Cam Sync Timing???

[Chris Duncan]

Setting up my '90 HO 302 with Accell DFI and FAST eDist distributorless electronic ignition.

Have one of those oil pump drive cam sync sensors, in place of the distributor, like comes in an Explorer (I think). Anyway it has 3 wires so I assume it's a Hall effect sensor.

From the looks of the wheel inside it only has one pulse per cam revolution, and it's on for half the cam's revolution and off for the other half. .

Where do you set this thing as far as timing?

 

[Paul Thompson 'Hooligan']

Hi Kalun

Don't know for sure what the Accell system specifies, but for the Motec, I would set the sensor such that the rising edge signal occurs midway between two of the reference pulses (from crank) assuming you have only 4 points on your crank. The ECU is then programmed with a value in degrees, that the crank turns before the reference pulse that relates to cyl 1 on compression occurs. 'Rising edge' will usually occur when metal tooth is leaving sensor.

Of course if you are using a multi-tooth crank trigger, the specification might be 'no of teeth' before TDC cyl 1 and is likely to be different if using wasted spark where the cyl reference can be one of two depending of firing order.

Hope that helps. (probably as clear as mud now.. /ubbthreads/images/graemlins/frown.gif)

 

[Chris Duncan]

The crank trigger is 4 magnets 90deg apart

wasted spark

The FAST eDist handles the ignition side of things more so than the Accel ECU. The Accel only has one ignition output, it doesn't handle distributorless. I think the FAST unit coordinates the two triggers then signals the ECU, but I'm not positive.

So the metal "tooth" trailing edge leaves the sensor right as your TDC pointer is centered between two of the crank magnets. Does it matter which two? Like would #1 and #2 be best?

I was going to ask a Ford dealer tech but now you've got me thinking I should ask a FAST tech because Ford is a 32 tooth crank and FAST is the 4 magnet.

I want to check any ideas anyone has because this thing is buried under the cool air box, which is under the T-bodies, only want to R&R it as little as possible.

 

[Paul Thompson 'Hooligan']

Hi again Kalun

I've had a search on the web and found www.fuelairspark.com who sell the eDist product but I found nowhere there was a user manual to download. From what I see, the unit does not actually 'time' the spark signal - it just distributes the signal to the correct coil to be fired. (a bit like an ignition expander on the Motec system)

It says it supports 2 to 8 cylinders as individual coils sequentially, or up to 16 coils in pairs as wasted sparks. All of this is set by 'dip switches' and requires just 4 reference signals from the crank and a single signal from the cam.

Tell me more about your setup, has the motor been run with the Accell DFI and a normal distributor before? and you are just replacing the distributor and single coil setup for 'no distributor and 4 double ended coils'. Are your injectors currently batch fired (in pairs) and hence you have had no need for the cam sync before?

If that is the case I would think that you will need to connect the timing signal output from the Accell EFI (mapped ignition) to the appropriate input on the 'eDist' unit, + also provide the crank trigger signal and cam sync signal to the 'eDist' unit. It will then take the correctly 'timed' spark from the ECU output and direct it to the correct coil, or in your case, pair of coils.

With respect to the cam sensor position, I would think that the only thing it governs is which cylinder is about to fire. With wasted spark systems, the double ended coils fire once on compression and once on exhaust and hence each of 4 spark signals is directed to a specific pair of cylinders (plugs). Getting the sequence wrong will be exactly the same as mixing up the plug leads on a normal distributor and if you know your firing order, the sequence can be correctly identified fairly easily.

Rather than ramble on about how to determine this, post some more details, firing order, how system is wired and I'm sure this can be sorted relatively easily.

ps - looks like quite a neat product, especially as it is NOT manufacturer specific and can hence be used to enhance many different system configurations. What sort of cost is it?

pps - this will make you laugh - how we used to distribute the spark back in 2000 BEFORE switching to Motec and multicoils. /ubbthreads/images/graemlins/grin.gif

 

[Chris Duncan]

Paul,

""I've had a search on the web and found www.fuelairspark.com who sell the eDist product""

Ok, I called FAST, they say the Accel ECU has preference, the eDist can be set either waste spark or sequential, and either smart coil or regular coil.

""Tell me more about your setup, has the motor been run with the Accell DFI and a normal distributor before?""

No this is a new install, never run.

""Are your injectors currently batch fired (in pairs) and hence you have had no need for the cam sync before? ""

Injectors will be sequential, don't know about the coils, haven't decided on which ones to run.

""If that is the case I would think that you will need to connect the timing signal output from the Accell EFI (mapped ignition) to the appropriate input on the 'eDist' unit, + also provide the crank trigger signal and cam sync signal to the 'eDist' unit.""

that makes sense with sequential injectors, it has to have a cam sync correct?

"" It will then take the correctly 'timed' spark from the ECU output and direct it to the correct coil, or in your case, pair of coils.""

Agree

""With respect to the cam sensor position, I would think that the only thing it governs is which cylinder is about to fire.""

If it's waste spark, if sequential then it needs to know if #1 is compression or exhaust? Excuse me if I repeat the obvious I'm still learning some of this stuff.

""With wasted spark systems, the double ended coils fire once on compression and once on exhaust and hence each of 4 spark signals is directed to a specific pair of cylinders (plugs). Getting the sequence wrong will be exactly the same as mixing up the plug leads on a normal distributor and if you know your firing order, the sequence can be correctly identified fairly easily.""

Agree

""Rather than ramble on about how to determine this, post some more details, firing order, how system is wired and I'm sure this can be sorted relatively easily.""

