Ignition timing for turbo or supercharged renesis - post your maps
12-03-2010, 11:04 AM
#151
hehe, the timing math is so bad, I have been working on it for literally years.
We have the basic equations done... the code to run is is almost 120,000 lines.
As for the rest, load determines timing, and it isn't a one-to-one kind of thing, so there isn't a perfectly smooth curve.
We have the basic equations done... the code to run is is almost 120,000 lines.
As for the rest, load determines timing, and it isn't a one-to-one kind of thing, so there isn't a perfectly smooth curve.
12-05-2010, 03:45 PM
#152
Asshole for hire
iTrader: (1)
Join Date: Jun 2006
Location: Colfontaine, Belgium
Posts: 3,214
Likes: 0
Received 3 Likes
on
3 Posts
question though, it seems like there are large steps in all these timing maps. Just as an example take Kanes map on this page. At 4000 rpm the first 5 load columns are all at 43.5 degrees then the next column steps down to 40 degrees. Why is the timing not tapered down for a smooth curve? I see large chunks like this in all the maps shown.
Also what is the mathematical equation for determining timing? Google has failed me here. Seems like if you know peak pressure in the chamber, AFR, RPM, Load, spark duration and heat, you should be able to plug that into a calculation to determine the optimal spark timing?
it would be simple(in relative terms) to model it mathematically if we had a combustion chamber that only changes shape/volume in 1 geometrical plane, like a piston/cylinder. the complication is that our chamber moves in a fairly complex to define manner, across multiple planes. Oh, and dont forget we have a split ignition factor as well
12-12-2010, 12:19 AM
#153
there are no abrupt changes the way you see them. the PCM interpolates the values for any point in between said cells. so its not a "step", its a steep curve. make transitions steeper where it is acceptable so that you may make finer more controlled transition where it matters for how it drives/driveability
dude isnt joking, he was working on this at least 2.5 years ago when we were both in hawaii
it would be simple(in relative terms) to model it mathematically if we had a combustion chamber that only changes shape/volume in 1 geometrical plane, like a piston/cylinder. the complication is that our chamber moves in a fairly complex to define manner, across multiple planes. Oh, and dont forget we have a split ignition factor as well
dude isnt joking, he was working on this at least 2.5 years ago when we were both in hawaii
it would be simple(in relative terms) to model it mathematically if we had a combustion chamber that only changes shape/volume in 1 geometrical plane, like a piston/cylinder. the complication is that our chamber moves in a fairly complex to define manner, across multiple planes. Oh, and dont forget we have a split ignition factor as well
love this car, hate this car!
beers
12-12-2010, 12:59 AM
#154
Asshole for hire
iTrader: (1)
Join Date: Jun 2006
Location: Colfontaine, Belgium
Posts: 3,214
Likes: 0
Received 3 Likes
on
3 Posts
yeah seriously, wtf kane
i dont remember if it was Kane that showed me, or if i found it myself being curious... I've seen models for piston timing. And although I understand the premise, and can follow the math/chemistry/physics when looked at in small managable pieces, it really is stupid complex. And the variables and complexity of piston modeling compared to rotary is like comparing a mouse trap to a 1:1 tracking kilowatt laser rodent removal system
i dont remember if it was Kane that showed me, or if i found it myself being curious... I've seen models for piston timing. And although I understand the premise, and can follow the math/chemistry/physics when looked at in small managable pieces, it really is stupid complex. And the variables and complexity of piston modeling compared to rotary is like comparing a mouse trap to a 1:1 tracking kilowatt laser rodent removal system
Last edited by paulmasoner; 12-12-2010 at 01:01 AM.
12-12-2010, 01:17 AM
#155
HAHA, yeah Paul I think you were there when me and Faille found that first physics paper, not only could I not do the math programmatically, I couldn't even tell what the symbols meant in relation to modeling it programmatically (IE breaking down equations until you get to an Algebra 1-2 type equation).
12-12-2010, 01:58 AM
#156
Asshole for hire
iTrader: (1)
Join Date: Jun 2006
Location: Colfontaine, Belgium
Posts: 3,214
Likes: 0
Received 3 Likes
on
3 Posts
HAHA, yeah Paul I think you were there when me and Faille found that first physics paper, not only could I not do the math programmatically, I couldn't even tell what the symbols meant in relation to modeling it programmatically (IE breaking down equations until you get to an Algebra 1-2 type equation).
12-12-2010, 05:18 PM
#157
modeling timing advance in any useful way requires proprietary data about the engine and expensive software. Why do you think OEM's spend so much money on this stuff?
as for the whole step change in timing maps... the Rx-8 does not have very high resolution, so that's part of it. You should see newer GM PCM's. The C6 Z06 has 32x32 main timing maps
as for the whole step change in timing maps... the Rx-8 does not have very high resolution, so that's part of it. You should see newer GM PCM's. The C6 Z06 has 32x32 main timing maps
12-12-2010, 07:31 PM
#158
Asshole for hire
iTrader: (1)
Join Date: Jun 2006
Location: Colfontaine, Belgium
Posts: 3,214
Likes: 0
Received 3 Likes
on
3 Posts
arghx7, what parameters do we use to define resolution, as in what you refer to as 32X32?
I may be missing how its supposed to be viewed, but AccessTuner is showing me 16X14 cells for the main Ign tables.
I'm just curious though I do not know how one would quantify when the need for more granularity becomes more/less of an issue considering interpolation. I would guess that every motor would have its own unique needs for specific points vs interpolating a curve inbetween
I may be missing how its supposed to be viewed, but AccessTuner is showing me 16X14 cells for the main Ign tables.
