Alternative to Yellow, Overboost Relay?

[Alan L]

My thought also. All happened in slow mo. Aquaplaned then slowly half rotated as I tried to get it back. Almost had it - then the concrete wall jumped out and attacked the front. I quickly put the engine in the back and saved that bit. Not much up the front anyway. A 964 right in front had same, but managed to save it.
The crash crew arrived , asking if I was OK
My concern was I couldn't get reverse to get the car off the wall. They kept asking if I was OK, I kept complaining I could not find reverse. The car had been shortened enough the clutch cable would not work. Needed a new adjustment.
Alan

[boosted79]

Get rid of all that BS and wire in an inertia switch. Wire a sw into the pump coil circuit so you can turn the pumps off with the ign sw on if you want to since the pumps will be on as long as the ign is on. Inertia sw is out of a Taurus.

[flightlead404]

Originally Posted by full quack

I still have the airflow plate sensor connected and only have a red relay in the rear fuse/relay panel and nothing else {see picture}, plus no frequency valve, no lamda stuff, no O2 sensor.

I have owned the car for 11 years, put 63,000 miles on it. Never once had a starting issue caused by this topic. If the engine stalls or stops for any reason, the pumps stop immediately!

The car still retains the factory several second run on delay when you turn of the engine...all the normal stuff, just none of the headaches.

Sure if the engine is running and a fuel line gets severed, it's going to keep pumping until low fuel pressure shuts down the engine.....but the yellow relay won't save you there anyway. The yellow relay mainly deals with overboost protection, not crash protection. The only crash protection we have is our feet on the pedals and our heads not up our ass.

Mark

The run on delay is from the time delay relay that controls the CDI.

If you have the airflow plate sensor in the circuit the fuel pumps ground through that so it should shut off for you.

[boosted79]

I should have added that the red jumper from 85 to 86 is not necessary for the inertia sw install. I jumpered it to send power to the air meter contact connector which I then used to supply 12v to my Pierburg valve. The inertia sw mod eliminates two of the most common problems on these cars, the air meter "overboost" relay and the air meter contact.

Also, the air meter "overboost" relay, red or yellow, is a misnomer, it has nothing to do with overboost protection. The boost limit sw located on the intake provides that by opening the ground side of the pump relay coil circuit. The only thing that triggers the air meter "overboost" relay is the air meter contact.

This is on a '79, pretty sure the later years are the same except they added a time delay circuit in the "overboost" relay so they can charge $100+ for a stupid $5 relay. Get a $5 Taurus inertia sw at a pick and pull.

[ScottDAnderson]

What do those fuses ( below the relay 's )control .?
My middle fuse is missing the bottom one was burnt out / broken.
Replaced the bottom one and dropped the one for the middle.😡
Was wiggling everywhere and now car won't start today .

[Rawknees'Turbo]

Originally Posted by boosted79

. . .
This is on a '79, pretty sure the later years are the same except they added a time delay circuit in the "overboost" relay so they can charge $100+ for a stupid $5 relay. Get a $5 Taurus inertia sw at a pick and pull.

How about $245 for the official, Porsche badged relay (more than the cost of a good, new 8000 BTU window a/c unit)! I know that Porsche, Ducati, etc. charge ridiculously high prices for parts because they can (people are willing to pay to play), but when I see things like that, I still get a feeling of disgust over the criminality of it.

I was thinking of you when I made this thread and was hoping you'd chime in (forum leg humping and butt snorkling) - I really like your idea and may copy it.

Really weird that the yellow relay has become known as the "overboost relay" - I'm pretty sure that it is even labeled "boost, or air pressure relay" in the PET - strange stuff.

[Rawknees'Turbo]

Originally Posted by ScottDAnderson

What do those fuses ( below the relay 's )control .?
My middle fuse is missing the bottom one was burnt out / broken.
Replaced the bottom one and dropped the one for the middle.��
Was wiggling everywhere and now car won't start today .

Scott, if you have the plastic cover for the engine compartment, fuse and relay panel, there is a label for the fuses and relays cast into the back side of it.

The middle fuse on an 87 Turbo is not used (it is for the "engine compartment fan" used on non-turbo 911s)

The bottom one says "passenger compartment fan", but I don't know which one they are talking about.

The top fuse is for the rear window defogger element.

[boosted79]

The top fuse for the rear defroster grid is good to supply power to an MSD after disconnecting the heater grid wire.