Do I really need 4"?..opinions?
 

My truck is from New Mexico and still has the factory exhaust installed and is in good shape. The only Mod I have done or plan on doing is a little pump tweak and a BHAF.I would like to get the exhaust to breath a little better. Is there reallly a benefit for me to go to 4" exhaust? About $375 - $500 I fiure it will cost. What about just removing the muffler on the stock system? Will less backpressure hurt anything? How much difference would that make? How much noisier will it be without a muffler and will it sound good or just noisy? Please give me all of ya'lls opinions.

I did`nt notice that much of a performance gain, but the 4in did lower my egt`s and helped the spool a bit. The egt`s also cool down much faster when i go to shut her down. As far as sound, that depends on if you straight pipe it or put in a muffler and also what muffler you decide to go with. I have a Diamond eye and my truck has a nice "noticable" but not loud tone to it, for me it`s just about perfect. If oyu don`t plan on BOMBing much you can save some coin and keep the stock downpipe, also makes for an easier install as the 4 in DP has to be fabbed where it mates to the exh housing.

I have been told the biggest restriction in the stock system is the bend going over the rear axle, I guess it is crimped. You could have a better tail pipe installed and a better muffler. weigh out the cost of doing that as apposed to a new system.
On a turboed engine like ours, the less restriction the better.
4" would be great for performance, lower EGTs and cool down time.
The question is, after a couple of small modifications, will you have the self control to not want to go more :cool: Its called bombing! when you see how much power you can get with such simple changes you might get the bombing bug [duhhh]
good luck

You will not get a big SOTP gain from 4". Fuel = power on a diesel, air just lets you use the power longer. If you do not have EGT problems you do not need 4".

If you are concerned about noise, do not straight pipe it. The best advice I can give you is to say this: If you think it might be too loud, it will be.

I suggest bigexhaust.com's 4" if you want to upgrade. Skip the downpipe, it is no better than stock. That way you will not have a lot of money in the system, you will have removed the big restriction, and you will have a good sounding system. If you wanted to you could just get the muffler and tailpipe, along with a 3" to 4" adapter and do it even cheaper.

When I went to 4 inch exhaust (kept the 3 in downpipe) I got 3 psi gain at wot and much quicker cool down time...a little quicker spool up....and that's with a muffler in the system as well.
I say it's well worth going to 4 inch.
Jay

I have essentially the same results as everone else, after installing my 4" system. It cut the egt down about 150 degrees give or take a little, whether accelerating and pushing 15+ lbs of boost, or cruising at highway speed. It cools down very quickly and I noticed a slight gain in power. I have a rip rook downpipe, which unfortunately costed $160 or so and was somewhat hard to retrofit, but ti was well worth it. I had an exhaust shop install everything behind the downpipe. The exhaust pipe exits in front of the rear wheel, because the elbows were costly. I have some pictures in my gallery.

Directly after getting the pickup, I had the muffler knocked off. It sounded too high pitched, like a tractor, and didn't seem to help performance. With a big, quiet muffler, it is still louder than stock(not much, though), and it has a nice deep rumble.

I would have to say that it is my best mod yet, despite the fact that it ended up costing about $450. I suppose that I could have did it for less, but the downpipe was spendy. I would say that if you have the money, go for it! :)

I have my exhaust exiting in front of the rear tire. This gets rid of the bend and crimp over the rear axel. I also installed a magna flow muffler. otherwise it is the stock pipe. I gained cooler egts and boost but it stays quiet even exiting where it is. It is a cheap fix. :)

I dunno. The 4 inch straight piped 1st gen sounds real nice. Inside the cab is also quiet, no droning on mine at all.

Ditto.. I've had mine 4" straight pipe, minus the 3" dp for a month or so now and I love it because it sounds nice and quiet inside the cab with the windows up but roll the passenger window down and WOW
I was thinking of trying out a muffler but had my GF drive it up and down the street for me at various throttle launches , etc. and found it to be rather tame, a lot less raspy than you hear echoing back into the cab while driving. Actually I was amazed, there was no raspyness at all from the outside... which is good news, I won't have to down more $$$ for a donaldson 51" X 9" muffler heheheheheheh [director]

Don't really have enough experience to say if you need 4" or not but, I had been running a piece of 5" in front of the rear tire. Now I have a 4" stack and I can tell a difference in the seat of the pants. Of course, I have two 90's that I didn't use to so that could be part of the problem.
Sam

I just installed a Stans's complete 4" system. Complete 4" from the Turbo back. If fit perfect, I was impressed. The cool thing is they will flange the down pipe to fit whatever turbo you have. It come with a huge straight threw muffler that sounds great, no louder than stock, just a little deeper. I'd let you know how it performs but my truck is not doing to well right now in power department.

http://www.stans-headers.com/diesel.htm

Even with "mild" pump tweaks, a 16cm housing, and a BHAF, I had problems with EGTs when towing with the stock exhaust. The 4" system lets me use the power I have - I can keep my foot in it on even the long, steep grades instead of crawling up at 25-30 MPH. It was worth every penny of the $500 or so I paid to have it installed.:)

Do you really need 4" ????? I'd say double that cowboy!!!! [tapdshut]

I have been pondering the same thing. Until I get my gauges in I am holding off. I want a 3" downpipe with the rest 4" at a minimum but not sure about 4" downpipe. If you are sticking with a non wastegated housing I would definately go for a FULL 4" turbo back. I want to add a W/G housing in the near future and I am not to hot with fabricating so I am not to sure about the 4" downpipe. Stan told me his 4" is a no go with a waste gated housing. Everyone mentions the bad spot in the factory exhaust above the axle but with but with my 89 and 91.5 4x4's there were crunched spots around the transfer case also even worse than the axle crunch. Mmmmm choices choices choices....

My truck was bone stock when I got it. My second mod was a muffler delete 4" system. My truck had stock exhaust for the first few months I owned it. I did remove the stock muffler after the first week (first mod) and saw a mileage and performance improvement. But, a few months later the stock pipe rotted out right behind the muffler. A friend of mine works at an exhaust shop and bid the stocker 3" setup at $300 or $400 for a 4" mandrel bent system. I again gained power and another 3 miles per gallon going 4" and the sound was much deeper.

Diesel fuel has a greater expansion rate when combusted than gasoline so larger pipe is needed to get the fire out of the hole to make way for the fresh air charge to the cylinder. Turbos also seem to perform at thier peak without backpressure. Any fueling enhancements will benefit from a larger and less restrictive exhaust system.