I'm just curious though I do not know how one would quantify when the need for more granularity becomes more/less of an issue considering interpolation. I would guess that every motor would have its own unique needs for specific points vs interpolating a curve inbetween
Last edited by paulmasoner; 12-12-2010 at 07:45 PM.
12-13-2010, 07:31 AM
#160
As a rule of thumb what amount of timing retardation are people running on boosted renesis engines? 1,2,3 degrees per PSI? Haven't seen the factory map yet so can't tell how retarded you guys are 
12-14-2010, 07:36 AM
#163
If either of you could point me to the post where a stock timing map is or a post on the degrees retardation per PSI that would be great. You can't though because they are not found within this post. The stock ignition dwell table is here, as well as a comment by MM about how much retard is being run at peak torque and where the resolution needs to be. All the EMS reading I've done seems to show tuning a boosted NA engine requires 1-3 degrees retard per PSI boost and I'm just trying to figure out if that's what people are running or if they are running even more conservative based on the rotary sensitivity to detonation.
Also the comment "Abject laziness rising to its most elevated level." Is just bad English. The word abject already refers to an elevated or extreme state. Next time you flame someone with that one you should say "Abject laziness." or "Laziness rising to it's most elevated state." Less redundant redundancy here.
Also the comment "Abject laziness rising to its most elevated level." Is just bad English. The word abject already refers to an elevated or extreme state. Next time you flame someone with that one you should say "Abject laziness." or "Laziness rising to it's most elevated state." Less redundant redundancy here.
12-14-2010, 08:08 AM
#164
https://www.rx8club.com/showpost.php...&postcount=144
I can't see if the image is still there....
https://www.rx8club.com/series-i-engine-tuning-forum-63/how-kane-tunes-fi-renesis-turbo-ported-ceramic-seals-188514/
And that one has some info too...
I can't see if the image is still there....
https://www.rx8club.com/series-i-engine-tuning-forum-63/how-kane-tunes-fi-renesis-turbo-ported-ceramic-seals-188514/
And that one has some info too...
11-10-2011, 08:17 AM
#167
bumping old thread.
Reason: I have observed such a wide variety of ignition timing lately in different cars with the same set up. Pettit SC cars mainly but one turbo car with approx the same level of boost.
I have seen leading timing anywhere from 8 ( wot at 7.5K and approx 180 load) to 19. I have seen both retarding lead ignition timing with increased rpm, i have seen flat, and I have seen advancing. All the cars perform about the same??
Fuel injectors of these cars and a/f's are about the same. grams per sec of the maf are all about the same. Maf's are not scaled.
What the heck is going on...................????
leading timing from 8 to 19 degrees makes no noticeable drivability or power difference?
Reason: I have observed such a wide variety of ignition timing lately in different cars with the same set up. Pettit SC cars mainly but one turbo car with approx the same level of boost.
I have seen leading timing anywhere from 8 ( wot at 7.5K and approx 180 load) to 19. I have seen both retarding lead ignition timing with increased rpm, i have seen flat, and I have seen advancing. All the cars perform about the same??
Fuel injectors of these cars and a/f's are about the same. grams per sec of the maf are all about the same. Maf's are not scaled.
What the heck is going on...................????
leading timing from 8 to 19 degrees makes no noticeable drivability or power difference?
11-10-2011, 09:03 AM
#169
You have to consider all the factors in play at the time you are datalogging. What you describe is entirely possible with identical maps, but dependent on the exact operating conditions at the time and their overall impact on the final PCM output determination
11-10-2011, 11:28 AM
#170
Yep understand that, the circumstances during these observations where as close as they could be on the street--sans abient temps that were a little different, maybe 10F ? Dunno?
Like Kane said (and I am beginning to understand a little on rotary engines), advancing the leading timing really doesnt result in much except more risk for detonation. It makes me wonder why the wide range is being used? Guess maybe the indivual tuners have different ways of approachs.
I THINK I am beginning to understand that ignition timing settings are not as important in reducing detonation as in recips? I mean they have to be reasonable, but the rotary can tolerant a wider range than recips without giving up much power, if any?
Could a general statement that the reason for rotary engine detonation is more realted to heat/fuel issues than ignition timing? Given ignition system etc is up to par?
The changes in the ignition timing observed were at max TQ/ rpm and above. Below that level--everyones were basically the same.
Like Kane said (and I am beginning to understand a little on rotary engines), advancing the leading timing really doesnt result in much except more risk for detonation. It makes me wonder why the wide range is being used? Guess maybe the indivual tuners have different ways of approachs.
I THINK I am beginning to understand that ignition timing settings are not as important in reducing detonation as in recips? I mean they have to be reasonable, but the rotary can tolerant a wider range than recips without giving up much power, if any?
Could a general statement that the reason for rotary engine detonation is more realted to heat/fuel issues than ignition timing? Given ignition system etc is up to par?
The changes in the ignition timing observed were at max TQ/ rpm and above. Below that level--everyones were basically the same.
11-10-2011, 11:43 AM
#171
IAT, baro (which you likely didn't measure), etc., they all interact heavily on the timing map
IMO detonation on a Renesis is more prevalent than most people probably realize. I'm also not entirely convinced that Cobb (or anyone else, including maybe Mazda) has all of the anti-knock system figured out correctly.
IMO detonation on a Renesis is more prevalent than most people probably realize. I'm also not entirely convinced that Cobb (or anyone else, including maybe Mazda
) has all of the anti-knock system figured out correctly.
