Standard exhaust manifold

[Trip]

I read somewhere that people port/polish the standard manifold for a better flow.

I took a look at the manifold and I noticed the internal surface is rough which would help smooting it out. Also on the turbo flange side, there is that divider, do people remove that when porting the manifold ?

 

[ashills]

on the manifold ive got on car at minute i spent a couple of hours with a die grinder and a couple of these
http://www.tyrolit.com/dataarchive/...thumb-250x252-fit.jpeg.thumb-250x252-fit.jpeg
and theres a lot of metal that can be taken from gasket areas etc and took the rough off everything i could get to and took what i thought was safe off all the lumps that stick into the airways then used some real course wet and dry as little pads and did all the bits u cant get grinder to just to try and flat them off a bit as the sandpaper is never gonna be that great on cast lol
and i didnt take alot of that divider away as its a kind of twin scroll set up so just smooth the top into a semi point but would take a lot of time to fully remove it and may make air flow worse in some ways

 

[Trip]

I doubt how will i manage to smoothen out the surface at the back. On the gasket side, there is metal bulging out (internally) simply to keep the thickness of the walls since on the outside its recessed to allow enough space for the studs. I wouldn't wish to smoothen out these bulges and end up with a thin wall or worse a hole.

 

[youngsyp]

I wouldn't wish to smoothen out these bulges and end up with a thin wall or worse a hole.

The casy manifold is heavily over engineered. As a result, I wouldn't worry about taking those bulges right down, to not be in the way of tehgas flow. The spot will still be a good 3mm or 4mm thick and is not one of the heavily heated areas so, it should be fine.
On the spare manifold I have, that I'm porting and polishing, I've taken them right back, so not to disturb the gas flow.

Just for info, if you get an S15 3 layer manifold gasket, you can use that as a template, to port match the manifold. This gasket is also a much better design than the stock N14 part so, has larger holes around the exhaust port.

 

[kirko]

this is what you need to do 8)

 

[kirko]

ive run 403BHP on my ported manifold and standard elbow;-)

i know its not groundbreaking stuff but it does show with standard parts you can get more than enough power for a daily driver

 

[youngsyp]

@kirko - Good work there mate, that looks very good.

 

[stevepudney]

ive run 403BHP on my ported manifold and standard elbow;-)

i know its not groundbreaking stuff but it does show with standard parts you can get more than enough power for a daily driver

Thats the kind of kit I used as well, air die grinder with 6 - 10mm carbide burrs.

I made a template of the ports on the head and transferred that to the manifold to get an exact as possible match. I also used some silicon carbide brushes like this to clean out the parts of the bore I couldn't reach with the carbide burr.
I even went so far as to use the carbide burr to remove the webbing between the pipes and the oem heatshield turrets on the top so I could heatwrap the whole manifold.

I would guess to be running about 440 ish break atm using this manifold

 

[Trip]

Great guys. Thanks very much for all the info you provided

About the divider piece on the turbo side, will that help too by removing it..

Last but not least, was there any before and after noticable gains ?

 

[youngsyp]

Great guys. Thanks very much for all the info you provided

About the divider piece on the turbo side, will that help too by removing it..

Last but not least, was there any before and after noticable gains ?

Ashills has mentioned this above but, it would be best to keep the centre partion. This will go a way to equalising the exhaust pulses from cylinders 1 and 2 and 3 and 4. Removing it might create turbulence in the collector.

As for gains, I'd expect a better spool up and response with the ported manifold but, not a huge amount of power and torque. Maybe 5 or so bhp and lb's/ft across the rev range ?!

 

[Trip]

I will purchase the tools needed and I will start grinding

 

[campbellju]

The last time I installed my manifold I gave it a going over with a dremel for about 6 hours (Shiney but not much metal removed).

After the 4 Brach manifold I was after fell through because it cracked and hearing first hand of some other people's experiences I decided to have another go at porting the standard part.

A huge thanks to Stumo for his help with some decent tools. 3 hours later I've got a similar result to the above.

It might not look as fancy as a 4 branch manifold but I was surprised at how good it looked internally once you've removed the restrictions.

It will still be frustrating to take off but its not bad for free.

 

[Trip]

The last time I installed my manifold I gave it a going over with a dremel for about 6 hours (Shiney but not much metal removed).

After the 4 Brach manifold I was after fell through because it cracked and hearing first hand of some other people's experiences I decided to have another go at porting the standard part.

A huge thanks to Stumo for his help with some decent tools. 3 hours later I've got a similar result to the above.

It might not look as fancy as a 4 branch manifold but I was surprised at how good it looked internally once you've removed the restrictions.

It will still be frustrating to take off but its not bad for free.

Where there any noticable gains ?

 

[campbellju]

Not yet, I need to get the engine back in the car first. I've tweaked a few other bits too so I won't be able to tell really. Looks alright though ;-)