exhaust Question

[walkerkd]

ok here we go.. why arent any of you guys running the stock exhaust with a better muffler. i was looking and the differnce between the flowing rate of a 4" pipe and a 3.5" pipe is very slim. i mean down to 10ths so i was just wondering why everyone went to 4 inch.. if you wanted a significant change why not 5 inch.. atleast you maybe gain alot more flow. just a question can someone eleberate on this???

[Kennedy]

Leaving math, volume, sizes out of it, most who have gone to straight pipe 3.5" have noticed an improvement. Those who have gone from 3.5" straight to 4" have noticed a similar improvement. From 4" to 5", the difference seems to be more of a "mine's bigger than yours" thing...

[walkerkd]

oh ok.. well i was playing with the math of it and there was a little less than .01 of a differnce in flow at the numbers i was crunching.. just wanted to know would it be worth loosing the nice factory system.. or would the benifits truley be in the muffler or going streight pipe.. thanks Kenndy.. im going to be getting with you soon on parts.. and maybe one of these days i will install my bypass system. haha its been 4 weeks and its still under the back seat.. hahah

[hoot]

Volume-wise the difference between 3.5" and 4" is substantial. There is a point of diminishing returns.

If you remove the exhaust at the downpipe, you will have zero backpressure from that point out. Add a 3 1/2" dia pipe with multiple bends and a muffler and you will add significant restriction simply due to confining the exhaust stream and internal friction.

There is no doubt in my mind that going to 4" increases flow capacity substantially.

Don't let dia. difference fool you. Doubling a pipe dia. doesn't double flow. It's exponential. I beleive it's like 10 times the flow by doubling the pipe dia.

[ 08-01-2002: Message edited by: hoot ]</p>

[walkerkd]

Hoot,
yea i was thinking that too but i crunched the numbers on both the 3.5 and the 4 and with a 10' section of pipe there was not much of a differnce.. keep in mind i did a streight piece of pipe.. because i assmued that to replace the stock pipe the aftermarket piece would have to have the same bends.. but like i said thats just the numbers.. i have to beleive that there is a great differnce between the two on the truck because everyone wouldnt be going that route.. on my 99/00 ctd.. i went streight pipe.. and talk to many guys that did the same and dyno'd both 4" and 5" plus steight pipe and there were loses on the 5" and the gain between the 4 and 3 was like 3-5 hp but with a cost of over 400 bucks. and there were gains of 10-15 with a amsoil filter(35 bucks) i just wanted to play with that option.. know what i mean?

[Idle_Chatter]

Walkerkd, afp replaced his factory muffler with a Magnaflow 4" that he had a muffler shop weld in using two 3-1/2x4 adapters. I'm going the same route, I ordered in the Magnaflow muffler and the adapters, waiting for four Torc-Tite band clamps to arrive (I'm going to go with the band clamps and if that doesn't seal I can always run down to the local muffler specialty shop for some welding). The muffler is a stainless beauty, the adapters and clamps are stainless too and I should have a free-flowing all-stainless system for under $300. When I get it all together I'll post some pictures.

[stevem]

walkerkd

I have a Dynomax straight thru 3.5 inch muffler welded to the factory pipes.

Yes it is louder than stock when I have the pedal to the floor, but it is nice and quiet inside the truck when on the freeway.

EGT's have never gone above 1300 at full throttle while funnin around or towing(with Juice on level 4

:eek: )

I did not like the sound of the Dynomax at first, but now with the Juice it sounds great and the EGT is within the safe range.

Steve