[hellsie]

Good day all,
my car is a 15 all stock and so I want to pin the crank and upgrade the pulley while at it, is there a downside to upgrading the lower ? I heard you lose electric power or something? please correct me or just enlighten me thank you.

 

[2fast4u]

Not sure where you got that info...any oversize bottom pulley, (9-10%), will actually spin all the accessories faster, HP Indy used to have batches of undersized accessory pulleys for sale time or 2 that would slow them back around OEM speed for the ATI lower.

 

[hellsie]

Not sure where you got that info...any oversize bottom pulley, (9-10%), will actually spin all the accessories faster, HP Indy used to have batches of undersized accessory pulleys for sale time or 2 that would slow them back around OEM speed for the ATI lower.

I did on this forum, but oh yes I seen that ..like 15%, so is that to counter the effect the smaller pulley effecting accessories? does that mean. essentially you end up with 2 pulleys installed in 2 places?

 

[2ndgen]

The accessory pulley size is independent of the SC pulley size. Adding an ATI 10% lower SC pulley doesn't change the accessory pulley speed--no adjustment necessary, no change in electrical power. There is an option to put a 15% underdrive accessory pulley on along with it, which is claimed to free up 10-15HP. This could definitely affect electrical power--but usually only around idle RPMs is there a possibility for concern--and only if you're drawing a lot (stereo cranking, heater fans blasting, seat warmer on...)

 

[hellsie]

The accessory pulley size is independent of the SC pulley size. Adding an ATI 10% lower SC pulley doesn't change the accessory pulley speed--no adjustment necessary, no change in electrical power. There is an option to put a 15% underdrive accessory pulley on along with it, which is claimed to free up 10-15HP. This could definitely affect electrical power--but usually only around idle RPMs is there a possibility for concern--and only if you're drawing a lot (stereo cranking, heater fans blasting, seat warmer on...)

Much appreciated!

 

[baabootoo]

The con? Isn't it a lot harder than the upper?

 

[Jonx96]

If just wanting to do one or the other the upper can make more boost even on pump gas. The lower is a harder install. But the 10 percent lower is nicer than the factory. Some people switch to just a stock size dampener from ati.
You'll need a tune for the 10 percent lower.

 

[hellsie]

The con? Isn't it a lot harder than the upper?

As I mentioned I want to pin the crank first and before all , 1% chance for engine damage is too many , hence wanna mod while at it

 

[hellsie]

If just wanting to do one or the other the upper can make more boost even on pump gas. The lower is a harder install. But the 10 percent lower is nicer than the factory. Some people switch to just a stock size dampener from ati.
You'll need a tune for the 10 percent lower.

I think I might go for the over sleeve 6% so I don't worry about tune for now and kinda do all the magic on the upper later on then

 

[Jonx96]

I think I might go for the over sleeve 6% so I don't worry about tune for now and kinda do all the magic on the upper later on then

Well not doing a tune is your choice. I wouldn't recommend it. I have seen many cars peg the fuel system on stock boost. I have also seen many stock cars pull timing because of knock volts.
Adding more boost will just add to all of this. I'm not saying it is a bad part I am just saying you take a risk.

 

[Jonx96]

Any reason you don't want a tune? There are good tuners out there who do not charge a fortune.

 

[hellsie]

Any reason you don't want a tune? There are good tuners out there who do not charge a fortune.

I will tune it just maybe not right away is all

 

[hellsie]

Well not doing a tune is your choice. I wouldn't recommend it. I have seen many cars peg the fuel system on stock boost. I have also seen many stock cars pull timing because of knock volts.
Adding more boost will just add to all of this. I'm not saying it is a bad part I am just saying you take a risk.

I will tune when I do the upper all at once and hopefully soon But let me ask you. If car pulls timing due say bad tank of gas , etc.. does it readjust automatically after? Just curious

 

[Jonx96]

I will tune when I do the upper all at once and hopefully soon But let me ask you. If car pulls timing due say bad tank of gas , etc.. does it readjust automatically after? Just curious

It depends on if you get long term knock on top of the short term knock. In most cases a stock car will just see short term knock. Short term isn’t remembered long term is the memory.

 

[2ndgen]

What's the difference between short term knock and long term knock?

 

[2fast4u]

^^ Jonx96 just answered that in the post above yours...

 

[Unholy707]

Let me de-mystify this. The main reason many people have lowers or did them in the first place is because that’s the first pulley that was out for the hellcats, there was no upper. Going smaller on the upper requires an idler pulley/bracket, which exist. In my opinion, there’s no reason to get a 10% lower anymore, because you can go all the way down to a 2.52 I believe up top- just run an idler to take up belt slack and wrap belt, and you’re fine. With just a lower, you may be able to get away without pinning the crank, but I strongly advise doing it always.

 

[baabootoo]

The first option I would get is a tune!!!!!!!!!!! A MUST TUNE after a pulley swap. You are inviting disaster w/o one. Years ago, I did a lower swap on a GM 6.2 SC for one reason: stealth.

 

[Unholy707]

The first option I would get is a tune!!!!!!!!!!! A MUST TUNE after a pulley swap. You are inviting disaster w/o one. Years ago, I did a lower swap on a GM 6.2 SC for one reason: stealth.

I only half read most posts didn’t realize OP wasn’t tuning his car after doing mods 🤦🏼‍♂️

 

[2ndgen]

^^ Jonx96 just answered that in the post above yours...

No. He explained the behavior. Not the cause.
How does the computer decide when to remember any particular knock as a long term vs classify it as short term and forget it ? Is there some tunable threshold? Some heuristic? Is there a hysteresis? Can the memory/long term be reset by just pulling a fuse or running a new tank of better gas?