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View Full Version : How smooth should spark tables look?



Blk02Ls1A4
January 19th, 2005, 09:19 AM
Looking at my high octane spark table it looks like it is very rough, has quite a few peaks and troughs that seem like it would be better if they were smoother. Mind you, this is after a "tune" from a pretty reputable place. When I smooth the table about 4 times it looks a lot better. Wouldnt a smoother spark table lend itself to smoother engine operation throughout the rpm range?

vzsv8
July 20th, 2005, 10:41 PM
If you look at the off idle section of the 220-235KW from 2000 to 2003 there is a strange looking spike 15 Kpa 1200 rpm, 50% higher than anything near it! This is just ridiculous, gas can not change velocity this fast. Can anyone explain this one. :?:

GMPX
July 21st, 2005, 12:21 AM
The way the PCM works with it's table look up routines it smooths between cells anyway, having said that, I know people swear that smoothing the graph makes a big difference in the seat of the pants feel.

There is certainly no harm in smoothing it.
Strange, some factory GM cals are smoothed for sure, others are not.

Cheers,
Ross

GMPX
July 21st, 2005, 12:29 AM
If you look at the off idle section of the 220-235KW from 2000 to 2003 there is a strange looking spike 15 Kpa 1200 rpm, 50% higher than anything near it! This is just ridiculous, gas can not change velocity this fast. Can anyone explain this one. :?:

You mean the VE map right?.
15kPa, not really an issue, I can't remember even seeing that kind of vac value even when my engine was stock. If it were there, the thing would probably be in Decell Fuel Cut (DFCO) anyway.
Chances are the cal guys at GM never really 'looked' at the values in graph form, it's pretty easy to miss just looking at a bunch of numbers.

Cheers,
Ross

bink
July 21st, 2005, 01:20 AM
Ross - Is your avatar a pregnant belly that says" We're not afraid"?? Just curious. If it is - TOO DAMN FUNNY!

Cheers,
joel

GMPX
July 21st, 2005, 01:35 AM
Ross - Is your avatar a pregnant belly that says" We're not afraid"?? Just curious. If it is - TOO DAMN FUNNY!

Cheers,
joel

I have no idea what it is, but I think you are right.....
http://www.werenotafraid.com

Cheers,
Ross

bink
July 21st, 2005, 01:52 AM
Ross - Is your avatar a pregnant belly that says" We're not afraid"?? Just curious. If it is - TOO DAMN FUNNY!

Cheers,
joel

I have no idea what it is, but I think you are right.....
http://www.werenotafraid.com

Cheers,
Ross

Wow, quick reply. Shouldn't you be sleeping? Great link...very nice to see. I've shown it to everyone here.
Cheers,
joel

GMPX
July 21st, 2005, 02:27 AM
Wow, quick reply. Shouldn't you be sleeping? Great link...very nice to see. I've shown it to everyone here.
Cheers,
joel

Yeah, 1:24am right now, sleep might be a good thing.
Now you guys stop asking for new features and we can all get some sleep :wink:
Hey, what else would I be doing, watching Springer or Home Shopping network?. I'm a true computer person, late to bed, late to rise, just gotta remind the kids of that at 7:00am, yeah, under 6hrs away.

Cheers,
Ross