poolman

I have a '00 cab & chassis with a flat bed I use for work. I am going to be installing exhaust, edge ez, 275 injectors, and gauges. My question is do I need 4" exhaust or 5". I have seen on bigexhaust.com that they offer both for my truck. What is to better to run with the mods I have planned. ???

Ray,IN

Although much more money, the 5" should work better-only if a complete system is installed. The bigger exhaust must be from the turbo back to be effective. You need to get rid of the heat as quickly as possible, and retaining the stock down pipe defeats the benefits of any size increase downstream.

poolman

The system bigexhaust carries is a 4" downpipe then 5" from there back. Is it just a waste to have the rest 5" if the downpipe is only 4"? Also what about torque? Will the bigger 5" system hurt my low rpm torque?

RickCJ

Do you even need 4" exhaust?? I just towed my 2 car trailer, gcvw of 20,000 lbs. With my Comp set on 5x5. Never went over 1100 deg. on the biggest hills. This is with stock air box and 3" exhaust. How much air can a low revving diesel move???

rharveysr

They move a lot of air! I went from a muffle'd 3&quot; to a straight 3&quot; and now I have a complete 4&quot; and a Scotty II. The easier it is for the motor to pull air in and push it out the easier the motor works.<br> Some say you dont need 4&quot; or a different breather..NO FLAME Intended... but I know my truck and how it ran before and I know how it runs now. There is no comparision between the 2. It runs soooooooooooooooo much easier...turbo spools up quick...If I were to go out today and buy another truck(stock)..there are 2 things that I would do as soon as I got home. <br>1. Order a new Scotty II(to get the cooler air in)<br>2. 4&quot; exhaust(to get the volume of exhaust out)<br><br>Rick

poolman

I am not familiar with the Scotty II. What is this, an FIPK type system?

Shovelhead

Check it out here:
www.scottyairsystems.com

DieselDaze

[quote author=RickCJ link=board=7;threadid=13376;start=0#125883 date=1049864831]<br>Do you even need 4&quot; exhaust?? I just towed my 2 car trailer, gcvw of 20,000 lbs. With my Comp set on 5x5. Never went over 1100 deg. on the biggest hills. This is with stock air box and 3&quot; exhaust. How much air can a low revving diesel move???<br>[/quote]<br><br>This may really show my ignorance here, but this is how I look at the engines in our trucks.<br>These engines are a 5.9 liter 6 cylinder.<br>Thats roughly 1 liter per cylinder. <br><br>Using this same logic, put this in terms of the standard V8. (gas or diesel)<br>At 1 liter per cylinder, that would be some 8 liter engine.<br>So, if my thinking is correct here (and Im not saying that it is) then, yes, these engines move a lot of air.<br><br>Just food for thought.<br>Rich.

BigBlue

Chevy makes an 8.1L V8 that is a gutless wonder bone stock. Throw an exhaust on it and .

SjLingenfelter

I finally hit 900 ont he egt on my Dad's PSD. with 4&quot; exhaust.<br>SD03

Brett

4&quot; is cool and will provide you with significantly lower egt's, enough to save you turbo under high stress and heat, but have you ever heard what it sounds like with 5&quot; exhaust w/o the muffler. <br><br>So Cool, You can hear the turbo spool out the back of the exhaust. And when you shut off your truck you can hear the whole system continue to push and pull air for about 5 or 6 seconds after your truck is shut off. <br><br>I bet you can guess that I personally vote for the 5&quot; muffler or not.

poolman

Anyone have any real world proof of power increases? Dyno tests, speed comparisons pulling a load on a hill before and after exhaust, etc... I know they are advertised to make horsepower gains, but I want to know if you really do &quot;feel&quot; the power increases, or is the exhaust just mainly for the big rig sound. ???

boehunter49

;D Hay Poolman Let me tell you , yesterday we changed my exhaust over to the 4 inch from big exhaust .com. We did it at Ultra Motor Sports shop, it was a little work but I'll tell you what, when I left there I had to call Mike an tell him the noticeable differance in power an exhaust temps it was unbeleaveable. I wish I had changed the exhaust before, you go with 4 in or 5 in what ever I think you will be happy.<br> I don't see how 5in will fit off the turbo cause mine was really tight with the 4in an we had to dimple it in one spot to get it to clear the trans cooler line.<br> BUT THIS IS JUST MY FEELINGS WITH MY TRUCK<br> BOB ;D

poolman

Thanks for the input, I am probably going to order the 4&quot;. I am ready for some more punch and power!!!!!!!!!!!11