J-Rod

I doing a bit of reading I have a couple of questions.

Just to make sure I am completely clear on this.

For part throttle. If you run your car in the standard closed loop mode which 99% of the people do, you are stuck @ 14.7 (stoich). The car will basically fight you all the way as the o2's etc... are set to use 14.7 as the reference value. So, that is what most folks are tuning to, correct?

To do anything other than this requires you to go open loop, correct?

So, if you don't mind 14.7 tune your L-Trims to 0 or just slightly negative, again correct?

WOT is a whole different animal.

Looks like that is all about tuning with a WB to get the proper A/F ratio.

On spark timing advance. It looks like a lot of folks just keep feeding spark advance until it knocks, and then back it down. I'm just curious if this is the general consensus. My only reason for asking is that max timing is not always max power.

I'm just trying to make sure that I understand some of the basics and am not making some incorrect assumptions.

HumpinSS

iTrader: (1)

Your LTRIMS correlate to how far off you are. + trims you are lean - trims you are rich

Yes and yes
Yes because to o2's are no longer in the loop and arent accurate. A WB is a necesity at this point.

Me personally would spend an hour on the dyno for this

jimmyblue

iTrader: (11)

From what I've read, max power is about 3 degrees
back of max timing. But this is all generalities from
other motors.

Without a dyno, a G-meter or some other way of
quantitative performance measurement, find the
ping point (given near-ideal mixture) and back off
a couple of degrees, seems like the cheap ticket.

Once you meet the PE threshold criteria you go
to open loop. There are also other ways (who
knows them all?) to get into open loop.

J-Rod

Agreed, I guess my question or statement that I wanted to be clear on is to make sure I understand clearly that because of the feedback nature of part throttle operation, any tuning for part throttle A/F in closed loop other than 14.7 is a fight because of the natue of narrow band 02 sensors. Also, because of the non-linear nature of NB o2 sensor response on either side of stoich they are "basically" worthless for any sort of part throttle tuning if you want an A/F other than stoich.

WOT requires a WB to ensure a proper A/F ratio.

On the timing I had just seen several commnets about jacking up timing till you get KR and then back it down. My only reason for questioning this was the fact that someone borrowed the dyno on a stock Z06 and jacked the timing from 22 to 32 in 2 degree increments, and saw no power increase.

One other question:

I see some folks gathering info on LTRIMs and tuning that via scaling the MAF.

I see other folks gathering the same data and scaling the injector flow rate table.

Both do the job, any particular reason why MAF table tuning seems to be preferred over scaling the injector rate?

jimmyblue

iTrader: (11)

I don't think there's any widespread agreement.

In my opinion, you should fix whichever table is
currently misrepresenting reality. Two wrongs not
making a right, and all that.

MAF for aftermatket MAFs, ported MAFs, etc.
IFR for upsized injectors, different fuel pressure,
that kind of thing.

MAF affects many things - spark timing, A4 line
pressure etc. MAF table has little effect on the
low-airflow LTFTs.

VE affects the speed-density tune, affects low-
flow LTFTs, affects transient-throttle, transient-
MAP operation. Same load effects on spark and
trans I expect but only under more limited regions
of operation.

IFR affects only the fuel shot.

Timing is how you position the burn to optimum.
That optimum moves, with air/fuel ratio. The
best-torque curve has a flat-top to it where
there is not much timing sensitivity. Ones I've
seen look like a 5-10% falloff between best and
ping (where the charts seem to stop) and a
larger falloff as you go to the retard side.

Not sure about that Z06 experiment, the extra
engine torque management and electronic throttle
make me suspicious. I'd like to see a family of
dyno curves for an F-body with optimum AFR
over the same stepping.

HumpinSS

iTrader: (1)

To a point yes it is a fight. Our only goal is to get the trims slightly negative so they lock at 0 right before WOT anyhting other than that is a slippery uphill battle.


I wouldnt mess with the maf if it is stock and i wouldnt mess with the IFR table if it is stock. The ve table is where it is at some have had success and others havent. there is a few programs that will help calculate ve for you. And HPTuners LTFT histogram is referenced by map and rpm and you are able to take these values right back to the ve table

TXNC5

What's up J-Rod?

Actually, I thought most people gave up on modifying the MAF function as one of the primary tools for tuning. That definitely used to be the way to do it. Shoot, I wonder how many MAF Translators are sitting around people's garages. Although, I believe in some instances (certain setups) this tool can still be useful.

I remember there would be posts (fairly regularly) regarding what to log. It took a fairly long time for that stuff to get settled. Nobody has written a "how to tune" in a long time (at least that I have seen), and much has changed over the last couple of years.

Just compare these two threads:

https://ls1tech.com/forums/pcm-diagnostics-tuning/84933-changed-ve-table-now-i-have-slight-hesitation.html

https://ls1tech.com/forums/pcm-diagnostics-tuning/149741-ve-table-cracked.html


I remember when the first thread started over a year ago. There were many people then that believed the VE tables had little or no impact. A year later, people are performing all kinds of statistical analysis trying to develop a formula for a VE calculation/correction.

Along time ago, ChrisB put up his tuning guide: http://ls1edit.slowcar.net. I think his basic steps still basically apply:
1. Set absolute parameters
2. Start car, verify
3. Tune idle
4. Tune part throttle
5. Tune WOT

Now, how to actually go about doing all of this, well ... that seems to be $50,000 question. The most frustrating thing to me is the lack of detail of relationships between the tables. This is where HP Tuners and Carputing could help out a lot.

Sent you a PM.

HumpinSS

iTrader: (1)

Since many people are making a living and feeding their children tuning it will be a long time before we see a comprehensive guide. Until then its trial and error...............