merchauser

interesting...so if you did alter its settings with a sharktuner, would you want to change the parameters, and why....?

FredR

If and when I ever know Porsche's engine better than Porsche I might consider changing the set point!

I dare say that when one dick's around with exhausts, camshafts, cam timing and whatever else it may well be that the optimal transition point changes a bit. To determine such one would have to obtain dyno curves for for the various permutations with the flappy full open and full closed for each case one wants to consider and superimpose the curves. I seem to remember that such has been tried but who what and when is not registering in my decrepit grey matter.

worf928

white93nsx

Can you share how to test the flappy with the tape over the bolt method as Bill Ball tested mine at last year's Sharktoberfest and mine was not working. Thanks, Mike

worf928

Pull the rubber cap in the center of the intake plenum. Stick a piece of tape on the thus-exposed spindle top. Start car. Tape should cycle 90° and then back.

If not, then the flappy isn't working.

firemn131

What sizes do you recommend?

Geza

Does anyone know what the resistance of a functioning flappy actuator coil might be? I measured ~27 ohms, which seems reasonable. My flappy valve ('87) appears inoperative (based on not cycling during start-up) and I'm trying to determine whether it's the actuator or the electronics controlling the actuator. Thanks.

worf928

I've yet to find a failed flappy solenoid valve (FSV). It's always vacuum in my experience.

Get your vacuum hand pump. Remove the rubber elbow (still attached to the vac line) from the FSV that runs to the intake. Attach your hand pump to the elbow and pump it to ~12 PSI. Do you see the tape on top of the flappy spindle rotate? No? Intake refresh.

If yes, connect your hand pump to the other vacuum line from the FSV. When you disconnect this line from the FSV do you here hissing? No? You are not storing vacuum in the vacuum reservoir or your lines to the FSV are switched.

Make sure your vacuum lines are connected correctly to the FSV. The line from the 4-way check valve at the booster goes to the FSV port that points towards the water pump. The vacuum actuator line that goes under the intake plugs into the FSV at the port that points at the sky.

Do these tests and report back.

worf928

@Geza BTW, picture of correct vacuum line connection to the FSV is Figure 32 in my inspection guide (download link in my signature.)

Geza

Thanks Dave. That inspection guide is a nice piece! I just completed an intake refresh and the FSV vacuum connections are correct. The flappy valve easily opens with mouth generated vacuum, and the source line back to the brake booster seems to hold vacuum, too, but I need to recheck with a soon to be acquired pump. Both check valves at the booster are new. I'll keep working it - I see the guide has some electrical tests to be conducted. Thanks again.

worf928

Thanks.

Great.

Good. (Yuck. But, good )

Ok. At the risk of being labeled a pedantic a$$h0le we need to parse this out.

The source line should not 'hold' vacuum; it should 'pass' vacuum. A collapsed vac line will hold vacuum but will not pass vacuum. This is why I asked if you heard hissing from that line when it was disconnected from the FSV.

If when the engine is not running, you pull that line and you hear no hissing then either the line is collapsed (rare) or you are not storing vacuum in the reservoir due to leaks (common.)

If you hear no hissing from the line, then disconnect it from the 4-way and see if it has collapsed: your vacuum hand pump should not be able to draw a vacuum on it (or, alternatively, you can see if you can blow through the line.)

If the line is not collapsed then the next test is to make sure you have vacuum on the line when the engine is running. For that you'll need your gauge-equipped vacuum hand pump. Attach the pump to the source line at the FSV with the other end attached to the 4-way, start the car and see if you've got vacuum.

If you have vacuum with the engine running then the reconnect the source line to the FSV and rev then engine past 4k rpm (best let it warm up a bit) and see if the flappy spindle tape moves. This 'reving' is not an exact science. It takes more than a stab IIRC: the LH isn't fooled by a stab you have to bring the revs up from idle past 4k over 2-3 seconds.

IIRC (it's been 10 years since I wrote that guide) it doesn't go into flappy diagnosis except for vacuum.

While you are waiting for your vacuum hand pump you can test the FSV. It's a simple 12v switch. If you have a 12v power supply (I dis-recommend using a car battery) you can, with the engine running (so that you have source vacuum) apply 12v to the FSV's pins and see if the flappy spindle tape rotates. Look at the FSV harness plug to figure out polarity. Black wire is + and green/red is -. (But, double check the wiring diagrams just in case my quick look at them is wrong.)

Last but not least, you can hook up a voltmeter to the FSV harness plug and see if it's getting 12v for a fraction of a second after startup. An analog meter is best for this, but a DVM might work too.

Geza

Did some testing: Takes ~7 in. Hg to fully open flappy valve; FSV appears operational - applying a 12V source makes it click. Upon start-up, I'm getting 14-15 in. Hg at the FSV source line. Running the engine up past 4000 rpm does not open the flappy valve. I did not measure the voltage at the FSV at start-up.

After a drive today, during which I ran the engine hard on occasion, I experienced a noticeable upward surge in torque around 4K, during full throttle acceleration. I'm thinking the flappy is working during operation?

The inspection guide does have some electrical test info for making the flappy operate - see fig. 42

worf928

Based upon what you’ve so far reported - no cycle at start - along with your tests, you need to determine if vacuum storage is working or not. I’ve mentioned this before —^. No vacuum storage will result in no start-up cycling and inconsistent operation when running. If you are storing vacuum with, at worst, only slight leakage such that after sitting for a hour or so, you still have >8 in-mg vacuum on the source line then we have to diagnose LH to FSV.

Geza

Failed to mention this: I also tested the vacuum input line to the small check valve at the brake booster. Took a while to pump it down, but I got it to15 in. Hg. It did not hold steady, but lost vacuum very slowly. With this under vacuum, I pulled the FSV supply line off and did hear it "hiss", and watched the vacuum drop.

worf928

Ok. So you are storing *some* vacuum. Let's completely rule out vacuum issues:

1) Operate the engine to 'fill' the vacuum reservoir. (A t-fitting for the FSV source and your vac gauge would be handy so that you can monitor vacuum while keeping the system closed.)
2) With engine off manually cycle FSV with 12v and verify flappy rotation.
3) Reconnect FSV electrical, ensure vac at >8 (what ever your flappy threshold was)
4) Start engine see if flappy rotates.

If #2 fails then FSV is not doing its job despite 'clicking'
If #2 works then vac system is ok(-ish).
If #2 works and #4 fails then use multimeter to verify lack of 12v cycle on FSV plug during startup and then prepare for LH/wiring diagnosis.