

jackal2513

thanks guys

arms moving nicely when ignition turned on

is that any guarantee though that the flaps will work at 5160 & 5920 ?