I need the FAST tuners to weigh in and help me out.

[disco stu]

Got my computor back and starting to get the swinging o2 corrections under control. I thought because it was adding more fuel it needed more sensor gain. But it was rich when it was adding fuel so I was going backwards and adding too much.

Notice the wide swinging o2 correction on before compared to after. It's still got correction til the bubble levels vertically. But it's more linear, and my rich knock that I was starting to get has gone away.

Actual AFR: pink
o2 correction: green
target: blue

 

[norbs]

Looks like you made some good progress. Now post some screens of some off idle acceleration tip in.

 

[Mad_Trbo]

VE file

What I am curious to know is what your VE table looks like when you transition from one RPM cell to another horizontally or vertically from one KPA cell to another.

I noticed that if the transition wasn't smooth, the car hunted and the swing in correction was wide as you describe. If you are up to it post your MAP file and let us take a look. The idea with transitions in my opinion is you want as granular a transition as you can get with the range of operation. So make the most use of your RPM scale on the x axis and your KPA scale on the y axis. That way you have more control.

 

[disco stu]

It's like banging my head against a wall. Look, I'm past the VE table thing. It's smooth, linear, and dead on when the bubble stops moving fast. I know for damn sure the 10-20% correction is not because I have my VE table that screwed up. I've asked this question about gain table before, got mostly "VE Table". I ask about AE, people say "VE table". THERE IS MORE TO IT THAN VE TABLE and I have a pretty good idea of how important this is. So can move past this day one crap? Have you even read my posts in this thread ? If you have, and it makes sense to you, then you probably won't tell me to check my VE table again since I've said, a couple times, I've tuned evey row from 6 psi up.

Because I wasnt progressing, I did jack my VE table numbers up in the cells it rapidly transitions through to temporarily band aid the situation. I've even had some pros tell me this is the way they do it. This is the wrong way to do it but it's getting me closer and when I get the swinging corrections I will start to take that additional fuel back out.

I'm not some know it all, but I hate repeating myself, and I don't need some new jack telling me to check my damn VE table. Tuning a drag car is one thing. Tuning a street car that you want as seemless as possible is another.

Thanks NORBS. It's getting there. It's like trying to hit three moving targets. Before 100 kpa I know it's AE. You can see it in corrections and actual AF for about .5 seconds when my datalog triggers at 50%.

 

[norbs]

I think we need to move on to AE tuning. Its very difficult to tune in AE, but the main thing you want to see when you snap the throttle is that it does not go lean during the tps movement. I think there is no way to prevent a slight over-rich after the acceleration event. You may wan;t to log your a/f at 20 frames a sec, and log theMAP AE, PW,and TPS and Rpm, and snap the throttle very quickly and watch the what is happening. DO SMALL changes in your 4 different AE tables and log each time and compare to the previous log.

No one on this board has posted logs of this sort and it would be helpful to the board. I no longer own any aftermarket ecu;s so I can;t contribute with logs for you.

ALso you have to remember that your corrections will be fine one day, until the weather changes, then the whole general corrections will be off a few %, this is not a big deal, but this is where the stock ecm uses BLMS and self compensates for this, compared to aftermarkets that don;t.

 

[disco stu]

AE is affecting it up to about 120 KPA obviously. It is limited to 100, but is still seeing the affect of AE after that for about a half sec. Then after that it seems to be how O2 gains are affecting the O2 corrections. Sometimes it's hard to tell which way to go. But if it's adding fuel while it is still richer than target it seems I still have to take numbers out here.

All the AE's are next. But it seems guesswork at best and have yet to see anybody REALLY discuss it. I've tried to log delta MAP and delta TPS but you can only catch a blip if anything at all. Hard to tell what the curve is supposed to look like. And I usually end up creating more problems with tip in stumble etc.

I would have taken that training course if I knew they would cover this stuff at length. Glad I did not. Heard it was pretty basic. We all know what a VE table does. If they would discuss more advanced topics (spark tables vs driveability and emmisions, AE tables, individual corrections, spool fuel and spark theories etc) I'd get on a plane.

 

[disco stu]

Also, does GPW factor in added PW from AE and O2 gain? Because according to FAST it's BPW+ATS and CTS corrections, with no other mention.

