5.0 SEFI - how exactly does it work?

November 06, 2007, 10:12:23 PM

Ok, I get the general idea of what sequential injection is going to do....

My particular question is what are the general sequence of events and sensors involved as it relates to the 5.0 SO motor?

I'm personally familiar with the basics of the GM 3.8 SEFI (PRIOR to the 3800 Series I, as found in the 1986-1988 LeSabres, Delta 88s, and in RWD turbo version in the Regals).

However, that particular engine is distributorless, uses camshaft position sensors and crankshaft position sensors, and is mass-air.

Given that the 5.0 is speed-density, and has a distributor, well, presumably, no cam position sensor. Is there a crank position sensor? Does the distributor actually provide information back to the computer as to its physical position (basically allowing it to do what a cam/crank sensor combination would do?) etc, etc.

Is there a sort of summary on how this works on the 5.0?

Thanks.

5.0 SEFI - how exactly does it work?

Reply #1 – November 07, 2007, 12:26:23 AM

Quote from: King_V;186491

Given that the 5.0 is speed-density, and has a distributor, well, presumably, no cam position sensor. Is there a crank position sensor? Does the distributor actually provide information back to the computer as to its physical position (basically allowing it to do what a cam/crank sensor combination would do?) etc, etc.

Is there a sort of summary on how this works on the 5.0?

Thanks.

No crank or cam sensor, dist provides all info for cylinder ID... Same on HO 5.0 with Mass Air...

5.0 SEFI - how exactly does it work?

Reply #2 – November 07, 2007, 11:42:39 AM

Yep.

Stator in distributer tells the TFI moduel where the distributor is in its rotation. The TFI then tells the coil to fire and vola spark.

5.0 SEFI - how exactly does it work?

Reply #3 – November 07, 2007, 05:26:21 PM

Quote from: thunderjet302;186550

Yep.

Stator in distributer tells the TFI moduel where the distributor is in its rotation. The TFI then tells the coil to fire and vola spark.

The TFI sends the PIP (Profile Ignition Pickup) pulse to the EEC and the EEC tells the TFI when to fire the coil with the SPOUT (Spark-out) pulse.

5.0 SEFI - how exactly does it work?

Reply #4 – November 07, 2007, 06:51:04 PM

Quote from: thunderjet302;186550

Yep.

Stator in distributer tells the TFI moduel where the distributor is in its rotation. The TFI then tells the coil to fire and vola spark.

Quote from: softtouch;186585

The TFI sends the PIP (Profile Ignition Pickup) pulse to the EEC and the EEC tells the TFI when to fire the coil with the SPOUT (Spark-out) pulse.

Eh close enough

lol

5.0 SEFI - how exactly does it work?

Reply #5 – November 07, 2007, 06:56:27 PM

Interesting . . . how precise is the distributor position information? ie: within 1 degree? 5 degrees? 10 degrees?

Also, a minor nitpick, but, say, for example, the dist has an additional 10 degrees of advance while running - does the stator then submit info that's 10 degrees off, and thus the computer knows to compensate (ie: the computer knows it told the distributor to advance 10 more degrees, and so subtracts that 10 from what the stator says), or is the stator completely independent of the advance mechanism?

5.0 SEFI - how exactly does it work?

Reply #6 – November 07, 2007, 08:45:20 PM

Post #6 good Q id like to know the answer too. I’m a little unclear on this too some one said, though its SEFI its actually bank.

5.0 SEFI - how exactly does it work?

Reply #7 – November 07, 2007, 11:35:14 PM

Quote from: King_V;186598

Interesting . . . how precise is the distributor position information? ie: within 1 degree? 5 degrees? 10 degrees?

Don't know the answer to this, but it is driven by the cam shaft.

Quote

Also, a minor nitpick, but, say, for example, the dist has an additional 10 degrees of advance while running - does the stator then submit info that's 10 degrees off, and thus the computer knows to compensate (ie: the computer knows it told the distributor to advance 10 more degrees, and so subtracts that 10 from what the stator says), or is the stator completely independent of the advance mechanism?

The distributor is set at a fixed 10 degrees BTDC. There is no centrifugal or vacuum advance.

All spark advance beyond 10 BTDC is controlled by the EEC computer.

