Testing for proper AE fuel

[dennisL]

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?

[PacecarTA]

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

[Steve Wood]

I always have just set it as lean as possible with no hesitation when giving it some pedal

[dennisL]

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.

[PacecarTA]

considering 42s are nearly 30% larger than 30# injectors , the AE PW would need to be trimmed by 30%

[motorhead]

Err... did you just say you swapped injectors without swapping chips and are now trying to tune for it?

Please clarify.

[Steve Wood]

He is making a new chip

[dennisL]

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?

[daveismissing]

I would think the physics dictate that the inertia of the moving parts set a minimum
usable pulse width?

[$1987 GN$]

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___

[dennisL]

With no pulse width you have no fuel

.
[/size]I was going to say something smart here but I'll just leave it at DAAAA.
[/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.

[$1987 GN$]

ok 

AJ___

spelling error

[dennisL]

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.

[dennisL]

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. 

[daveismissing]

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.