17' Sierra Whipple Supercharger Smaller Pulley?

[Tanner Smith]

I have a 2017 GMC Sierra 6.2 with a whipple 2.9L with a 4.125'' pulley. I want to go smaller on the pulley. Maybe a 4'' or 3.875''. Would I need to do fuel upgrades? This is a daily driven truck and sometimes I tow with it. Would it be worth it to put a smaller pulley or would it be risky for reliability?

[UnlimitedMatt]

6 hours ago, Tanner Smith said:

I have a 2017 GMC Sierra 6.2 with a whipple 2.9L with a 4.125'' pulley. I want to go smaller on the pulley. Maybe a 4'' or 3.875''. Would I need to do fuel upgrades? This is a daily driven truck and sometimes I tow with it. Would it be worth it to put a smaller pulley or would it be risky for reliability?

You will definitely need to adjust your tune to add fuel to keep your air/fuel ratio safe. Depending on your current tune, you may need to upgrade your fuel system.

 

I say this as I had a supercharger on my GMC Canyon and needed to put on a smaller pulley as I live at a higher elevation.  I was unable to get the factory fuel system to provide enough fuel with the smaller pulley so I ended up keeping the larger pulley.  I did not want to have to start spending money on fuel system upgrades. 

[Tanner Smith]

1 hour ago, UnlimitedMatt said:

You will definitely need to adjust your tune to add fuel to keep your air/fuel ratio safe. Depending on your current tune, you may need to upgrade your fuel system.

 

I say this as I had a supercharger on my GMC Canyon and needed to put on a smaller pulley as I live at a higher elevation.  I was unable to get the factory fuel system to provide enough fuel with the smaller pulley so I ended up keeping the larger pulley.  I did not want to have to start spending money on fuel system upgrades. 

yeah you make a good point. I have a dyno tune this saturday. Maybe I could slap it on there and see what the afr shows with the smaller pulley. I don't want to have to do fuel changes as of right now. Maybe down the road if i get bored. Ill ask whipple if i can run a 4'' without fuel upgrades.

[CamGTP]

You need to be concerned with injector pulse width and duty cycle.

 

If you are on stock 6.2 truck injectors they won't have much wiggle room at all. They for sure won't support a change to E85 because that requires 25-30% more fuel than regular pump 91-93.

[Grumpy Bear]

Something not often though of is ring gaps will not support sustained boost. (Towing long grades)  Especially when more boost than the original kit was set up for. Know what happens when ring ends butt heads? Just say' n. 

[Tanner Smith]

21 minutes ago, CamGTP said:

You need to be concerned with injector pulse width and duty cycle.

 

If you are on stock 6.2 truck injectors they won't have much wiggle room at all. They for sure won't support a change to E85 because that requires 25-30% more fuel than regular pump 91-93.

Yeah I would Definitely have to do Fuel upgrades for E85. I'm curious because some whipple kits I've seen on this forum have a 4'' pulley with their 6.2 and they say it came with the kit. So i wonder why mine has come with a 4.125? Could it be since its a CA Truck? Maybe the fueling is different or something? 

[Tanner Smith]

15 minutes ago, Grumpy Bear said:

Something not often though of is ring gaps will not support sustained boost. (Towing long grades)  Especially when more boost than the original kit was set up for. Know what happens when ring ends butt heads? Just say' n. 

Yeah you have a good point there as well. Definitely not designed for the boost to begin with.