Tuning out high idle from cold start?

SilverSurfer18 · 09-22-2021, 10:13 AM

Is it possible to tune this out? Ive heard this is to warm the cats but i dont have any, anymore so i am wanting to turn this off. Sounds like crap and i have tried 3 different exhaust setups and none of them sound good at start up. Thanks!

Gunkk · 09-22-2021, 11:25 AM

5-10 seconds of high idle is useful to build oil pressure to flow lubricant to the top of the engine, fill lifters, bearings, journals, etc. So I would keep the high RPM part of the cold start.

You'll likely want to tune out the RICH part of the high-idle @ cold start, which lights off the cats the car no longer has.

Megahurtz · 09-22-2021, 11:37 AM

Disable cat warmup in HP Tuners. All you have to do is change the temp settings to a value the car will never see. This will remove the Catwarmup where the timing gets pulled negative and the car gets really loud. You will still have the normal higher idle which is necessary to get the oil and coolant flowing, but it will be far less noticeable noise-wise. There is no need to change fueling. The cat warm up is done by allowing the combustion event to complete while the exhaust vales are open, shooting much hotter gas directly into the cats. You need the richer startup on a cold engine as cold pistons don't light off stoich (14.1/14.7) very well until they get a little heat in the combustion chamber.

MakCamaro · 10-14-2025, 07:23 AM

Apologies for reviving this thread, but it seems the Exhaust tab that included the Max and Min ECT fields that had to be modified for the purpose of eliminating the cold start "bark" is not available in the VCM Editor any more (due to emission regulations it seems). Even in the beta version of the VCM Editor, despite the fact that the Exhaust tab is there, the Max and Min ECT fields are not there any more. Therefore there doesn't seem to be a way to eliminate the cat warmup in HP Tuners in order to quiet down the cold start "bark".

Is there any other way to do that by changing some other tables by any chance? Can these Max and Min ECT fields be found somewhere else in the VCM Editor?

KingLT1 · 10-14-2025, 06:58 PM

Not that I know of. Afaik, this can only be done on 2016-21 cars with a older variant of HPt 4.x. maybe Jason aka Megahurtz has a workaround. You can play with the torque model some to keep the timing from going negative on cold start. That is what makes the engine loud.

6spdhyperblue · 10-14-2025, 07:20 PM

Quote:

Originally Posted by KingLT1

Not that I know of. Afaik, only this can only be done on 2017-21 cars with a older variant of HPt 4.0. maybe Jason aka Megahurtz has a workaround. You can play with the torque model some to keep the timing from going negative on cold start. That is what makes the engine loud.

Was there issues with 2016s and this setting?

KingLT1 · 10-15-2025, 10:58 AM

Quote:

Originally Posted by 6spdhyperblue

Was there issues with 2016s and this setting?

no it was a typo.

MakCamaro · 10-17-2025, 04:47 PM

It seems that they removed most settings that have to do with exhaust parameters due to emissions regulations in the US. I contacted them to ask if they would open these settings for me, considering that my car is imported and licensed in the UK, but they don't want to do that.

Megahurtz · 10-18-2025, 10:20 AM

The cold start "bark", assuming you're talking about the half second rev up in RPM's when you start and NOT the cat warmup where it stays loud for about 20 seconds.

The bark is controlled by Startup Airflow tables.

MakCamaro · 10-18-2025, 10:27 AM

Yes that's what I am talking about. As far as I know though, the "bark" is part of the cat warmup.

Don't take me wrong, I like my car to be loud! I simply want to be able to quiet it down when I park it in certain places, out of respect to my neighbours - I replaced the stock exhaust with an AWE Touring and I lost functionality of the active exhaust.

Can you tell me what exactly to change?

RobZL1 · 10-18-2025, 05:00 PM

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.

MakCamaro · 10-18-2025, 05:14 PM

Apologies, I am not familiar with this and I don't want to do any changes if I don't know exactly what I am about to do. Thank you very much for clarifying.

RobZL1 · 10-18-2025, 09:58 PM

My bad. No bad vibes intended. Since you were talkng cat lightoff and hp tuners, I made some assumptions.

MakCamaro · 10-19-2025, 02:37 AM

No worries. I appreciate the explanation

09-22-2021, 10:13 AM	#1
SilverSurfer18 Drives: 2021 1SS Camaro Join Date: Nov 2018 Location: Tulsa Oklahoma Posts: 121	Tuning out high idle from cold start? Is it possible to tune this out? Ive heard this is to warm the cats but i dont have any, anymore so i am wanting to turn this off. Sounds like crap and i have tried 3 different exhaust setups and none of them sound good at start up. Thanks! __________________ 2021 Wild Cherry 1SS, LT2 Intake, Rotofab, Borla S-Type, Texas Speed longtubes, SMG flex fuel sensor, GPI Tuning, Bronze 1LE replicas

10-14-2025, 07:23 AM	#4
MakCamaro Makis Drives: 2020 Red Hot ZL1 A10 Join Date: Apr 2019 Location: London - UK Posts: 813	Apologies for reviving this thread, but it seems the Exhaust tab that included the Max and Min ECT fields that had to be modified for the purpose of eliminating the cold start "bark" is not available in the VCM Editor any more (due to emission regulations it seems). Even in the beta version of the VCM Editor, despite the fact that the Exhaust tab is there, the Max and Min ECT fields are not there any more. Therefore there doesn't seem to be a way to eliminate the cat warmup in HP Tuners in order to quiet down the cold start "bark". Is there any other way to do that by changing some other tables by any chance? Can these Max and Min ECT fields be found somewhere else in the VCM Editor? __________________ Red Hot 2020 Camaro ZL1 A10 <-- Enjoying the hell out of it Mosaic black 2018 Camaro 2SS A8 (sold)

