Tuning Issues

[darkdragon]

Since my last thread went nowhere fast, I decided to try this out a different way. I have retuned my MAF fairly well using the open-loop method. Using the attached tune my AFR stays reasonably close to commanded AFR.

Unfortunately, with this tune I have to lower my timing a lot to prevent knock. See log for example of this.

I've been playing with this a while and I'm running out of ideas. Any help would be appreciated.

I'm starting to think that my Wideband (AFX) is to blame but from everything I've read, it should be pretty reliable. I should say that the AFR readings in the log match the displayed AFR on the AFX at all times.

Edit: I restarted from a completely stock tune and have redone the OL MAF calibration with similar results. New resulting tune and log posted.

[Perforator]

Have you tried running a little richer?

[darkdragon]

Yeah, if I run richer then it helps, however most tunes that I've seen run 11.5-11.7 with similar mods as mine. I'm trying to figure out why this difference since I was hoping not to have to dump so much fuel and I was planning on going with a 3.2" pulley once this was fixed.

I still see something really wrong with my MAF readings since they are nowhere near readings from other similar cars. Only things left I can think of are intake or exhaust restriction, or misreadings from the AFX.

[Perforator]

You know, I wouldn't put to much weight into what other people run. Personally I think 90% of them are full of shit.

[JerryH]

OMG, someone is reading my mind!

[Perforator]

lol, Jerry you're definitely in the 10%.

[darkdragon]

Well, after playing around with this some more, i am becoming convinced that the AFX is reading too rich at higher flows. Just looking at the log above, you can see that during the second WOT run that goes from 4200-5400RPM, my MAF flow is reported rising from 9400-10300Hz which is expected, but to maintain a reading of 11.5AFR on the AFX, the injector pulse width has to remain at around 17.6ms for the whole run.

This does not make any sense to me. Keeping the pulse width constant with rising MAF values must make the AFR leaner, but the AFX reports it as constant. Anybody else running an AFX on TOGs that can comment on this?

[darkdragon]

Tried removing the cat, but I have the same issue. Another way to look at it is that for any given MAF flow, the AFR reading is richer at WOT than at part throttle. I'm gonna try dropping the exhaust and moving the wideband further down the pipe to see what happens.

Come on guys, no one here is running a wideband on TOGs that can provide insight into their own experience? I'm just looking to see if anyone with similar mods as mine can run more than 10 degrees of timing without knocking after calibrating the MAF with the wideband.

[Perforator]

I don't remember if you mentioned this or not but where do you have the wideband mounted?

[Eddie-98GTP]

I don't remember if you mentioned this or not but where do you have the wideband mounted?

Being as the O2 volts are 457 fo the entire scan I would guess it was in the B1S1 spot - but why is the B1S2 the same also? Was that when the cat was not hooked up?

Also, is the A/C voltage suppose to be your wideband? I didn't see a wideband pid, but couldn't figure out why you were scanning A/C pressure voltage.

For what it's worth, I run about 15-16* WOT timing with pretty much 0 KR on a 3.4 pulley. I have a cam instead of rockers, but I am also running 89 octane fuel instead of 93 (not sure what your running).

Attached it a short WOT run, just for reference. My IPW is not changing too much as you have noted about yours staying close also. Note - my wideband was not hooked up.

It would not let me upload a csv file, so I just took a screen shot...

[Perforator]

I have different mods but the same results as Eddie. If you look at my scan starting at frame 1304 to 1324 my ipw's stay pretty constant at 16.x as the maf reading increases and my wb reading are consistently 11.0-11.2.

[darkdragon]

Thanks for the info. I'm impressed that you can run 18* without knock in that log!

Yes, I had the WB mounted in the B1S1 spot and the scan above had the cat installed. I indeed use the AC pressure input for the WB, and I verified that the readings are equivalent at all times. Note that since I'm using an AFX, stoich is displayed as 14.57, hence the 1.008922 factor. The PID for AFR is:

"Air Fuel Ratio,AFR,120,92,(([PID.7101]*1.4)+9.02)*1.008922"

I have since temporarily removed the cat and moved the WB to the old B1S2 position. Scan is posted below.


