Ecotec 2.5bar fake - commanded vs actual spark advance - Tuning Forum

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Ecotec 2.5bar fake - commanded vs actual spark advance
Tuesday, September 13, 2011 4:05 AM
So here's what I"m seeing. When commanding a max of 18* in the highest kPa column I see, I can easily hit 20-21* advance at that kPa. However, my IAT spark modifiers seem to be out of my control. When I have -5* in the 156*F row, I get pretty much no reduction in spark when i'm in that IAT range (supercharged). If i step up to -7* in that same row, timing tanks to about 17-18*, which is where I want to be when the temps are lower lol. Now, just for @!#$s and giggles, I upped the commanded timing from 18* to 23*, and left the 156*F IAT modifier at -7*, and i saw about 1* increase in advance, rather that 5* like i should. In other words, it seems like the IAT modifier has more sway on actual advance than the damn tables do. FWIW, this seems to be worse in PE than in closed loop. At light loads, actual timing is quite close to commanded.

The same sort of thing has happened on another 2.5bar fake car I've worked on,. The IAT spark modifer was fairly conservative (-6 or 7*), and the commanded timing was also fairly low. We upped the commanded timing but were not getting much if any more actual advance back. Then we dropped the IAT spark modifier slightly and BAM, commanded timing overshot what was commanded in the table.

Now, the only thing I can think of is a baro or altitude modifier that we don't have access to. I realize we have access to a knock retard baro modifier, which has been set to 1.0 across the board, but what about a hidden baro modifier for base advance? If you think about it, at key on, it should be seeing 100-105kpa, and at best it's seeing like 40-45kpa. It would make sense that if a modifier exists for baro, it would add more timing for being way above sea level right? What gets me is why the IAT modifer is so touchy. On our cars, this modifier NEEDS to work properly to save the car from a dead meth pump, or dead IC pump or both. So I think the next step, which scares me a little, is to zero out ALL base spark modifiers (IAT, ECT), lower the commanded timing in PE to something rediculously low and try to figure out if there is a consistant baro modifier that can be worked around.

Thoughts, comments, suggestions?




Re: Ecotec 2.5bar fake - commanded vs actual spark advance
Tuesday, September 13, 2011 4:14 AM
I know Ryan E and I have been saying we are missing hidden IAT modifiers for some time now. He and I have ran into similar issues with timing, and of course fueling that can not be explained by the fields we have.

I do not think it matters if ti is a 1, 2, 2.3, or 3 bar map sensor.



FU Tuning



Re: Ecotec 2.5bar fake - commanded vs actual spark advance
Tuesday, September 13, 2011 4:54 AM
Well, your baro reading makes no sense. What are you at, 20000 feet of elevation? Haha. I would look into that before anything else.
Re: Ecotec 2.5bar fake - commanded vs actual spark advance
Tuesday, September 13, 2011 5:17 AM
Wagonwes wrote:

Well, your baro reading makes no sense. What are you at, 20000 feet of elevation? Haha. I would look into that before anything else.
This is using a 2.5 bar map, hence 2.5bar fake. Actual pressure is 2.5x what you see in hpt. So there's nothing wrong with the reading, just potentially how the OS interprets it.

I know at least as far as timing, all the 1 bar tunes I've done behave quite well with respect to actual vs commanded, and the IAT modifier actually working like it should. I'll post up results when i get a chance to zero out modifiers and see what happens.



Re: Ecotec 2.5bar fake - commanded vs actual spark advance
Tuesday, September 13, 2011 6:22 AM
That's right. Disregard my previous comment.
Re: Ecotec 2.5bar fake - commanded vs actual spark advance
Friday, September 16, 2011 6:46 AM
So in my area today we had ~45*F weather this morning. My whole rationale for switching to the 2.5bar fake was to see if the tune would hold AFRs more steady with drastic weather changes. The car was tuned in ~75*F weather, and my AFRs were about a point leaner this morning. Hence, I think I"m going back to 1 bar. It's not worth it to me to screw with the wack timing you get on the 2.5bar when I KNOW the 1 bar works, and the 2.5bar fake has no additional advantage... I would have liked to spend the time to figure out how the commanded vs actual timing correlates, but oh well.

On another topic. I think the (lack of) AFR compensation with weather changes is at least in part due to the water/meth injection. The controler doesn't know when it's cooler out, so that contribution to fueling is static. The only way i can think of to compensate is to try to run a higher concentration of methanol when it's cooler out, meaning seasonal, not day to day.



Re: Ecotec 2.5bar fake - commanded vs actual spark advance
Friday, September 16, 2011 6:55 AM
oldskool wrote:

So in my area today we had ~45*F weather this morning. My whole rationale for switching to the 2.5bar fake was to see if the tune would hold AFRs more steady with drastic weather changes. The car was tuned in ~75*F weather, and my AFRs were about a point leaner this morning. Hence, I think I"m going back to 1 bar. It's not worth it to me to screw with the wack timing you get on the 2.5bar when I KNOW the 1 bar works, and the 2.5bar fake has no additional advantage... I would have liked to spend the time to figure out how the commanded vs actual timing correlates, but oh well.

