What am i looking for when using the OBD II??? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 08-03-2004, 06:17 PM   #1
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Default What am i looking for when using the OBD II???

i have seen a lot of posts on using Auto-Tap, the OBD'*, etc. what should i be looking for? how can i use the data to determine if i need a colder t-stat, or a smaller pulley, etc. if not for these reasons (i.e. better tuning), why are you all talking so much about it? What is the point?
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Old 08-03-2004, 06:55 PM   #2
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Some of the big ones are your KR counts o2 sensor readings, and Intake temperature.
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Old 08-03-2004, 06:57 PM   #3
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okay, what can i do about them when there out of norm . . . .and what would be the norm?
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Old 08-03-2004, 07:03 PM   #4
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A LOT of GP guys use Autotap. Check out a state website like ILCGP, MNCGP etc, the big one will be a PITA.

Basically the more knock you have, the more dangerous it is to drive/mod the engine. Many mods are devoted to eliminating knock. Knock robs power, and true knock is caused by detonation in the cylinders. If you're reading a lot of KR, you'll want to use that information, and some trouble shooting to get rid of it. You can also use it to find your limits on mods before an IC, etc.

O2 readings are key to see how Rich or lean your car is running. This is important once you start doing things like a Cam, Rockers, Nitrous, blower upgrade, fuel system upgrades.

Intake temps are important if you're trying to build a CAI. If you're within 10 degrees of ambient that'* a good start usually.

There'* no book on this, you just use it when you want to know exactly what you're doing.
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Old 08-03-2004, 07:09 PM   #5
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What kind of mods can i do to reduce KR?

What do i do if i am running too rich or too lean? which means i can install a smaller pulley?
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Old 08-05-2004, 12:13 AM   #6
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The only way to reduce KR is to eliminate the hot spots in the cylinders or use harder to detonate gas (higher octane). The best way to reduce hot spots in the cylinders is to flow the air better. By removing hotter air (combusted) out quickly and efficently (by rockers, cam, headers, better exhaust) you keep the cylinder walls cooler. By cooling the intake charge (intercooler, better air intake, larger pulley) you keep the cylinder walls cooler.

Basically you want to let the engine breath better while forcing as much air through it (more boost) as possible maintaing a 0 to very low knock threshold.

An autotap can help you gauge the effectiveness of mods and their performance.

Your first step is to scan the as is for KR. You probably have some. Your second step is make a plan to remove that KR. Depending on budget and how far you want to go you will most likely want to do rockers to open the exhaust up, a good air intake and an INTENSE PCM to remove all the TM crap.
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Old 08-08-2004, 07:28 PM   #7
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TM Crap????

What is that?
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Old 08-08-2004, 07:35 PM   #8
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Torque Management
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Old 08-08-2004, 08:25 PM   #9
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What TM stuff do i need to remove?
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Old 08-09-2004, 12:41 AM   #10
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Quote:
Originally Posted by Xac Xado
What TM stuff do i need to remove?
Depends on your mods and if you take it to the track. There are a ton of tables in the PCM that tell the Bonnies to pull timing for various reasons. I found a few at Norwalk this weekend. For instance, 30 seconds of complete timing pull after an exagerated burnout. Not much fun launching with 3 degrees of timing :(
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