Timing tables

[pass1over]

Background: I put a roller cam 5.0 in my 66 Mustang, used an a9l ECU and wiring harness out of a 91 and have been running that for a few years.
I recently got rid of the a9l and switch to a standalone unit, speed density. But I'm having a little trouble with the timing table.

I don't know if any of you guys has messed with tuning an a9l ecu or not. I have attached the table that my car was running on with the stock Ford computer. The instructions are to stab the distributor at 10° btdc with spout out.

So does that mean that this table also has 10° added to it because of how the dist is installed? If so, where does that 10° stop being applied? Because I certainly don't and shouldn't have 46° of total timing up top.

Most everything I know and read about 302 says 14 to 18 degrees of initial timing. So why would my initial timing be the 10° the distributor is installed at plus the 34-37° that's in those bottom cells on an EFI tune? If I'm understanding the way these tables work, then that would be 44 to 47° of initial timing at idle.

Or am I not understanding this concept?

 

[RED09GT]

Since there is no crank sensor on these engines, there is no way for the ECU to tell where the crankshaft is vs. the distributor position. When we used to set base timing to 14° with the spout connector out and the stock ECU, it basically added 4° globally.
With your standalone, the timing table would be with the base timing set at 10°, if you set it at say 14°, your actual timing would be 4° higher at every point than in the table. Since you now have control over the timing tables, no need to set the distributor advanced.

 

[pass1over]

I have my distributor set at TDC now.

So basically, with the dist installed at 10 degrees initial, spout out, it was adding nothing to these tables?


What i'm having issues with is backfire at 2000rpm and up. Everything with fuel I changed did nothing, but I pulled around 20% timing from a few columns and was able to free rev the motor up to 2800 before backfiring started. I didn't adjust timing in the columns above and ran out of time to go further. I haven't experimented with adding timing to see if the backfiring stopped but can/will if I have time.

I have checked everything else to fix the backfiring and it's all good. Fuel pressure, fuel pump, fuel filter, compression test, spark plugs, wires, vacuum leaks, etc. It's definitely something with the timing tables.

 

[RED09GT]

Re read your post and edited my first part of the response.
What is the timing light showing at 2000 rpm? Or is is just breaking up and erratic?

 

[pass1over]

idle is great, i've checked like 5 times and im on compressions stroke. I haven't had timing light on it while revving it, I can see it on the computer.

I was going to re-re-re-re-verify I was on tdc and at tdc on the balancer (just in case it slipped). Dont know if it can, its a fluidampr.

I was test driving it for LTFT data and pushed through the backfiring one time and like above 2500 or so it started pulling clean up to around 4k or so.

I would like to add ... I went from running fine car with the A9L. Swapped in the stand alone and started having these problems. I don't think it's a mechanical issue as nothing mechanical changed on the car.

Long story as to why I swapped ecu/tuning styles.

 

[RED09GT]

I'd get someone to hold it at 2000 rpm and verify that what the computer says is actually what you are seeing on the light as the computer still has no way of verifying where the crankshaft is.

 

[JEWC_Motorsports]

What standalone are you running?

 

[pass1over]

What standalone are you running?

Haltech 950 elite

 

[pass1over]

I'd get someone to hold it at 2000 rpm and verify that what the computer says is actually what you are seeing on the light as the computer still has no way of verifying where the crankshaft is.

I'd get someone to hold it at 2000 rpm and verify that what the computer says is actually what you are seeing on the light as the computer still has no way of verifying where the crankshaft is.

This ECU does though, with my input. I set the distributor to TDC and then I tell it at what degree mark it fires at TDC in relation to my harmonic balancer inside the software. They call it setting the crank angle or something similar

 

[pass1over]

So if the total timing on an a9l timing table is set to 36°, the computer is assuming the distributor is set at 10 degrees btdc. Does that mean it's really only adding 26° of timing?

 

[RED09GT]

So if the total timing on an a9l timing table is set to 36°, the computer is assuming the distributor is set at 10 degrees btdc. Does that mean it's really only adding 26° of timing?

That is correct

 

[Juice]

Setting distributor to anything other than factory spec of 10* was done to tune timing when not using any type of chip on the a9l (a9p in my case).
Once you start tuning with any type of a programmable chip, set dizzy at factory 10", and tune your timing with the chip. You can easily verify this with a timing light.
Removing the spout connector disables pcm timing control so you CAN set base timing.
Now for timing to cause any type of misfire, it would have to be really far out of spec. Again, can be verified with timing light.
Now, are you sure the TDC mark is actual TDC? Your balancer could be coming apart and the mark may have moved. Or, it could be off from the factory.
Finally, my gut feeling is you are experienceing a lean misfire. Since it is speed density, and there is no MAF, your fuel tables must be close.If you think they are, than maybe injector data is not correct. Is fuel pressure correct?
I have no experience tuning speed density stuff, except for my GSXR. And all I did was load a Powercommander supplied map. So I cannot call that tuming.

 

[pass1over]

fuel pressure is correct, changing the fuel tables massive amounts in either direction (rich or lean) had no effect on the misfiring. It was only when I modified my timing tables that I was able to rev the engine higher than 2k.

I checked TDC on the piston and it aligned with the 0 mark on my balancer. I am going to check all of this again when I have some time to get back out there.

We're basically starting from scratch on this tune, but not really. I was able to get all my injector data (breakpoint, slopes, dwell), and timing table. However, the timing table that it ran on before, it doesn't now. I was trying to wrap my head around how the A9L handled the dist being set at 10 deg or whatever you have base timing set to and if/how I needed to modify my tables to reflect that.

 

[pass1over]

checked TDC again, it's on.
marks on balancer show what's in that cell while idling. However, if I rev to motor up the timing shoots way up, I would guess to around 50 or so rather quickly and then it starts popping.

What could cause my distributor to advance more than the computer is telling it to?

 

[Juice]

I was chasing a bouncing tach issue with my 91. Turned out the ground was lose on my MSD box.

 

[RED09GT]

What are you using for an ignition box? Is it a stock distributor or an aftermarket unit?
And as Juice said, check all your grounds.

 

[pass1over]

Stock distributor, stock coil, stock tfi unit, all motorcraft.

I'll check grounds when I get back to the workshop. Since it was a running motor before with no issues, it's gotta be either the ECU install or something in the tune, nothing mechanical has changed.

 

[JEWC_Motorsports]

checked TDC again, it's on.
marks on balancer show what's in that cell while idling. However, if I rev to motor up the timing shoots way up, I would guess to around 50 or so rather quickly and then it starts popping.

What could cause my distributor to advance more than the computer is telling it to?

Stupid question, but does the distributor have a mechanical advance? (springs)

 

[pass1over]

Stupid question, but does the distributor have a mechanical advance? (springs)

It's not a stupid question, as I was wondering the same thing. I've never had one apart. I was thinking that ... if I had an old school dist it seems like the weights are too much or the springs are too weak ... But I believe this one is all computer controller inside.

It's a standard, stock motorcraft distributor out of any fox body mustang 5.0 86-91. Mine has the TFI module mounted on the dist rather than the fender.



I was doing some reading online and have a table in the tuning I need to go check. I don't have my laptop with me here at work, so it's going to have to wait until I get home unfortunately.

 

[Juice]

There is nothing mechanical in those dizzies.
There is an "octane rod" that can be changed, but all it does is lock the pickup down.