Detonation

[Pentroof]

Is it a factory balancer or a new one?

New balancer and verified with TDC

[My427stang]

The Sniper uses a delay versus an advance.  Generally, they have you set it up to a 45 degree reference angle, then adjust the rotor.

This essentially has your engine at rest at 45 degrees advance +/- a degree or so for tolerance stack.  The system then calculates the amount of delay needed for initial and total, and the entire curve along the way for all conditions.  The extra amount is used for high vacuum conditions, like vacuum advance.

So, if you are right on the edge of pinging, you can a few things, turn the distributor a degree or two, it will shift the whole curve down, but it's really not the clean way to do it.  You could lower initial and total by 2 degrees, which would also shift the whole curve down.  Or you could change initial to a lower value, which will make the curve less steep, but the change will be less dramatic. Remember, the EFI will adjust your idle so no worries there.

Personally, I'd try setting the initial at 12 first leave the 36 total, and see what it drives like, then try 14 and see if the ping comes back.

Your engine certainly doesn't sound like it has an issue and I would hate to retard that cam more for that use

ON EDIT: Two other points

1 - Just my opinion but my guess is that your parts are under 10:1 not 10.5, Brent's info was right on.  You'd need to measure to be sure, but if really 390GT with Edel heads and 1020 gasket, it could even be closer to 9.75:1

2 - As far as the 16-36, using the Sniper,  are reference numbers not actual numbers in my opinion and totally based on how precise the distributor setup was.  16-36 could easily be 18-38 or even more depending on distributor location or rotor correction, both are variables as is the balancer marking if .  I would not worry about what the number is, as much as trying changes and writing settings and evaluating behavior.

[Pentroof]

Ross, that makes no sense to me. The timing is at 36 when I'm experiencing the pinging. Are you suggesting the cruise advance will drop by reducing the initial?

I understand the reference angle thing and how the system arrives at timing for a given point in the "map". What I don't understand is the generation of the curve. For example, my timing is never above 36. So, there apparently isn't any higher vacuum, low load timing advance built in. If I'm cruising, the timing is at 36. I add load and there is no timing change.

With this engine, where would you expect the timing to be at cruise with a correctly set distributor? I'd say well North of 40.

[Pentroof]

2 - As far as the 16-36, using the Sniper,  are reference numbers not actual numbers in my opinion and totally based on how precise the distributor setup was.  16-36 could easily be 18-38 or even more depending on distributor location or rotor correction, both are variables as is the balancer marking if .  I would not worry about what the number is, as much as trying changes and writing settings and evaluating behavior.

Agreed. After phasing the rotor, I went to great detail to set the initial, and verify actual with the ECU. Holley also has you verify stability of timing control and allows an adjustment for this with their static timing check and inductive delay offset. Testing proved I didn't need any offset with my setup.

That said, I'll spend some time this weekend to understand this more. I'm still interested in your train of thought regarding lowering the initial timing. I really don't want to increase temperature without need either. It will definitely build more heat at idle at 12 degrees advance.

[My427stang]

So some of this is educated guess, some WAG, some deduction, I haven't seen what the curve is on a Sniper, but did some reading and applied it to some others I have seen, so no doubt I think we can get you there, but take the specifics with a grain of salt

So, first, if you indeed are at full advance when you are cruising and it doesn't fall out at all when accelerating (assuming you are watching it) AND that is why it's pinging, then I would just drop total and see what happens.  You are right on the edge, so this is tweaking, not a problem with the vehicle, and certainly not a cam timing/DCR issue. 

Second, I didn't assume you were there, I assumed this was happening when you were not at full advance or it was in the period of time you were running on cruise advance (vacuum like) just before it fell out.  So in that case, lowing initial changes the whole curve right up until total.  You can draw two lines one from 10 - 36 and another from 16 to 36 and see what I mean, the whole curve is lower until the end.

Third, I would not say heat WILL increase if you drop to 12.  12 is still plenty of initial for a mild cam.  FWIW, a similar cam to that in 1969 in a CJ would be running 6 degrees BTDC and have a much slower curve.   I would try it and see, remember, this thing won't vapor lock now

Fourth, I would expect that if the Sniper has a vacuum advance that kicks in during cruise, it would indeed be over 40.  In fact, it seems to me that setting the reference angle at 45 degrees as I read in their instructions, would tell me that's the max it puts out.  However, I wonder if there is a field there somewhere that allows or disallows that from happening.

Finally, how does the Sniper pick the a/f ratio?  I have been seeing more people look for 14.5:1 stoich, and with the wide range of fuels out there, it's likely safer to run a little richer.  In fact, I doubt there is any fuel in any commercial tank that has a fuel with those characteristics anymore.  Do you have the opportunity to adjust?  Slightly richer, even ever so slightly, will help, especially if targeted to a time when it's just a little too lean

Again, if I understand the problem, you got a little bit of controllable pinging, the easiest way, like Brent said way back, pull a couple degrees out and evaluate

[My427stang]

So I did a little research after I posted.  Some additional questions, but I won't be back until late night....

