[SONiC MOjO]

I have a question about pulley boost and what would be the best option.

I have a ‘18 ZL1 with a 2650 with a 90mm and
9.1 lower pulley. I’m at 3-4K ft and it does have FED
Ported heads. I’m trying to get to the 15-16# range and
I don’t think this will get me there, with the variables.

I was wondering if anyone has ran a 80/75mm upper with the
9.1 lower. What was your boost at?
I figure I’m losing 4-5# with the elevation and heads.

If anyone has setups similar and can help I would appreciate it.

[laynlo15]

I would consider a 80mm Griptec and that should get you there with the 9.1 lower and 80mm upper. When I was at Magnuson our rule of thumb was for every 5mm of pulley change up or down you'd typically see 1.5 to 2 psi of boost change depending on other mods that can affect boost. You might exceed that a sea level. What is your elevation? I know when we had guys in Denver they would see about 2 psi of boost lose so a 5mm pulley change would generally bring it back to where it would be a sea level. My old Camaro with a 80mm and stock lower was at 12-13 psi and the 9.1 will add a couple lbs of boost. I think you'll be stellar with the 80.

[SONiC MOjO]

Originally Posted by laynlo15

I would consider a 80mm Griptec and that should get you there with the 9.1 lower and 80mm upper. When I was at Magnuson our rule of thumb was for every 5mm of pulley change up or down you'd typically see 1.5 to 2 psi of boost change depending on other mods that can affect boost. You might exceed that a sea level. What is your elevation? I know when we had guys in Denver they would see about 2 psi of boost lose so a 5mm pulley change would generally bring it back to where it would be a sea level. My old Camaro with a 80mm and stock lower was at 12-13 psi and the 9.1 will add a couple lbs of boost. I think you'll be stellar with the 80.

Thanks, yea I’m at about 3000ft above sea level, I also have ported heads.
I’ve read that those can reduce boost too.

[laynlo15]

Yes, both can lower your boost. The 3000 feet will probably be a 1 to 1.5 boost loss and with the ported heads probably 2 lbs total. So 80 or 85 mm would bring that back to stock boost levels that Magnuson figures at sea level.

[SONiC MOjO]

Originally Posted by laynlo15

Yes, both can lower your boost. The 3000 feet will probably be a 1 to 1.5 boost loss and with the ported heads probably 2 lbs total. So 80 or 85 mm would bring that back to stock boost levels that Magnuson figures at sea level.

Thank you

[laynlo15]

Originally Posted by SONiC MOjO

Thank you

Your welcome.

[IneedAZ]

If you go with the smaller pulley to offset your altitude will you have to compensate with extra fueling?

[Joshinator99]

Originally Posted by IneedAZ

If you go with the smaller pulley to offset your altitude will you have to compensate with extra fueling?

Not likely. Higher elevation will have less oxygen to burn, so less fuel needed. Dropping a pulley size just helps bring the boost level back up closer to what you have seen in a “closer-to-sea level” setup. Still have to watch your fueling as always, of course...

[JANNETTYRACING]

Originally Posted by SONiC MOjO

I have a question about pulley boost and what would be the best option.

I have a ‘18 ZL1 with a 2650 with a 90mm and
9.1 lower pulley. I’m at 3-4K ft and it does have FED
Ported heads. I’m trying to get to the 15-16# range and
I don’t think this will get me there, with the variables.

I was wondering if anyone has ran a 80/75mm upper with the
9.1 lower. What was your boost at?
I figure I’m losing 4-5# with the elevation and heads.

If anyone has setups similar and can help I would appreciate it.

You will run out of fuel supply at that boost level.

Ted.