Effect Of Ae On Ltft

[krunchss]

Let's say we are doing a VE tune. PE is disabbled, but AE is still part of the equation. I'm sure it has to be or you would probably never be able to accelerate while tuning fuel trims without the car knocking it's brains out due to lack of fuel I guess.

Now, we are VE tuning and adjusting fuel trims. Does the LTFT you see once it has settled in INCLUDE fuel supplied by the AE table? If it does, if you adjust VE to remove fuel, how do we know it was becasue the VE table was too rich and not the AE table being too rich?

Krunch

[streetcar]

You touched on a very important topic. This is why VE is tuned during steady state conditions (10 seconds in that load cell) - to avoid picking up the affects of transient wall wetting.

AE fuel contributes to LTFT as it asynchronously adds to the base pulse width.

VE table should mimic the torque curve, up with rpm, highest at torque peak, settling back down to red line.

[krunchss]

So scan data while accelerating should never be used for VE tuning?

Maybe I need to understand AE better...

I thought when cruising, your fuel is "X" for example, which is constant, let's say 10% TP for example, now we are going to accelerate, but not enter PE, let's say 20% throttle. I thought the "X" remained constant, but an additional factor got added to "X" due to the new accelerating 20% TP, AND that "AE" factor remained on, or kept adding a constant ammount of fuel until the 20% TP went back to cruising @ 10% TP for example. Or is AE only active for the duration of time to transition from 10% to 20% throttle?

Krunch

[krunchss]

Hmmm, another point, you said VE should mimic the torque curve. I always thought that VE should be relativley flat? Or is this another difference in tuning with HPT vs. DHP?

Krunch

[damojo2003]

I always thought that VE should be relativley flat?

Krunch

Where did you get this info? VE is supposed to be the amount of fuel required for the rpm vs map and all modifiers like timing are involved. obviously you need more fuel at 5000 rpm than 800 rpm

[JerryH]

A simple way to look at AE is that little initial splash of fuel on throttle tip-in. It assists in reducing flash KR and improves conditions during times of transitions from low to higher loads.

Now, since while doing VE tunes one is not pushing WOT conditions, you don't need to worry about them at this stage. Where they come into play is (usually) after the MAF tune to dial out flash KR (to some extent) and throttle response.

Now I cannot talk about all cars, but again, on my car, I can dial in my fuel trims via VE and MAF tunes and then play with AE without much if any changes in my trims. Over time, I've simply come to know my car and can tell you that (from my PT days, since AE doesn't need to be changed since), that I set and forget the settings to the following in the PT (since this is what you have):

- AE MPH Modifier: on my 3.4 pulley it's stock and with the 3.2 , I set to 1's in all cells
- AE Enrichment: on my 3.4 pulley it's stock and with the 3.2 , I globally increase all vales by 25%

[krunchss]

What I am getting at here guys, and Jerry has seen this on my car, is I was wondering if the part throttle KR in my car going up slight inclines while cruising MAY be addressed by AE If I was tuning VE / MAF trims close to 0, maybe I was taking away that "little splash" you are referring to when you "tip in" to the throttle to maintain your cruising speed on the highway for small hills. If AE was combined with LTFT and I tuned it close to 0, I wondered if I had tuned out the "Little splash"

I think I have maxed out changes to the TCC lock unlock, it already does this nice. I live on the praries and for the most part, the roads are flat with not many hills. unlocking the TCC, on a gentle incline should not be the way to go.

Krunch

[JerryH]

It may, but you should get the VE (if it does affect your car), and MAF down before playing with AE.

If I recall correctly, you are using a cartuning bin as a starting point. How far off stock is your bin as it currently is?

[krunchss]

Fuel trims sit in the - teens right now. Cartuning runs 100% OEM VE table and OEM MAF except below 1875 HZ. Below 1875 Hz they raised the values.

Cartuning has AE_TPS_Re-allow set to 30, OEM was 5, someone else told be it should be much higher, maybe 80.

