Fg Turbo Stock Exhaust

[Jake F6]

Hi guys.

The FG Turbo exhaust is 3" but splits into two 2.25" pipes for a small section in the middle ahead of the centre muffler...

Using mathematics:

a) The area of a signgle 3" pipe = (1.500*1.500*3.142)*1 = 7.07 Inches Squared

b) The area of twin 2.25" pipes = (1.125*1.125*3.142)*2 = 7.95 Inches Squared <--- 12.5% more area for air flow

The question is, why has Ford decided to put this section of twin pipes in the middle section,

and does this need to be considered when changing the stock centre muffler section?

In other words by removing the centre muffler section, and replacing it with single 3" does this have a potential adverse effect?

By the way a 3.5" single pipe has 9.62 Inches Squared of flow area.

I would have thought that Ford has put the twin pipe section in simply to modify exhaust note...?

Cheers, Jake.

[Benny]

Jake,

I don't have a definate answer for you but I can only assume that the decision to go with 2 pipes instead of 1 is purely for clearence. Where the exhaust splits into two there is a small brace that crosses the car which I assume is for improved chassis torsional strength. It's only a small brace but I can't think of what else it could be for. I'm sure Ford would have minimum clearance measurements to prevent the exhaust knocking or heating sorounding parts so with a 3 inch pipe this may be too close to the drive shaft or floor pan.

As for a 2 x 2.25 pipes flowing more that a single 3 inch you also need to take into account the extra pipe wall area in using two pipes over one as the more pipe wall area you have the more resistance to flow there is. So the calculation also needs to take pipe wall area in account. Obviously there's more wall area using 2 pipes than 1.

From experince with my FG the mid and rear section of exhuast had no trouble flowing up to 87rwkw over standard rwkw figure. If I was aiming for say approx 400rwkw in an F6 I'd probably use a 4 inch dump tapering to 3.5 inch. If I was going to 400rwkw plus I'd go 4 inch.

Benny.

[JETURBO]

yeh good q weird set up isnt it I reckn its for the noise reduction cant really think why else

[kink]

When they remove the centre muffler is it solely the muffler or some piping too?

[Jake F6]

I've seen replacements which are single 3" all the way, so basically you throw away the whole factory centre section...

[Dillz]

It is strange, you would assume it would be clearance but if you can fit a 4inch in there I don't see how a 3inch could be a problem. Maybe it's for noise?

[Henz]

My moneys on clearance, the 3.5" and 4" systems hang pretty low.

Edited 29/08/11 06:05 AM by Henz

[f6mark]

iv got the CES 3.5 with twin dump on my fg f6. it fit's nicey.

[Bomber]

Trevor at CES recommended replacing the twin centre merge with 3.5" single. Other than the factory cat, in his opinion this is one of the restrictions in the FG zorst. Ran out of time in the end so just did the Venom cat. Still made 313.4rwkw at 13psi so can't be too bad.

Edited 29/08/11 09:38 AM by Bomber

[Jake F6]

  On 29/08/2011 at 9:36 AM, Bomber said:

Trevor at CES recommended replacing the twin centre merge with 3.5" single. Other than the factory cat, in his opinion this is one of the restrictions in the FG zorst.

I'm going to swap the whole centre section with single 3" (in other words no merge, or twin pipes merge, or muffler). This means it will be single 3" all the way.

Booked in at Dandy exhaust- $250 for a complete replacement section fitted with flanges. I keep my stock section in case I need it later.