I have been trying to think of a cheap way of coming up with a signal for Sequential FI's crank position sensor. then I saw this thread:

"Is this a automatic or manual transmission? Manual transmission will have a single-pickup distributor. Automatic transmission will have a dual-pickup distributor."

am i reading this correctly that there is a distributor with two pickups and therefore two signals. If I used another GM ignition module on the pickup that I am not using to actually trigger the ignition, could I use the signal generated to act as a crank trigger signal.

I guess what I want to know is:

Is this distributor dual pickup as in two places to get a signal or something else?

is the signal for the crank position sensor the same as the one that comes out of the GM ign module? I am assuming yes since that signal works as a signal for batch fire stuff.

Or am I just wrong all the way around?

any ideas on a cheap Crank position sensor?

cratsmarx@hotmail.com

I know rather little about the topic, but one possible approach would be to specially-modify a vibration damper and use the '78-up timing cover with the tubular boss for the diagnostic timing pickup. I don't know how these crank position sensors work (magnets?).
:
: am i reading this correctly that there is a
: distributor with two pickups

Yeah, the dual-pickup distributors were used with certain emissions packages without vacuum advance. One pickup, used only for starting (when the key is in the "start" position) is a few degrees advanced from the other ("run") pickup, to aid with starting. The dual-pickup distributor is NOT the hot ticket item for any kind of performance work.

DS


redbear@vrx.net

But if I used the entire computer/FI/ignition off of a 3.8, I could let it control the timing and everything. I wouldn't have to worry about the vaccum advance. All I need is a consistent signal to trigger the computer and let it know where everything is. Plus, I guess coil packs on a slant would be neat too. Well, at least different.

I would however have to figure out how to get the signal acting as the crank position signal to occur at the right time in relation to the firing order.

Does anyone know how many magnets are used on the crank on the GM 3.8s?


cratsmarx@hotmail.com

Right, but it seems to me like the distributor magnetic pickup isn't a good enough place to get this consistent signal. There's just too much slop between the crank and the distributor. Think about it: You have to go through the timing chain, through the camshaft worm gear-distributor pinion junction, through the distributor bushings, through the distributor cam plate bushings...all that spaghetti adds up to some serious and inconsistent slop. You really should take the crank position signal...off the crank!

(and then remember that this kind of magnetic pickup does not produce a very sharp or clean signal. It doesn't have to, the ignition amplifier box doesn't need a super-clean signal to do its work.)

DS

redbear@vrx.net

I think you are actually talking about a cam sensor, not a crank sensor. A crank trigger (sensor) can't tell you when a specific intake valve is about to open. A crank sensor has no way of "knowing" what stroke the piston is on, only a cam position sensor can "know" this. You need a cam position sensor for sequential FI. Of course a distributor is a "cam position sensor". The problem with using the signal from the distributor pick-up coil (even if the signal were "cleaned up" with an AC to DC signal converter such as the GM ignition module) is that it would fire all injectors at once unless you have some way of directing the signal to the ECM to fire the injectors individually. Much like the rotor in the distributor directs the ignition spark.

Bob D



BBobbias@aol.com

One possibility here would be to use a small inductive pick up on each plug wire or dist cap terminal to send a signal for each cylinder in time with their sparks. Kinda dirty, but just a thought...

Lou

Either one of these will work...with one problem. The ECU has to be able to pick out the #1 plug firing, so it knows which cylinder is which. Most Cam sensors have a different signal (dual teeth, usually) where the #1 cylinder is. Seems to me the easiest way to duplicate it would be to customize a Mallory Unilite distributor. Since it's an optical pickup, you could double the slot at the #1 position (add a second slot, seperate from the first). Since it's a digital signal, it might work...

Brett



savant83@hotmail.com

Bob,

How does GM do cam position sensing? Flying magnet? Hall effect on a missing tooth ring on the cam.. rotery encoader.. seems whatever type of sensing GM uses could be replicated in some way on the slant..

A magnet inserted on the cam gear and a sensor mounted through the cam cover doesn't seem too difficult.. One would probably want an adjustment method to degree it in somewhat, that would create a sealing isses if done through the cam cover.. Of course, this would all depend on what kind of signal the ECU wants to see..

