LS1 Sounds

iTrader: (11)

MAF for sure, but what about the PE mode? My PE MAP enable is set to 15 kPa which leads me to believe that PE mode is on all the time.

Holden LS1 Tonner

The main PE enable is in the PE Enable%TPS vs RPM (the cold one i think) , thats the one that determines what tps PE comes in at across the rev range.

Theres quite a lot of good information here
http://www.hptuners.com/forum/YaBB.p...4562;start=0#0

txhorns281

iTrader: (12)

The PE MAP enable is like your arming switch. The TPS vs rpm is your trigger

Steve Bryant

iTrader: (1)

First, will you be using a wide band AFR to set up VE or will you plan on relying on LTFT. This will determine whether or not you want to disable closed loop or not.

Regardless, you will want to get the influence of the MAF out of the picture first. There are several ways to do this in software without unplugging anything. I would set the MAF Fail upper limit to zero and then se set the MAF Fail Monitor {P0103 as I recall} to No MIL (disables Malfunction Indicator Lamp also known as the Service Engine Soon/SES light) to prevent a service engine soon light while you are tuning SD.

Disable Deceleration Fuel Cut-Off (DFCO) so that your low MAP values don't get misrepresented when the engine goes into DFCO.

Then if you are using a WBAFR, disable Closed Loop by setting the Closed Loop Engine Coolant Temperature (ECT) to the maximum (252 degrees F or anything above 230 will do). That way, the engine never reaches the enabling temperature to begin closed loop.

Now you will need to log the actual AFR versus the commanded AFR (14.68:1 for normal Stoichiometric operation) with a Map/Histogram. For each cell, you will use the measured AFR from the wide band as the numerator and the commanded AFR and convert that to a decimal fraction to use as a multiplier for the current VE for that cell. This will produce a new VE Value for the cell which should then be readjusted a couple of more times to get it right.

The method for using LTFT (or actually STFT is better) is similar but less precise. If the fuel trim function is positive, the VE is too lean for that cell and the VE value needs to be increased in steps until the fuel trim value goes to zero or slightly negative.

One thing that I want to emphasize is if your injector flow rate (IFR) is properly set up for your vehicle (let's assume that your injectors are original equipment and you have the factory IFR values in the IFR table) avoid tuning via IFR at all costs. I've seen a lot of posts where people try to tune using IFR which will alter anything and everything about mixture. Use the VE table only to adjust VE.

BTW, unless you have done head/cam changes, induction system or header changes, the factory VE table will be pretty well right. You'll know if it's close right away once you've disabled the MAF and have logged some data.

All my best,

Steve

LS1 Sounds

iTrader: (11)

Thanks for the link, I actually have that entire procedure printed out and stored in my laptop case. I agree that the PE Enable %TPS vs. RPM table is what comes into play for adjusting the AFR after PE mode is engaged. But PE mode should never come on if the PE Enable MAP value is set for 110+ (on a naturally aspirated car). Correct?

LS1 Sounds

iTrader: (11)

I will be tuning with the stock narrowband O2's so I'll need to stay in closed-loop mode.

I'm with you on this one, although I left the SES light on as a reminder that the MAF fail frequency is set for zero.

This is a step that I haven't seen mentioned before, and it would explain why I get some crazy numbers during deceleration!

I'll have to remember this one when I can afford the WB O2.

I'm also with you here. It is the same method that I have been using to adjust my VE up to this point.

Once again, I've read this information and totally agree. My IFR values are still stock.

Basically my car is strictly bolt-ons: stall, LT headers, cutout, lid, and the free mods. My stock LTFT histogram reading (in SD mode but with DFCO still turned on) showed variations of +/- 10. I will post a screenshot of this as soon as I get back from lunch.

LS1 Sounds

iTrader: (11)

Thanks to everybody for all of the responses!

I'm thinking I now need to disable DFCO and PE modes and then re-tune my VE table. The problem I'm trying to solve is showing up when I try to tune the PE table, as I lower the divisor value my LTFT's aren't staying locked at zero. They are going positive and adding fuel back in and keeping the O2 values up around 925-930. My PE table is set for around 1.15 and the OL F/A table is 1.13 for map values above 95kPa so it shouldn't be effecting anything.

Any ideas on what is causing the LTFT's to go positive at WOT?

Steve Bryant

iTrader: (1)

LS1Sounds,
I forgot to mention about disabling PE. The easiest way to do that is to set the time delay to 60 seconds (or similar value).

Another thing you want to do when logging is to put the vehicle in like third gear and make slow steady acceleration/deceleration changes so that the logging of the cell values represent pretty much steady state conditions for each cell. Log higher MAP and RPM values in second gear the same way. If you're getting some knock retard while you're doing this in Stoch at higher power settings, retard the timing in the High Octane Table by a few degrees across the board (like -6 degrees everywhere) and make a note of this so you can reset it back to baseline later. The car will run like a dog with a lot of retard, but it's the only safe way to check out VE at high power settings with risking the potential of knock damage at Stoic.

Have fun. Tuning is a lot of fun and frustration mixed together. However, you'll get an education about your vehicle that you couldn't get any other way. The frustration is what makes the satisfaction so good as you get everything to run the way you want it to.

All my best,

Steve

LS1 Sounds

iTrader: (11)

Thanks Steve, I will try your suggestions for tuning the VE table. Hopefully after it's all said and done my LTFTs will stay locked at zero while I'm leaning out my PE table right?

BTW, here's that screenshot I promised earlier. I had already reset the LTFTs and driven about 120 miles before starting this log, and this log was from a 30 minute drive. This is all stock with the MAF disabled by setting the fail frequency to 0:

txhorns281

iTrader: (12)

Not too bad....

LS1 Sounds

iTrader: (11)

That was with the stock VE table, this is after VE tuning:



I was fully satisfied with the LTFT results here, but then I started trying to lean out the PE Multiplier table and my LTFTs started to go positive (not being caused by the open loop F/A table, it was set leaner than PE). The more I leaned it out, the more positive they went. I'm going to disable PE mode and DFCO and go retune my VE table and see if that helps.

Is there anything I should be logging to help figure out what's causing the LTFT to go positive under WOT?

LS1 Sounds

iTrader: (11)

OK, I did some experimenting tonight and here is what I found. Disabling DFCO makes the car stop popping and crackling through an open cutout when you transition from decel to accel. If you tune your VE table with DFCO disabled, then turn it on and log your LTFT histogram it looks something like this after a very short logging period:



These results make sense to me; positive LTFTs indicate fuel is being added because of a lean condition. Well, I'm now taking away the fuel away that was being used while tuning the VE table with DFCO turned off. Kind of like a double negative, hehehe.

The question I have now is: Which method is correct? How independent is the VE table? Should you turn off ALL outside influences while tuning it such as MAF, PE mode, and DFCO?

LS1 Sounds

iTrader: (11)

Oh, and re-tuning the VE table with PE mode disabled also seems to have fixed the problem I was having with positive LTFTs at WOT. I now have the PE table set for stock O2 readings hovering right around 900mV which is good enough for me until I can get it on a dyno. I am getting some KR now though and didn't have a chance to pull timing tonight to see if it was real or false (laptop battery was dying). Here are some screenshots of two WOT runs I made tonight, any input on the KR is appreciated:





-Chad

Steve Bryant

iTrader: (1)

Chad,
It looks like you're making good progress. You can be proud of what you've accomplished in a short time.

All my best,

Steve

LS1 Sounds

iTrader: (11)

Thanks Steve! Now I need to figure out a way to tune the pounding sensation out of my head, it was a real cram session over the weekend.