Can someone verify my timing issue?

Ok, so I figured out why I'm getting knock under load. I've been pondering this the last couple days and realized that I'm running too much advance under load, somehow. 28 to 36 degrees doesn't seem like too much, but thats what my symptoms were indicating.

So I started playing with the trigger offset in Megasquirt while tuning today. I bumped up the trigger offset by 10 degrees (positive) to retard the timing all over the ignition map by 10 degrees. Lo and behold, the engine ran much better with virtually no knock and I actually got up to 5 psi of boost at one point safely.

So it got me thinking as to why does it seem to run better with 18 to 26 degrees of advance compared to what should be 28 to 36 degrees. Then I realized that the EDIS tone ring is already preset to 10 degrees BTDC. The Megasquirt doesn't know this unless I offset the ignition 10 degrees to get the ignition advance that is what Megasquirt is changing via the ignition map. So by offsetting by 10 degrees, I cancel out the mechanical 10 degrees of the tone ring leaving me with ACTUAL timing that is denoted by my ignition map.

So does anyone follow me on this? I believe I matched the timing light reading to the "big number" in the trigger offset correctly when I first got it running, and the EDIS configuration says to set the trigger offset to "0". But shouldn't it be 10 degrees offset because of the mechanical preset the the EDIS already has?

Does anyone follow me on this?

Ok, so apparently the 10 degrees mechanical advance from the tone ring is ignored once the EDIS is controlled by the Megasquirt. So that blows my theory out. Am I just running too much advance?...Apparently I am according to the results I get when I retard it by 10 degrees in the offset.

8) there are a few causes of detonation, those being excessive cylinder pressure, too much timing, and a lean fuel mixture. it sounds like in this case you have too much timing.

Yep, I was. I backed the whole curve off by 30% and it performed much better. Now I either need to see what the knock is when I'm around 7 to 8 psi boost. It's only sometimes but it's there. I may have to bump up to the next octane level, or take some more timing out at that intake pressure.

8) you might take out another degree or two of timing when the boost level reaches 8psi, but a better choice might be to bump the fuel mixture up a bit, say 5% richer.

According to my wide-band, I run about 10.5 to 11.5 AFR thereabouts under that kinda load. So I have a feeling its more of an ignition issue. I think I'll do a little of both.

I think you need to re-look the trigger offset. Don't try to shift the curve by moving the trigger. Unless you have that right, you'll never know for sure what the timing really is.

The 10 deg base timing on the EDIS is what you'll see during cranking. Once the MS takes over after start, the timing goes to the table value. Any changes to the table have no effect on the base timing number.

I would make sure the trigger offset is good first. Save the current table as a .vex so you can use it again. Set the table values to something you know that the engine will idle well at (10-14 degrees?). Just pick a number and put that value in for all the MAP ranges for all RPM bins up to 1500. That will give you one timing number that won't change at idle. See the attached sample.

Then open the trigger wizard and adjust the offset until the timing light shows the same thing as the display. One thing that confused me at first was that I didn't realize that I was supposed to be moving the timing mark, not the display number.

After trigger offset is determined you can reload the .vex of your original table. The timing should rise as rpm rises, but as the load rises, timing should begin to back off. At a high load (higher MAP), your timing should be lower. Another typical sample is attached. The idle advance in this table is kind of high, but that's what my engine seems to like.

Jack,
Is one of these tables for you 200Xflow?
Do you still have the megasquirt files you could send me?
I was thinking of using a locked LOM with a pertronix unit for a signal on my 200 instead of the TFI in yours. What do you think?

Thanks,

That should work. The pertronix is just a hall sensor that works almost like the one I built from TFI parts. Only difference is that it is moving magnets past the sensor to interrupt the field and mine is interrupting the field with a moving shutter past a fixed magnet. The square wave output should be the same as far as the MS is concerned. Just wire up a 1k ohm resistor to provide a pull up for the MS to see.

Also be sure to adjust the max dwell in the .ini file if you're using an MSD. I would use a resistor in the coil hot circuit to keep current down if you're using direct coil control and keep the dwell to 3.5ms or less to avoid frying the driver.

I'm using 19lb injectors, MSD6a, Hall sensor ingnition, and a narrowband O2 sensor. I may switch to wideband if I don't switch the car to webers.