Matt-

mhaskell@reliant.com

After re-reading my original post, I realize that I was wrong about the cam position sensor having to "distribute" signals to the ECM. Once the ECM receives a reference signal from the cam position sensor, it can sequence the injectors by knowing the engine's RPM. Sorry for the confusion.
Bob D


BBobbias@aol.com

On the 3.8L Buick it's a Hall effect device driven by the cam gear just like a distributor. It tells the ECM where the #1 piston is. I also assume that there is an AC to DC converter involved much like that used in the ignition module (perhaps it's in the ECM). This reference signal is then used by the ECM to properly sequence the injectors. I don't think there is any reason why a distributor can't be made to do the same thing. The problem is getting the distributor to perform both functions at once. Perhaps something like the distributor that Qwimby suggested could be made to work.
Another possibility might be to convert to a distributorless ignition, and in that way free up the distributor to be used as the cam position sensor.
Bob D


BBobbias@aol.com

I believe that is what I was kind of thinking. If you robbed everyhting from the donor car including the coils pack and all that stuff, what would you need to get spark and fuel at the right time?

If I remember correctly, there is a cam position sensor and a crank position sensor on the GM SFI stuff. Am I thinking of the right thing? it seems like there is a sensor made into the timing cover near the cam and another sensor near the balancer (kind of behind it actually). I think. I have not taken a good look at one in a while and I don't have a schematic for one.

does anyone have a schematic they could possibly email me? or post somewhere? I know Bob has the pin layout for the batch fire stuff and teh schematic for his car but what about for the Seq.?

Do I remember correctly that you (Bob) had hooked up a seq. comp. from a turbo car? I know the computer I have for the Seq. has a different pin layout for the connectors (actually an extra connector I think). For instance, some wires that are in one place on your diagram are moved around on my stuff. Maybe I looked at it weird?


cratsmarx@hotmail.com

I posted a thread about the fuel rail for the /6 about two weeks ago (I'm pretty sure I've got that figured out now). I managed to find the parts I need for the batch fired EFI setup, but I had to look at at least 20 cars to find the right stuff. The sequential setups are far more common (at least where I live). So at the risk of sounding as useless as a cheerleader, I think devising a low-cost way of "camshaft position sensing" would certainly be a worthwhile effort. If I can think of a way to do it, I'll be sure to bring it back here so you guys can kick it around and see what you think.


thelogs@cox.net

You would need a crank sensor and a cam sensor for sequential injection.
:
: If I remember correctly, there is a cam
: position sensor and a crank position sensor
: on the GM SFI stuff. Am I thinking of the
: right thing? it seems like there is a sensor
: made into the timing cover near the cam and
: another sensor near the balancer (kind of
: behind it actually). I think. I have not
: taken a good look at one in a while and I
: don't have a schematic for one.
:
: does anyone have a schematic they could
: possibly email me? or post somewhere? I know
: Bob has the pin layout for the batch fire
: stuff and teh schematic for his car but what
: about for the Seq.?

Lots of schematics for the various V6 systems can be found in Chilton,s "CELEBRITY/CENTURY/CIERA/6000 1982-85 REPAIR MANUAL" (8252) 28360. This manual costs less than $20 and is available at most discount auto stores.
:
: Do I remember correctly that you (Bob) had
: hooked up a seq. comp. from a turbo car? I
: know the computer I have for the Seq. has a
: different pin layout for the connectors
: (actually an extra connector I think). For
: instance, some wires that are in one place
: on your diagram are moved around on my
: stuff. Maybe I looked at it weird?

What is the Serv. No. of the ECM. I might be able to get you some information. You're right though, some of the ECMs use different plugs.


BBobbias@aol.com

You're right; the mid 80's batch fire set-ups are getting hard to find in the pick-a-part yards. These yards like to crush the old cars and get newer ones as soon as possible. That's where they make the most money.
The good news is that I'm quite sure you can use some of these newer sequential set-ups as batch fire systems in a SL6 with a distributor. I think you can do this, even though they are sequential, because I believe they will default to batch fire with the lack of a cam sensor signal. I want to emphasize that I haven't completely verified this yet. I do plan on getting one of these ECMs and trying it when the good weather returns.
What I do know is that when I substituted the sequential ECM from a turbo Regal for my batch fire ECM, it run well except under heavy acceleration. The turbo ECM expected to see higher flowing injectors than I now have, so I think that was probably the problem. I'm speculating that ECM provided a pulse width to the injectors (based on the MAF signal) that would have supplied enough fuel with the larger injectors, but not enough with my smaller injectors.
Bob D



BBobbias@aol.com

serv. no. 1228253
I'll take any info you can get.

-qwimby

cratsmarx@hotmail.com