Joined

·
265 Posts

1 - 20 of 26 Posts

Joined

·
265 Posts

Joined

·
265 Posts

Joined

·
265 Posts

Joined

·
265 Posts

Joined

·
6,352 Posts

No by going w/ bigger crush bent piping you will create an "hour glass effect" and kill your flow velocity.atlimport26 on Sep/23/02 said:

Joined

·
31,217 Posts

btw exhausts use tubing not piping. the correct term is tube not pipe which is a common mistake (eg. B pipe) .

a pipe is measured and ordered from the manufacturer

based on its INNER diameter (ID).

a tube is measured and ordered from the manufacturer based on its OUTER diameter (OD).

any muffler or custom exhaust builder will confirm this distinction in terms with you if you ever want to order and make your own custom exhaust.

custom exhausts are ordered based on OD sizing , not ID, and therefore use tubing not piping.

Joined

·
6,059 Posts

Thnx,

A beginner to physics and definatly flow dynamics ;-p

mandrel bends for cheap

Joined

·
69 Posts

Joined

·
31,217 Posts

now granted, from the university mechanical engineering graduate's perspective, Bernoulli has several limitations: the biggest one assumes that in laminar flow, all of the parallel layers of a liquid's flow behave the same way. So flow at the center of a conduit (like a tube or pipe) behaves identically to the layer at the periphery near the walls. Therefore, if you sample any single layer, the assumption is that it represents all layers. This is not necessarily true. However, I am not a mechanical engineer and I'm not going derive the better model that represents laminar flow at different subsections of a conduit.

So, when you are talking to me, we are accepting Dr. Bernoulli,... lock, stock, and barrel.

Now how does a mechanical engineer actually measure and calculate flow?

Well, there are 2 devices:

1. a pressure manometer

2. a pitot static tube

a pressure manometer which is a pressure plate attached to a spring in which the amount that the spring is compressed is proportional to the amount of a calibrated known pressure value.

The second device is a Pitot static tube. This device looks like a glass tube in the shape of an upside down capital "L". This device measures flow speed at a very specific point.

theory for measuring flow using pitot tubes

so we can calculate bulk flow of a compressible elastic fluid by an equation:

bulk flow = Pressure + ( [density of air/2] x flow velocity squared] )

They take 2 measurements along the length of the tube and obtain the pressure manometer readings at these 2 points. The density of air is a constant for a given temperature. You can sample in different layers (because they are supposed to be all identical) or you can sample in the same layer at 2 different points along the length of the tube. We can do this on a crushed bent tube and on a mandrel bent one and then compare after we calculate out the value for the equation.

The other way to calculate flow is by taking a pitot tube measurement and calculating the total area.

Flow(cfm) = Flow Velocity(ft/min) x Average Path Area (ft^2)

So when it comes to crush bent vs mandrel bent, we must see the effect of a change in the cross-sectional area of the tube for a mandrel bent tube vs a crust bent tube. If we say a perfect circle has an area of Pi x radius squared, then it is the square of the reduced amount of radius that affects the amount of flow. It's NOT a straight linear 1:1 relationship.

If Magnaflow says the equivalent diameter of a crushed bent 2.5 in. tube is 2 in., then I am incorrect in my statement. How they arrived at that value, I do not know.

If it's true then, the 2.25 in. mandrel bent tube would flow 27% better.

Joined

·
6,059 Posts

Joined

·
3,856 Posts

Um its really not that expensive lol. I dont know what kinda crazy shops there are around you. I did my full 2.5 Mandrel for a little under 300 and that included my 2.5 muffler. The only thing that i need is a donut gasket for the end of the header because the one i have on there now is leaking. As for the part that the shop did...i had them mandrel bend everything from the cat back, put hangers on there, and weld the muffler on there and it was only like $120. If that is more than crush bent then i think i would rather pay a little more for good quality exaust.ICC96INTEGRA on Sep/23/02 said:

Cross sectional area for 2.5" mandrel bent pipe:

(1.25^2)pi = 4.91 sq. in.

Reduce cross-sectional area by 20%

4.91*0.80 = 3.93

Find equivilent pipe diameter.

(r^2)pi = 3.93

r^2 = 1.25

r = 1.12

d= 2.24

So according to Magnaflow a 2.5" crush-bent pipe would give the equivilent cross-sectional area of a 2.24" pipe at the bends.

Joined

·
31,217 Posts

Cross-Sectional Area for 2.5 in. mandrel bent tubing (using pi x radius squared) = 4.91 sq. in.

Proper Adjusted Cross-Sectional Area for Crush Bent Tube = 4.91 x 1.25 = 6.14 sq in.

area = PI x radius squared = 6.14 sq in.

radius = SQRT [ 6.14 / PI ] = SQRT [1.95] = 1.40 in.

where SQRT = square root

Therefore,

Diameter Needed For Crush Bent Exhaust to have the same Area as the 2.5 in. OD Mandrel Bent Exhaust is :

2 x 1.40 = 2.80 in.

So if you are going to get a crush bent exhaust made for a 2.5 in. system, use a 2.80 in. exhaust Bpipe. You must weigh the size of the diameter in the straight portions to see if it's still within your power range without going to large though.

thanks SurferX.

1 - 20 of 26 Posts

Join the discussion

Team Integra Forums

The Team Integra community is a forum dedicated to Acura Integra enthusiasts to discuss engine building, suspension, repair, detailing and anything else Integra related.

Full Forum Listing
Explore Our Forums

Recommended Communities

Join now to ask and comment!