Spark Table Inverse of VE Table

[RSTinOKC]

Was reading one of Banish's books this morning and there was a line that stuck out at me: "The spark map should look like an inverse of the volumetric efficiency map". This sounds like a viable alternative for dyno tuning to me.
Now, from what I remember of math vocabulary, inverse means opposite. Where I am stumped is in how to make the spark table look like an inverse of the VE Table and what data to log and how to log it to get the data I need to achieve this. Any pointers would be appreciated.

[Rinkrat456]

I never thought of it that way before but it makes sense now that the writing is on the wall. Low load, low rpm situations have high spark advance whereas high load high rpm situations have less spark advance. Keep chugging away with this idea...you've got my attention. I wonder if there's any way to enter VE table data into a spreadsheet which gives you the inverse table in terms of degrees of advance.

[bene]

interesting... I'm subscribing...

[Wnts2Go10O]

O_o

[smokeshow]

I wonder if there's any way to enter VE table data into a spreadsheet which gives you the inverse table in terms of degrees of advance.

That would be application specific. They aren't literally inverse, but the high of one matches the low of the other. One approach to this would be to find MBT at your maximum VE value and MBT at your minimum VE value and draw a linear relationship between the two. The theory is simple, the more airmass in a cylinder, the less timing you need because the flame moves faster.

[Higgs Boson]

Lol, it's not going to be exactly inverse..... It just means that the VE table will grow with RPM and load and timing will need to be reduced with RPM and load..... It doesn't mean you can create a VE table and then use a formula to make a timing map. You'll shoot your eye out!

[motorheadmike]

If you need to visualize this a bit better I made a simple spreadsheet that lays it out in the form of a line graph: http://www.hptuners.com/forum/showpo...51&postcount=5

I include PE in this as well, and while there is a dip in the PE table (which might be seen as PE table rape by some), if you tune for this situation (MBT) when doing your VE tuning it is accounted for properly. Again it is theory vs. application and a little trial and error. Obviously dyno tuning would be ideal to help determine the benefits of a non-linear PE AFR.

GM used a non-linear AFR in the 2007 TBSS which richened up PE slightly approaching MBT and if you buy the theory it makes sense.

[sarg]

This is more of a general rule than a law I would think. It would by no means replace street or dyno tuning. This idea just gives you a general beginning shape.

[RSTinOKC]

Thanks for the spreadsheets motorheadmike and nice work by the way.
I wasn't really trying to suggest that this could be used in lieu of street tuning but may be a way to get in the neighborhood before getting on a dyno.
In my situation my VE is way different than stock with the new cam yet I'm still running a stock spark table with roughly 5 degrees added across the board.
What I'm after may be a little beyond my skill level at this point; just trying to find a method to tune for mbt on the street with my setup.

[motorheadmike]

Just to be clear I have never paid for a minute of dyno time, all of my tuning is done on the "street" (read: empty country roads) and at the drag strip. I've never been one to worry about every last pony, but rather building safe and usable tunes which put up good numbers. Tuning to MBT is just part of this.

At any rate I am just glad to help.

[sarg]

Last I checked, cars don't spend a whole lot of their life on the dyno.....much more time on the street I always felt street tuning to be an essential part of the tuning process.

[Rinkrat456]

If you need to visualize this a bit better I made a simple spreadsheet that lays it out in the form of a line graph: http://www.hptuners.com/forum/showpo...51&postcount=5

That's a pretty neat spreadsheet.