Send me you email address and I'll shoot the msq to you.

PM sent.

The EDIS is supposed to have a an offset of zero, given the tone ring and/or sensor are setup correctly to provide a limp home of 10 degrees. I did check that a while ago and I do have it setup correctly. I unplugged the SAW to the MS (or "spout" as Ford called it) and checked the base timing. It was at 10 degrees.

One thing I notice you have on your table is a wider range of ignition timing (19.3 degrees) from 60 Kpa down toe 25 Kpa and up to 1700 RPM or so. My ignition range is much smaller than that at that area. Mine is setup with only about 4 cells reading the same timing advance inside my idle range. I wonder if expanding it will help out at all.

There are soo many things I can do to get a result here or a result there. The Megasquirt is nice because it is so flexible, but it makes it difficult sometimes BECAUSE it is so flexible.

When I installed my homemade Hall sensor I checked base timing by setting cranking rpm to 1000 in "Other Fuel Settings", unplugging the fuel pump, and cranking the engine so that I could observe the timing light. That way all I would see was the base cranking timing. I moved the distributor until it cranked at 12 degrees. You can do the same with the EDIS by moving the relative location of the pickup and tone ring. The EDIS doesn't know where the 10 degree mark is, so you have to index it. Then no matter what EDIS does for base timing you still have to tell MS how far off the pickup is from the igniition event so that it can calculate the firing. I was getting confused myself by trying to mix apples and oranges at first, but I figured out that base timing and MS timing were separate events with the trigger offset the difference.

My engine actually idles in the 40-45 kpa range at about 1000 rpm. I am running a healthy cam, but I have the bins down to 20kpa because it will pull down to that at light cruise and decelerating. I could probably get rid of the 500 rpm bin and add one at 5500, but it wouldn't make any difference since the max advance would be the same. I have the timing drop from 19.3-19.6 down to 13 or so at 100 kpa because when you romp on the throttle it takes a second or two for the engine to rev from 1000 to 2000. This eliminates that little initial ping you get from a rapid throttle application. After that I have the advance rise rapidly with rpm to be just about all in by 2500 rpm.

The way i arrived at this table (and I am still tinkering with it) was to start by eliminating the vacuum part of the equation. I plugged in a value for each rpm bin that make the MS act like a mechanical advance distributor. Every kpa at 500rpm=17 degrees, 1000rpm=19degrees, 1500rpm=21degrees, 2000=25 degrees, 2500=30 degrees, and 3000-up=33degrees, for example. I adjusted the timing in each rpm bin until I got something very close, then started adjusting for vacuum levels. I did it by ear, but a knock sensor would have been nice to have.

So your saying I should move my base timing via adjusting the tone ring so that it is not at the EDIS standard 10 degrees, but where the engines base timing should be, for ease of starting? That makes sense as long as the EDIS indeed does not send a SAW signal at cranking speed. I don't remember what the required minimum engine speed is for the EDIS to start sending a SAW signal to the MS though. I'll have to research that.

The way i arrived at this table (and I am still tinkering with it) was to start by eliminating the vacuum part of the equation.

Click to expand...

Thats pretty much how I have done it as well, I just put too high of numbers in at first, causing the mixture to ignite too soon and therefore knock. After I scaled it all down by 30%, it made a world of difference. It's also tough to decipher a small problem in the drivability and decide if its fuel or timing. It would be nice to be able to have both fuel and ignition tuning tables up at the same time so you could have a ease of switching from one to the other to determine what is causing the problem you have.

Yep. You can set base timing to whatever you want. EDIS says 10 degrees when the tone ring and TDC are at the factory setting, but by moving the pickup, it will fire when you want. That's one of the mods you can do to later Ford engines to get more total timing. You are just setting the event to happen sooner or later as you need.

10 degrees may not be enough for some engines. Mine likes to have 12-14 degrees just to crank and 19-20 for best idle. But what I've done is to set the timing low at 100kpa, then rising to the idle setting at 40 kpa just to keep the ignition from "whacking" the starter on that first event before the engine builds significant vacuum. A soft landing, if you will.

I've also set "skip pulses" to 2 just to give the engine a chance to rotate before MS starts to calculate ignition events. 2 or 3 is a good value for a six cylinder.

Give me your email address and I'll send you a copy of the msq.