How to calculate a base ignition table - Page 2

flightlead404 · flightlead404's Garage

Quote:

Originally Posted by Tippy

I reread your OP.

I don't understand why all of the brain power you are putting into this if you are simply dumping off at a tuner?

None of your numbers will be reused if using a load dyno and dialing in MBT?

I gave you my method to get a quick rough map in that is actually a great way to tune it all and just check for knock afterwards and adjust accordingly.

lol, well Tippy, I'm not sure. A personality quirk?

I really hadn't intended to spend this much effort on it tbh. I just thought that starting with the stock curve would give me something safe and reasonably driveable to do my basic checkouts, run a few miles prior to doing an oil change, and thence to a tuner.

It turned into an exercise of much more thoroughly understanding the stock curves and the why's and wherefore's.

Scope creep is something I've always struggled with

To that end I'm going to take the math I have now, build a much more granular table so I can see where the greatest and least advance #'s are and where the slopes are the steepest, and use that info to collapse back down into a 12x12 table with tighter spacing at the peaks and troughs and wider spacing where there isn't much change.

One more question: Tuner studio/microsquirt allows me to have two ignition tables (three actually, but for this question two is what I care about). I was considering having an offboost table and an on-boot table and automatically switching as my MAP passed 100 kPa. This would effectively give me double the granularity on the load axis of the graph, although the rpm axis would still remain at 12 bins wide.

Has anyone done this? Is it a good idea?

Tippy · 01-11-2019, 10:18 AM

Quote:

Originally Posted by flightlead404

One more question: Tuner studio/microsquirt allows me to have two ignition tables (three actually, but for this question two is what I care about). I was considering having an offboost table and an on-boot table and automatically switching as my MAP passed 100 kPa. This would effectively give me double the granularity on the load axis of the graph, although the rpm axis would still remain at 12 bins wide.

Has anyone done this? Is it a good idea?

I wanted to always do that same thing.

Please report back if it works (I can't logically see why it wouldn't).

But, I will throw this out there from reading from professional tuners.

Boost fuel delivery is completely linear. Meaning, you don't need granularity at all. So, you can have say only 3 rows of boost and the rest PT, idle, and overrun vacuum figures as the remaining 9 (or whatever system you are using).

flightlead404 · flightlead404's Garage

Quote:

Originally Posted by Tippy

Boost fuel delivery is completely linear. Meaning, you don't need granularity at all. So, you can have say only 3 rows of boost and the rest PT, idle, and overrun vacuum figures as the remaining 9 (or whatever system you are using).

Why would that be? Why would it be any different than off-boost just because the intake is above atmospheric?

Is it because turbo chargers are close to on/off in terms of mass of air delivered?

16Volt · 01-11-2019, 11:59 PM

Something to consider - here is a previous necro thread on this.

Ignition Map, Electromotive XDi-2

I have a XDI-2, twin plug, knock sensing, cammed, K27 hybrid turbo that I am planning on trying jwasbury's map on.

On full standalone VW 16V Turbos I used to drop a degree of timing per PSI but I am not sure how applicable that is on a 930. Here is jwasburys map for reference. Be nice to get folks thoughts (though its for a CIS car, like mine fyi).

s5uewf · s5uewf's Garage

The map above looks pretty conservative, though I am sure it works well. I have attached a single plug 3.3 map from a dyno and you may be able to use this as a guide, as well - I believe you would want dual plug timing to be a little less aggressive. Maybe you want to end up somewhere between the two.

My single plug uses this map, more or less, and runs very well. I think I backed off a few degrees in the low mid range rpms to smooth my car out...

Full EFI, but not sure that really makes a difference in terms of timing if you are able to manage your timing with your installation.

I had trouble loading the image earlier today, so if it does not load I will re edit and re load for you.

spuggy · 01-12-2019, 09:06 AM

Quote:

Originally Posted by Tippy

But, I will throw this out there from reading from professional tuners.

Boost fuel delivery is completely linear. Meaning, you don't need granularity at all. So, you can have say only 3 rows of boost and the rest PT, idle, and overrun vacuum figures as the remaining 9 (or whatever system you are using).

I think MAP-based maps are supposed to look very flat. Mine pulls -10% fuel at idle, and same again at high kPA (when the venerable K27/HF runs out of CFM, to keep AFRs correct).

Interesting to hear of the MS row/column restrictions; MoTeC allows you to insert/delete rows/columns anywhere you feel like - so if you want cells every 50 or 100 RPM or 5 kPA around, say, idle, to zoom in and get something sorted, no problem.

However, this mostly seems useful to isolate a specific area to get it sorted - and once done, you generally remove almost all of them. If the values on your ignition map are a straight line on the graph, you only really need the 2 end points as all the intervening points are extrapolated...

flightlead404 · flightlead404's Garage

Quote:

Originally Posted by s5uewf

The map above looks pretty conservative, though I am sure it works well. I have attached a single plug 3.3 map from a dyno and you may be able to use this as a guide, as well - I believe you would want dual plug timing to be a little less aggressive. Maybe you want to end up somewhere between the two.

My single plug uses this map, more or less, and runs very well. I think I backed off a few degrees in the low mid range rpms to smooth my car out...

Full EFI, but not sure that really makes a difference in terms of timing if you are able to manage your timing with your installation.

I had trouble loading the image earlier today, so if it does not load I will re edit and re load for you.

Any chance of a larger image? Just the table part even, to make it more readable?

flightlead404 · flightlead404's Garage

Quote:

Originally Posted by spuggy

I think MAP-based maps are supposed to look very flat. Mine pulls -10% fuel at idle, and same again at high kPA (when the venerable K27/HF runs out of CFM, to keep AFRs correct).

Interesting to hear of the MS row/column restrictions; MoTeC allows you to insert/delete rows/columns anywhere you feel like - so if you want cells every 50 or 100 RPM or 5 kPA around, say, idle, to zoom in and get something sorted, no problem.

However, this mostly seems useful to isolate a specific area to get it sorted - and once done, you generally remove almost all of them. If the values on your ignition map are a straight line on the graph, you only really need the 2 end points as all the intervening points are extrapolated...

Remember, these are ignition maps we're talking about, not fuel maps.

Ignition advance needs to be adjusted for rpm regardless of the mixture. The speed at which the charge burns is fairly static, so as speeds increase the charge needs to be ignited earlier and earlier BTDC to keep the point of max pressure in the same location ATDC. So, regardless of fuel delivery being flat, ignition would change I think.

MS2 (which is what the microsquirt is) allows 12x12 tables for ignition, and up to three tables with a variety of ways to switch e.g. based on pressure, or an external switch for example. The 12x12 limitation is expanded to 16x16 for MS3 I think. The cells can be anything you want, they don't need to be equally spaced.

Regarding spacing of the bins, yes I agree. So where the slope on the graph hits a min or a max you need a cell. And where slopes are steeper cells need to be closer together, and where shallower they can be further apart.

spuggy · 01-12-2019, 10:36 AM

Quote:

Originally Posted by s5uewf

I have attached a single plug 3.3 map from a dyno and you may be able to use this as a guide, as well - I believe you would want dual plug timing to be a little less aggressive.

At a quick glance - and mentally converting PSI to kPA and/or inHG - this looks similar to what I ran last, twin-plugged. Car seems to drive nicely.

Out of interest, I tried twin-plug maps (at least off-boost portions of them) with much less advance. Those were much less responsive/fun.

My engine builders general advice was to focus less on preconceived ideas of what the motor "should" need, and instead watch how it responds in order to figure out what it actually "wants". That does seem to work.