How does the older 3 Cyl Metro advance the spark?

On my thread about rings and the Head, I wanted to ask a question about spark
advance, but decided to start a new thread on that topic.

My '93 Metro 3 cylinder has no vacuum tube going to the Distributor.

The Distributor is quite a simple device on the '93 Metro.

How is it possible for such a simple setup to advance the spark when one
accelerates?

Or doesn't it?

If you tell me that the Computer Module does it, I would ask how's that at all
possible!

DoctorBill

it reads the rpms and the signals from the tps and map and adjusts timing to a pre-programed curve. thats why you have to use jumper on the conector by strut, it locks the advance out so you can set the timing

Is that why the Distributor Rotor has such a wide, sweeping "tip?"
Is 'rotor' the right word?

So the spark can still get to the plug, even though the Distributor cannot change
its timing at all - ever...like one with a Vacuum advance rotator of old could?

The spark just jumps the gap between the Rotor and the specific Plug conductor
inside the Distributor Cap as the rotor is going around inside the Cap.
It can do that because the Rotor's contact is long and sweeping...it is designed that
way so that the spark can still jump even if advanced.

http://img206.imageshack.us/img206/1690/findistrotorno2.jpg

Then the normal spark jump point (no advance) must be maybe halfway down
the copper Rotor Contact (?)

I must not forget the Jumper when I time this creature!

Neat! Engineers amaze me! They come up with new ideas and make what we
grew up with obsolete.....

I will Philosophize now......

I guess I am getting to be obsolete...I grind and make friction more every day.
I don't mean within - I mean against the "system"....is that why we die?

If we kept on going, we'd be so pissed off and bitter, we'd make life Hell for the
young ones who never witnessed "our" system....when it worked then.

How did that resolve itself during our Evolution.....what selective force was that?
Hmmmm.....

DoctorBill

PS - my difficulty making my engine idle wouldn't be due to the TPS being out
of adjustment, would it...!? Could it actually zap any idling?

Yep Bill, that's why the rotor has such a large contact area. So when the ECU decides to fire, it's got contact area to do it with. And yes(as answered in the other thread), and out of whack TPS will cause the car to not idle, and do other funny things.

Yes your TPS being out of adjustment will effect the idle. Do you have the big vacuum hose to the brake booster connected to the intake manifold?

The computer gathers information from the sensors that indicate engine load, ambient temperature, engine temp, throttle position, unburned fuel, fuel knock, road speed, engine RPM, and intake air flow. With the input of info the computer determines the best signals to send to actuators like Idle air control and how long the fuel injectors atomize a spray of fuel. The computer also determines and sends the spark signal to the coil at the best time based on the constant collection of information.

You are exactly right about the necessity of the sweeping arc contact on rotors or wider contacts in distributor caps. Over 15 years ago the most sophisticated Electronic Engine Control systems (in Sweden) were capable of signalling different spark timing and fuel delivery to each individual cylinder and change the individual signals for each consecitive four stroke series. ECC systems continue to do more and more each year, adjusting cam timing and duration profile as well as working with electronic automatic transmission computers.

OK - I will attempt to set the TPS to the voltage it is supposed to have.
Will also check Fuel Pressure at the Fuel In tube today.

With Throttle closed - 0.9 - 1.02 volt.
Throttle wide open - 4.85 - 4.95 volts

I also had ECL give 23 - Manifold Air Temp Sensor - is that the one in the
air filter housing?

NOW - exactly where is this big vacuum hose to the brake booster supposed
to be located?

I do not see it in my engine compartment....

Is it visible in this picture I posted back in January of this year?
http://img436.imageshack.us/img436/5364/morerightside3ev.jpg

DoctorBill

the hose for the booster connects to the intake manifold on the other side of the air cleaner. follow the line from the brake booster along the firewall and make sure its connected. its just under the idle speed control solenoid

The brake booster is between the fire wall and the brake master cylinder. The air temp sensor on the air cleaner would be ambient temperature. Manifold temp would be in the manifold. That code may go away when everything else is right. The computer can opperate in closed loop and get by and make adjustments similar to humans making adjustments to their system and getting by when they are not properly dressed for the climate.