Datamaster for AFR Data?
11-13-2007, 12:22 PM
#1
Datamaster for AFR Data? Ok, guys sorry for beating a dead horse as I am sure you have answered this question many times but here we go again:
I recently did some modifications to my PCM tune by using Catstuner and it worked great, but I think I am still running a little too rich. I was wondering if the datamaster program will record enough to get a generic idea of the AFR as I don't wanna spend all the money for a separate wide band O2? If I record a session and post it up or email it to someone will you be able to tell where my prob lies? Here is some generic info on my motor setup:
95 LT-1 OBDI
383 Eagle Stroker kit
Not sure on compression but I think it is 10.5 or 11:1
Cam is comp cams 276-HR-14 xtreme energy
and 44 fpsi w/30# SVO Injectors
Let me know what I need to do and if datamaster will give me the info I need?
FYI - I have also attached my bin file from the programming if you have any input there as well?
I recently did some modifications to my PCM tune by using Catstuner and it worked great, but I think I am still running a little too rich. I was wondering if the datamaster program will record enough to get a generic idea of the AFR as I don't wanna spend all the money for a separate wide band O2? If I record a session and post it up or email it to someone will you be able to tell where my prob lies? Here is some generic info on my motor setup:
95 LT-1 OBDI
383 Eagle Stroker kit
Not sure on compression but I think it is 10.5 or 11:1
Cam is comp cams 276-HR-14 xtreme energy
and 44 fpsi w/30# SVO Injectors
Let me know what I need to do and if datamaster will give me the info I need?
FYI - I have also attached my bin file from the programming if you have any input there as well?
11-13-2007, 02:12 PM
#2
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I wrote this yesterday in an email to someone, we were talking about tuning an LT1. Might help you out here...
You have a couple of different 'stages' of fueling (well, several, but...). Just driving around (which is what we do most of the time) is driven by the long term fuel trims (Left and Right LTFT aka BLMs). These are numbers that go from 108 to 160, depending on how the PCM views the O2 sensors. If the tendency is that the PCM thinks the engine is running lean, it'll start to add fuel, and pushes the BLM to 160 max. If the pCM thinks the engine is running rich, it'll start to take out fuel, and pushes the BLM to 108. To ride between these rails is OK, the PCM is supposed to do that. To ride on the rail is bad (if you see your BLM stuck at 160 or 108). Ideally, you want it just below 128 (I prefer the 115-122 range). You can get it there a number of ways, tweaking the fuel injector constant is one easy way, or you can tweak the mass air flow meter calibration values. That gets you closer in "overall" fueling, but for detail work (specific RPM ranges) you can work the Volumetric Efficiency tables. Your lower RPM loading up can be reduced by going in to the VE table, reducing the VE number by a percentage (say multiply table values from idle to 2200 RPM by 90%), and then go drive the car around, and watch the long term fuel trims. If your fuel trims are split by a difference of 10 or more, you may have a bad O2 sensor, an exhaust leak, or something else going on. You don't want your fuel trims split by more than 10 (say, for example, you have a 120 on the left side and a 160 on the right... what that tells me is that the PCM is detecting a lot of oxygen on the right side - which means you'd probably have an exhaust leak on the right side that is screwing up the O2 sensor reading).
Wide Open Throttle fueling is typically accomplished by modifying the PE vs RPM table (Performance Enrichment vs. RPM). The O2 sensors can't really be used for this. This is where a wideband O2 sensor comes in. Stock O2 sensors (narrowband) cannot be used to determine any fuel ratio other than 14.7:1 (at 450 mV). Anything else is just a guess. Above 450 is 'rich', below 450 is 'lean'. Some people use ~920 mV at WOT as a guideline for a 'reasonably safe AFR' on NA motors for WOT performance. But it's still just a guess, and is not guaranteed to be any specific "good or bad" AFR.
This is just how I perceive things, others will have their own interpretations as well. Keep in mind that these are the words of an internet expert and how I tuned my own car. I am not a professional tuner, your mileage may vary, please keep hands and feet inside the car at all times, and make sure your tray tables are stowed in an upright and locked position...
You have a couple of different 'stages' of fueling (well, several, but...). Just driving around (which is what we do most of the time) is driven by the long term fuel trims (Left and Right LTFT aka BLMs). These are numbers that go from 108 to 160, depending on how the PCM views the O2 sensors. If the tendency is that the PCM thinks the engine is running lean, it'll start to add fuel, and pushes the BLM to 160 max. If the pCM thinks the engine is running rich, it'll start to take out fuel, and pushes the BLM to 108. To ride between these rails is OK, the PCM is supposed to do that. To ride on the rail is bad (if you see your BLM stuck at 160 or 108). Ideally, you want it just below 128 (I prefer the 115-122 range). You can get it there a number of ways, tweaking the fuel injector constant is one easy way, or you can tweak the mass air flow meter calibration values. That gets you closer in "overall" fueling, but for detail work (specific RPM ranges) you can work the Volumetric Efficiency tables. Your lower RPM loading up can be reduced by going in to the VE table, reducing the VE number by a percentage (say multiply table values from idle to 2200 RPM by 90%), and then go drive the car around, and watch the long term fuel trims. If your fuel trims are split by a difference of 10 or more, you may have a bad O2 sensor, an exhaust leak, or something else going on. You don't want your fuel trims split by more than 10 (say, for example, you have a 120 on the left side and a 160 on the right... what that tells me is that the PCM is detecting a lot of oxygen on the right side - which means you'd probably have an exhaust leak on the right side that is screwing up the O2 sensor reading).
Wide Open Throttle fueling is typically accomplished by modifying the PE vs RPM table (Performance Enrichment vs. RPM). The O2 sensors can't really be used for this. This is where a wideband O2 sensor comes in. Stock O2 sensors (narrowband) cannot be used to determine any fuel ratio other than 14.7:1 (at 450 mV). Anything else is just a guess. Above 450 is 'rich', below 450 is 'lean'. Some people use ~920 mV at WOT as a guideline for a 'reasonably safe AFR' on NA motors for WOT performance. But it's still just a guess, and is not guaranteed to be any specific "good or bad" AFR.
This is just how I perceive things, others will have their own interpretations as well. Keep in mind that these are the words of an internet expert and how I tuned my own car. I am not a professional tuner, your mileage may vary, please keep hands and feet inside the car at all times, and make sure your tray tables are stowed in an upright and locked position...
