initial ignition table generator in MS Excel

[ubercamaro]

everyone,

attached is a spreadsheet i made using some assumptions and calculations from lance. below is a short description.

the benefit of this is you and play with a timing curve to see what effects like fuel octane would have on a timing table.

The first page establishes the assumptions based on motor, bore, fuel, cyl head and then inputs the 100 kPa values. The remaining is the boosted vs na and each cell is calculated from your formula by the 100 kPa advance and the kPa. Note, afar from discrepancies from the fact ms excel 2003 only has 3 conditional formats, it is quite flexible. if one should change the kPa settings, it will update that entire row, same if they change the ignition from premium gas to regular for example.

On the boosted portion, the calculations don't adjust for ensuring the value is no more than half the 100 kPa Timing.

as time permits i will try to add some if/else statements for the boosted portion of spreadsheet but no deadlines as to when i'll have that done. of course, anyone is welcome to modify the calculations to their needs.

btw, i made this in 2003, i believe it should be backwards compatible but with microsoft who knows?

If you have questions or comments send me a message on the forum.

for more info on lance's post regarding the calculations and assumptions see: viewtopic.php?t=9941

[ronsonol]

Thank you this is a great help. I am using Excel 2002, and it works fine.

[Jon k]

How come if I say idle advance of 10, when I look at hte tabel around 600 - 800 rpm @ 50 - 30 kPa its all like 24+ degrees?

Also, how are we to use the table generated? It's way larger than 12x12, its like 34x12 or something. Also what do the colored areas mean?

[ronsonol]

I think I can answer your questions.

The colour are just the scheme to represent values, eg 0-10 degrees is green, while a value of 50-60 degrees is red.

The 10 degrees your set at 'idle', should really be called your base timing. Actually your idle timing value will depend at which rpm/map value you idle at. The calculations are done by increasing the base ignition timing .3 degrees for every value of 1 map. So a lower 10 in map (80-90)will increase the timing of 3 degrees. This is the vacuum advance.

As for the table size, you'll choose the values and points you want relative to your actual table in use, the best way is to just manually change your table by hand using the values generated by the excel sheet.

Remember, this table generator should be used with caution, what works for your application may not for others.

[ptegler]

Hey Jon K

...just like the rest of us RTFM! It's all there

ptegler

On Fri, 30 Jun 2006 08:47:35 -0700
"Jon k" <jkensy@comcast.net> wrote:
> How come if I say idle advance of 10, when I look at hte
>tabel around 600 - 800 rpm @ 50 - 30 kPa its all like 24+
>degrees?
>
> Also, how are we to use the table generated? It's way
>larger than 12x12, its like 34x12 or something. Also
>what do the colored areas mean?
> _________________________________________________________
> This post is at:
> viewtopic.php?p=128407#128407

Paul Tegler
ptegler@cablespeed.com
Posted by email.

[Jon k]

I think I can answer your questions.

The colour are just the scheme to represent values, eg 0-10 degrees is green, while a value of 50-60 degrees is red.

The 10 degrees your set at 'idle', should really be called your base timing. Actually your idle timing value will depend at which rpm/map value you idle at. The calculations are done by increasing the base ignition timing .3 degrees for every value of 1 map. So a lower 10 in map (80-90)will increase the timing of 3 degrees. This is the vacuum advance.

As for the table size, you'll choose the values and points you want relative to your actual table in use, the best way is to just manually change your table by hand using the values generated by the excel sheet.

Remember, this table generator should be used with caution, what works for your application may not for others.

well i know my engine idles @ ~45 kPa @ 710 rpm or so, but the table generated says it'll be doing like 25.5 degrees?

[ronsonol]

Yes that seems reasonable.

Lower map values tend to indicate leaner conditions. Leaner conditions require longer burn times - hence the need for more advance. Spark sooner, burn longer.

