Power Porting The Standard Manifold

[Bass Junky]

Ash, that's exactly why we are 50/50 on the porting.

If the restriction is in the turbo housing itself, then opening up the exhaust manifold isn't going to make much difference, however if I was running a monster turbo, then the more flow I can get through the standard exhaust manifold, they better.

[SLY33]

or, you guys could all continue to wait until i finally swap over my extrude honed manifold and get some results, unfortunately dont hold your breath tho

Wow, im pretty damn sure i didnt pay 600 bucks!

One thing i remember him saying was the smoother flow resulting in less heat. ie, before where a manifold would glow red hot after some hard dyno runs, it wouldnt do so once ported. So possibly benefit there too.

Cubes, i think i remember that thread you refer to, and if i remember correctly, it was the 'extrude honed' standard mani that flowed some figures similar to some of the aftermarket ones, not the untouched version. ?

edit, actually cubes your sort of right, i just checked, the HKS cast mani was shown to flow just 10cfm more than the stock untouched mani, meaning the ex honed std mani would far better the stock HKS in terms of just 'flow'.

Setup is as in sig, not with stock turbo

Edited September 25, 2007 by SLY33

[R31Nismoid]

what setup Sly? Again, i dont think its a stock rear housing is it?

[The Mafia]

I talked to a Extrusion Honer just recently, and he said to me that you have to watch out for the people that don't do the honing correctly.

He says the best way to do it was to Block off 5 runners, and do each runner at a time, because a lot of people try and cut corners to increase speed and do all 6 at once. If you do all 6 at once then the easiest flowing runner is going to recieve the bulk of the abrasive fluid that hones these manifolds out.

He said he charged $550 for a Sinle RB25 manifold.

I too was a bit disappointed at the price, but when you compare it to a HKS item, for $100 more, you could easily have a External Gate provision fitted.

Pros:

1. Looks dead stock

2. Flows more than the HKS Item

3. Half the Price of a HKS item \ Stainless job from the expert fabricators here

4. A lot stronger than the Stainless items

5. Heat stays inside cast better than stainless (meaning more pressure through your turbine, increasing response)

6. Bolts straight back into factory position

Cons:

1. Not Shiny

2. Maybe not tuned length? (does this matter?)

3. Still a bit pricey

4. Only a low mount option

5. Need to find someone that will do it properly

[Cubes]

Sly33,

Yeah that would be the thread.. I also remember the China highmount manifold apparently flowed worse than the std manifold. :S

[discopotato03]

And no split external waste gate mount .

You're going to find that its the pressure drop over each manifold runner thats important not its constant flow rate . Piston engines don't have a constant gas flow rate on either side because the valves are opening and closing . However if the cylinders feel a consistant pressure drop through the exhaust manifold it tends to equalise their flow velocity and thats what the engine and turbo prefer .

What the HKS manifold also does is angle the compressor end of the turbo away from the block so packaging is a bit easier . Also if you drill/tap the four extra holes you can use a T4 flanged single/twin entry turbine housing . The RB26 version suits only the T4 flange size .

Cheers A .