XJGPN

I have been searching and reading posts non-stop and I am still a bit confused. Mainly regarding which table to use for Part Throttle Tuning, and how to do it. Here is the specific situation. I just got HP Tuners, and the first thing I did was the standard baseline items (raise rev limiter, used NoGo’s recommendations for baseline idle setting etc.). Now that I have done that I want to go on to Part Throttle Tuning. I have a set of new O2’s that I have not installed yet. I was planning on getting the tune in the ballpark before swapping O2’s to avoid the risk of fouling them out. I have run a couple of Logs and it seems as though my LTFTs and STFTs combined hover between +5 through +15 for the majority of the table. My Wideband shows my AF to be hovering right around stoich, It’s not rock solid, but for almost all part throttle driving it stays between 14.0-15.5 or so. (Don’t yet have my wideband logging to HPTuners so I’m just going by what I’ve seen on the display. I wasn’t really going to worry about the wideband readings too much until I have my LTFT’s in check). So, basically, here is where I’m stuck. I’m not really sure where to go from here. I’ve read a lot on both this forum, http://ls1edit.slowcar.net/, and the HP tuners forum and I keep getting conflicting information. On http://ls1edit.slowcar.net/ he describes starting with the Maf Transfer Function. Meanwhile most people on this board and the HP Tuners forum keep talking about dialing in the VE table. To confuse things more, you have a lot of people talk about simply scaling the IFR table. I’ve read from several places that if you haven’t changed the Maf (Mine is stock) and you haven’t changed injectors (once again, mine are stock), you should leave the Maf table and IFR table alone and concentrate on the VE table. I’m not really fond of the idea of scaling the IFR table since I’d rather tune by making tables more accurate, not by fooling the computer into thinking the injectors are smaller than they are. Since you can adjust the VE Table without the Maf, but not the other way around it seems as though the logical thing to do would be to try to get the VE table accurate through the SD tuning method, then reconnect the Maf. Once that was done I would once again start logging LTFT’s and STFT’s relative to Maf signal and then re-scale the Maf based on that (probably using the method outlined on http://ls1edit.slowcar.net/ ). I have been reading up on the SD tuning, and now I’m noticing a bunch of posts (notably some by NoGo and Chris B) that said that for tuning out higher LTFT’s you should NOT be using the VE table. Meanwhile I have seen a ton of posts saying that almost all tuning should be done in the VE table. Basically I’m stuck. I think I’m getting mixed information because people are talking about different stages in the tuning process (initial tuning vs. fine tuning). I just want to know where do I go from here. Starting with a clean slate, car is running stock tune with only Idle and general parameters modified. Car seems to be running close to Stoich, and has no obvious drivability issues, but it has high LTFT’s. Where do I go now.

Rays C5

This should be good ttt.

XJGPN

I hope you mean because it is a good question Honestly, I've seen this same question asked dozens of times in many threads... I just have yet to see an answer. I don't know why that is, is it just that nobody knows? Or nobody wants to give up the information? There has to be SOMEONE out there who has successfully tuned their car Maybe It's just the wrong question

tici

iTrader: (1)

XJGPN, I'm in the same situation as you (and probably as 95% of the forum's members).
I had to try all the methods I saw on the web to find out a reasonable way to tune.
Every method is right somehow, but takes care only about a certain issue.
Every table is somehow connected to the others, so as soon you mess with some numbers expect to have changes somewhere else.
To my opinion the tuning strategy depends on the mechanical changes you made to the engine.

What I did (and know it works):

First be sure that the car is mechanically ok (fuel pump, injectors, spark plugs, exhaust, O2's, air filter, MAF and so on).

Scale the IFR table to be somewhere close to 0 LTFT (-4/-2). If you go too close to 0 you'll go positive depending on the day (and also positive in cell 22!)

Modify the maf table in the lower range to modify the lower cells (0, 1, 2, 4, 5). In my case this has been necessary as soon as I replaced the stock filter: if the air doesn't flow as planned by GM the MAF will work differently.

VE: if the internals are stock I wouldn't change it. My 98 VE table is a little strange (too low before torque peek and too high after that). So I changed it to the 02 VE table. You can use this table to tune certain spots of the RPM/MAP table, but it's not easy and the results aren't that clear.
VE helped me a little fighting part throttle KR, but again it's not easy.

Only after all of this stuff is perfect and you are sure you won't mess with it again get a PE vs RPM tune. Make a scan to compare your O2's to the WB.

Timing & Transmission: two other time consuming things...

I'm not saying this is THE way, just that it worked well for my car.

