Varioram flappers not operating, need advice

[Porsche84]

Hi Guys

I installed a Varioram engine in a 74 911 and the engine runs great but the Vari-ram flappers do not seem to operate. The 993 shop manual says that the flappers should cycle when the key is switched on, they do not. I have plenty of vacuum. I do not see a voltage signal to the solenoids when the key is switched on. If I put external power to the solenoids, the flappers all work. Any thoughts on why the ecu is not providing the voltage pulse?

Also, I'd like to find out when each of the flappers is supposed to operate. Any info on that would be appreciated.

Thanks a bunch for any input. Happy Holidays.

[axl911]

The dme doesn't provide 12v to activate the vram flapper. It actually grounds the 12V incoming signal.

In short, there should always be 12V on one lead of the vram connector. The when the DME wants to activate the flapper, it will ground the other lead to ground.

So check to make sure you have 12V on one lead (should be the red/white wire). Once you have that, check the other lead for resistance to ground. Normally, it should be infinity to ground, and zero when the DME flaps.

[Porsche84]

Thanks for the input, I was testing for voltage across the leads.

Do you know when each flapper is supposed to operate? It looks like it is set up to operate under two separate conditions, most likely rpm related. Since this is a track car, and usually operating in the 4,000 to 6,000 RPM range, I was considering trying the car with a button on the steering wheel to operate them, if I can't get the ecu to do it.

Thanks

[axl911]

Sounds like you don't have the 12V source hooked up.

Both flappers should cycle when you initially turn the engine to on position. Then one activates at 5160 and the other one at 5920 rpm.

If your ECU can't do it, I would simply buy two RPM switches and use them. These info are all on Rennlist including a posting on how to convert a non-vram 993 into vram. BTW, that is how I know these things.

[axl911]

Here is the info posted:

When the ignition is switched on, the DME control unit activates the solenoid valves. If the engine is started, the intake pipe extensions and the tuning flap are cycled. When the engine has run up to idle speed, the signal to the solenoid valves is deactivated and the intake pipe extensions and tuning flap are set to their basic positions.

If the engine speed reaches 5160rpm and the throttle valve is at least 50° open, the DME control unit transmits an electrical signal to the solenoid valves of the intake pipe extensions and the extensions are operated, switching the intake system over from vibrating tube to resonance mode.

If the engine speed is higher than 5920rpm and the throttle valve is more than 50° open, the DME control unit opens the tuning flap, increasing the resonance tube crosssection.

[Porsche84]

Thanks for all the help. I do have voltage to both connectors, but it does not provide a ground when the key is switched on. I think we'll try it on the track as is. It has been driven quite a bit without the flappers working because there was no vacuum hooked up. Now that I have all that sorted out, I think the owner can feel the difference if they are working. If they don't I'll go the RPM switches you mention. Thanks a bunch

[Bill Verburg]

Originally Posted by Porsche84

Thanks for all the help. I do have voltage to both connectors, but it does not provide a ground when the key is switched on. I think we'll try it on the track as is. It has been driven quite a bit without the flappers working because there was no vacuum hooked up. Now that I have all that sorted out, I think the owner can feel the difference if they are working. If they don't I'll go the RPM switches you mention. Thanks a bunch

Are you using the DME and wiring harness that correctly goes w/ the engine? chip?

It sounds like the engine isn't receiving the signals from the chip

[Porsche84]

That's an interesting question. The engine was purchased from a very well known shop in Arizona and was supposed to be "plug and play". It was promised with a euro brain and harness to avoid the lock block issue (about 4 years ago). I could not make the car run. The owner took the car to NJ where an elerical wizard worked on it for three days using an oscilliscope etc. He finally found two wires reversed in the crank sensor (I think). Nothing I did. Along the way I sent the ecu and igniter off to a well known person who does 3.6 conversions to verify that the ECU was good, but that turned into a mess. I got it back after many calls with out the igniter. So, the short answer is, I do not know about the ECU. Can you tell me what ECU number it would be if it was a euro one? The car really runs well. I had the engine out to work on the tranny and noticed that there was no vacuum to the flapper solenoids, so that's why I am chasing that issue now.

[Bill Verburg]

Originally Posted by Porsche84

That's an interesting question. The engine was purchased from a very well known shop in Arizona and was supposed to be "plug and play". It was promised with a euro brain and harness to avoid the lock block issue (about 4 years ago). I could not make the car run. The owner took the car to NJ where an elerical wizard worked on it for three days using an oscilliscope etc. He finally found two wires reversed in the crank sensor (I think). Nothing I did. Along the way I sent the ecu and igniter off to a well known person who does 3.6 conversions to verify that the ECU was good, but that turned into a mess. I got it back after many calls with out the igniter. So, the short answer is, I do not know about the ECU. Can you tell me what ECU number it would be if it was a euro one? The car really runs well. I had the engine out to work on the tranny and noticed that there was no vacuum to the flapper solenoids, so that's why I am chasing that issue now.

You probably have the same info that I do as to parts #s, i just lok it up in PET or go to Steve Wongs site


You may have to do some digging in the wiring harness but one common variant is using a '95 non vram DME and harness on a vram motor.

if that is the case then the trigger for the resonance flap is the white/yellow DME wire at 21 pin connector X60 pin #4 this goes to the gray/white engine harness wire. Overall the signal goes form DME pin #32 to the grey/white engine wire

the trigger for the vram is the grey/white that is the resonance flap wire on non-vram cars. the this goes to connector x60 pin18 which will have a greeen/white on the engine side. When done there should be continuity between the DME connector #1 and the GREEN/WHITE connector on the VRAM Solenoid actuator connection.

[Jaskas]

Thanks again fellow pelicanites, this thread helped me to find out that my v-ram was infact working as it should