CalEditor

iTrader: (1)

I have some information on your setup.
You don't have a fuel pump control module.
You have DOD.
The software to run DOD without a FPCM is unique. When the injectors turn on and off the fuel pressure fluctuates in the rail. The software compensates for this fluctuation. BTW the injectors and lifters switch on and off to build up the air cushion in the combustion chamber so the engine doesn't suck in oil.
Anyway the DOD with no FPCM software was only use for a little while. It has some extra fueling algo's

DrkPhx

iTrader: (15)

I switched to E85 a couple of months ago and bought a cheap fuel composition tester so I can confirm what is actually in the tank when I fill up. I also switched back to tuning in lambda because I found it much easier compared to AFR.

joecar

If the net change is zero (4% - 4%) then why do it...?

You're not injecting 4% more fuel because you're calculating 4% less airmass... zero net gain, as you said above.

Leave your MAF and VE alone (undo your changes), and make your OLFA and PE tables slightly richer at higher loads, this will give you extra injected fuel when not in CL, and change your stoich AFR to get extra injected fuel when in CL.

nmp0098

I know that was a retorical question, but I'll answer anyway. There are two possibilities:

1) I think I'm tuning with gas and I am tuning with gas.
2) I think I'm tuning with gas and I am tuning with E6 or E10.

In option 1, then my virtual alcohol sensor is working even though HP Tuners displays the units as Hz, and all is gravy. The evidence I've gathered so far suggests that option 1 is the case. In option 2, I don't have a virtual alcohol sensor, but it's trivial to correct later on. It will take less than two minutes to fix now that I can flash just the calibration to my E67 ECM. I would correct for E10 because I would rather that my ECM lean things out for gasoline than richen things up for E10 when I go closed loop again. I don't have any plans to stop going to the gas station on the corner.

Yes we both understand the issue.

I appreciate your taking the time to post, but I will not take your suggestion because I strongly disagree. You are telling me to enter PE during normal driving, rape my PE table, and fudge my open-loop corrections to compensate for something. I strongly prefer tuning so that I get what I command, not get what I want by fudging the command. What I have done is tune the engine to perform reliably regardless of driving conditions. Even if I'm wrong, at least my solution has proven robust.

I'm not claiming that adjusting slope of IFR is actually correcting my true issue. It might be the short pulse adder. It could also have something to do with all of the extra EGR I'm getting from my cam or with how much fuel is making it out the tailpipe. It could be something similar to the lean reading I get at idle because all of the blow-through and misfiring is detected as lean by an O2 sensor. It could be that I need a better flowing fuel rail or something else mechanical. Maybe if I had a five-gas analyzer, a load-bearing dyno, or some additional sensors I could more effectively root cause the issue. I don't know, otherwise I would not have posted my question.

The one and only thing I am sure of regarding my original issue is that it is not alcohol content. If no one has any other ideas, I'm going to just move forward and consider an issue that had been bothering me solved.

CalEditor

iTrader: (1)

I have a calibration that is in use that sets EQ/PE in a 3D table.
RPM --- TPS.
The Table is in % of Lambda
I can target my AFR to TPS angle at (X) RPM's
Say every thing over 40% is in PE, but not 12.5 ARF. I have it set to be progressive. I actually found I can lean it out at high RPM's and make more power.
Again I am looking at Commanded AFR/EQ%. I make the tune match my Target

joecar

I'm sorry, I don't understand what you just said... ...isn't the PE table a table of commanded fuel/air...?

nmp0098

Is this a custom cal? If not, which vehicle/year? Other than PE, my open loop tables are for ECT vs IVT, MAP vs IVT, and Injector Temp vs. Time. In my buddies' modded GTP the PE table also has a time element that he uses to run it leaner through 1st and then richer in 2nd where the slower acceleration rate makes the engine more prone to knock. I have the enrichment rate to play with once I finally get all of my fueling perfect, but for now I'm running at 12.7 across the board with an enrichment rate of 2. Once I find the time to modify a timing gear and advance my cam to straight up I'll do a final tune and then buy some dyno time to see what's what at WOT.

nmp0098

Yes, and maybe I misunderstood you. My problem was that I was not getting the commanded Lambda for a constant amount of metered air. Rather than change the command to get my desired Lambda, I adjusted the fuel side of the equation and got better than expected results. I was seeing this most prominently under 40% throttle, which is where I (just like Caleditor) have PE turning on. After filtered out all of the transient data and made a 2D histogram of MAF frequency and Injector Pressure Delta, I found the same trend everywhere.

