Gen 5 Camaro External Bolt-On Tech - Underdrive Crank Pulley

Looking at a doing this mod soon, any pros or cons to it? which brands are best? and will it void warranty?

The con would be that your belt driven alternator and A/C compressor will spin slower. Some have claimed to have voltage problems at idle if you have all your accesories on like stereo and A/C. The power you pick up will be hard to notice by the seat of your pants. The time to do it is if you do a cam swap or timing chain upgrade since you are allready there. A cam swap will usually require a idle speed increase which will negate any posible low idle voltage problems. It is a good mod when you are after every last horse you can find.

AJG383 hit it right on the head. I did mine when we did the cam swap, the dyno tune afterwards will take care of any potential issues.

The con would be that your belt driven alternator and A/C compressor will spin slower. Some have claimed to have voltage problems at idle if you have all your accesories on like stereo and A/C. The power you pick up will be hard to notice by the seat of your pants. The time to do it is if you do a cam swap or timing chain upgrade since you are allready there. A cam swap will usually require a idle speed increase which will negate any posible low idle voltage problems. It is a good mod when you are after every last horse you can find.

AJG383 hit it right on the head. I did mine when we did the cam swap, the dyno tune afterwards will take care of any potential issues.

yea im not looking to do a cam swap anytime soon, just looking to see how much it would put to the wheel

An underive pulley will let you pick up maybe 7-8 hp. I think the potential problems out weigh that gain. I have never done an underdrive pulley on any of my vehicles.

Fluidampr makes a specific 25% underdrive pulley for the LS3/L99. The A/C pulley is stock diameter so there is no loss of compressor RPM. The Camaro charging system is very sophisticated and raising operating voltage is not just as simple as raising operating RPM.

The purpose of the charging system is to maintain the battery charge and vehicle loads. There are 6 modes of operation and they include:

* Battery Sulfation Mode
* Charge Mode
* Fuel Economy Mode
* Headlamp Mode
* Start Up Mode
* Voltage Reduction Mode
The engine control module (ECM) controls the generator through the generator turn ON signal circuit. The ECM monitors the generator performance though the generator field duty cycle signal circuit. The signal is a pulse width modulation (PWM) signal of 128 Hz with a duty cycle of 0–100 percent. Normal duty cycle is between 5–95 percent. Between 0–5 percent and 95–100 percent are for diagnostic purposes.

The generator provides a feedback signal of the generator voltage output through the generator field duty cycle signal circuit to the ECM. This information is sent to the body control module (BCM). The signal is PWM signal of 128 Hz with a duty cycle of 0–100 percent. Normal duty cycle is between 5–99 percent. Between 0–5 percent and 100 percent are for diagnostic purposes.

Fluidampr makes a specific 25% underdrive pulley for the LS3/L99. The A/C pulley is stock diameter so there is no loss of compressor RPM. The Camaro charging system is very sophisticated and raising operating voltage is not just as simple as raising operating RPM.

The purpose of the charging system is to maintain the battery charge and vehicle loads. There are 6 modes of operation and they include:

* Battery Sulfation Mode
* Charge Mode
* Fuel Economy Mode
* Headlamp Mode
* Start Up Mode
* Voltage Reduction Mode
The engine control module (ECM) controls the generator through the generator turn ON signal circuit. The ECM monitors the generator performance though the generator field duty cycle signal circuit. The signal is a pulse width modulation (PWM) signal of 128 Hz with a duty cycle of 0–100 percent. Normal duty cycle is between 5–95 percent. Between 0–5 percent and 95–100 percent are for diagnostic purposes.

The generator provides a feedback signal of the generator voltage output through the generator field duty cycle signal circuit to the ECM. This information is sent to the body control module (BCM). The signal is PWM signal of 128 Hz with a duty cycle of 0–100 percent. Normal duty cycle is between 5–99 percent. Between 0–5 percent and 100 percent are for diagnostic purposes.

That's interesting information on how the generator is regulated but what does it mean as to operation with an underdrive pulley at 25% less than standard rpm?

Fluidampr makes a specific 25% underdrive pulley for the LS3/L99. The A/C pulley is stock diameter so there is no loss of compressor RPM. The Camaro charging system is very sophisticated and raising operating voltage is not just as simple as raising operating RPM.

The purpose of the charging system is to maintain the battery charge and vehicle loads. There are 6 modes of operation and they include:

* Battery Sulfation Mode
* Charge Mode
* Fuel Economy Mode
* Headlamp Mode
* Start Up Mode
* Voltage Reduction Mode
The engine control module (ECM) controls the generator through the generator turn ON signal circuit. The ECM monitors the generator performance though the generator field duty cycle signal circuit. The signal is a pulse width modulation (PWM) signal of 128 Hz with a duty cycle of 0–100 percent. Normal duty cycle is between 5–95 percent. Between 0–5 percent and 95–100 percent are for diagnostic purposes.

