IHADAV8.com - Turbo Buick Tech, and Nonsense
Tech Area => General Buick Tech => Topic started by: dennisL on November 09 2012, 02:22:27 PM
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I was wondering if you folks (being much smarter than me) could help me with a good way to test Acceleration Enrichment (AE). I've changed the AE values in the chip several times and don't seem to notice a difference. I'm referring to the AE fuel based on change in throttle position.
I understand the goal is for throttle response with no lag but beyond that is there anything I should be looking for?
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injector duty rise above what you would see if you slowly accelerate
the smaller the injector the less noticible changes will seem
if you were to monitor with a wideband you would be looking for a slight richening while ae is added
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I always have just set it as lean as possible with no hesitation when giving it some pedal
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Thanks guys. I have 009 (42.5#) injectors and I'm tweaking the numbers after replacing Tomco green stripes. I'll log a bunch of throttle "blips" both in and out of gear and watch the afr.
The numbers I used with the 30# injectors seemed to work well, but I didn't have a wb then. I reduced the AE pw 15% for the larger injectors but don't see a change or dip in afr. I probably should go back to a "fat" pw then gradually reduce it and watch the results.
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considering 42s are nearly 30% larger than 30# injectors , the AE PW would need to be trimmed by 30%
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Err... did you just say you swapped injectors without swapping chips and are now trying to tune for it?
Please clarify.
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He is making a new chip
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I got side-tracked on the AE testing but now back into it. I'm looking at all parts of the program that deals with AE and understand the logic but I do have a question. Before the calculated AE pulse-width is applied, it is compared to a minimum AE pw. Can anyone think of a reason for having a minimum size pulse?
I plan to take the min check out and see what happens but thought I'd better ask the experts first. Does a fuel injector need a minimum pulse-width?
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I would think the physics dictate that the inertia of the moving parts set a minimum
usable pulse width?
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I got side-tracked on the AE testing but now back into it. I'm looking at all parts of the program that deals with AE and understand the logic but I do have a question. Before the calculated AE pulse-width is applied, it is compared to a minimum AE pw. Can anyone think of a reason for having a minimum size pulse?
I plan to take the min check out and see what happens but thought I'd better ask the experts first. Does a fuel injector need a minimum pulse-width?
With no pulse width you have no fuel.
AJ___
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With no pulse width you have no fuel
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[/size]I was going to say something smart here but I'll just leave it at DAAAA. :icon_eyes:
[/size]
[/size]I think Dave makes a good point on the minimum pulse needed to pull open the injector but its interesting that the program makes the pw = 00 when the calculated pw is below the min. Almost as though a "too small" pw would cause a problem.
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ok :cheers:
AJ___
spelling error
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Thanks AJ. I have a scope but no flow meter so won't be making that test.
The min asynchronous pw for stock injectors is set to 488 mS which seems large for a minimum. (???) A few mSec makes sense for a true min and adding a margin of 100 - 150mS would seem reasonable to me, but I'm only a computer geek.
I mess with this stuff for the education benefit and didn't want to break something if I made the pulse too small. I'll leave it alone for now as it only comes into play at hot temperatures and minimal tps increase. Each calculated AE pw is added to the previous total so the pw grows rather quickly until it reaches the max allowed. From what I see on Power Logger, most of time it jumps right to the max pw.
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I just looked at the stock min AE pulse with my glasses on and its 0.488 mS. Big difference - that little decimal point makes. :icon_redface:
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I suspect the part to part variance becomes significant around the minimum pulse width so we need to be careful to cut them all off for the "slowest" injectors. The semiconductors driving them are much faster but still have slew
limitations, they get hottest in that analog transition region from off to on and on to off.
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My AE testing got slowed down after I decided to rewrite the AE portion of the program. There was just too much useless stuff, like multiply by 1, runtime multiplier, and more. I'm back into it now.
As to the minimum pulse width issue, I've learned that there is a min usable pw. Here's a quote from something I found:
[size=0pt][/size]
[/color]Injectors should not be operated below 1.5-2.0msec PW’s due to the non-linear portion of the curve. At extremely low PW’s, the injector’s coil does not have time to reach its magnetic potential, thus the opening and closing action of the injector becomes erratic.
