silverTA2002

iTrader: (1)

Mods in sig. Car just ran a 12.8 at 111mph tonight with clutch slipping on the launch in 70 degree weather, 60% humidity, sea level.

My tuning process has been as follows (other than the little tweaks) over the last 2 years:

Adjusted IFR until LTFT were at -3 or so.

Adjusted PE until O2s were around 900, and there's no knock (more knock if leaner).

Adjusted timing everywhere so that 1 degree more basically anywhere gets KR. (24-25 at WOT). I have about 11.3:1 compression.

Adjusted the heck out idle crap for multiple months to get it right. Now it idles fine, and doesn't float.

BUT, one thing that I didn't do was to redo the IFR after heads/cam because the LTFT are still barely negative (except for the last week they average -2 and -10).

I've got a stock MAF and stock throttle body. I've never recalibrated the MAF or done anything more than the above for WOT tuning.

Your thoughts? I should note that I don't plan on removing the MAF.

white2001s10

iTrader: (4)

Forget the stock O2's.
Put a wideband on it and log through the RPM range.

MeentSS02

iTrader: (11)

1. Don't use the IFR to get your trims in line.
2. Don't use the narrowband O2 sensors to tune WOT.

Yes, you are leaving a good amount on the table IMO. Get a wideband, and go from there.

silverTA2002

iTrader: (1)

Will 3 passes on a dyno with a wideband be enough?

Or, would I be better off buying a wideband?

Should I use my VE table to change my LTFTs? The only thing I've used VE for so far is getting my idle in line.

RedHardSupra

iTrader: (1)

WOT is a sideeffect. having IFR reflect the flow of your injectors and having VE reflect the flowing characteristic of the motor is usually enough to get your fueling right. PE mode is a derivative of the normal closed loop mode, that's why PE table is filled with a division ratios. you do not need a wideband or a dyno to get your IFR or VE right. if they're done right, and PE and timing is set to something sensible, your effective AFR will be close to the desired AFR.
dyno and wideband is to account only for these tiny little differences in the end. nothing else. use the AFR/rpm graph to alter your PE divisors so your effective AFR is closer to what you want it to be. do NOT alter IFR/VE for that, they have nothing to do with WOT!

silverTA2002

iTrader: (1)

"use the AFR/rpm graph to alter your PE divisors so your effective AFR is closer to what you want it to be."


I'm not familiar with the AFR/rpm graph. What is it?

I've also read a bit about VE tuning, and I still don't really understand what needs to be done.

Also, with my LTFTs, what does it mean if bank 1 is -2 and bank 2 is -10?

white2001s10

iTrader: (4)

He means the PE vs RPM table.

My guess is it means that you may have a header leak on bank one. I don't know for sure on that one though. It would take some troubleshooting.

silverTA2002

iTrader: (1)

Actually, until yesterday, I did have another leak on bank 1 (driver's side).

I've got the Jet hot catted Y pipe. It has like 7 pieces that each fit together with band clamps.

There's ALWAYS a freakin leak popping up somewhere. So frustrating.

My "solution" is using sensor safe high temp RTV on every connection, covered that with high temp muffler tape, covered with stainless steel band clamps tightened as tight as they go.

And STILL every few months a clamp will slide around a bit and cause another leak.

I don't want to weld. If I had originally, the heads/cam swap would've been a bit more difficult.

Long story short, I did fix another leak. So, I'd bet if I logged right now, I'd be right at -2 and -4 LTFT just like always.



So........ Should I "recalibrate my MAF?" Or does that really make a difference in power?

RedHardSupra

iTrader: (1)

recalibrate MAF only if your VE is done properly. and yes, it will give you a huge difference. i can send you some dyno charts/logs demonstrating what happens when your maf is off. sneak peak: scary!

98Z28CobraKiller

iTrader: (17)

LTFT's are to be logged in a histogram using the editor. The histogram will give you LTFT values on a graph that looks just like your VE table. You want to log for like 20+ minutes and try to hit as many cells on the histogram as possible. Once you have the values in each cell from the histogram, you then go to your VE table and adjust those values (in the programmer). For instance, if you get a value of -8 in one of the cells, you will then find the same cell (same manifold pressure and RPM) on the VE table (I believe that you are supposed to adjust the Primary VE unless you have a 1998 model year PCM. If 98 then adjust the secondary VE table) in the appropriate VE table and add -8 (or subtract positive 8. Same difference) to value shown.
Rinse and repeat. You want all values to be from 0 to -4 in the histogram once you are done. Sometimes you have to use a slightly lower value than the one shown. For instance, you make the change above and then the next histogram that you log may show (+)4 in the same cell. What I do here is that I split the number in 1/2 and add it to the cell in the VE table basically adding 2 into the number instead of the 4 value that the histo gave you. When VE tuning, the MAF should be unplugged. I am new to this also so that is why I added so much detail. I think that some of the more knowledgeable guys on here dont remember what it was like to be a noob at this (like me).

Also, the VE table is not idle tuning. You have to look at LTIT and STIT and add the values together in order to get your idle at it's best.

I am just getting past this part of the tuning process on my 402 (talk about starting on the tuning in the deep end). PE tuning and spark advance tuning are next for me.

98Z28CobraKiller

iTrader: (17)

RHS,

I am just getting to this point on the tuning of my 402. I am a little confused about the conflicting information that I have seen with regards to WOT tuning. I don't want to blow my new motor. Alot of experienced guys on here and the HPT forum say that you cannot tune the PE table w/o a WBO2 sensor. Because I am not working on a stock cube motor, should I trust the Stoich value that is in my tune? How does the computer know? I guess what I am asking for is a basic lesson in Stoich. Based on what I took from your quote above, pretty much all cars should have the same values in the PE vs RPM table and the WB02 is just to check and make sure that it is correct in the real world and that the narrow band O2's are reporting properly. Is this correct or did I misunderstand. The only 2 reasons why I am lending any weight to this is because 1) all of the so called experts say that you are one of the more knowledgeable people and 2) because I dont have a WB02 or a dyno handy

Also, should you tune the spark or the PE first?

Thanks in advance.

98Z28CobraKiller

iTrader: (17)

ttt.....

98Z28CobraKiller

iTrader: (17)

ttt......

chrisj6

When tuning the VE table, that is a percentage. You want to multiply by % - half instead of adding or subtracting from the table. Multiplying by 1/2 percentage avoids overshooting.

Chris

silverTA2002

iTrader: (1)

Ok,

So if you have a value of -10 LTFT in cell X, what percentage to you multiply that particular VE cell # by?

From what I've read so far, people are adding and subtracting the LTFT from VE.


What's kinda interesting is that tuning VE sounds a lot like tuning Base airflow for you idle. You log, make changes, log again, make changes......... Until the STIT and LTIT don't move much.

So, for VE you log, make changes, log, make changes until your STIT and LTIT don't move much.

OR, are you saying that if cell X is -10 then subtract 5 from VE?

That's what I ended up doing with my base running airflow changes. Everytime I'd only change them by HALF of what the "formula" told me to. That way I wouldn't overshoot, undershoot, overshoot........

98Z28CobraKiller

iTrader: (17)

You are the first person that I have ever heard say to multiply these values. Multiplication would yield very different results and I would varify this with a known tuner/expert ie. redhardsupra, magnus, soundengineer, foff, horist, or another.

Chrisj, you may be using a dfiferent method that logs different values which may require multiplication but none of the methods that I have seen (using narrowband O2's) require multiplication. Once I get close on the VE table and I start to overshoot, then I split the value in half but I still add the value (whether negative or positive).