Pipe Flow

[F6 UTE]

  F6_Tornado said:

Actualy they are the ones I used and at that price you cant go wrong unless you scrimp and try and use only one which will do you no good at all.

Say a single 3.5" Cat has an area of 9.6"

A 4" Cat has an area of 12.5"

so I used 2 x 3.5" which is equal to 19.2"

That coupled to 3.5" twin works great.

<{POST_SNAPBACK}>

But you have twice the contact area and resistance to a single pipe. Wouldn't this be a catch 22, and reduce the margin between twins and single??

Which is somewhat beneficial, as you have twice the cooling through heat transfer, although thus negating the need for 3.5" pipes.

Pity we didn't see how restrictive the rear mufflers were.. Maybe when my quads are fitted, we'll see how the twin cats fare aginst a single 4".

[Eugene]

  F6 UTE said:

  F6_Tornado said:

Actualy they are the ones I used and at that price you cant go wrong unless you scrimp and try and use only one which will do you no good at all.

Say a single 3.5" Cat has an area of 9.6"

A 4" Cat has an area of 12.5"

so I used 2 x 3.5" which is equal to 19.2"

That coupled to 3.5" twin works great.

<{POST_SNAPBACK}>

But you have twice the contact area and resistance to a single pipe. Wouldn't this be a catch 22, and reduce the margin between twins and single??

Which is somewhat beneficial, as you have twice the cooling through heat transfer, although thus negating the need for 3.5" pipes.

Pity we didn't see how restrictive the rear mufflers were.. Maybe when my quads are fitted, we'll see how the twin cats fare aginst a single 4".

<{POST_SNAPBACK}>

F6 UTE, you have lost me a little with the above, when you say twice the contact area and resistance, are you talking about the face of the cat or the wall of the pipes from the cat.

If you mean the face of the cat (frontal surface area), they are side by side, giving a total surface area (frontal of 19.24 square inches, a single 4" cat has a surface area (frontal) of 12.5 inch, so there is an increase of area of app 60%, which will lower resistance to the exhaust gas going through the cat.

I dont know if twin 3.5inch pipes are required, mine has asingle 3.5 and flows fine, but F6-Tornado may be chasing more power down the road and hence is setting the car/ute up now so no further upgrades are required in that area later.

If I missunderstood what you ment, please let me know.

[F6 UTE]

I've chatted to F6 regarding his exhaust quite a bit..

I have no qualms about the twin cats being the go. From a neatness point of view, and practicality. 4" just hangs down that bit too much. It's the dump pipes fault, not the cat.

The 'contact' area I was referring to was the side wall of the pipes. I'm also clutching at straws because the big yellow Camel is edited, has it's squirts in, aswell as that dirty big exhaust...

The ute rear mufflers are, in my opinion, the restriction. I was chatting to the guy that did my exhaust and he agrees. He has seen very good gains from changing them.. F6 got massive gains over his previous cat only incarnation, and nice gains on this system aswell. Ford changed the cat to a huge one on the BF, so were all the gains attributed to the twin cats, I doubt it..

I'm looking at getting quads fitted to the ute sometime, and I'll then see if my power vs boost levels change considerably..

[Xtreme F6]

I tested a twin cat set up over 8 months ago, I had 2 cats that flowed 390 cfm each 4 inch inlet split into twin 3.5 into the cats, I then flowed it, the cats flowed 390 each so you would have thought it would flow 780 cfm, it didnt it flowed 580 confusing hey... I didnt get a chance to flow gregs, I wish I did, I use the same on my car as F6_Ute and have made upto 400 rwkw's with that. the smb cat flows 660 cfm I have just found a cat that flows 990 CFM ill use that after new engine is tested with currect cat to see if it makes any more power before I change to the bigger one.