Grs Corr.(%) – The gross percentage correction being applied to injector pulse width of both ATS and CTS combined.. A positive number is adding fuel. A negative number is decreasing fuel.

 

[norbs]

I agree with your statements, I don;t think gross % corection contains any fuel brought in from AE fueling, only cts and ats fueling. However, there is a unit called HR.inj open (ms) and I think this would show the actual fuel in ms that the injector is producing. You would have to log this do a change in your ae tables and see if there are any changes in ms pw in your graphs. If the graphs change then you know this term will work for you in logging your ae changes. But please log anything you do here in open loop.

AE MAP is only fuel added via the map sensor, not the added AE from other AE tables, just remember that too.

MAP AE – The additional injector pulse width in milliseconds (mS) being added synchronously by the MAP based acceleration enrichment feature. This is controlled by the AE Fuel vs. MAP Rate of Change Table.


Closed loop gain is like a input level on a microphone, its just amplifies the "sensitivity" of the rate of changes applied to the o2 correction, do not think of it in any other way. It is out of the picture in open loop.

 

[Mad_Trbo]

Further review

New Jack here(lol) with AFR's hitting my target when transitioning from vacum to atmosphere to boost.

This may make no sense to you and I can't explain why it works, only explain why I did it. What I actually did, was tune ae fuel vs map to zero and used ae fuel vs tps for acceleration fueling. Before I did this in the transition under wide open throttle I would always get this rich dip in my AFR's. My logic was the tps system and the map acceleration systems were competing against one another so I chose to use one. I chose TPS because it seemed closest to something I understood which is the acceleration pump on a carb.

With that change, I can now control my AFRs and when in closed loop I see a consistent 4% swing of adjustment. that is -2 to 2%.

 

[norbs]

Jack would you care to post a log of this transition? Or email it to me and I will post it.

 

[disco stu]

What I actually did, was tune ae fuel vs map to zero and used ae fuel vs tps for acceleration fueling.

now that's interesting. Never thought about that. Been messing with that for weeks. Zeroed it out and already a huge improvement. And I did not have alot of ae vs map in the first place. I'll see what happens WOT. But things seem more manageable just cruising. Thanks. And sorry for the new jack thing. But that's the only advice anyone has for everthing it seems like. As if I did not think about the fuel map.

 

[JDEstill]

This may make no sense to you and I can't explain why it works, only explain why I did it. What I actually did, was tune ae fuel vs map to zero and used ae fuel vs tps for acceleration fueling. Before I did this in the transition under wide open throttle I would always get this rich dip in my AFR's. My logic was the tps system and the map acceleration systems were competing against one another so I chose to use one. I chose TPS because it seemed closest to something I understood which is the acceleration pump on a carb.

Just found this thread... I don't have much experience with FAST tuning, but I was going to suggest this myself. It makes perfect sense to me. I don't see the two terms as competing against each other, I think of it as a double whammy. You give it some throttle and the manifold pressure comes up, so you get AE from the TPS change AND you get AE from the MAP increase. So AE on top of AE. And trying to tune it, sheesh, do you take it out of one table or the other??? If you eliminate one (and it makes the most sense to me to eliminate the AE vs MAP) then it makes your life a LOT easier.

I also set the AE vs coolant temp to zero for temperatures of 140+. Once the engine is warmed up, what's the need for more or less AE if the engine is at, say 190F instead of 175F? So that eliminates another AE contributor from the tuning mix, and now there is just the AE vs TPS rate of change and the AE% vs TPS position. Not sure the best way to figure out the interaction between these two, but at least the tuning problem is a lot simpler.

One question I've got is with regards to the AE vs TPS position table. In the help (see attached) they show an example with the enrichment going negative after 21% TPS. At 36% TPS and higher they show -70% enrichment. I interpret this as taking fuel out. WTF is that all about? On the car I've been playing with, I just made a curve that goes down to zero and stops there. No negative enrichment anywhere. Does anyone have an idea why the Help file shows this, and am I mistaken in my thinking? Is there actually a good reason for this negative enrichment? Why would they make this table go from +100% to -100% if there is no good reason for negative enrichment? I would have thought that this table would just go from 0% to 100%.

