I keep reading like 10 different ways to tune closed loop. Some say no need to tune VE but some say you have to, some say need to tune MAF some say dont need to. Some say tune IFR some say dont. Is there like no right or wrong way to do this or what? Obviously there are people out there that have good experiences doing it all these different ways.
Example: the ls1edit user guide says not to mess with MAF or IFR unless you have replaced or modified each device respectively. It then says that VE will have the effect on closed loop fuel trims. Then I hear people saying you need to tune the MAF tables and more saying to tune the IRF table. Its just kinda confusing to a new tuner when we hear like a million different ways to bascially do the same thing. I am just about to do it like the damn user guide says to and just tune the VE table since I have not changed my MAF sensor or fuel injectors/fuel pressure.

 

When I tuned mine, I did not change the IFR table since the injectors are still stock. Then, I tuned the VE Table in Speed Density Mode since I changed the cam. After that, I tuned the MAF Table since the airflow has changed with the airlid, ported TB and so on. If you do not have a wideband sensor, I would tun use the STFT's since they are realtime. The LTFT's take awhile to update.

 

Yes what he said.

Here's a little practical advice to a new tuner.
By definition "closed loop" tunes itself up to about 25% correction which is a LOT.
Your best bet is probably to stick to the VE table, especially if you are near stock. Your normal driving takes place in a fairly limited area of the table and mostly uses just a few of the LTFT cells. Make changes in these most used areas of the VE to keep the corrections between -5% and 0 and you can call it done.
Keeping your corrections low and on the negative side will generally keep the fuel trims from throwing off your WOT tune. Positive trims can add to your WOT fueling unless I'm understanding that wrong, and you don't want that to happen.

I don't like closed loop myself.

 

here is a link about ve tuning that i read.See what I mean??
http://teamzr1.com/ubb/ultimatebb.ph...c;f=8;t=000059

 

Can I get the VE table dialed in using LTFT only since ls1_scan does not log STFT? I need to get autotap or something.

 

To answer your original question. Between IFRs, VE and MAF, the IFRs and MAF can generally be calculated, and therefore typically not significant variables on a moderately stock engine. VE, on the other hand seems to move around quite a bit.
My suggestion is to use the accepted calcuation for IFR and MAF, and then tune to get the VE correct. After that, you can adjust/fine-tune the others

 

wow talk about the pot calling the kettle black.
After looking through his data, it looks okay and he seems to understand how everything is working, but it looks like the conclusions drawn and stated are the fatal error.

His test case is a 372 cube engine, with 40 lb injectors and a 85mm Z06 MAF. Throwing together parts like that and coming out half-way O.K. is more about luck and how close his injector flow data was, since he obviously would've had to correct for the non-stock injector size. It is hardly grounds to conclude that VE tuning is just "hype".

He even states that it's (the VE) only used for under 4000 RPM and therefor NOT used under most engine conditions.... absolutely rediculous statement.
For most people an easy 95% of their driving is under 1800 RPM.

Keep in mind that all tuners are a little different and there are several ways of working on the calibration to meet the same end. The phrase "there's more than one way to skin a cat" applies here.

It sounds like the guy making that post either knows enough to be dangerous or was simply trying to stir up contriversy with some data that happened to work out in his favor of opinion.

Yes you can tune using the MAF table, but in most cases it's more practical to work with the VE, and only make changes to the MAF table when it's absolutely neccessary, as in when you port or swap to different size MAFs, and sometimes if you relocate or re-clock the MAF sensor.

Some people feel that re-caling the MAF is just fooling the output of the sensor to make up for a VE table that is no longer correct for the engine.
They are for the most part correct IMO.
The VE table may be old-school, but it still is the base fuel map that other corrections get applied to.

 

In ls1 scan, I see LTFT AVG and LTFT. Is the Average the actual LTFT and the other LTFT actually the STFT because I notice while driving that the LTFT changes a lot like when I push the gas more, but the LTFT Avg stays around the same.

 

I don't know for sure about the LS1scan as I stopped using that a LONG time ago.

Your LTFT's will change when you push the gas because you move through different trim cells (load ranges) which each will contain their own value.
You need to log what cell you are in along with your LTFT's too.
Without knowing the cell it's in, the LTFT's won't mean a lot.

As was said earlier it takes time for the LTFT's to settle-in to a final (semi-final) value, but when you're far off you'll usually see the basic trend show itself within only 5 minutes of driving.


STFT's should be labeled as such, and I don't think most people look at those. You should probably consider investing in a better scan tool I suppose.

 

You want to just forget about averages. Lies, damn lies
and statistics, right? Right.

One thing that will make your closed loop clean up a lot,
is to fix the fuel trim cell boundaries if they are insane
like mine were, stock. You would really like to crowd a
lot of (most of) the cells down into the lower RPM, lower
MAP regions where street happens and where the engine
is most variable in its airflow, thermal, other behavior.
My car only had half of the cells active and split them
at 2500RPM. Look at your VE table, the difference in
air pumping alone between 800RPM and 2500RPM is a
fair bit (and worse on cammed cars). One size fits all,
means you're wearing a muu-muu to the 100 meter
hurdles. Good plan.

Once your cells are individually covering less ground
they begin to give you more meaningful info on the
fuel situation - not a time averaged ball of bitching.

Changing in software, only what pertains to changed
hardware, is the best place to start. Begin with the
mods list, what dimension(s) might have been
affected, and concentrate on the cleanest bits first.

 

Damn I think this is the best piece of advice I've seen yet. That is an excellent point for closed loop tuning.
I never think about that stuff since I'm a hardcore open-loop guy.
Way to use your head!

 

So for the most part I can ignore the short term trims and just concentrate on long term?? I had long term dialed in earlier but I tried to get short trim dialed in more and got my long term all out of whack, gotta go fix it soon.

 

Ok, so I think I am getting the hang of this now. Today I unplugged the MAF and logged in SD and my fuel trims seemed to be right on where they should be about 0 to -1. So then I went MAF and was very positive, so i scaled sections of the MAF table and now I am a little too negative in the low MAF frequencies. Im getting there though.

 

Can anybody tell me why I cannot seem to get anything but zero's for LTFT / STFT's above 4000 RPM?
I try to keep the TPS low, so I don't go into PE mode, but it don't seem to help.

 

Some people disable PE for while they're doing a closed-loop tune.
See if that changes it.

 

Definately disable PE, It can trigger at as low as 34% TPS in some PCM's