Magnaflow 4"

[mroodzant]

I am looking for a turbo back 4" exhaust for my 2003 HO. Ive read alot of posts here on exhaust. I think I'm set on the Magnaflow. Any advise before I place the order?

 

[red-rider]

duals put the pieces together.

 

[Gary - K7GLD]

I'm getting a Magnaflow system put on by Rip Rook next Tuesday, along with a set of 1. 6 injectors - just be aware the Magnaflow system is NOT a true "turbo back" 4 inch - the turbo downpipe section is smaller, and only goes to 4 inches from the muffler on back...

 

[mroodzant]

How is that different than the stock system?

 

[Gary - K7GLD]

How is that different than the stock system?

I haven't actually measured each section of my stock system, and certainly don't know the inner diameter if the muffler or resonator - but the stock downpipe is 3 inches - and other diameters are 3. 5 inches downstream I think...



It seems some aftermarket exhaust system makers use 4 inches from the turbo on back, others like Magnaflow stick with a smaller diameter downpipe as DC does with the stock setup - *I* sure don't know the rationale for that choice, or what the goal is...

 

[mroodzant]

Any thoughts on which system to get, 409 SS or 304 SS?

 

[Gary - K7GLD]

Any thoughts on which system to get, 409 SS or 304 SS?

That pretty much depends upon what road conditions your truck most often is exposed to, and what sort of life expectancy you want from the exhaust system - no real point in buying a 20 year lifespan exhaust for a truck you will only keep for 3 years - or in salty conditions, having a nice shiny exhaust on a badly rusted out body... Lower grade stainless WILL rust, but whether it will deteriorate more/less than aluminizwd steel, *I* sure don't know! And while the pretty polished hi-grade stainless IS nice, how often do you or other crawl under the truck to admire it?



Decisions, decisions! :-laf :-laf

 

[Mark Craig]

MRoodzant,



The Magnaflow is a 3. 5 inch down pipe system, they have a 409 and a 436 stainless system. They are the same system just made from different materials. The stock down pipe is 3 inches. To my knowledge their system is not designed for the 12 valve trucks, their first application is 1998. 5 and newer, so check that before you buy.



We do have the MBRP products available in aluminized, 409 and 304 stainless in singles and duals. If you need any info just call.



Mark @ DPPI

 

[Gary - K7GLD]

MRoodzant,



The Magnaflow is a 3. 5 inch down pipe system, they have a 409 and a 436 stainless system. They are the same system just made from different materials. The stock down pipe is 3 inches.

Mark @ DPPI

SO, Mark, maybe you can explain WHY a user would/should go for a downpipe that is SMALLER than the rest of the system - what exactly are the expected benefits - OR possible liability?



I personally still have mixed feelings about a "4 inch" system that is only providing a 3. 5 inch downpipe - and not real sure that I'd want to sacrifice, say, 10 HP in the 1800-2800 RPM range merely to gain that amount down below 1800 RPM. .



All informed comments appreciated... I hafta make my final decision by next Tuesday - and sure don't want lingering questions as to whether the difference between a 4 inch downpipe or a 3. 5 one, makes a difference that costs me power where *I* want and use it most!



Some might say the power difference is negligible - and if you already have one system installed, that's OK, but I'm still in the deciding stage, and don't want or plan to be doing another exhaust system upgrade in the forseeable future - so THIS one has to be RIGHT!

 

[CORed]

I'm interested in exactly the same thing Gary is... smaller downpipe than the rest of the system vs same diameter downpipe as the rest of the system. What are the benefits, if any?



Inquiring minds want to know from those THAT know.

 

[kblranch]

The other option is to buy a factory 2004. 5/2005 exhaust elbow and down pipe which are both 4 inch. You can then buy a down pipe back system from Mark at DPPI (or someone else) and have a true 4 inch exhaust. The advantage of going with the factory exhaust elbow and down pipe is that if you decide to add a turbo mounted exhaust brake like Jacobs or Pacbrake you just buy the 2004. 5/2005 model and it bolts right up. I have the part numbers to do this if you want them.

 

[Gary - K7GLD]

The other option is to buy a factory 2004. 5/2005 exhaust elbow and down pipe which are both 4 inch.

WELL, actually, that isn't the question - FULL 4 inch systems are readily available without need to "piecemeal" one together - the QUESTION is, WHY do some makers, like Magnaflow, USE the smaller diameter downpipe to start with? Is there some unexplained benefit with the smaller downpipe, and if so, WHAT?



Again, it's been suggested the smaller downpipe provides improved low end torque - but how much if any, and at what expense to upper RPM power - or is there another reason entirely - and for towing, is the smaller downpipe better or worse for EGT?



SOMEONE in this group has to have a knowledgeable answer - otherwise, we're just dealing with theories...

 

[RDedrick]

I have an 03 and would like to know to. I looked under my truck and it looks like mine is a 4" from the turbo down, no cat? Is a 03 suppose to have one? I am thinking about getting duals? Will duals hurt torque or hp on the low end? Looking at gettin MBRP.

 

[mroodzant]

Speaking of cats I thought my 97 had a cat. So i assumed so did my 03. But reading so many posts it sounds like no cat on the 03.

 

[Gary - K7GLD]

Unfortunately, probably the only ones able to REALLY tell us the reasoning, and advantages/disadvantages of the smaller downpipes, are the guys who make and dyno them...



Probably precious few random owners have started out with a smaller downpipe on a 4 inch system, dynoed, then at some point swapped to a 4 inch downpipe and dynoed again to see the actual difference...