The generator provides a feedback signal of the generator voltage output through the generator field duty cycle signal circuit to the ECM. This information is sent to the body control module (BCM). The signal is PWM signal of 128 Hz with a duty cycle of 0–100 percent. Normal duty cycle is between 5–99 percent. Between 0–5 percent and 100 percent are for diagnostic purposes.

That's interesting information on how the generator is regulated but what does it mean as to operation with an underdrive pulley at 25% less than standard rpm?

yea im def confused lol

The point I am making is, charging system voltage is determined by the ECM and BCM based on need. Never mind the under drive pulley. I have read posts on this forum and others where members are saying just turn up the RPM with your tuner to compensate. This is wrong and not necessary. Yes RPM may need to be adjusted for a cam or torque converter but that is a different subject. I have had the Fluidampr 25% under drive pulley on my Camaro and the charging system operates perfect. 2 things I did notice with the under drive pulley is a 7° increase in coolant temp. But I have a 160° thermostat so I run consistent 185°. The second thing I noticed is a slightly tighter steering feel at low speeds.

The point I am making is, charging system voltage is determined by the ECM and BCM based on need. Never mind the under drive pulley. I have read posts on this forum and others where members are saying just turn up the RPM with your tuner to compensate. This is wrong and not necessary. Yes RPM may need to be adjusted for a cam or torque converter but that is a different subject. I have had the Fluidampr 25% under drive pulley on my Camaro and the charging system operates perfect. 2 things I did notice with the under drive pulley is a 7° increase in coolant temp. But I have a 160° thermostat so I run consistent 185°. The second thing I noticed is a slightly tighter steering feel at low speeds.

the steering issue would make me concerened, not sure if i want that

MGw3 thank you for that input.

Mrgoodwrench seems to know a bit about the charging system on these cars, I need to power a 14V battery setup in my 2011, they said its native at 14.8. Any suggestions or info you can give me on making my alt work for that battery or an alternator that will?

Mrgoodwrench seems to know a bit about the charging system on these cars, I need to power a 14V battery setup in my 2011, they said its native at 14.8. Any suggestions or info you can give me on making my alt work for that battery or an alternator that will?

I'm not understanding your question? You want the charging system to always be at 14.8V ?

I am wanting to have my charging system run at about 16.5-16.8 to charge a 14v battery

I ran a Power Bond 25% U/D pulley on my Camaro. It was good for a solid tenth and I never had any issue with charging or the A/C. I drove my car a lot in the summer because my DD at the time didn't have A/C and it was an all black car and it stayed cool all through last year's hot Chicago summer. Never had an issue with power steering either.

as far as your warranty is concerned its only voided if a modification causes a failure. GM and others are too eager to void warranties and imo are pushing their luck.

an UDP installed correctly shouldnt cause any problems.

as far as your warranty is concerned its only voided if a modification causes a failure. GM and others are too eager to void warranties and imo are pushing their luck.

an UDP installed correctly shouldnt cause any problems.

If you have any sort of power train failure they will not cover it under warranty if they find that underdrive pulley. I have a 2.5" front leveling kit on my truck. Front right wheel speed sensor quit working. They would not cover it because the front suspension had been altered. Per them it doesn't matter if the aftermarket part did or did not cause the failure. There was a modification associated with the part of the vehicle that failed.

IMO if you're concerned about keeping your warranty do not modify your vehicle. That simple. Unless you have the time and money to get a lawyer.

If you have any sort of power train failure they will not cover it under warranty if they find that underdrive pulley. I have a 2.5" front leveling kit on my truck. Front right wheel speed sensor quit working. They would not cover it because the front suspension had been altered. Per them it doesn't matter if the aftermarket part did or did not cause the failure. There was a modification associated with the part of the vehicle that failed.

IMO if you're concerned about keeping your warranty do not modify your vehicle. That simple. Unless you have the time and money to get a lawyer.

still, im not aware of any law changes concerning modifications.


as FOS as car makers are now and their eagerness to void warranties for anything be ready for a fight though a letter from an attorney can change attitudes very quickly.

a tech i know told me how a guy blew his motor on his solstice racing it. they wouldnt cover it. he threatened to sue GM because he claimed he used it what it was intended for.


they covered the repair.

I am wanting to have my charging system run at about 16.5-16.8 to charge a 14v battery

I'll have to check next time I boot up the toon laptop but I think you can specify all of it in the tune.

with that said, I doubt the factory wiring is up to task.....