The PCM's flash is programmed through the diagnostic port - no more chips. GM tends to leave more on the table with trucks versus vettes and f-bodies. Notice the delay when you floor the H3 from a standstill? The WOT (wide open throttle) parameters for the H3 are more conservative than the vette's parameters (just look at WhiteH3's A/F ratio on the dyno plots from K&N), and there are some pretty big flow restrictions in the air path that contribute to the "blah" when you floor it. Because of these, the H3 likes to be eased into WOT. The torque management is pretty intrusive; the shift firmness and shift speed are pretty slow too. This is not intended to be a knock against the H3 - it was designed for a different purpose than the vette.
Here's one of my articles showing what be gained from tuning on a 345 HP Silverado SS truck (over 30 HP gain and at the wheels which would be much larger at the flywheel):
http://chevyhiperformance.com/techarticles/0508ch_obd/
I can only do about 15 - 18 HP gain on a stock 350 HP LS1 vette as a comparison.
There's plenty of HP left in other areas of the H3. For example, I have a custom throttle body that made a significant difference (in a much early post I thought there was not much to be gained from the TB - I was wrong). Along with a custom intake, the "blah" going into WOT is probably 80% gone. These two added over 30 BHP easily, and I'm getting about 1 MPG better. The exhaust is next.
For what you pay for an aftermarket programmer you can have a really good custom tune or buy a package like LS1 edit, HP Tuners, etc. and do it yourself after some research.
I've talked to the R&D heads at a few of the programming companies and they are not sure how much can be gained. I was told that early Colorados and Canyons had their PCM programming done overseas (maybe f5fstop can verify this) which makes the reverse engineering more difficult, but the H3's PCM was done somewhere else which makes it easier. This is just what I was told.
Here are some of the WOT fuel parameters that can be tweaked that you'll never be able to touch with an aftermarket programmer:
PE Enable
Enable MAP: This MAP value must be exceeded to enable PE mode
Enable MAP Hysteresis: This value is subtracted from the enable MAP value. If the MAP reading drops below this value then PE mode will be disabled.
Mode Delay RPM: PE mode is delayed if RPM is below this value.
PE Enable %TPS vs. RPM
Hot Power Enrich Enable %TPS Threshold vs. RPM: These tables defines the minimum TPS% vs RPM that the VCM requires to enter WOT and is required to enable PE mode. There are two tables labeled Hot and Cold that allows different thresholds depending on whether the coolant temperature has exceeded the Hot Select temperature (see below). If the coolant temperature exceeds the Hot Select temperature then the Hot table is used, otherwise the Cold table is used.
Cold Power Enrich Enable %TPS Threshold vs. RPM: These tables defines the minimum TPS% vs RPM that the VCM requires to enter WOT and is required to enable PE mode. There are two tables labeled Hot and Cold that allows different thresholds depending on whether the coolant temperature has exceeded the Hot Select temperature (see below). If the coolant temperature exceeds the Hot Select temperature then the Hot table is used, otherwise the Cold table is used.
Hot Select Temp: This value selects either the Hot or Cold TPS threshold table (see above).
Power Enrichment
V8 Power Enrich Fuel Multiplier vs. RPM: This is the main table that is used to tune WOT fuel for post 1999 V8 engines. The values in this table are Fuel/Air multipliers (or AFR divisors) ie. values greater than 1 are richer, values less than one are leaner. The values relate directly to the Stoich AFR and the resulting commanded AFR is Stoich divided by this PE multiplier. Eg. if the multiplier is 1.1 then the commanded AFR will be 14.7/1.1 or 13.36.
Power Enrich Fuel Adder vs. Coolant Temp: This table adds to the PE multiplier (above) in relation to engine coolant temperature (ECT).
Power Enrich Fuel Adder vs. Intake Air Temp: This table adds to the PE multiplier (above) in relation to inlet air temperature (IAT).
V6 Power Enrich Base vs. ECT: This table sets the base AFR for Power Enrichment on V6 engines. Note this is an AFR value, higher is leaner.
Power Enrich Fuel Adder vs. Throttle Position Sensor: This table adds to the base AFR in relation to throttle position. It is generally used to lean the fuel at smaller throttle settings.
Power Enrich Fuel Adder vs. RPM vs. Time: This table adds to the base AFR in relation to RPM and time in PE mode. It is used to provide additional RPM and time based enrichment and is similar to the PE vs RPM table on V8 engines, but with an additional time component. Remember, this value adds to the Base PE AFR so positive numbers here are leaner and negative numbers are richer.
Enrichment Rate: This is the rate at which Fuel is added to reach the desired enrichment value. The small this value is, the slower the VCM will reach the desired PE AFR.
Boost Enrich
These values are for 2bar or 3bar Speed Density packages.
Boost Enrich: This table is a Fuel/Air multiplier (just like the PE table) and referenced to MAP. The PCM will use the richer of this table and the PE table to determine fueling. It is useful for some supercharged and turbocharged engines where boost does not always correlate to RPM.
Enable Map: This is the minimum MAP to enable the Boost Enrich table. Additionally, above this MAP the engine will enter open loop.
MAP Hysteresis: This is the MAP hysteresis to disable the Boost Enrich table.
11-07-2005, 02:03 AM
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