LT1 8051 tip-in lean? Anybody had success curing it?

[sherlock9c1]

One clarification - The area where I need to make the biggest drivability improvement is during clutch engagement with a cold motor. Once the motor fully warms up, the stumble is mostly gone.

Okay so I looked in TunerPro; give me some pointers here:
PE Enable Min MAP is set to 15kPa - I'll look at the logs and see if I can leave this value as-is.
PE mode Coolant temp boundary is set to 151C, so only the cold mode tables are used.
PE enable TPS vs. RPM is set to 66% from 0-2800rpm - seems like I should drastically lower this for 0-1200rpm, and that way I can allow PE when coming off idle but not engage PE during part-throttle cruise.

Am I on the right track?

Anybody used both modes successfully on an LT1?

[sherlock9c1]

So I spent some time looking at data logs and came up with 9kPa as the MAP threshold and a TPS threshold of 3% for 0-1200rpm. My goal is to get the PCM to go into PE mode as quickly as possible when the driver presses the gas pedal, but only in the idle/clutch engagement area. I'll probably get another opportunity to tune it in a couple of weeks (are supercharged cars ALWAYS science projects?) and will report back.

[lionelhutz]

The "pump shot" part of $EE is stil unknown.

It might work having the %TPS very low just in the 0-1200rpm range to hit PE mode quickly but then it might start jumping in and out of PE mode a bunch when driving.

I'm not convinced the %TPS tables are what they're labelled. I found that using 20% TPS kept the engine in PE mode when cruising even though the actual %TPS was below 20%.

[sherlock9c1]

Thanks for the tip. Wouldn't surprise me. I did a lot of transmission tuning in Tunercat awhile back and their "max line pressure (psi)" scalar is completely mislabeled, as are the units for their main and extended line pressure. I'd see people raise that scalar with no concept of how it really worked. :)

[Maxzillian]

This would be for a 96-97 PCM, but there was a MAF adder table referenced to TPS that I found worked as an acceleration pump. Using this table, if I recall correctly, I was adding up to 5 to 10 gm/sec dependent on throttle position and tweaking this table had an effect on tip-in.

[lionelhutz]

Care to provide a bit of insight into what you found the line pressure scalar/units mean?

You can put 0% TPS into certain parts of the %TPS for WOT table to run open loop in those parts. Others have done it below 1200rpm to run open loop at idle. You then put 0 for the PE AFR vs rpm table in the same rpm are so the AFR is correct. You might want to play with that and then change the VE table area that is reached at tip-in to see if open loop works any better.

[Rocko350]

Sherlock,

Have you locked the car in open loop and calibrated the MAf sensor table using afr error and a wideband? Yes they take quite some time to do properly. Have you looked at a higher ratio fuel pressure regulator.

Chris

[sherlock9c1]

Chris, it's next on the list. The car is currently down for some repairs (who knew forced induction cars could be such science projects!?). Once it's back online, that's the next step.

On the line pressure question, without cluttering this thread, the TunerCat units as of mid 2014 are wrong - it's not PSI, it really should be defined as "max line pressure threshold (counts)." The rest of the transmission tables simply add together their counts which then is translated into a duty cycle to the electronic pressure control solenoid based on the percentage value relative to the scalar. Thus, raising the max line pressure scalar actually has the opposite effect - it actually causes a lowering of pressures across the board except when the total line pressure adders equal or exceed this value. I'll make a thread about it soon.