I am going to be putting in my 2nd gen IC and was just cleaning out the garage and found alot of good junk, and came up with a plan. I found some genuine Cummins 3.5" intercooler boots with T-bolt clamps and also have alot of 3.5" stainless pipe with many different bends. I'm thinking about making all new boost tubes to install when I install the 2nd gen IC. Think the difference in flow will be a good thing or will it slow velocity too much? I also will be making a custom intake to get rid of the stock intake horn.

 

I'm no guru, but I'd say with the amount of airflow you have currently it would hurt more than help.

 

I know that upgrading from 2.5" to 3" boost tubes you gain 19whp and almost 40wtq on a Dmax. Thats in stock form, from low rpm all the way up to 3200rpm. So I know up to a point the bigger IC and boost tubes will help, but 3.5" is pretty big. Larger tubes will help spool faster, but I'm afraid 3.5" tubes will act more like air tanks than air tubes and make it take longer to fill there volume with pressurized air.

Not sure if what I'm thinking makes sence?

 

That's what I was thinking, larger tubes slowing the velocity to the point it hurts spoolup. Also the 6.6L engines in the duramaxes move a lot more air thru them than our 5.9L engine does. But this is just my opinion, don't have proof one way or the other. Maybe you should try it and report back.

 

When you do a banks intercooler for a 3rd gen the elbow and the piping is 3.5"