[Megahurtz]

Cat Warmup and the startup "bark" are two different things. And are two different things in the tune.

Bark = The quick Rev up on startup. It lasts about half a second.

Cat Warmup = Right after the bark, the car pulls ignition timing and does a double pulse DI injection to "warm up" the cats. This specific timing, fuel and valve events make the car very loud during the 20-30 second window.

The Bark can easily be adjusted as I mentioned above. But the Cat Warmup cannot depending on the model year of your car. HP Tuners removed the wat warmup adjustment tables on 2018+ vehicles. Well technically they did it for all Gen V ECU's and newer, but some of the 2014-2017 models can still be edited using an earlier version of HP Tuners. Otherwise you need a custom User Defined Table now to be able to edit the Cat Warmup.

Strange thing is, HPTuners left this function in all Gen 3 and Gen 4 ECU vehicles. I'm guessing the EPA came after them on the Gen V stuff only. The irony is that I tune other vehicle brands than American, and the Cat Warmup tables are defined and usable even on the latest 2026 models.

[MakCamaro]

Originally Posted by RobZL1

I think he just did. Startup airflow. Reduce it in the left columns. Maybe copy the 1.0second column into the 0.0 and 0.5 columns to start.

Originally Posted by Megahurtz

Cat Warmup and the startup "bark" are two different things. And are two different things in the tune.

Bark = The quick Rev up on startup. It lasts about half a second.

Cat Warmup = Right after the bark, the car pulls ignition timing and does a double pulse DI injection to "warm up" the cats. This specific timing, fuel and valve events make the car very loud during the 20-30 second window.

The Bark can easily be adjusted as I mentioned above. But the Cat Warmup cannot depending on the model year of your car. HP Tuners removed the wat warmup adjustment tables on 2018+ vehicles. Well technically they did it for all Gen V ECU's and newer, but some of the 2014-2017 models can still be edited using an earlier version of HP Tuners. Otherwise you need a custom User Defined Table now to be able to edit the Cat Warmup.

Strange thing is, HPTuners left this function in all Gen 3 and Gen 4 ECU vehicles. I'm guessing the EPA came after them on the Gen V stuff only. The irony is that I tune other vehicle brands than American, and the Cat Warmup tables are defined and usable even on the latest 2026 models.

Thank you both, much appreciated. When you say "Startup Airflow" I assume that you are referring to the "Cranking Base Airflow", found in Engine -> Airflow -> General -> Cranking Airflow and Torque -> Base Airflow? If yes, then today I had the opportunity to work on my stock file and made the following changes, as suggested by RobZL1:

The first screenshot shows the Stock Crank Base Airflow table and the second one shows the modified "Low Bark" Crank Base Airflow table.

If this what you are suggesting, then I can write the new file containing the modified "Low Bark" Crank Base Airflow table to my car and see how it sounds. Maybe I can even copy the values of the 4th column (1.5s) to the first three (0s, 0.5s, and 1s). Should I be aware of any issues?

[Megahurtz]

I wouldn't do it that way. I would copy the stock values from 0.5 column to the 0.0 column and then interpolate between column 0.0 and 1.0.

Your screenshots will likely cause a stumbling rough sort of startup, especially when warm. You need to just reduce the bark, not eliminate it.

All of that said, test it and find out. Don't be scared.

[MakCamaro]

Thanks. This is what I prepared. I will write it to the car some time this week and will let you know.