3" - 4" - 5" ? What's too much? - Diesel Forum

Runboy · 03-23-2005, 12:58 AM

Exhaust that is. What is the optimum size on a 7.3 with a Banks Non-wastegate turbo?
Is there any benefit to running a pipe size larger than the outlet on the turbo?
Mike

towcat · 03-23-2005, 03:36 AM

the larger the diameter the less high rpm "bark" downside is the noise. Its enough to bring the law down on you.

nosliw · 03-23-2005, 07:45 AM

IMHO, Once you get up to 8" or so [img]/ubbthreads/images/graemlins/phoney.gif[/img] stovepipe size, that might be a little big. LOL

beretzs · 03-23-2005, 10:52 AM

Towcat is right about the bark, once you get above a 3" pipe you will cut down on the bark and loud rap at higher RPM's. The 4" sounds really nice and deep, not a sharp bark. If you are going to do it, it really can't cost too much more to run 4" pipe. Scotty

JCDiesel89 · 03-23-2005, 01:37 PM

So you will get more power out of a 4 inch cause it breaths better but you wont get the noise? Im thinking about going duals straight out behind the rear bumper with no muffler or with a good sounding one. Will a 3inch or 4inch perform and sound better. Im guessing the 4 will perform better but not as good, im not sure. What am I better to go with if I put on a banks wastegated turbo?

beretzs · 03-23-2005, 03:15 PM

I went from the Banks 3-3.5 inch system to a 4" straigth pipe and it looks, sounds and perfroms better, but most of the performance is due to not having the muffler. If I had just deleted the muffler, I probably would have gotten the same results. Scotty

Vek · 03-23-2005, 03:46 PM

I just completed a 5" exhaust system for my '89 cc 4x4. I have the Hypermax turbo system. Here's the system, from the turbo back:

I went with the first half of the factory 2.5" downpipe. This piece has a bracket which bolts to the turbo mount bracket on the back of the starboard cylinder head. This piece ends right as it clears the firewall under the truck.

From there, instead of attaching the rear half of the hypermax 2.5" downpipe, I attached the hypermax exhaust system's 2.5" x 3.5" reducer, welded to an appropriately-shaped chunk of the hypermax 3.5" over-the-axle pipe. The tailpipe section I selected ends up puking straight back, right beside the transmission.

From there, I welded my 3.5" x 4" reducer, and 4" x 5" reducer. This ends right behind the tranny crossmember.

From there, I clamped a straight ~8' length of 5" pipe.

From there, I welded the front half of the 5" tailpipe for a '99-'03 from shopdiesel.com.

From there, I clamped the back half of the shopdiesel 5" tailpipe.

I welded supports to match the factory hanger locations, all the way back. I made the supports out of 3/8" steel rod, bent to match the pipe contour, and made to hang the system as high in the chassis as possible. In front of the axle, almost all of the pipe is obscured by the frame rail. It spits out at an eye-appealing (not too low, as I've seen on other systems) level behind the rear axle, angled slightly downward and backward.

The turbo kit came from my totaled '88 x-cab, and I wanted a bigger exhaust, as the aftermarket 3.5" systems are a bit "hissy" for my taste. No more of that! The truck sounds flat-out angry now. You don't notice it in the cab with the windows up. With the starboard rear window down, you notice a rumble. But, when you get beside a concrete divider, wall, or overpass, you can really hear the bark if you get on it. I haven't been harassed yet (only 3 months along), but it is quite a bit louder than the straight 3.5" pipe.

Not a difficult install, just a bit time-consuming. A muffler shop should be able to set something like this up for pretty cheap, if you supplied the tailpipe (and hardware, if they gouge you).

I'd do it again in a heartbeat. It sounds great.