Ok since FAST said the ECU has preference I actually read the directions for the ECU because I've already purchased the ECU. (but not the FAST eDist yet). It's generic instructions but details several ignition setups, non of which though has the Ford cam sync sensor. The closest description to my setup says take a multi tooth distributor reluctor wheel and break off every tooth but one for the cam sync, and then set it up 45 degrees before TDC #1, which would be like what you first suggested. It doesn't say rising or falling although that can be set either way in the ECU. The only difference would be the duration of the signal because a single tooth from a multi tooth wheel will be much shorter than the Ford cam sync which is about 60 percent rising and 40 percent falling?

So I guess the question is what's better falling or rising for the cam sync signal at 45degree BTDC #1, because the ECU can set either way. And a related question the cam sync event should be at 45 degree BTDC on the COMPRESSION stroke of #1 correct?

And another question, rising edge is when the tooth edge is leaving the pickup, is this the timed event that the ECU is looking at? It's like a switch right and it turns on and off, the ECU is only looking at when it turns on correct? And the rising edge is when it turns on?

""ps - looks like quite a neat product, especially as it is NOT manufacturer specific and can hence be used to enhance many different system configurations. What sort of cost is it?""

It is nice and universal, the Accel doesn't do distributorless (YET). The other choice was the factory Ford EDIS but that has the heavy/ugly 32 tooth crank trigger. The FAST eDist uses the 4 magnet and costs about $300.00. US. It's set up for LS1 coils if you go with smart coils and any coil if using regular, If you have time explain "smart" coil I didn't have time to ask the FAST tech.

""pps - this will make you laugh - how we used to distribute the spark back in 2000 BEFORE switching to Motec and multicoils.""

I remember seeing this pic before, I see an MSD trigger wheel there. It looks like the timing marks are set up for if you lose your reading glasses. 8&gt

 

[Paul Thompson 'Hooligan']

Hi
Correct, for sequential injection or Non-wasted spark, you need to know when cylinder 1 is approaching TDC on compression, thus the cam sensor. For batch fired injectors and wasted spark (or if a distributor is being used) you only need the crank trigger. This is how the MSD flying magnet unit operates as the ditributor actually sends the spark to correct plug.

Looking at wasted spark, if your firing order was 1-5-4-2-5-3-7-8 and your 4 coils were A B C D. Assuming the coils were wired to fire in the order ABCD. Then they would be connected thus
A 1 + 6
B 5 + 3
C 4 + 7
D 2 + 8

So that when coil A fires, #1 would be on compression when #6 was on exhaust and visa-versa.

One disadvantage of wasted spark is the leads from the coil packs will have to go to opposite sides of the engine (1&6) (5&3) etc etc, which means long HT leads. Not a problem but not ideal. That is why we use 8-coils, which can be mounted each side of the engine, may require HT leads of only say 4 to 6 inches max, one spare lead will 'neatly' fit all positions as a replacement and you cannot get the leads on the plugs in the wrong order. (which you can more easily with wasted spark).

With the cam phase sensors I have fabricated, the rotor, or piece of metal that activates the sensor is usually about 10mm wide on about a 60mm rotating diameter. This therefore only covers about 20 degrees of cam rotation, or 40 degrees of engine rotation and can therefore occur 'between' two reference signals from the crank. I don't think the duration is a problem as the unit will operate on an edge.

With regard to which edge, I use the rising edge, but for no particular reason, it just informs the ECU that the NEXT CRANK SIGNAL, relates to cylinder #1. The actual timing accuracy is governed by the crank signals. Hope that made sense.

The actual positioning of the cam sensor (sync) will only govern which cylinder is to get the fuel/spark next. If you imagine it as 8 sections of 45 degrees each, if you get it in the wrong position, you will send the spark/fuel to the wrong cylinder. Of course if you were running a distributor, or wasted spark system, you could still route the plug leads so the motor will run, if the cyl was incorrect the fuel will sit in the inlet until valve opens anyway. (not ideal) This cannot happen with 8 coil + sequential injection (providing wired correctly!) because the cylinder that gets the spark is HARD WIRED and leads cannot be miss-routed.

With 8-coil sequential, you can keep turning the sync pickup between the 8-sections mentioned earlier until you get the correct starting point. (better still, think about it and work it out - no. of degrees engine turns BEFORE the sync pulse indicates that the next cyl is #1 = CRIP - crank index posn (motec)).

Re coil type, smart / normal - I'm not positive but I would guess 'smart' coils have in-built ignition amplifiers and do not need external items. Ignition amplifiers buffer the electronic outputs to be able to sink the current required to fire a normal coil.

Again - hope the above helps... /ubbthreads/images/graemlins/smile.gif

Paul

ps - working on Daves R42 the other day, getting the sync in the wrong section (advanced) resulted in about a 4ft flame from the inlet (which was filterless at the time) that took all the hairs off of the back of my forearm!! - very exciting! /ubbthreads/images/graemlins/grin.gif

 

The ls1 smart coils do have the igniters built in. The "smart" idea is that it controls the dwell required to properly saturate the coil, then waits for a 5v signal to light it, no signal when it wants to see one, it fires off anyways.

 

[Chris Duncan]

Paul,
Finally got in contact with the Accel techs and they confirm your advice, 45 degree BTDC on compression of #1 AND falling edge of sensor is the preference over rising edge.

Apparently there's less chance of electrical noise/interference on the falling edge.

Oh, and I did figure out also, rising edge is when the tooth gets to the sensor and falling edge is when it leaves the sensor.

Sequential coils it will be, the plug wire clutter has always been a pet peeve of mine, one of the reasons that distributorless is desireable.


Eric,
Sounds like the LS1 smart coil is the way to go. Where's the best place to get these?

 

Oddly enough, I found mine on ebay for a good deal, paid $75 for the whole set including the harness. I seem to remember there being alot of them on there, some went as high as $200, just have to wait for someone to word it wrong so he gets few hits.