New exhaust idea

[Slow Ride]

As you guys may know I have a new job at Pierce Manufacturing Inc. We make firetrucks and I work in the chassis and cab division. Well the other day I was looking at the 5" exhaust running down the side of one of our chassis and thought how nice it would look under my Blazer. What do you guys thing about a 3" y-pipe into a 5" single?

Dual 3" pipes have a hydraulic area of about 14.13
Single 5" pipe has a hydraulic area of about 19.625

A well tuned single exhaust should perform better than a dual exhaust without a x-pipe. I am going to be making a new tranny crossmember with my TH350 swap so I could make it work with the huge pipe.

What do you guys think???? I can get the stuff out of the junk bin for FREE in stainless!!!

[1SLO5.0]

You better be making alot of horsepower if you are going to use that big of a pipe.

[Slow Ride]

A 500hp diesel needs that size pipe, just a thought maybe next engine?

Would I even need a muffler with this size pipe? Could be pretty quiet.

[bohn]

that pipe would be so big..you would loose all back pressure..deisels like to breath because that make so much compression. That big of a pipe would look like shit and probaly sound like shit also..just go with some 2.5 duals and some 40 series flowmasters.

[67Mike]

Something different is always cool. Question is can you tuck it up high enough under your Blazer so it doesnt hang down low and look funny.
It will sound much better with a muffler than a straight pipe.

[abot316]

i don't think the reason you would lose horsepower is because of backpressure. the real reason is that the exhaust gases come out as a column or "pulse". if your pipe is too big,you can not channel it, otherwise it will tumble or shear. it works just like the size of the intake ports perportion to the size and revs of a engine. just look at a set of old school hogged out small block chevy heads and smaller new vortec's. remember anytime you have some sort of mass going through another, you have vacuum behind it.. this creates scavenging of the cylinders. if your pipe is too big, no vacuum, no scavenging. just look at how time and $$$ winston cup teams spend making 180* headers. these headers "work" by timing every exhaust pulse in order. much like the effect of "drafting" or slipstreaming in a car, each pulse helps pull and push more exhaust out of the engine. remember an engine is nothing more than an air pump, the more you get in, the more you get out, more power. yes sometimes a muffler w/ more backpressure will make more horse and torque downlow, its just that its matched to that rev range, like the primary size of header tubes, intake ports, carb venturies etc- its all about balance.

also a diesel motor is usual 12 litres, yours is about 6, not to mention they are turboed. they work on totally different physics

[1SLO5.0]

Very well said Steve.

[jdsgallops]

Almost well said. If we were talking about 5" Header diameter versus 3 inch I would agree. But once you are past the collector wave tuning and exhaust pulses are minimal and it is more a concern of proper tube sizing to maintain velocity for the exhaust gases to exit. You want large enough to not restrict but small enough to maintain the velocity. In theory a mild 5.0 should loose power with a 2 1/2 inch exhaust, versus a 2 1/4 like it comes with from the factory, yet that is what is marketed because it makes more power. When your talking about header design, then wave tuning and tube diameter come into play. Once the tube ends at the collector, after a pre-determined theoretical optimum length(which is usually too long to fit in the chassis), the wave is reflected back towards the exhaust port helping scavaging. Same thing applies to cylinder heads and intakes. If the head and intake are not matched, when the column of air is reflected off the closing valve, it will bounce back towards the valve when hitting the mismatch between the head and intake, disrupting the correct wave reflection for best power.

[Slow Ride]

I know all this stuff I just thought it would be cool. I was talking with one of our engine engineers, and we were just shooting the shit is all.

[abot316]

come to think about it, it would probably sound and pop like a UPS truck letting of the gas- just remember its proven everyone loves the brown truck

[1SLO5.0]

That would trigger false alarms about the UPS man being in the area. Thousands of people would be dissapointed as they see a white blazer drive by and not the UPS truck.

[snowseeker]

Paint the blazer brown!!

[Stud]

Drive that truck Knudsom

[nasty sn95]

Originally posted by knudsonm
As you guys may know I have a new job at Pierce Manufacturing Inc. We make firetrucks and I work in the chassis and cab division. Well the other day I was looking at the 5" exhaust running down the side of one of our chassis and thought how nice it would look under my Blazer. What do you guys thing about a 3" y-pipe into a 5" single?

Dual 3" pipes have a hydraulic area of about 14.13
Single 5" pipe has a hydraulic area of about 19.625

A well tuned single exhaust should perform better than a dual exhaust without a x-pipe. I am going to be making a new tranny crossmember with my TH350 swap so I could make it work with the huge pipe.

What do you guys think???? I can get the stuff out of the junk bin for FREE in stainless!!!



your car would never start with that size pipe...