Well here goes....I talked to a diesel supplier the other day who offers a 3" exhaust, another offers a 3.5" and a 3rd offers a 4". I know I don't need the 4" so...my question is ,is there much of a diiference in performance from the 3" vs. the 3.5"? and is it legal to punch out the catalytic converter or to even eliminate it as far as emissions are concerned?. Hate to take to emissions for new tags and find out I broke the law.

It's illegal to tamper with the catalytic converter in anyway. If your state requires it. The 3" is a waste of money IMHO. I would go 3.5" if straight or 4" if you need bends. The down pipe is the big hold up. Most start at 2.5 and then up to 3" then 3" to the catalytic converter which then goes to 3.5" or 4". Only a few systems goes from 2.5" to 3.5" or 4" on the down pipe. Those are the ones I like.

3 inch will do just fine if you don''t plan on doing a lot of major power upgrades, if you do more upgrades then 3 1/2 works better 4 inches is more for show than go. The soot trap needs to be inplace for inspections, I think you guys have those in AZ, folks have passed them with no soot trap or a gutted soot trap. I not recomending it but have heard of guys who take the trap out knock all the guts out so it's only a shell, reinstall it and it passes visual inspection for being on and they pass the test as long as their boost is working good for complete burn of fuel.

Thanks gents..That addresses my concerns but makes me wonder why the supplier(H) sells their kit with the 3" exhaust, while supplier (K) sells the 3.5".... Maybe I'm better off with supplier(H) for some parts, supplier (K) for the exhaust and supplier (SS) for the rest.:think:

I bought one off the auction site last week. Looks very good, clamps good, muffler good. 3" downpipe to 3.5" to 4". I will be installing tomorrow. P.M. me for details. Dan

You going to do it in the rain? You should do mine at the same time. ):h



I bought one off the auction site last week. Looks very good, clamps good, muffler good. 3" downpipe to 3.5" to 4". I will be installing tomorrow. P.M. me for details. Dan

Thanks gents..That addresses my concerns but makes me wonder why the supplier(H) sells their kit with the 3" exhaust, while supplier (K) sells the 3.5".... Maybe I'm better off with supplier(H) for some parts, supplier (K) for the exhaust and supplier (SS) for the rest.:think:
Sometimes multi vendor is the ticket, look at sigs will give you a good idea of what the trend is.

The 3" is a waste of money IMHO.3 inch will do just fine if you don''t plan on doing a lot of major power upgradesIMHO, 3" pipe is more than adequate to handle the volume of exhaust a 6.5 can make, works like a charm on mine.

IMHO, 3" pipe is more than adequate to handle the volume of exhaust a 6.5 can make, works like a charm on mine.Maybe so but my wife's got a 4" on hers..... I was going green with "pipe envy".
http://www.dieselplace.com/forum/images/smilies/hihi.gif

I am very satisfied with my 4" ebay kit, I believe from pennicle exhaust. 3" down pipe for about 18" then up to 3.5" for about 36" to 4" in and out mufler 4" out the rest of the way.

TDG

To me the cost to change the exhaust is not that big of a difference. A 3" cost a little less than a 4". Now with the heat problems the 6.5 has the 3" would be fine to help them, but if you decide to do any other mods you would end up back to where you started.

IMHO for the cost and time it takes to do it I would get the biggest pipe I could. So if I ever lose my mind and start doing chip and other fuel upgrades I wouldn't have to worry about the exhaust.

As they say. What works for me might not work for you.

Yes...I was planning on the works...Chip, Turbo master, FSD Heat sync, exhaust, gauges, intake upgrade e.t.c. I was shooting for the 3.5"exhaust but the 4" is not totally out of the question.The 3" just didn't seem like that much of a gain for the $.Exhaust temp is important to me especially on days when I am pulling a 6500 lb. load and it's 110 degrees outside going up a 6% grade. Every little bit would help.

In the situation you are describing, get some kind of charge-air cooling! Intercooler or WMI to get back that lost HP from high IAT fuel clipping.

I live in Northern Nevada and I am going to do WMI at the very least and if I can save enough, an intercooler too!

Damn! The list of things I need/want gets longer the more I do to the truck!

For what I have been reading the IC is the way to go. Cost more up front but worth it in the long run. Install and mostly forget. The WMI is a hassle to me. Pumps alot of water and to have to keep refilling, plus the extra weight?

Just MHO!

I agree with you. WMI could be more of a pain to deal with. However, I live where 10% humidity adn 100 degrees is a norm. It would seem that WMI for my rarely-towing rig would be the way to go until I can pony up $1500.