I currently have my MAFT set for BASE +5% and WOT +6%.

I just did an autotap and found my LTFT average is - 1.6798. I think that translates to 1.6% Rich ?

Anyway I never went over 50% Throttle during the run so the WOT should never have been a factor.

I did a TAP a few weeks ago with BASE 5% and WOT 2%

That returned a - 0.12358 Is this perfect ? with the error on the rich side?

I have a powerloader so that probably account for a 5% rich right out of the gate for my BASE. Most folks with my mods and a MAFT are set at 10% BASE.
My Mods are listed below.

 

:rolleyes:

 

ttt

 

chuck, Id go back to your previous settings, drive a while to normalize, then do some WOT runs to see where you timing, o2's, and KR is at.

 

I think I'll do that.
I am so confused now. Before TPIS I was running PERFECT at 5% Base and 6% WOT

Now with TPIS I am running rich. WTF!

Also, why is WOT leaking into my BASE setting. My run today was less than 50% throttle

 

Chuck what RPM levels did you achieve? That could have triggered the WOT addition.

I couldnt say for sure, but its quite possible your headers are scavenging the chambers quite well. This increases power by drawing in the mixture at a greater rate, however, scavenging also brings out a little raw fuel (if scavenging is in fact agressivly occuring), and could be showing your rich condition at the O2's. Just a hypothesis :)

 

Damn you are one smart ****. :D Scavenging hmmmm Maybe I could benefit by a better burn before it gets yanked out of the chamber. NGK's and Magnecor?

 

scavenging occurs due to the high escape velocities of gases which serve to cause a suction in the other tubes during cam overlap periods when the exhaust valve is still slightly open during intake valve opening. So firing your spark more "powerfully" or "efficiently" would not effect buring any extra fuel since all valves would be closed during combustion. Any gas that escapes, has allready escaped.

However on the other hand you may want to monitor missfires, You could be getting too much fuel in the chamber that doesnt get fully burned for whatever reason, in one or more chambers causing rich readings at the o2's. are you getting the same fuel trim values on both banks?

 

one other question. In the beginning, did you tune out to roughly 0 percent with BASE for LTFTs, while the WOT setting was a 0?


[Modified by kewlbrz, 10:30 PM 11/8/2001]

 

However on the other hand you may want to monitor missfires, You could be getting too much fuel in the chamber that doesnt get fully burned for whatever reason, in one or more chambers causing rich readings at the o2's. are you getting the same fuel trim values on both banks?[/QUOTE]

Good Point. I always wondered why Bank 1 was not always the same as Bank 2

Here is what I found

When Using Base 5% Wot 2%
LTFT B1 Average = 0.08045
LTFT B2 Average = -0.3276

When Using Base 5% Wot 6%
LTFT B1 Average = -0.89844
LTFT B2 Average = -1.43752

That is a consistant difference!

These averages are 20 minutes of driving. Before these taps I had misfiring after my headers were installed. This I discovered was loose plug wires in multiple locations. I have since snugged them up. Could I still have Plug/wire probs?

 

Chuckster, do you still have the stock plugs and stock wires.

I would definatly start there. Go with NGK TR55 and Magncor Wires. That should really freshen it up. Especially if any of the platinum pucks have popped off the stock plugs electrodes. Then lets see what she does .

 

I am going to do that right away. Can I gap the plugs at .50? My rationale is that the plug gap usually widen with time. Also I want to make sure I have the hottest spark available. Any probs with this idea?

Also Who has the best deal on Magnecor/NGK's?

 

The general rule is you want to decrease plug gap with an increase in power. Because increased in power add greater combustion chamber velocity and turbulance. This can blow out the spark prematurely.

My suggestion is to gap them around 55 with your mods. They come pregapped at around 57 thousandths. Make sure you use a proper tool to narrow the gap on them.

