do you not tell the computer by the ve that it needs xx amount of fuel for xx afr? and if oyu change the commanded afr it would change the ve? its just a guess but then i think of this...

im just wondering if when the car warms up it uses different numbers or so. cause the olfa table stock has all different settings so it should cover it all no problem to whatever you change it to because the commanded afr is constantly changing so you cant change the ve for that, you would have to have a table for ve per commanded afr. under general fuel, what is your afr? and does this happen above certain temps or no? there has to be something else in there that has to be changed i would think...

 

Once you get the ve table dialed (step 2)in you re-enable closed loop, which will commanded 14.63, why would the ve table be inline if you tuned it for a afr of 12.96? That is my question.

Step 4. If you had efilive, you could do it with a histogram in 10mins.

 

The reason the olfa table has rich values for most of the cells is because it serves two purposes. 1) To provide fuelin got he car up startup 2) A backup table in case the o2's fail, resulting in a safe rich table instead of a lean one.

My afr is 14.63, but remember, I do not use o2's. My afr is commanded solely by my open loop multiplier.

 

Okay, from my understanding, there is a big difference between Open Loop SD (what you are running), and Closed Loop SD (which I'm attempting to do). Now, please correct me if I'm wrong, but in Open Loop, you are taking away the eyes and ears of the engine, so it essentially doesn't know its elbow from its *** hole. In this mode, the PCM is relying solely on the VE table to figure out its fueling. That is why you are using your Wideband in conjunction with your scanning software to compare what the PCM's trying to get vs. what it is actually getting. Once you get this in line, it should be good for any A/F ratio you put in (at least that's what I've been told by other people).

Now, closed loop SD is what I'm having a hard time understanding. Now, you are still using the VE table as the mother of all calculations (so no MAF influence), but your O2 sensors can be used to trim the engine due to whatever fluctuations there may be. I'm guessing that the trims will be next to 0 if you keep having days like the one you tuned on, but will stray if you go from an 80 degree day to a 32 degree day. But the trims will still be doing their job of keeping the commanded AFR.

Does any of that make sense to you? I'm posting this more to get some better info on all of this...there just aren't enough people that are smart on this topic, and if they are, they apparently don't use this forum very often. I wish the HPT website had a better search function. It is impossible to find what you need over there.

 

Here is the deal on this. With a wideband o2, it is accurate at a given AFR (9-21), where as a narrowband is only accurate to 14.63(stoich). What you do with the narrowband, is essentially the same thing as with a wideband, excpet it is only accurate at stoich. Does that make any sense? What I am saying is if you tune with closed loop, you command 14.63 so the values for ve that you come up with are for a afr of 14.63. Now if you tune the car off the bat in open loop with a commanded afr of 12.96 or even stock, when you put it back in closed loop, it will be off.

 

Hmmmmmmm...in closed loop, the PCM is looking for information from the MAF sensor to compare against the VE table. Without the MAF information, it has to rely mainly on the VE table (and I think IAT and some other odds and ends).

When you are tuning the VE table, you do it so that you aren't getting any excess fueling information from any outside sources (like PE, DFCO, etc.). This is why you need the trims zeroed out. Now you are getting fixed fueling, a commanded AFR, and you are seeing how much air you are getting into the cylinders by looking at the % difference.

Once you see what the difference is between commanded and actual (with a wideband), it shouldn't matter what you command. The VE table should have the information it needs to produce it.

Where am I going wrong here?

 

My brain hurts. Let me do some checking and I'll get back on this later this evening.

 

Chad and I have talked about this in the past. It was to my thinking and understanding the ve table is nothign more than an airmass table. Once you get the table to represent the air requirements of the engine and supporting mods it shouldnt matter what Commanded AFR you use, the pcm should hit its target. At the point of changing the multiplier all you are pretty much telling the pcm to add or subtract the appropriate amount of fuel for a hardcoded amount of air entering the enigne.


I would like to see timing values for these two logs to see if that has changed. -2* of timing makes the WB read a little lean with the same tables

 

This was posted by TXHorns281 to me a while back:

We tune the VE for one sole purpose. To produce the AFR that is commanded. In closed loop, you will always be running 14.7 but if your tune is way off (ie. the motor itself is not producing 14.7 when commanded) then your trims will compensate (+ or - trimming). The idea is to have as little trimming as possible since that indicates the fuel system is not having to compensate for a too rich or too lean operating condition.

When you tune in open loop, you are essentially taking all your fuel control sensors offline that way you can directly manipulate the VE to produce the sought after AFR. You want to command 13.0 across the board for open lopp tuning so that you can map out your VE table at a safe AFR from idle all the way up to where you shift. (13.0 is rich for part throttle and idle, but it is necessary to use one consistent AFR across your whole VE table to align it with commanded AFR).