I got the impression that you were suggesting that I change PE to command say 12.4 so I could get 12.7, or have PE turn on above a set MAP (which is an option) and use PE to compensate. Some people do that, but there are unintended consequenses. Same with adjusting, for example, the IVT vs. MAP table so my commanded Lambda is richer at higher MAP. Just like you said, this would solve my issue open-loop, and the fuel trims would compensate in closed-loop. I ran closed loop like that for several months, and the car ran OK.

There are a couple reasons why I strongly feel that adjusting the fuel is better than adjusting the command. If you are always getting what you command, then it is easy to adjust the command to tune for performance and power. You also don't have large LTFTs messing with WOT, and your STFTs don't have to work very hard to compensate for different driving conditions. More important to me, your transient behavior is much better. Open-loop is always faster than closed-loop, but it can't account for disturbances. Imagine you are need to go around a corner, but you can't see it until you are already supposed to be turning. That's closed loop, and you'll spend the entire turn correcting. Now imagine taking the same corner, but all you have is a robot programmed with the ideal steering input. That's open loop, and you'll nail the corner perfectly as long there isn't a bump in the road. That's why the ECM uses open loop to get around the corner and leaves closed loop on just in case there is a pot hole or a patch of ice. Unless your open-loop is dead nuts for ideal conditions, your transient fueling goes to crap. All the calculations about the amount of fuel that impacts port walls and the amount that evaporates won't help unless the open-loop calc is correct. During transients, seperate from the fuel impact and evaporation calcs, the ECM looks at MAF and VE and then uses a complex calculation to figure out how much extra fuel to add beyond what the MAF is seeing. The cylinders draw from the plenun and the plenum draws through the throttle and MAF. The plenum acts as a buffer between the cylinders and the MAF. That's why the MAP and RPM sensor (VE) are used; they see the change much sooner than the MAF. It's all difference based though, so if the MAF is wrong the correction calculated from VE will be wrong. If you just use a modifier like PE, all of the transient calcs in the ECM are off in the weeds. They are better than nothing, but hardly optimized. Why bother at all? In the real world this translates to getting that neck snapping feel or not. The final benefit is something I didn't expect. My idle is much more stable because as the engine lopes, MAP bounces up and down quite a bit. With the IFR change my fueling is much more consistent and my idle quality has improved drastically.

I looked through hundreds of posts on here and in the HP Tuners forum (where I posted the same question without any responses), and I didn't find anyone else describe what I saw, let alone suggest something besides adjusting IFR. I'm still open to try something besides adjusting my commanded fueling if anyone has any thoughts.

I'm serious when I say that I appreciate the responses because every time someone brings up something I get a chance to think about this more. If you knew everything above already, then I apologize for explaining it to you and I hope that someone who doesn't know all of that reads this and gets something out of it.

CalEditor

iTrader: (1)

I would pull it out and the lifters. Get rid of the DOD/AFM. I have heard guyss are getting the same MPG with a good tune.

nmp0098

Just to close the loop on one point, I did a simple ethanol check with a mason jar, water, a magic marker and some gas. I found ethanol. I talked to a different guy at the gas station who pulled up the receipts from the tanker truck, and it shows that they were buying fuel with a target of E10. I adjusted stoich and scaled the MAF curve, and as expected there was no net change in fueling behavior.

So, if you live in Michigan, ask to see the receipt from the delivery by the tanker truck!