3.5" or 4" downpipe?

[JSPulliam21]

I would like to buy a 4" exhaust for my 02 CC LB Dually, but I don't know which down pipe would be best. There will not be any chips or programmers for a looooooooong time, so take that into consideration. I also want to be able to install the dp without beating up the firewall for clearance. Thanks.

 

[Rex-a-FORD]

On the 99's and newer you don't have to worry about beating the firewall. A 4" DP will go in slick as a whistle.

As for 3.5" vs. 4" either will prolly work just fine. 4" should help a little with EGT's but so will a 3.5" over stock.

I wouldn't worry too much about the stories on less torque with the 4". The torque is still there just a little higher in the RPM band with the 4".

I'd say make it easy on yourself and get the 4" turbo back.

 

[ranger boy]

go with the 4", it should fit and it just sounds so much bigger than 3.5" (when saying it)

 

[DavidJ]

If your going to continue the mods even if not for awhile, do it now, do it now. It's done and out of the way. %)

 

[dzl_x_4x4]

Just installed the 4" turbo back and rex_a_FORD is right. There is no noticable lag or turbo surge/stall (maybe I'm just lucky). It did move my powerband up +/- 500 RPM. But it works out because I like running it a little higher to hear the rumble..........

Also any improvement in MPG's was negated because of the smile factor (I smile when I run it hard)

2005DIESEL has it right.......It just sounds so much bigger!!!!!!

 

[powerboatr]

go with the 4", it should fit and it just sounds so much bigger than 3.5" (when saying it)

yep and size is everything
both of mine had 4" dp
then you add a gaint 5 or 6 inch tip :ZigBang:

 

[f100cleveland]

I G-teched mine before and after my 4" turbo back system. I lost a tenth or so on the 0-60mph time but gained some mph and lost time in the 1/4 mile. Like what was said it moves the tq. up a little in the rpms. Do it

 

[JSPulliam21]

Thanks fellas. 4" it is!!!