John

 

[JDEstill]

oh yeah, I was going to mention - another reason I don't feel bad about zeroing out the AE vs MAP, is that as soon as the ecu sees the increase in MAP, it increases the fuel anyway. Higher MAP, even with no AE at all, will result in more fuel squirted. (Well, unless the VE table is really screwed up that is. For a given % increase in MAP, you'd have to have a corresponding % decrease in VE specified to keep the fuel squirted the same or less, and that seems pretty darn unlikely.)

So anyway, my point is that when you crack the throttle, and the manifold pressure goes up, you automatically get more fuel just because of the MAP going up, and then you put some AE vs TPS fuel on top of that, and if you also put AE vs MAP fuel on top of that, well then I can see why you end up with a rich spike!

John

 

[norbs]

I agree that table is silly to go below -, I don;t understand it myself. If someone could post some logs of there a/f ratio and bpw and pw and MAP AE it would be most helpful, but no one seems to want to post logs if AE enrichment on here.:frown:

 

[Eric Stage I]

The AE pulsewidth is calc'd based on the delta TPS table (rate of change). Then the AE pw is modified by the AE vs TPS% table. You want more AE at lower TPS positions because the manifold pressure will change way faster going from say idle to 1/4 throttle, compared to starting at 60% throttle and going to 80% throttle. So setting the higher throttle openings to -100% would put the AE pw back to zero.
I usually leave the AE vs TPS% table at zero across the board, and try to get it at close as possible with the delta TPS table. Then touch up the AE vs TPS% if necessary.

Trying to tune AE with the wideband can run you around in circles. I've found its best to do by "feel" and how the engine sounds and responds when blipping the throttle.

 

[JDEstill]

Eric, I'm confused.

I assumed that the AE vs. %TPS was a multiplier, so that if the AE vs. TPS rate of change table gives a value of 2.0 ms, and the AE vs. %TPS gives 50%, then the actual AE applied would be (2.0)(0.50) = 1.0 ms.

It sounds like you are saying that it doesn't work this way, that it is actually taking the % from the AE vs. %TPS and adding that amount to the AE determined by the AE vs. TPS rate of change table. So using the same table readings as above, you would actually get 2.0 ms + (2.0)(0.5) = 3.0 ms of AE. Is that the way this table actually works??? If so, that sure is counter intuitive, at least it is to me!

If that is the case, then I can see why it would be best to start off with the AE vs. %TPS table zero'ed out, and I can see why they made the table go from +100% to -100%.

John

 

[Eric Stage I]

Your 2nd example is correct. So if you put 50%, it means "add 50% more AE pulsewidth to the original AE pulsewidth".

 

[JDEstill]

Thanks for the clarification Eric. But I have to ask: are you sure? Having the table go from +100% to -100% only makes sense when doing it that way, and yet the FAST help file says the operation is done the other way:

"Displays a 2D graph of the total percentage of acceleration enrichment fuel applied based on the current throttle position. In other words, this graph shows, based on throttle position, what percentage of the total pulsewidth added in by the A/E fuel vs. TPS and MAP Rate of Change graphs will be used. As an example, if 2 mS of fuel are added from the TPS rate of change and 2 mS are added from the MAP rate of change, the total A/E fuel would be 4 mS. A percentage of this 4 mS value is then figured from the graph based on the throttle position when the MAP and TPS rates of change were detected. "

So, to be clear, the help file is wrong?

John

 

[TurboTR]

Yes something's a bit out of whack in the explanation of AE vs %TPS there. I agree with John, think the help file is right. The easiest to understand analogy is the carb mechanical accel pump, which the rest of that paragraph alludes to:

"...This could be compared to the volume of fuel in an accelerator pump diaphragm. At half throttle, the accelerator pump arm is already halfway through its travel and would only have half of the fuel in the diaphragm available."

I've also always just zeroe'd out the AE vs Delta MAP as well. IME, usually AE vs Delta TPS is enough to handle tip-in transients.

TurboTR

 

[Eric Stage I]

John,
That particular definition you have there is wrong, or at least worded funny. Also, I've never seen the AE vs TPS position affect MAP AE. I believe that's wrong also.
I'm not sure what help file you have there, but let me look around to find more info. Is that from the FAST manual?
Eric