Most people only think about rpm advance. eg 3000 rpm 36 degrees advance at WOT. But at crusing speeds on the highway, vacuum is higher, and the map value is lower - thus is advance is a higher number.

[Jon k]

Yes that seems reasonable.

Lower map values tend to indicate leaner conditions. Leaner conditions require longer burn times - hence the need for more advance. Spark sooner, burn longer.

Most people only think about rpm advance. eg 3000 rpm 36 degrees advance at WOT. But at crusing speeds on the highway, vacuum is higher, and the map value is lower - thus is advance is a higher number.

I see - I have been comparing to this map which is supposedly from my stock ECU:



You can see numbers much lower, unless I am reading that table wrong?

For instance 800 rpm with the lower load on the map says 9.75

[ronsonol]

Looks to me like the lower load is actually in the opposite direction, along the top. I am not really sure what I'm looking at though. Its hard for me to relate the number along the top to an actual map reading megatune expects.

[ubercamaro]

ronsonol,

you answered his questions better than i

JonK,

Here's what ptegler was saying:
http://www.megamanual.com/ms2/ign_timing.htm

one thing i noticed about your images in the post is that it is liters/min (i believe) whereas the Megasquirt is looking at pressure kPa, so you're not quite comparing apples to apples, its volume vs pressure.

I don't know how to make the spreadsheet cross over to volume using the supplied formula from Lance and don't look to either because the intent of the sheet is for Megasquirt.

However, in the "how do we use this" on the table size, i wanted to cover both boosted and naturally aspirated so that's why it is bigger than the 12x12 in MT. You can change the KPAs in the spreadsheet (like you would in the ignition table) and it will re-calculate that row. So, since the KPAs are in increments of 5, you could change them to increments of 10 or 15 and it will do the work for you.

Also, a clear example of how the cells are calculated are as follows:

Ignition advance at 100 kPa and 800 RPM is: 10 Degrees advance.
So to determine the timing at 800 RPM and 30 kPa it would be-
10+0.3*(100-30) = 10+0.3*(70) = 10+21 = 31 Degrees advance at 800 RPM and 30 kPa.

I will say that I have 2 goals for moving forward with the sheet.

1) try to add some "safety" in the boosted section as I noted previously the retarding of timing under boost really shouldn't go more than 1/2 of the timing at 100KPA.

2) I want to export the ignition table from MT to see if I can get the spreadsheet to export the data so that it may be able to be imported into MT. This could save some typing from cell to cell; HOWEVER, like noted before this is only to set a general ignition table and your setup will likely require more tuning. Its just easier than guessing values to begin with.

Deadlines for these goals you ask yourself? Not sure, maybe after I resolve some other things (like yard work ) i can see what happens this weekend. I will keep all posted.

l8r

[ronsonol]

Yes its easier to answer some questions after reading what Lance has to say. I've learned a bunch from hours of reading his docs and posts.

[Jon k]

Yes its easier to answer some questions after reading what Lance has to say. I've learned a bunch from hours of reading his docs and posts.

I am trying - I am good with physical stuff but the timing stuff confuses me so I hope everyone can bear with me.

[ubercamaro]

NP, we've all been there.

OK, so i looked at the export .vex file and it doesn't correlate to the spreadsheet, i.e. an advance of 30 kPa at 800 RPM is 31 degrees doesn't equal a similar value in the .vex files.

[blueman803]

Hey, I thought I would help you out and added the conditional statements for the boosted area. You meant the max the angle should retard to should be half the 100 kPa angle, correct?

[ubercamaro]

Hey, I thought I would help you out and added the conditional statements for the boosted area. You meant the max the angle should retard to should be half the 100 kPa angle, correct?

blueman803 - right, the amount of retard in timing shouldn't be more that 1/2 of the ignition advance at 100 kPa.

I'll download your sheet and check it out.

Thanks for contributing!

[houlster]

everyone,

attached is a spreadsheet i made using some assumptions and calculations from lance.

Where is the attachment?