Stock airbox + K&N = 8.6 psi before the shift

I just ordered a 3.25 pulley to replace my 3.4, should see 9.5-10psi

 

I get 7 to 7.5 psi boost with the stock 3.7" pulley. My engine is a 4.8 so it needs less air.

 

Holy **** *****-maybe i should keep my stock air box and stick in a k&n. Thats awesome #'s. We need to meet up sometime so i can see this!!!!!!!

 

Do you have the Joe Gibbs truck? Just curious what the 3.7 comes on, I thought the highest was 3.6

[edit - brian just told me the 4.8 kits come with the 3.7 ]

 

No, mine isn't a Joe Gibbs, just an aftermarket unit I bought from Magnacharger. I read somewhere that the JG trucks have a 3.9" pulley, sort of an extra safety net for their warranty I guess. Also I heard that the pulley is mounted using a proprietary method so that regular aftermarket pulleys can't be used. However, modders, always an ingenious lot, found a way around it by just swapping out the whole drive snout. (Try and stop US from modding our truck will ya??!!! LOL).

 

So having a cold air intake lowers the boost on a radix setup. I always thoght it raised the boost a little. Might have to find me a stock air box with a drop in K&N. What made you want to try the stock box?

 

losing any boost in this scenario is not a big deal. It's still moving the same cfm and has a more dense Air charge to boot.

 

I agree. An engine is a big air pump. A CAI will usually allow you to run more cfm through the supercharger because it uses a larger filter and is less restrictive. Moving less air at a faster rate is the same as moving less air at a slower rate. The amount of air does not change. However, a CAI usually allows a denser air charge like moregrip has stated.

There was also a thread awhile back about all boost being equal which most people disagreed with. They used the example of a big turbo at a certain psi and a small turbo at the same psi and how the cfm was different. Something like that I think.

 

i used to see 10.5-11# with a 3.25 pulley.