OK, I've just now started to learn how to create my own custom EPROMs so please excuse what may appear to be stupid questions.

Background: I've already purchased the pocket programmer, a UV eraser, downloaded tunercat with the $42 calibration file. I have read many articles on burning custom chips and 3 books on EFI. Also, I have the factory, 'custom' CarPro, SLP, and Hypertech memcals. I've pried off the EPROM from the Hypertech memcal and have used the procket programmer to read and save the BIN file.

Now for my questions:
1) Because I have disabled the 9th fuel injector (no provision for it on my Superram), the engine is hard to start. I need more fuel for startup. What table or tables should I begin to modify?

2) My scanner tells me that I am running a little lean at WOT, about 825mV on the O2 sensor. I believe that the engine needs about 5 to 10% more fuel. I am maxed out on fuel pressure. What table or tables do I modify in this case to get more fuel only during WOT runs?

TIA

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'87 L98 TPI IROCZ, AFR190 heads, 3.70 gears, ZZ9 cam, 2400 Art Carr TC, SLP 1 3/4" headers, SLP cat-back, no cat, no AC, no MAF screens, Accel manifold base & SuperRam, Edelbrock double roller timing chain, MSD ext coil & distributor, trans cooler, 52mm TB with airfoil, TB coolant bypass, AFPR(58psi), K&N filters, Hotchkis lowering springs, Car-Pro custom chip, Lay Ind. ram air kit, 265/45R16 Kumho V700 tires.
ET 13.39sec @ 107.21mph
'90 Eagle Talon AWD, no rust thru 9 winters
'99 Camaro SS, red, 6-spd, T-tops, Mcleod clutch, Pro 5.0 shifter, MAF processor, Direct Flow airlid, K&N filter.
313.7Hp & 320.6ft-lbf, ET 13.55sec @ 105.1mph
next mod: 4.10 rear gears

 

For question #1, you'll need to add fuel to the "Open Loop Fuel/Air Ratio %Change Vs. Coolant Temp" table. If you get the $6E tdf file, download the ARAP bin (or any other '89 bin) and look at this table to give you an idea of what the values should be.

For question #2, there are 2 tables to modify, depending on if you're lean the whole time or just at certain rpms. If it's lean throughout the whole revband, then you'll want to modify the "WOT %Change To Fuel/Air Ratio Vs Coolant Temp" table, but only at the coolant temps that you normally run at when you're engine's warmed up. If you're running lean on in certain parts of your revband, you can modify the "WOT %Change To Fuel/Air Ratio Vs RPM" table. Have fun!

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Greg Westphal
'87 IROC 305TPI/A4

 

I would recommend first starting with ARAP bin. I wouldn't even bother doing a compare ... just start with the ARAP base image. The ARAP bin is $6E and already has the cold start fuel worked into the standard tables (since $6E did not use the cold start injector). Second, more of a question ... how do you know that you are running lean?

Tim

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• Program your own PROMs!. Read my article to get started!
• Research and Experiment before asking questions.
• This is not a chip store. Go to the classifieds if you want someone to sell you a chip or give you a BIN.

TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

Doc, the O2 sensor on these cars are not accurate. The best way to determine if you are "rich or lean" is to set the BLM to 128 (min and max) and then watch the INT value only. You will need to get the car into closed loop, so you may have to alter the "timer".

I rely on the locked BLM and using the INT to determine the changes to my fuel tables.

 

>I rely on the locked BLM and using the INT >to determine the changes to my fuel tables.

How much does the ECM use the O2 sensor for feedback ? Is the INT based on that or is that the difference in commanded A/F ratio vs. calculated A/F ratio ?

Paul

 

thanks for all of the replies.

I just received the $32B calibration (definition) file from Tunercat, so I can get busy learning what I need to know and experiment one step at a time.

 

TRAXION & Glenn,

I have an XP240 scanner. With different heads and cam, the car seemed to run best and have lower ETs when the scanner showed 880mV for the O2 sensor during WOT runs.

The scanner may be off (I read that it reads 10% high, but my scanner may be different) and the O2 sensor may be off. I take the number 880mV as a relative number. Higher than 880, the car slowed down, while lower than 880, the car slowed down.

I do intend to use a digital voltmeter to read the O2 sensor output and compare to my scanner. Also, I'm going to buy a good air/fuel meter this Spring to ad my tuning effort.

 

doc,

The main point is that you cannot rely on O2 for determining if your car is running at the best AFR. A LOT of people do it ... he11, I was doing it for awhile. I strived for around the same O2 millivolts yet found later that the car was running rich (checked the plugs and pulled the heads). The best way is to just check the plugs or to use a Wide Band O2.

Tim

------------------

• Program your own PROMs!. Read my article to get started!
• Research and Experiment before asking questions.
• This is not a chip store. Go to the classifieds if you want someone to sell you a chip or give you a BIN.

TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org