Why are our kPa increments so odd?
 

All this talk of maps and values got me to thinking...

We all seem to be using pretty much the same basic VE and Spark tables. I'm guessing that DIY was the originator. Does it bother anybody else that the steps between kPa values on the veritcal axis of all of our tables are really uneven?

Take the attached picture. The numbers in green are the actual kPa values that appear on the left side of my VE and spark tables, and the numbers between them in orange represent the difference in kPa between the two adjacent cells:

http://img238.imageshack.us/img238/2701/kparf7.gif

Up in the boosted area, there are 28kPa between each cell, apart from the top-most one (which is really just a pad, I don't plan on boosting to 230kPa.) Down in the atmospheric area, it gets weird.

I can understand why you'd want a little more resolution down at the very bottom, but what about the cells from 35kPa to 100kPa? 20 kPa each for the first two steps, then 9, then 16. Whiskey Tango Hotel? Is there some amazingly straightforward and logical explanation for this that I'm missing?

haha I noticed that when I was porting my hydra map over too.

I think you'd want 3 cells for idle/fast idle, then maybe around cruise, moderate load, then right around 101kpa, then every couple PSI.

so like 10 kpa, 25 kpa, 40 kpa, 65 kpa, 83 kpa, 101 kpa, 120 kpa, 140 kpa, 160 kpa, etc.

I thought about that the other day... as in last night when working on a new basemap mishmash.... I didn't go past it though, as the donor maps I was grabbing from were using that setup.

Only reason I have kept it scaled like that is because I ran their timing map for the longest time and I didn't feel like making up a new one. You could easily rescale though and enter your own semi-conservative timing values in by looking at the DIY map.
I keep my fuel map scaled that way just so that they match. It's also nice to have everyone on the same scale when comparing things.

i set the second from the bottom cell to whatever KPA i idle at, the 2nd one to my fast idle, the one above that to whatever I cruise at. Atleast that's how I used to do it. Makes it easier to tune by hand when its not interpolating between two cells. Now that MLV works for me though screw hand tuning.

What was not working before with it? If all goes well... this weekend is finally time to tune the darn car... and having more info... never hurts :)

I'm using the AEM UEGO and MLV had issues with some of the settings apparently. So i switched it to LC1 Linear and modified the .ini so that the guage and MT read the same, or close enough. Now it works fine.
MLV wouldn't import my target afr table accurately.

Crap, I'm using a NGK AFX... I hope they sorta play nice.

Maybe the VE values between these MAP values change linearly, so you would want to use the said kPa bins to hit the sweet spot using linear interpolation? Just a thought...

Jim

If it outputs a 0-5v 10-20afr feed then you can most likely use the lC1 linear settings, might have to adjust the .ini a little to get it to match megatune though.

Short answer for our particular maps: We've found that most engines need more resolution in the below 100 kPa off-boost area than on boost. Some of the closely spaced ones just needed a bit more tuning in the area where they were spaced closely together.