Hope this helps - good luck!

XJGPN

What is the significance of going positive in Cell 22? (I hate to ask that, since it apparently is something obvoiously very bad )

I thought with a cam change you usually have the oppositve happen (table is too high down low and too low up top) due to the shift in powerband... I take it that doesn't agree with your finding?

Luckily I have a stick... so that saves me that chunk of time

Thanks a bunch for the help! Definately appreciate the feedback.

ataylors

iTrader: (2)

IMO the IFR table is the devil, especially in part throttle

tici

iTrader: (1)

Cell 22 positive means that the PCM is adding more fuel at WOT than what you set in the PE vs RPM table. In this way it's impossible to tune WOT with a whideband because the effective enrichment is higher than what you have set.
If all cells are negative the PCM will set cell 22 at 0 during wot. If some cell is positive you'll have a positive cell 22 too. This won't be constant but depending on a lot of things so you'll never know if in that particular moment the PE is that what you want or not.
Same thing with COT: better disable it during the PE tuning or you'll have more fuel as what you want.

I don't have a cam so I can't tell by direct experiance. But usually it's as you wrote.
You'll have to find out the VE for your specific mods. If you use the NoGo method it's maybe better to reinstall the stock inteke setup to have accurate readings, this because it's based on MAF (unless you go with SD and a WB, but this is another story).

XJGPN

Very good to know. Thanks for the tip.


By the NoGo Method, do you mean that VE formula? Wouldn't changing the intake change the VE?

See, that goes more in line with what I have heard (and it also makes sense). Have Either of you used the Maf Transfer Function spreadsheet on http://ls1edit.slowcar.net/ ? I haven't yet (don't yet have a long enough log that includes Maf Frequency). The spreadsheet is really slick. If it works as well as it looks, then I'd be inclined to just keep using it until my L-trims all fall in line.

tici

iTrader: (1)

This VE formula:
https://ls1tech.com/forums/pcm-diagnostics-tuning/149741-ve-table-cracked.html
VE is just the mass of air the engine is able to suck at a certain RPM vs a certain MAP.
If you have a better intake you will have more air for the same throttle angle (for example), but automatically also more MAP. You're playing with the same table, but maybe you are in a different spot as with the stock intake.

The Maf Transfer Function spreadsheet works also.
My goal was to have all LTFT at the same level. Playing with the IFR wasn't enough, same with the MAF transfer function. So I used both. IFR for the raw correction ( I also installed bigger injectors) and the MAF for the lower cells.

XJGPN

I can't tell you how happy I am you brought up that formula :-) I was debating on bringing my other major question (that formula) into this thread, or just waiting it out and starting a second thread. I'm really shaky as to how I would use that formula. In HP Tuners I was seriously tempted to just use my saved Histograms of LTFT and STFT to figure out a % Modifier for each cell. Why would I use this formula, and more importantly, How would I use this formula? Log Massflow, IAT, MAP, RPM and then plug them in? Would the number that then gives me be my absolute in the VE table? Since the VE table is in MAP vs. RPM, wouldn't that then make the only variables you are solving for in the table your Massflow and IAT at that cell? As confusing as the formula is, what I really don't get is how you would actually apply it? I really need to understand the application of that formula more then understanding the formula so that I can just make an excel spreadsheet that will compile the data for me... But I'm not certain how to use it, because that thread you pointed me to kinda starts halfway in on a conversation that I never found the beginning of . I love how it keeps referring to older information. I never saw the older information so I have no idea what NoGo is talking about when he says: "My old method of "Divide by 30" works okay because we are inadvertantly solving for a volume ratio. The molar mass of air is 28.96 g/mol." What old Method? And what was he dividing by 30? What did that give you? When he said: "To solve for the massflow in g/sec simply re-arrange the equation. Massflow = (VE * MAP * RPM * Displacement) / IAT". What are we trying to solve for, Massflow or VE? I was thinking that you were logging the Massflow to solve for VE... but why did he then re-arrange to solve for Massflow? Where do we get the VE number to solve for Massflow? I'm really hoping that the information isn't over my head... but I'm lost in terms of the application of that information.

Okay, that makes a lot more sense then :-) That goes right into that theory that if you change Injectors/fueling, modify IFR, if you change induction, modify MAF, and if you change engine characteristics change VE (and MAF).

Bink

No flames here...but I don't think the devil is in the IFR table.

If you've changed anything in the intake tract the MAF is more inaccurate (i.e. using the stock MAF table) - of course it is inherently inaccurate at low RPMs and kPa (lower airflow).