AE_MPH_Modifier is OEM

Cartuning also reduced the AE_Enrichment table at 60% throttle and below.

I'd just like to know theie "Method behind their madness" on changing this stuff. It would suck to start VE and MAF tuning again where there are problems in these tables possibly affecting the VE and MAF tunes.

That's basically why I asked about AE.

Krunch

[JerryH]

So your car is basically running lean and the PCM is trying to compensate by adding fuel as evidenced by the trims.

The way that I have always done it is VE, MAF and if needed AE later, but again, as I said before, my trims remained the same. AE are more transitional tables, not constant on and later changes should not negatively affect your VE or MAF tunes.

Try it out, you will see the effects right away.

Now, as starting point suggestions, I would suggest the following:

- AE MPH Modifier: Set to 1's in all cells except the last 2, set the 2nd last one to 1.1 and the last one to 1.2
- AE Enrichment: Your turbo on boost will need some more fuel than your stock settings, but I would suggest that you start off with stock settings + 30% from the PE enable TP% and increase them perhaps 15% below that and taper them down to stock settings at the very lowest TP% levels.

Use that as a starting point.

[krunchss]

I thought that "-" fuel trims meant that the car was running rich and the PCM was taking away fuel? When I unplug the MAF, they go even MORE negative, that makes no sense, when my MAF fails my car runs even leaner?

Is there a methodology difference between HPT and DHP?

WRT the AE MPH modifier, not sure I understand your reasoning for this. Both an L36 and L67 have the numbers in this table starting at 1, then decreasing as you approach higher RPM, but you are saying make them all 1, except put 1.1 in teh second last cell, and 1.2 in the last cell. What is your reasoning to go in the opposite direction as the factory?

WRT the AE Enrichment, Cartuning has REDUCED the values from 0% to 60% throttle, BELOW stock! This is why I was wondering how AE worked and what it did. Could this be the cause of my part throttle KR when cruising on the highway?

Krunch

[streetcar]

What is the cylinder airmass before and after the knock is occurring?

There are many of parts of the fueling and spark equation at play here, including some we don't have access to.

Have you tried subtracting timing around the transitioning points of the two RPM / air mass values?

[krunchss]

Cylinder airmass....hmmm....still consider myself a noob, you mean MAP pressure? If so, between 70 and 80 Kpa IIRC. I can post an old scan from last year (still working on my car yet so no new scans) but it's gonna be a *.csv if you're interested.

Krunch

[streetcar]

Cylinder airmass is what GM uses to define load, but I can't remember if DHP has a PID for it. Log would be nice, maybe throw it up on scan depot? Knowing MAF airflow and RPM, air mass can be calculated.

[krunchss]

Posted a scan and deleted again, I didn't have MAF in the scan, so I will have to wait until my car is put back together to get a scan.

Krunch

[JerryH]

I thought that "-" fuel trims meant that the car was running rich and the PCM was taking away fuel?

Yes, it does, I saw that as a hyphen, not a negative symbol, sorry.

[krunchss]

Phew! While that is a pretty basic concept of tuning, and I was sure I was right, coming from someone like yourself made me re-think some stuff. DON'T DO THAT TO ME AGAIN JERRY

Krunch

[JerryH]

lol... sorry!

We'll take a look at your scans when available.

[dtabet2]

what i noticed is that at least on my Series III that WIDE BAND tuning of the maf that i could see ae kicking in and throwing off the af. in essence throwing off the maf tune... its my impression that LTFT's do not get effected by AE. BUT WIDE BAND DO in my case so i temporary disable it when tuning my maf... otherwise you will be playing hell when ae kicks in. NOW in reality i shouldn't be so unsteady with the throttle when tuning but street conditions to not allow for SLOW throttle changes so.... there you have it...

Dan

[krunchss]

You da man cool guy, greatly appreciated

Krunch

lol... sorry!

We'll take a look at your scans when available.