Myself and Higgins have been saying that for a while now.... I have done both, argued both, and now your conclusions are what mine have been.
oldskool wrote:


On another topic. I think the (lack of) AFR compensation with weather changes is at least in part due to the water/meth injection. The controler doesn't know when it's cooler out, so that contribution to fueling is static. The only way i can think of to compensate is to try to run a higher concentration of methanol when it's cooler out, meaning seasonal, not day to day.

This may have some effect, but I still feel its mosty due to lack of support...





P&P Tuning
420.5whp / 359.8wtq

Re: Ecotec 2.5bar fake - commanded vs actual spark advance
Friday, September 16, 2011 2:51 PM
I have a theory, but is so out there I dont even want to mention it until I test it and confirm that its correct. If it is, it will blow minds.


1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by: Kronos Performance

WPI Class of '12 Mechanical Engineering
WPI SAE Risk and Sustainability Management Officer
Re: Ecotec 2.5bar fake - commanded vs actual spark advance
Friday, September 16, 2011 8:34 PM
oldskool wrote:

On another topic. I think the (lack of) AFR compensation with weather changes is at least in part due to the water/meth injection. The controler doesn't know when it's cooler out, so that contribution to fueling is static. The only way i can think of to compensate is to try to run a higher concentration of methanol when it's cooler out, meaning seasonal, not day to day.


I have Water/Meth Injection (50/50) and the AFR play a lot with the weather. I also noticed that if you go WOT @ 3500 rpm to redline and after you go WOT @ 5000 rpm to redline, the AFR are not the same with this two situations.


Boost Lover
Re: Ecotec 2.5bar fake - commanded vs actual spark advance
Friday, September 16, 2011 9:54 PM
Well my theory didnt come out at planned, though I didnt disprove it. I can say confidently however that the alcohol spark tables have no effect on spark values on the 02 eco pcm.


1994 Saturn SL2 Home Coming Edition: backup car
2002 Chevy Cavalier LS Sport Coupe: In a Junk Yard
1995 Mazda Miata R-package Class=STR
Sponsored by: Kronos Performance

WPI Class of '12 Mechanical Engineering
WPI SAE Risk and Sustainability Management Officer
Re: Ecotec 2.5bar fake - commanded vs actual spark advance
Saturday, September 17, 2011 4:29 AM
Yoecotec wrote:

oldskool wrote:

On another topic. I think the (lack of) AFR compensation with weather changes is at least in part due to the water/meth injection. The controler doesn't know when it's cooler out, so that contribution to fueling is static. The only way i can think of to compensate is to try to run a higher concentration of methanol when it's cooler out, meaning seasonal, not day to day.


I have Water/Meth Injection (50/50) and the AFR play a lot with the weather. I also noticed that if you go WOT @ 3500 rpm to redline and after you go WOT @ 5000 rpm to redline, the AFR are not the same with this two situations.
My guess on that, as i also see a slight variation, is that the farther away the nozzle is from the intake port, the more inconsistency you will see when you punch it. Fuel injectors are right there, fuel is almost instantly in the cylinder. When the meth nozzle is in the intake tube of a s/c car for example, it has to travel through the TB, through the blower, through the intake manifold, then it's there.

Leafy (Club Jeffie FEA man) wrote:

Well my theory didnt come out at planned, though I didnt disprove it. I can say confidently however that the alcohol spark tables have no effect on spark values on the 02 eco pcm.
Ah, lol you should've just asked! I think that's been either disclosed by the HPT crew, or someone here tested it, maybe Ryan?




Re: Ecotec 2.5bar fake - commanded vs actual spark advance
Saturday, September 17, 2011 6:37 AM
oldskool wrote:

My guess on that, as i also see a slight variation, is that the farther away the nozzle is from the intake port, the more inconsistency you will see when you punch it. Fuel injectors are right there, fuel is almost instantly in the cylinder. When the meth nozzle is in the intake tube of a s/c car for example, it has to travel through the TB, through the blower, through the intake manifold, then it's there.


You're right. It's bad because during the water/meth travel to engine, the AFR are to lean and he have Knock Retard. It's really the big disadvantage of Water/Meth Injection IMO.


Boost Lover
Re: Ecotec 2.5bar fake - commanded vs actual spark advance
Saturday, September 17, 2011 7:00 AM
Yoecotec wrote:

oldskool wrote:

My guess on that, as i also see a slight variation, is that the farther away the nozzle is from the intake port, the more inconsistency you will see when you punch it. Fuel injectors are right there, fuel is almost instantly in the cylinder. When the meth nozzle is in the intake tube of a s/c car for example, it has to travel through the TB, through the blower, through the intake manifold, then it's there.


You're right. It's bad because during the water/meth travel to engine, the AFR are to lean and he have Knock Retard. It's really the big disadvantage of Water/Meth Injection IMO.


I have never ran across this on my setup.



FU Tuning



Re: Ecotec 2.5bar fake - commanded vs actual spark advance
Tuesday, September 20, 2011 10:37 AM
I also noticed a slight variation on AFR depend on gear (2nd, 3rd gear etc). I guess it's because my Turbo Lag are different on each gear but without Water/Meth injection, my AFR are more constant depend on gear load and weather.


Boost Lover
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