[/color]
At a "too small" pw the amount of fuel is not predictable. Each make and size injector has its own characteristic but the 1.5-2.0 msec min appears to be the accepted practice. I've been using around 1 msec AE for my Lucas 009s but now I'll be testing 1.5 - 2.0 msec to see if I notice a difference.
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http://www.msextra.com/doc/ms3/injdeadtime.html (http://www.msextra.com/doc/ms3/injdeadtime.html)
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http://www.msextra.com/doc/ms3/injdeadtime.html (http://www.msextra.com/doc/ms3/injdeadtime.html)
Thanks Mike, saved me the time of digging in my junk for something like that.
AJ___
Oh just thought of something else too. It would depend on what year you bought those things in . . .
Need to find my farting graph on the new 42's.
Nonlinear behavior is not the same for all injectors.
I am pretty sure they worked fine ~1ms.
Someone else has to have the data.
Where the heck is Chuck?
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Thanks Mike and AJ. That Megasquirt stuff is very interesting.
Since I don't have a flowmeter or Megasquirt I'm using the engine and Power Logger to test. I can't measure the dead time but the AFR curve shows the effect of low pw's. I started with a very small pw (< 1ms) and am working my way up. I can see the AFR actually go lean at the start of AE when the pulse is too small. There is also a hesitation between gas pedal and engine response. I'm up to 1.3ms and should be able to test some more today.
Dennis
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No problem.
No throttle cracker modifier in that chip? Might help with that tip in lean spot... but, only after you are happy with the injector tune. It has been a while since I looked at the stock binary.
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No throttle cracker modifier in that chip? Might help with that tip in lean spot...
I'm not sure what you're referring to (?)
The stock program triggers AE with a very small positive TPS increase (0.78%).
The AE pw = Coolant Temp. multiplier x delta TPS.
(There was another multiplier for TPS position, stock value of 1, which I removed).
Add pw to sum of all previous pw's.
[/size]The Max AE pw is selected by Coolant Temp.
[/size]If the sum of AE pw's is greater than Max, then limit pw to Max. This is 99% of the time.
[/size]Add injector battery offset to pw and squirt!
[/size]I'm not sure what I could add to make throttle stabs more responsive. :icon_confused:
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There should be something (a field or modifier) similar to an accelerator pump shot on a carb in the code that should fix things.
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Yea there is ... and that's what I'm trying to get straightened out. Its called Acceleration Enrichment (AE) and I listed what the program does to create the "pump shot" in a previous post.
Here's what I've learned so far: the minimum pw for my 009's is 1.358 ms @ 145°F. The coolant temp. does make a difference, so I have to make the pw larger for colder temps. I've got the compensation for injector dead-time spot on and the AE is now responsive. A few more tweaks for very cold and it should be done. Oh, and during a test drive today I thought my BLM was broke because all the cells were 127 and 128. The log confirmed the ecm was learning to those values during closed loop. This is the best I've seen for this car.
Guys, thanks again for getting me pointed in the right direction.
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Yea there is ... and that's what I'm trying to get straightened out. Its called Acceleration Enrichment (AE) and I listed what the program does to create the "pump shot" in a previous post.
Here's what I've learned so far: the minimum pw for my 009's is 1.358 ms @ 145°F. The coolant temp. does make a difference, so I have to make the pw larger for colder temps. I've got the compensation for injector dead-time spot on and the AE is now responsive. A few more tweaks for very cold and it should be done. Oh, and during a test drive today I thought my BLM was broke because all the cells were 127 and 128. The log confirmed the ecm was learning to those values during closed loop. This is the best I've seen for this car.
Guys, thanks again for getting me pointed in the right direction.
Sorry... the text in your quoted post was incredibly small.
1) Yup, now I see why you were interested in the "AE";
2) Yes, the AE will be temp dependent, and if we had an IAT input that was worth a damn it too would dictate fueling enrichment at various temps; and
3) At this time of the year (up North especially) there is going to be a fair bit of fuel added to compensate for air density. To this end I would revisit your figures in the dead of Summer to make sure your fuel trims (INT and BLM) don't swing way out of whack in the heat - that is assuming you do most of your driving in the Summer.