....what would be your suggested method. I have read "work with the MAF table" and others say no "work with the injector table" ...now it certainly looks like both will work but what say you <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> I am running with a stock MAF with stock internals and after my header install have LTFTs of +5 to +8.

 

I'm no expert by any means, but on here the long argument about messing with the MAF table changes more than just airflow, like shifting with an A4 tranny. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> Doesn't seem like the Injector table would hurt anything else.

 

J&J, what are you using to monitor your A/F? Autotap or EFILive?

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by 2K T/A Driver:
<strong> J&J, what are you using to monitor your A/F? Autotap or EFILive? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Both <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> but A/F is not something that either software does properly..... you really need to use a wide band O2 for that.

<small>[ February 20, 2003, 05:55 AM: Message edited by: J&JsTA ]</small>

 

It doesn't sound like you should be too concerned at +5 as long as the LTFTs don't start creeping higher. As you trying to get negative?

 

For such small LTerms, you could probably use either table and it wouldn't effect anything abnormally. Just make sure you tune your WOT a/f again after the adjustment.

The people that get into trouble using the MAF table are the ones that are shifting the MAF table too much (like 20% or more).

Good Luck,
Kevin

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by eallanboggs:
<strong> It doesn't sound like you should be too concerned at +5 as long as the LTFTs don't start creeping higher. As you trying to get negative? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">At first I wasn't to concerned but I have soot all over the tips on the car and I have a slight black puff of smoke when I hit WOT and my O2s are averaging .920 at WOT as well.

<small>[ February 21, 2003, 08:44 AM: Message edited by: J&JsTA ]</small>

 

I've had good luck using the IFR tables. My Ltrims were similar to yours, after adding cold air. Suggest you muliply across the board by 90 for starters. You should be in range at that point and can go up or down. My cell 22 never goes to 0 if my ltrims are positive. If you want you can then tune by cell.

 

Great thx guys.... I figured I would start with 95% and sneak up on it <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> ... Still waitin for the snow to GO AWAY.... I'm gettin antzy <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />

 

My short answer is:

If your MAF is stock, stay away from the MAF table and use the Inector Flow Rate table. Your reported MAF data will be incorrect for other PCM calculations.

You can decrease the Injector Flow Rates by a certain percentage to take Ltrims more negative, or increase IFR values to make them mroe positive.

Now for the long answer:

I acutally use what I consider to be a more intelligent and info-building technique.

To make myself clear, I will try to do a little timeline style explanation:

First, let me say JAS showed me this way, so I didn't think it up.
I think it has worked well.

Originally, my LTrims were like 20/25 left and right.
I had adjusted MAF table to zero/negate LTrims. But, based on arguments, believed this to invalidate/make inaccurate, my MAF Air Flow Rate readings.

I changed the MAF table back to stock.

Pull up John Skiba's Inj Calc Lite from my site with my final values entered in:

http://www.blackls1ta.com/tools/JohnsInjectorCalc.xls

You will be able to modify the fields I talk about.

Here's about where I started, based on the thinking that I had
42# SVO Injectors tested at 39.6 PSI running 56 PSI Fuel Pressure at the rail (just my FP Gauge reading). (My Inline pump drops me from 58 to about 55 or 56, but when I hit boost, when I first got it, it would raise fuel back to 55 or 56.)

To reflect/follow along with what I had in the spreadsheet, do these changes:

Change the:
"Tested Injector Flow Rate" (hereafter called IFR) = 42.
"Injector Test Pressure" (ITP) = 39.6
"New Fuel Pressure to be used" (FP) = 56

That gave this range:
6.29......6.88, but we knew this was too much due to LTrims and other monitoring.

(The Ltrim #'s I am about to give you are approximations to show the trend... I don't want to go back thru all those logs.)

Ltrims were, say, +15 or so.
That meant (after I'd checked/eliminated all leaks) the injectors either:
1. were not really 42's tested at 39.6
or
2. weren't performing up to par
or
3. my fuel pressure at the rail was lower than what I had previously observed.
or
4. I had some leaks, malfunctions, etc.

We changed ITP to 43.5 and got a range of 6.00 ... 6.57.
LTrims were still positive, though the decreased some.

Then we looked at Fuel Pressure and dropped the FP down to 52, then 50, then 48... all the way to 46 before we got consistently negative Ltrims at all speeds (and zeroing out at WOT).

Well... I checked my pressure more carefully, and indeed, it was less at boost than when I'd first began Forced Induction.
I was seeing about 51 or 52 PSI at the rail (pump may need overhaul after a mishap related to the pump I won't go into right now). As a matter of fact, I think since we started tuning a few weeks ago, it has actually dropped from about 53 to 51. Either my in-tank or the Aeromotive is weakening, we think.

STILL, however... 46 PSI in the spreadsheet did not account for 42# Inj, tested at 43.5 and 51 to 52 PSI rail pressure.

John had me grab the part# off the injector and we both located, almost simultaneously, an injector rating document
http://www.powerpage.dk/produkter/pic/injectors.pdf
(do a search on "280 150 558"), giving the injector specs at 418 cc/m. That converted to only 39.8 lb/hr capacity.

Now substitute
IFR = 39.8
ITP = 43.5
FP = 51
That gave 5.43 ... 5.94 range of Inj Flow Rate values

Ltrims zero'd at all speeds (sometimes a bit positive when I bump it to neutral) but they are about -2.3 to -8.3 depending on my speed, %TPA, and maybe some other factors.

Do you see how this approach actually helped us detect a problem that had slipped by me?
I'd rather approach it this way and learn, than just bump it up and down by some percentage. That should work, but may not reveal some things similar to what I encountered.

Of course, a pro tuner may not need this reassurance...

Great question and I hope I was clear (though a bit long).

<small>[ February 21, 2003, 09:08 AM: Message edited by: Black LS1 T/A ]</small>