BTW, no  priority order, just generating options, but I would do only one at a time

1 - I see that there is an idle, cruise, WOT, and acceleration enrichment - I am unclear of exactly when yours is acting funky and how much learning time you gave it, but my hunch is cruise and WOT richened by just a little bit may help

2 - I also see that there are three options for timing, idle, cruise and WOT.  I would look and see how they correspond, and depending on how it behaves, adjust cruise or WOT

3 - The system under advanced tuning uses load based enrichment, that is "power valve" to me.  Look close at that, if this is a pinging under a load, a slight enrichment there may be all you need

4 - AE TPS vs CTS - Another one you could look at, it changes when the "power valve" kicks in

A combination of those 4 things should fix what you are complaining about.  Recommend you change one at a time, run it for a while and make a decision.  FWIW, many of us disable learning and get things as close as we can without the computer "helping" and then when it's running well, you turn it on.  Just a technique, but if you want to dive right in, that's how many do it

[Pentroof]

Thanks Ross, we're on the same page. My plans are to investigate exactly those elements of the system, but in the order of 2,3,1,4.

I posted above on the initial, cruise and WOT timing and how my cruise and WOT settings are currently both set at 36 (?). To me, this is fundamentally wrong and therefore the first place to look. The System setup process only asks for idle and max timing, so....perhaps it's not done learning? Only a couple hundred miles on this so far.

Before changing them, I want to understand the I/O relationships and download the full software package. Plan is to do that tonight.

The next couple days will be warm and not that humid. However, just behind that, we're expecting temps approaching 100 and very high dew points. Should be good for testing.

I hope this discussion helps others as well, and doesn't deter from EFI acceptance for the old schoolers. This is great learning and just as simple as understanding how to properly setup a carb and distributor.

[My427stang]

I am in the same boat, Omaha in the upper 90s.  I have a 428 to disassemble and I don't feel like sweating LOL

[Tobbemek]

Before one know the timing curve from idle and up and what happens att different load att different rpm   WOT, CRUISE, and between that(part throttle) and exactly load and RPM when it pings, its just a guesswork. Yes one can pull out a couple degrees from total and "see what happens"
You have to take  total control  of your timing including MAP sensor to have it all POWER and MILEAGE and without detonation.

[Pentroof]

Just a quick note, as I did some minor testing on the way to and from Home Cheapo yesterday. Since the temp was in the low 80s in the early evening and humidity was low, I was surprised that a stomp on the throttle still produced pinging. This was previously not the case, as I remembered.

Since the Sniper is so easy to change, I made 2 successive changes to WOT timing. First, I dropped it from 36 to 34, then down to 32. Detonation is STILL present.

I got home and walked myself through the setup and build to understand what changed. Then it hit me...there was a significant change that could be causing this detonation: I addd a CD box with multiple sparks.

I first installed the Sniper using the "coil driver" that comes with the kit. This is a very small (pack of gum small) unit that is used to drive the coil, instead of a CD box. This is how the system was configured when I remembered being able to hammer it without it pinging.

I had initially wired the Pertronix Digital HP box and forgot to remove the factory 12+ from the coil, resulting in a fried box. To get the motor up and running while waiting for another box from Pertronix, I used the Holley coil driver.

A couple weeks later, Pertronix sent me a new box (seriously, at no cost or shipping) and I wired it in. The trigger configurations allow for power level selection between 187mJ and 145mJ and multi-spark ON or OFF. The EFI is still controlling timing, but the CD box is supplying the power.

I configured it at the lower power level with multi-spark. This is probably more than this motor needs, but I really wanted it for potentially better idle and crisp starting. It will take me about 5 minutes to change the configuration to single spark and test it.

Stay tuned....(see what I did there?)

[Pentroof]

For the record, this is a standard small cap Duraspark.

[Pentroof]

Well, that wasn't it. Changed to a single spark and still have pinging under WOT acceleration, even with reduced timing settings.

So, back to original plan. I have downloaded the full Holley PC software and will begin understanding what I actually have before continuing with any changes.

[Tobbemek]

What rpm is it att when you stomp it. Then  check what the timing is att that rpm.

[Pentroof]

RPM can be anywhere. Not correlated to RPM. Using the Sniper LCD, I have a defined set of gauges that show RPM, timing, AFR! and coolant temp simultaneously.
I can see when the ECU interprets a shift to WOT and drops the timing to whatever I have set for WOT timing. The AFR never really goes lean before dropping from enrichment.

I really need to view my tables to understand where I am before moving forward, IMO.

[Tobbemek]

Good thinking