10-14-2025, 06:58 PM	#5
KingLT1 Drives: 2016 1SS NFG A8 Join Date: Aug 2017 Location: 46804 Posts: 7,560	Not that I know of. Afaik, this can only be done on 2016-21 cars with a older variant of HPt 4.x. maybe Jason aka Megahurtz has a workaround. You can play with the torque model some to keep the timing from going negative on cold start. That is what makes the engine loud. __________________ 2016 NFG SS A8/Whipple 2.9/Fuel System/Flex Fuel Last edited by KingLT1; 10-15-2025 at 11:00 AM. Reason: typo

10-17-2025, 04:47 PM	#8
MakCamaro Makis Drives: 2020 Red Hot ZL1 A10 Join Date: Apr 2019 Location: London - UK Posts: 813	It seems that they removed most settings that have to do with exhaust parameters due to emissions regulations in the US. I contacted them to ask if they would open these settings for me, considering that my car is imported and licensed in the UK, but they don't want to do that. __________________ Red Hot 2020 Camaro ZL1 A10 <-- Enjoying the hell out of it Mosaic black 2018 Camaro 2SS A8 (sold)

10-18-2025, 10:20 AM	#9
Megahurtz Snackbar Tuning Drives: 2023 SGM ZL1 Join Date: Oct 2016 Location: Florida Posts: 1,513	The cold start "bark", assuming you're talking about the half second rev up in RPM's when you start and NOT the cat warmup where it stays loud for about 20 seconds. The bark is controlled by Startup Airflow tables. __________________ GM Gen V Calibrator

09-22-2021, 11:25 AM	#2
Gunkk Thank you Al Oppenheiser! Drives: Red Hot A10 ZL1 Convertible Join Date: Jun 2017 Location: Sarasota, FL Posts: 5,156 View My Garage	5-10 seconds of high idle is useful to build oil pressure to flow lubricant to the top of the engine, fill lifters, bearings, journals, etc. So I would keep the high RPM part of the cold start. You'll likely want to tune out the RICH part of the high-idle @ cold start, which lights off the cats the car no longer has.

09-22-2021, 11:37 AM	#3
Megahurtz Snackbar Tuning Drives: 2023 SGM ZL1 Join Date: Oct 2016 Location: Florida Posts: 1,513	Disable cat warmup in HP Tuners. All you have to do is change the temp settings to a value the car will never see. This will remove the Catwarmup where the timing gets pulled negative and the car gets really loud. You will still have the normal higher idle which is necessary to get the oil and coolant flowing, but it will be far less noticeable noise-wise. There is no need to change fueling. The cat warm up is done by allowing the combustion event to complete while the exhaust vales are open, shooting much hotter gas directly into the cats. You need the richer startup on a cold engine as cold pistons don't light off stoich (14.1/14.7) very well until they get a little heat in the combustion chamber.

10-18-2025, 10:27 AM	#10
MakCamaro Makis Drives: 2020 Red Hot ZL1 A10 Join Date: Apr 2019 Location: London - UK Posts: 813	Yes that's what I am talking about. As far as I know though, the "bark" is part of the cat warmup. Don't take me wrong, I like my car to be loud! I simply want to be able to quiet it down when I park it in certain places, out of respect to my neighbours - I replaced the stock exhaust with an AWE Touring and I lost functionality of the active exhaust. Can you tell me what exactly to change? __________________ Red Hot 2020 Camaro ZL1 A10 <-- Enjoying the hell out of it Mosaic black 2018 Camaro 2SS A8 (sold)

10-18-2025, 05:00 PM	#11
RobZL1 fo'shizZL1 Drives: 2017 ZL1 Join Date: Aug 2017 Location: ATL Posts: 1,805	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. __________________ 2017 ZL1 M6 Black \| Maggie 2650 // 103TB // Big Gulp // CSP LT's & Ultra Cats // BMR MM // BC Forged KL13 Mods being installed- oil pump, cam, ported heads, dual in-tank, Goliath and XDI, corn, etc., etc.

10-18-2025, 05:14 PM	#12
MakCamaro Makis Drives: 2020 Red Hot ZL1 A10 Join Date: Apr 2019 Location: London - UK Posts: 813	Apologies, I am not familiar with this and I don't want to do any changes if I don't know exactly what I am about to do. Thank you very much for clarifying. __________________ Red Hot 2020 Camaro ZL1 A10 <-- Enjoying the hell out of it Mosaic black 2018 Camaro 2SS A8 (sold)

10-18-2025, 09:58 PM	#13
RobZL1 fo'shizZL1 Drives: 2017 ZL1 Join Date: Aug 2017 Location: ATL Posts: 1,805	My bad. No bad vibes intended. Since you were talkng cat lightoff and hp tuners, I made some assumptions. __________________ 2017 ZL1 M6 Black \| Maggie 2650 // 103TB // Big Gulp // CSP LT's & Ultra Cats // BMR MM // BC Forged KL13 Mods being installed- oil pump, cam, ported heads, dual in-tank, Goliath and XDI, corn, etc., etc.

10-19-2025, 02:37 AM	#14
MakCamaro Makis Drives: 2020 Red Hot ZL1 A10 Join Date: Apr 2019 Location: London - UK Posts: 813	No worries. I appreciate the explanation __________________ Red Hot 2020 Camaro ZL1 A10 <-- Enjoying the hell out of it Mosaic black 2018 Camaro 2SS A8 (sold)

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