 

Due to the fuel rail design, there is always a difference seen between B1 and B2.
As to misfire I find that TPIS headers cause more misfire but unless your getting PO300 multi misfire, its a don't care. Check I/M tests and see if they are in a "complete" state or not, if they are, the misfire you have is just a pain in the butt. If misfire is more like pistons 7 or 8, cranj sensor thinks it is misfire but it is really coming from drivetrain ( via drivetube ) causing slight slowdown on crank. Even a warped brake rotor can be picked up as misfire, a yaw sensor can trigger it, even a rough road will trigger it.
Lastly if after draining PCM via no power, the crank position sensor has to be calibrated to PCM via the test procedure G.M ( I've posted on my forum ) or having a tech II and forcing the re-cal. If sensor is not cal'd, then of course PCM thinks sensor is pointing to zero, when its 1 degree past that.
Also cam postion sensor needs to cal to crank sensor so crank knows if piston is on fire or exhaust stroke.

One signal comes from MAF, MAFT sends out one signal to PCM, thus I see both MAFT switches as "additive" and not seperate functions.

I would do a testcase of WOT set to zero and Base set to +10 ( your not signing your numbers so assume since your using positive number your adjusting to lean) and then see what knock looks like ( who had more/less knock cells 1-19 or cell 22 at TPS greater then 99.5) and what timing is at WOT and then tune from there.
you might have to set WOT switch then -2 ( rich) but only test traces would tell me for sure which direction to go.

You don't go by what is rich or lean numbers as much as is there knock, if so where is it in the RPM/cells range, is WOT timing being effected, if so tune it out. For fairly stock engine shoot for about 28 degrees at true WOT,
do not average all trace cycles, two answers one for cells 1-19 and one for true WOT.

These engines run differently ( as to AFR) in weather under 75 degrees then above and thus tuning will require different MAFT setting for those two weather ranges.

 

John, WOT settings are added to the BASE at frequencies ranges greater than 8Khz thusly:

- min F-out := 1.3 kHz
- max F-out := 14.6 kHz w/ limiter
- input frequency sampling time := ~10ms
- WOT transition frequency := 8 kHz

- For F-in < 8 kHz
-- F-out = F-in * (0.03440 * BASE + 1)
- For Fin >= 8 kHz
-- F-out = F-in * (0.03440 * BASE + 1) * (0.00407 * WOT + 1)

For example. If you set BASE to +5%, at 8Khz MAF frequency in, and your WOT was set to 0, you would present 8.3Khz to the PCM. Thus the PCM would increase the injector pulse width base equation to meet 8.3Khz of flow, while the engine is still only getting 8Khz of flow rate at the MAF.

At 7Khz (below the threshold of the addition of WOT). at 5% base 0% WOT, you would send 7.25Khz to the PCM.

Now if you add 2% rich to WOT while BASE is at 5%, you get:

at 7Khz = 7.25Khz to the PCM
at 8Khz = 8.32Khz to the PCM

You can see how the addition of 2% WOT fine tunes the signal with the difference of 8.2 and 8.3


[Modified by kewlbrz, 12:40 PM 11/9/2001]

 

Yes, I agree, it's that people think they are two totally different functions and don't realize that some times you have to think of them as joining together as a mixer ( for lack of better word) and don't always look at them as a switch only used for certain trims cells.
Sometimes use Base setting that overall gives a better WOT outcome, so if a +5/+4 does not work, try a base +10 and then use WOT setting to fine tune.

 

So would it be better if I monitored the MAF Frequency on my Autotap. and kept it below 8Khz Id be interested in seeing the corelation of LTFT's and the Frequency.

I also spoke to Mike Lichtner. He told me that they were separate too. Only adding in after 8K

If they were truly additive there would be no differance between
(BASE +10 WOT 0) or (BASE 0 WOT +10)

 

chuck i messed up the calculation. see my post again :)

 

Why I am trying to say if you look at the switches as static meaning if you set base to +10%, its total is just for that, when in the final tune, for best performance, you will find that better may be more change like +5 (+) +5.

MAFT does not know about tps being more then 99.5 and at cell 22, thus the mass ( volume ) dictates when additive or not, so final tuning is not a simple seperation, but rather the best combination of two MAFT switches for least amount of knock at WOT.

Depending on the engine makeup, and what happens at the MOMENT of going into WOT, wil depend on what the AFR is related to WOT.

By law G.M can forget EPA at WOT and thus goes richer for WOT but the wrong combo of MAFT switches can cause increased rich, due to LTFT being too lean.

This techie stuff is explained better by voice then this hen-pecking, at least for me :)

 

John, I agree. :) And your right, many people get the switches confused regarding the whole overall picture.