Once your VE is producing your commanded AFR (in this case 13.0) for all histogram values, then it doesn't matter what you command of it, it should produce it. If you change the commander to 14.0 it will produce it, 13.5 it will do it, 12.0 it will do it... well, up to the limit of the fuel system, but you get the idea. The stock VE is not aligned with commanded AFR after modding, which is why most of us see trims stray from a good place. The VE does not create the AFR itself, the VE is sort of the mother of an airflow calculation so that your PCM knows how much fuel to shoot to produce your commanded AFR. If the VE airmass calculation is off, that means the fuel shot is off, that means AFR production is off from what is commanded, and inevitably you will have trimming to compensate for it.

But the idea is to have as little compensation as possible b/c that means that your motor was doing what it was supposed to in the first place. As said before, you will always be running at 14.7 in closed loop due to trimming. But in closed loop it's better to have less trimming even though you know you will always be at 14.7. Again, it's just getting the motor to run like it supposed to instead of having the PCM correct for its inconsistency. When you got to WOT, you switch over from closed loop to a fuel multiplier in PE mode and command a different AFR than stoich (12.0-13.0). If your VE was dialed in at one specific AFR (doesn't matter what AFR, but we pick 13.0 cuz it's safe for all RPMs), you would see 14.7 at part throttle with very little trimming (since in closed loop, non-PE mode you are always commanding 14.7), and 12.0-13.0 at WOT (since this is what you want to command for power production).

BTW, this is all assuming you don't want to put your MAF back on. If you do, then you must go through another process to align the MAF with your fueling. I would recommend though using the MAF since it helps anchor your tune despite weather changes. In SD Mode (MAFless) trims will stray around with the weather which is not a good thing. Even worse is running SD-mode and open loop operation. For a daily driven car you really do want to be running O2s and a MAF to ensure that your tune will be good in any type of weather. Running SD mode and open loop all the time is better suited for a track car, that way you can dial in your tune for maximum efficiency for that day or moment or track pass.


Now, all that being said, when I run SD in closed loop, I'm going under the assumption that my O2 sensors aren't being lazy (which you and I both know won't be true). I'll see how it pans out.

 

I just compared both tunes in EFI live and both are identical except for the open loop table in question.

 

This is great, but from personal experience, it doesn't work like that. I have to take my daughter to the hospital in an hour to have her arm rebroke (bad week last week) so my time today is limited. I will do two tunes tomorrow again and see what I come up with. One will have my VE dialed in with a open loop afr of 14.63, the other will have a ve of 12.96 like mentioned. Like always, maybe my car is weird. Would be nice if we could get someone else to check with their car and see the outcome. If it does in fact work like that, then I will admit I am wrong. like the rest of you.

 

I guess you would have a problem with this (getting your VE to give you the commanded AFR) if your fuel flow was F'd up...I would guess your computer would have a shitload of problems if you were telling it it was getting a certain amount of fuel, but your fuel system was fluctuating (and good luck trying to figure that one out).

 

The only personal experience I've had so far is getting my VE table dialed in to a 1.13 multiplier. I didn't get a chance to command something different. I will this weekend though and let you know what I find out. When I tried re-enabling my MAF with my new VE table, the trims were screwed all to hell. And that was with rescaling the MAF using RedHardSupra's sheet. Hence why I'm wanting to do SD in closed loop.

 

EFI Live - Done in 10mins for MAF calibration.

 

I know the tunes willbe the same but what about the timing values that the pcm was running at the time of the logs

 

I'm still willing to bet that your new fuel system might be messing with you...

 

My fuel system hasn't changed in a year.

 

Maybe think about it this way:

You are only getting a certain amount of air in each cylinder at each RPM/MAP value (thus the VE table). Now, this can change on a daily basis since the density of the air fluctuates, but it stays fairly steady.

The only thing that the computer CAN change is the amount of fuel it dumps in. From what I know of your setup, you have had to tell the computer exactly how much fuel it is controlling from your new pump(s) and injectors. What you told it it has available for fuel and what it actually has I don't know...and that may fluctuate without your knowledge (faulty parts, etc).

 

I am going to do some testing tomorrow and I belive HumpinSS is going to do some tonight on his setup as well. If I am wrong, then awsome. I just want to get the right answer on the matter.

 

everyone says how sd is thrown off by temps, with a maf on my car i had about a 5% fuel swing in winter to summer and in SD i havent seen that much yet. ive seen 2% but nothing more and that was in a 30* swing in one day that i was tuning, but when i have it dialed in right, well before i did the cam, they stayed consistent if it was 30 or 70 outside

chad, does you commanded afr equal your actual afr and just isnt lining up with what you have in the computer for it to be set to?