My scan tool is reading 750 800 mv.How can I get it up in the 850-900mv range?What is the proper spark table to alter at wot?How is engine load calculated?I have an 87 350 gta bin.

 

Ummm... Your O2 sensor reading is 750 to 800 mv ????? If so, you can try just increasing fuel pressure to 'richen' up the injectors a bit which should get your air fuel ratio richer and get higher O2 sensor readings. You can also change this by 'lieing' to the computer and putting in smaller fuel injector rating figures than what you really have (ie. if you have 22lb injectors and put in 21.5 for the injector constants, the ECM will pulse the injectors as if they were 21.5lbers which essentially will richen your WOT air fuel ratio (and your open loop stuff). In my limited experience, I have found messing with the injector constants to be an easier way to tune than adjusting the rail pressure all the time... I use the constants to get me close and fine tune with the rail pressure...

FYI, your post is a little bit difficult to understand what exactly you are after....

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1987 GTA L98 MD8
355, TFS Heads, LT4 Hot Cam
My GTA

The Minnesota F-body Club

 

My fuel pessure is at 48 right now so
I'm trying to figure out what table will raise the mv a wot.The injector constant is set right.My blm and int are real close to 128.Actualy the tend to run 120 or so.A little rich is better than lean.But at wot I'm running a bit too lean.

 

Use the "WOT %Change Fuel/Air Ratio vs RPM" to increase/decrease your fuel in PE/WOT once you BLMs/INTs are all around 128 in normal part throttle cruise.

It sounds like you are very close but still a tad rich at part throttle. You could lean that just a tad and then concentrate on the table I mention above.

Just a warning, don't pay too much attention to the stock O2 sensor readings on these cars. The O2 sensor is a "switching type" designed to work around .450 volts. For WOT you need a WB O2 sensor to get accurate readings. It is the only type of O2 sensor that will give accurate readings during WOT (or Highway Mode for that matter if you are running > 16:1).

 

I would like a wideband o2 sensor but heard they are expensive.I looked at the site for building one.It looks ok but is everything in stock at radio shack?Right now I can tell if I'm lean by spark knock and reading the plugs.I have alot of exp with old trans ams.So I can tell when I'm running lean.I will end up making that wideband o2 sensor sometime (and an apillar a/f guage)but for now I'll get it close.Now another thing is the maf tables.I know I am not exceeding the 255 limit.But what should I do to those tables to reflect the airflow of a 400cid instead of 350?

 

Another important question,is it normal if your blm at cruise are around 128,then at idle the slowly creep up over 128.Then when I eccel from the stop it will go back to normal.

 

With MAF and a mild cam, you really shouldn't have touch the MAF Scalar tables, other than a "mild tweaking"...and most likely not even that. Actually, to quote Grumpy "MAF Scalar Tables are not for the faint of heart". So unless you ABSOLUTELY have to; don't.

To the MAF, air flow is air flow (except when it isn't). So if your are never maxing the MAF at 255 and your BLMs are reasonably close to 128, then all is fine. Concentrate on WOT now.

[This message has been edited by Glenn91L98GTA (edited October 29, 2001).]

 

I still have the lean blm at idle problem.Or is that just normal?Or is my fuel pressure too high.The other main question is the "how to add fuel at wot?".It seems to run lean 2400-3500 rpms.Is it lv8accel inrich factor vs delta lv8 or bpw fuel vs load?I do have the cruise blms set up good though.

 

The Table is defined in virtually all of the TDFs I have seen from TunerCat. Pretty standard table.

 

Sorry I'm a little dense sometimes.I ment to say how does it work.The higher the %Change Fuel/Air Ratio vs RPM percent the more fuel?Would a 12-15 pecent change around 4000+ be too much?I'm learning so bear with me please!And what about the blms at idle problem?

 

No problem, I figured you didn't pickup on the "Table within the quotes".

Yes, this table works by adding a %Fuel (or subtracting) from your Fuel flow based on the MAF Scalar Tables (MAF) or VE Tables (SD). This table is invoked whenever you go into PE (or WOT).

IF you had "perfect" MAF Scalar (or VE Tables for SD), then add various percentages would equate approximately to these AF Ratios:

8% = 13.52
9% = 13.38
10% = 13.23
11% = 13.08
12% = 12.94
13% = 12.79

But that would ONLY be if everything was perfectly 128/128 throughout the powerband at the highest load (without PE engaging).

So ONLY use this %Add = AF Ratio as a guide; not the definitive answer. You REALLY need a WB O2 sensor to get your real AF Ratio and if you Fuel Tables are far from perfect then these AF Ratios are meaningless.