GM uses AIRMASS Calcs to provide a "crutch" for the MAF. If the MAF is skewed by mods then the AIRMASS Calcs (- Calibration dependent) will be wrong.

VE Table being an AIRMASS/Cyl Table further skews the Calcs.
We need an accurate VE Table and MAF as well as a Wideband O2 to get the setups as close to perfect as possible.

I think the Devil is in the MAF, AIRMASS CALCS and THE VE Table .

My $.02.
- joel

Rays C5

Very good question!!!!! I'll cut through the chase. With ls1edit, I have changed up to the ls6 intake, and the mods in sig. given this info should be
raising/lowering maf or ve tables??? car runs fine,ltft are 0 in all cells,no k.r., this being said what could I possibly gain from any of the maf and/or ve tables? sorry for all the questions

TurboBerserker

iTrader: (1)

My rule of thumb is to edit the tables for the parts that have changed...

So I change my IFR if I change my injectors (and I only do straight unit conversions), MAF table if I've changed the air track up to the throttle body, and VE table for everything else that effects the air being pumped through.

That isn't to say other methods don't work, it's just that I've tried them all, and this ended up being the most stable for me.

The thing is, there is a ton of information on 'tuning the ve table' that is old and not necessarily accurate. The best method of tuning VE that I found is the SD or MAFless method (search for this -- there are good posts describing this method here and on HPT).

WS6snake-eater

http://www.hptuners.com/forum/YaBB.p...num=1100894562

give that a shot for starters.

tici

iTrader: (1)

I used this equation:

VE (Edit) = (MAF * IAT) / (MAP * RPM * DISPL)
MAF = g/s
IAT = K
MAP = bar
RPM = min-1
DISPL = m3 = 0.005665

How to use it... oh well...

With Atap I logged all the necessary stuff, then you'll have to round up the values for RPM and MAP to match the steps in the VE table.
Then calculate the VE with the equation taking care of the units.
Then you smash all the numbers in a pivot table in excel: RPM vs MAP and the VE values in the middle.
Then make a nice 3D graph and smooth the surface.

If you know excel it's not a big deal, if not you can get some software do it automatically.

I have no whideband and I never tried SD... so I guess the tune is not really complete.
I just find out that the 98 table was 10% too low and that the 02 table was very similar to the measured numbers. This is what I'm running right now and it works well.
With or without blower

If you want to go serious follow the suggestions of Bink, TurboBerserker & WS6snake-eater. What I'm doing is not exactly the finest art of tuning: I just try to keep the car running

Good luck!

tici

iTrader: (1)

... I forgot: I used the stock filter assembly, stock MAF table, stock MAF, paper filter...
As Bink says as soon as you change something in the intake you'll have fantasy-numbers, especially at low air flow

S2002S

Excellent thread, but I'm not sure if we have the solution.

I also don't understand why improving the intake airflow such as a better lid, would throw off the MAF. The MAF measures airflow and has no knowledge of upstream or downstream modifications. Airflow is airflow right?

Also, if you modify the MAF table then what other areas are affected (what other functions use the airflow data)? It seems that these areas would be affected as well.

Rays C5

ttt need some pcm gurus to chime in here.

XJGPN

Well, I'll give my quick update. Tried the wideband speed density method as previously outlined. Car won't start with those settings. I think my VE table is just way too far off. I'm going to try to do 1 iteration of closed loop-speed density tuning now to see if I can get my VE table close enough to let me run the car open loop to tune with the wideband. I'll keep updating this through the day :-)

Another_User

Look at the stock lid. It has an oval shaped intake opening that pretty much directs air right at the sensors. Aftermarket lids push airflow above and below where the air is normally read, so until the intake is "saturated" with air it is going to read lean because of unmetered airflow. Especially at low rpms and high intake vacuum (closed to light throttle). You have to think of air more like a fluid. For example, if there is a 90 degree bend before or after the MAF, air is going to "flow" toward the outside of the bend, so you have to place your sensors accordingly. Look at the Holden. They have a 90 degree bend, and they also have to put their MAF in at a 90 degree angle from where we put ours, so the sensors catch the air better. Every MAF table is tuned specifically to the intake designed for that vehicle.

Oh, and lids are the devil. Or maybe just the fact that we don't have a way to caibrate our MAFs. If those buttheads that made the lids would flow the friggin things and give us a MAF table it would help. Heaven forbid they spend a few bucks at SLP. I wouldn't be surprised it moving the MAF 90 degrees would help. Unfortunately I can't try like I want because there is not hood clearance under a stock hood. Anybody out there with a cowl hood that wants to check it out?