I noticed something significant in my scan which shows clearly the root of the issue:

- @ Frame 804 at part throttle: MAF Hz = 9430, Calc CylAir = 0.95, IPW = 17.1 producing an AFR of 11.98 (NBO2 = 948)

- @ Frame 1630 at WOT: MAF Hz = 9430, Calc CylAir = 0.97, IPW = 17.5 producing an AFR of 11.54 (NBO2 = 932)

Now, since we use the AFR error % to calibrate the MAF, these two points in the scan will produce vastly different error % for the same MAF frequency.

--> This explains why I get error factors of 2% - 4% for the lower part of the MAF while I get -1% - 0% error for the upper part. This results in a MAF calibration which reports to the PCM that there is less flow than stock in the upper MAF range and thus leans out my fuel and thus causes premature knock.

The other real interesting thing is that looking at the narrowband O2 I left in the B1S1 position, it remains in the same general area!

Note that looking at Perforator's scan, I don't see the same phenomena when comparing WOT and part throttle AFR at a given MAF frequency; his AFR's stay consistent in both the WB and the NB.

What to make of this?

[darkdragon]

Here's an even better one. In this scan I took a series of gradually increasing TPS to try to find the transition from high AFR to low AFR. You can clearly see that my AFR error% is 2-6% right up until I hit WOT, and then it goes right down to 0%. Pretty crazy huh?

This happens on all instances, regardless at what MAF flow I hit WOT. In other words, if I hit WOT at 9300Hz, then AFR goes down at that point. If I hit it at 10200Hz, then AFR will stay high until that WOT point.

This PID will help you see it:

"AFR Error,AFR%Err,0,100,100*((([PID.7101]*1.4)+9.02)*1.008922-[SENS.121])/[SENS.121]"

It almost looks like the PCM is dumping a bit more fuel whenever TPS = 100%. Can't figure out why. Could it be OS related? FYI I'm running OS 9352809.

Getting closer...

[Eddie-98GTP]

Why are you commanding 11.5 AFR so much? It seems like most of the scan log shows and AFR of 11.5 - even when you are not touching the throttle.

[darkdragon]

Since I have been seeing different AFRs from the WB for similar MAF flows, I decided to just command the same AFR everywhere to eliminate that as a factor. This way I could see the AFR's response on throttle tip-in to full acceleration without having a change in commanded AFR.

I could set my PE table back to my regular settings, but it doesn't change the effect we see at WOT here.

Could AE be a factor here, like the WOT disable setting? Is it possible the PCM is dumping more fuel at WOT than what is reported by the IPW?

[Eddie-98GTP]

Since I have been seeing different AFRs from the WB for similar MAF flows, I decided to just command the same AFR everywhere to eliminate that as a factor. This way I could see the AFR's response on throttle tip-in to full acceleration without having a change in commanded AFR.

I was asking about the 11.5 AFR when not in PE. Your closed loop desired AFR is still 14.7, but your commanding 11.5.

I wouldn't think AE so much since it's only active for what, 30 reference counts? That's 10 crank shaft revolutions, not a whole lot.

[Perforator]

"AFR Error,AFR%Err,0,100,100*((([PID.7101]*1.4)+9.02)*1.008922-[SENS.121])/[SENS.121]"

Shouldn't your formula be (((([PID.7101]*1.4)+9.02)*1.008922)-[SENS.121])/[SENS.121]?
Not sure if it would make a difference...

[darkdragon]

In this tune I force PE over 2000rpm (i.e. PE table set to 0), so I get 11.5 AFR unless I'm essentially off the highway. I can reset the PE table back so that I'll get 14.7 during cruising, but it will still produce the same behavior as seen above.

The formula is equivalent since multiplication has higher precedence than subtraction. Still wouldn't have an effect on the major AFR change I see only at WOT.

[darkdragon]

For your entertainment, here's a new scan where I don't force PE, so commanded is 14.4-15.x when cruising (please note that since I'm running open loop, the commanded AFR by the PCM is everywhere when not in PE).

BTW, I forgot to mention that I run 93 octane. In this scan I'm knocking with an 11.5AFR and 15* timing, which is better than before. I also disabled AE at WOT to see if that was the cause of the issue, but alas it is not.

It is still very clear in this scan that the PCM is dumping extra fuel (that may not be reported) when I hit WOT as seen by both the WB and the narrowband. It is quite a bit since it brings my AFR down by half a point!

[Perforator]

That scan looks good. If your actual afr isn't matching your commanded you need to tune your maf in the wot range. Personally I don't like using histograms for this. I export it to a csv and use the maf worksheet to adjust. I like to see the numbers rather than just cutting and pasting. I don't trust computers.