De-tuning the LT4

Sephx1 · 06-21-2023, 11:29 AM

Odd title, I know

I’m planning on taking my car to a NASA club event soon where there is a 103db sound limit at 50ft. My car has headers, intake, ethanol, cam, 9.25” lower pulley and 3” Borla S-type NPP. I have Gesi 2 HO cats that have V-band clamps at each end and can be swapped for delete pipes. I usually run the delete pipes at the track.

I’m not only concerned about exceeding the noise limit but also when I run slicks on E60 the clutch seems to slip in lower gears under hard acceleration. Dyno numbers on E is 706 hp/745tq. The hp/tq gains are nice, but not necessary to run a good lap on the track. My thought is this:

Remove 9.25” pulley and run stock size pulley. Leave cats on for sound reduction. With reduced boost and cooler ethanol temps cats might survive one track day. Running at Sonoma so should be cool weather.

Thoughts?

Vtor_ZL1 · 06-21-2023, 11:54 AM

Turn down aimed away from mic location ?

20Bluezl1 · 06-21-2023, 12:01 PM

Get some Laguna pipes made like I made.

Sephx1 · 06-21-2023, 12:18 PM

Quote:

Originally Posted by 20Bluezl1

Get some Laguna pipes made like I made.

Good suggestions on the turn downs, but I’m looking for a quick solution. Wondering if the pulley change would work. I should still have plenty of hp for the track.

Keko · 06-21-2023, 12:35 PM

If a clutch is slipping it will start in the higher gears, not the lower gears, since there is more load on it. Are you sure it's not wheelspin or TC/PTM settings?

L78toLT1 · 06-21-2023, 01:28 PM

Based on your mods, your car should be just about identical to mine dB wise. I have some slip-in baffles that I picked up at the NCM track after getting black balled for sound at the last Camarofest. They slip right in and attach with one sheet metal screw. They got me under the 98 dB limit at NCM and at Atlanta Motorsports Park.
I'm running a ZL1 clutch in my SS and making slightly more power than you with no issues. As others have speculated, I believe you may be breaking traction a bit in the lower gears.

20Bluezl1 · 06-21-2023, 03:01 PM

Quote:

Originally Posted by Sephx1

Good suggestions on the turn downs, but I’m looking for a quick solution. Wondering if the pulley change would work. I should still have plenty of hp for the track.

So as far as quick I don't believe swapping a pull is quick as you will need to to get it tuned again for less boost. I have a JRE125 package and I'm about 680whp and have no issues with tracking my car.

Also you sure it's your clutch slipping?

JTS · 06-21-2023, 07:45 PM

You just did a new clutch , in you other thread. Have fun , Safe travels.

Joshinator99 · 06-21-2023, 08:30 PM

Smoothboost FTW. Need less power, turn the knob down. Need to murder the Hellcat in the other lane, turn the knob back up. Easy peasy.

AZ_1LE · 06-21-2023, 09:41 PM

I'd just return the blower back to stock specs.

1sickzl1 · 06-22-2023, 05:52 PM

Least hassle seems to be getting some Laguna pipes. Easy on and off without worrying about taking a belt off or having to deal with the tune. I'd go with the simplest option personally.

06-21-2023, 11:29 AM	#1
Sephx1 Drives: 18 ZLE, 18 SS1LE, 16 SS, 23 ZL1 Join Date: Jan 2021 Location: Phoenix Arizona Posts: 414	De-tuning the LT4 Odd title, I know I’m planning on taking my car to a NASA club event soon where there is a 103db sound limit at 50ft. My car has headers, intake, ethanol, cam, 9.25” lower pulley and 3” Borla S-type NPP. I have Gesi 2 HO cats that have V-band clamps at each end and can be swapped for delete pipes. I usually run the delete pipes at the track. I’m not only concerned about exceeding the noise limit but also when I run slicks on E60 the clutch seems to slip in lower gears under hard acceleration. Dyno numbers on E is 706 hp/745tq. The hp/tq gains are nice, but not necessary to run a good lap on the track. My thought is this: Remove 9.25” pulley and run stock size pulley. Leave cats on for sound reduction. With reduced boost and cooler ethanol temps cats might survive one track day. Running at Sonoma so should be cool weather. Thoughts? Attached Images