5.0 SEFI - how exactly does it work?

Reply #8 – November 10, 2007, 09:58:09 AM

if you advance the distributor say 3* its 3* advnced all the way to redline. the computer still thinks the dist is set at 10*

5.0 SEFI - how exactly does it work?

Reply #9 – November 10, 2007, 12:36:10 PM

Quote from: thunderjet302;186550

Yep.

Stator in distributer tells the TFI moduel where the distributor is in its rotation.

There is the key... One tooth on the stator is wider than the others, so the TFI module and EEC recognizes it as #1 cylinder... With good components(tight distributor shaft, timing chain, etc) timing is very accurate... With a lot of slop, not so...

Correct base timing is assumed by the EEC, so if base changes are made the whole advance curve is shifted... This is why it's easy to tweak the timing on a HO 5.0 and pick up 5-10 HP...

5.0 SEFI - how exactly does it work?

Reply #10 – November 10, 2007, 10:47:37 PM

Quote from: TurboCoupe50;186929

There is the key... One tooth on the stator is wider than the others, so the TFI module and EEC recognizes it as #1 cylinder... With good components(tight distributor shaft, timing chain, etc) timing is very accurate... With a lot of slop, not so...

Correct base timing is assumed by the EEC, so if base changes are made the whole advance curve is shifted... This is why it's easy to tweak the timing on a HO 5.0 and pick up 5-10 HP...

tom is talking about the metal round thing down in the distributor ,, that metal thing passes through the stator and its width stays within the magnetic fild down in there on the stator or pickup. While there is nothing in the way, the magnetic field can pass lines of flux over to the other side which signals cylinder spark fuel and timing.

With the sprout connector plugged in at idle,, your eec can advance as far as 30deg.

While running, the injectors are contolled from the eec on thier own specific pin,,unlike the 883.8 which is wired just like the 3.8CFI's from 87 and down.

Each injecotor will stay on and off depending on the voltage supplied from the variable resistor tps and the map sensor mainly. The time in which the injector stays on or off regulating the fuel to each intake stroke is determined by all this plus the eec software and other associated sensors which will tie back to desicions made by the map. theres really so much to explain but if you know how the 3800 FWD motors run,, nothing really changes. You just gotta remember our cars are slightly less complicated or should i say,, Integrated perse. If you have those cars nailed down,, then you can get all the minor issues with a mechancial dist nailed down fairly easy.

5.0 SEFI - how exactly does it work?

Reply #11 – November 13, 2007, 10:38:47 AM

Quote from: TurboCoupe50;186929

There is the key... One tooth on the stator is wider than the others, so the TFI module and EEC recognizes it as #1 cylinder... With good components(tight distributor shaft, timing chain, etc) timing is very accurate... With a lot of slop, not so...

Sounds logical. So, since I've never seen the stator, how many teeth does it have? I would assume 8, but, well, I know the whole "assume" rule.

Quote from: jcassity;186980

With the sprout connector plugged in at idle,, your eec can advance as far as 30deg.

This was sort of related to my other question. With the connector plugged in, if the EEC say advances the timing an additional 15 degrees, does the stator get physically advanced with it, or is it physically/mechanically independent of the top end of the distributor that does get advanced?

Yeah, I basically know how SEFI works in general, I just wasn't sure how it worked on the 5.0 with the distributor as compared to the distributorless systems with the seperate cam position sensor and crank position sensor.

Thanks for all the info thus far.

5.0 SEFI - how exactly does it work?

Reply #12 – November 13, 2007, 03:16:35 PM

Quote from: King_V;187393

This was sort of related to my other question. With the connector plugged in, if the EEC say advances the timing an additional 15 degrees, does the stator get physically advanced with it, or is it physically/mechanically independent of the top end of the distributor that does get advanced?

The distributor is a cam position sensor.
Nothing changes inside the distributor, it is fixed at the base timing.
The EEC changes the timing by varying when it sends the SPOUT pulse to the ignition module.

5.0 SEFI - how exactly does it work?

Reply #13 – November 13, 2007, 11:56:13 PM

Oh, ok, I was thinking of an admittedly very old GM distributor I was looking at . . the upper part with the springs and weights which would be right under the rotor would actually physically be able to be turned ahead to some extent independent of the main distributor shaft.

I had assumed that with the electronic ones, that a physical advance was still being done, just that instead of vacuum and springs/weights, that it was being done on an electronic signal.

(and there I went assuming again....)