06-21-2023, 11:54 AM	#2
Vtor_ZL1 Who Needs to KNOW? Drives: 18 ZLE Join Date: May 2018 Location: Left Side of the Moon Posts: 1,771	Turn down aimed away from mic location ? __________________ ing for grip. Are you in the NY/NJ/PA/CT region? Join us for autox fun at MetLife Stadium. HUGE lots, tons of runs. http://www.motorsportsne.com/

06-21-2023, 12:01 PM	#3
20Bluezl1 Drives: 2020 Zl1 A10 Riverside Blue Join Date: Mar 2020 Location: NJ Posts: 1,227	Get some Laguna pipes made like I made. Attached Images

06-21-2023, 12:35 PM	#5
Keko Drives: 2023 ZLE M6 Join Date: Jun 2022 Location: California Posts: 171	If a clutch is slipping it will start in the higher gears, not the lower gears, since there is more load on it. Are you sure it's not wheelspin or TC/PTM settings? __________________ 2023 ZLE M6 Borla S-Type Catback \| Rotofab CAI \| Soler TB \| MPI Lid

06-21-2023, 01:28 PM	#6
L78toLT1 Drives: Hyper Blue 2016 2SS 6M Join Date: Sep 2017 Location: North Ga Posts: 1,787	Based on your mods, your car should be just about identical to mine dB wise. I have some slip-in baffles that I picked up at the NCM track after getting black balled for sound at the last Camarofest. They slip right in and attach with one sheet metal screw. They got me under the 98 dB limit at NCM and at Atlanta Motorsports Park. I'm running a ZL1 clutch in my SS and making slightly more power than you with no issues. As others have speculated, I believe you may be breaking traction a bit in the lower gears. __________________ Baby Blue 2016 Hyper Blue 2SS/6m/MRC/NPP/Silver Rally stripes/ZL1 wheels & brakes/GForce DS and axles/ZLE Cradle Bushings/FE4 ARB front & rear/SEMA Grill/Rotofab dry/95mm TB/Magnuson 2300/Full LT4 fuel system/JMS boost-a-pump/E85 Sensor/Ported CID heads from LME/Cammotion PD cam/Thompson Motorsports forged shortblock/catted Kooks 1 7/8 headers /JRE remote tuned

06-21-2023, 07:45 PM	#8
JTS Drives: 2023 ZL1 A10 Join Date: Nov 2021 Location: Az Posts: 624	You just did a new clutch , in you other thread. Have fun , Safe travels. __________________ 2023 ZL1 A10 Shadow Gray Metallic

06-21-2023, 08:30 PM	#9
Joshinator99 Drives: 2017 Camaro 2SS A8 Join Date: Aug 2018 Location: Petersham MA Posts: 4,761	Smoothboost FTW. Need less power, turn the knob down. Need to murder the Hellcat in the other lane, turn the knob back up. Easy peasy. __________________ 2017 Chevy Camaro 2SS A8 Whipple 3.0, Mast Black Label heads, Fore triple in-tank pumps, 112mm TB, LPE +52% injectors, LPE BB HPFP, 15” conversion *1059 WHP/944 WTQ, 9.48@150*

06-21-2023, 09:41 PM	#10
AZ_1LE Drives: 2019 ZL1 1LE Join Date: Feb 2017 Location: Gilbert, AZ Posts: 648	I'd just return the blower back to stock specs. __________________ Old: 2017 SS 1LE Old: 2017 ZL1 Current: 2019 ZL1 1LE Last edited by AZ_1LE; 06-21-2023 at 09:52 PM.

06-22-2023, 05:52 PM	#11
1sickzl1 Drives: 2022 ZL1 M6 Join Date: Mar 2022 Location: Long Beach, CA Posts: 181	Least hassle seems to be getting some Laguna pipes. Easy on and off without worrying about taking a belt off or having to deal with the tune. I'd go with the simplest option personally. __________________ 2022 Black ZL1 M6 RF intake, Soler TB & TC, ADM v2 reservoir, AWE Touring non-resonated catback exhaust. 535 whp, 537 tq. SAE Smoothing: 5. DynoJet. No tune. 91 octane.

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