Porting exhaust manifold/exhaust ports?

[zarnah]

much gain to be made by giving the exhaust manifold a bit of porting like the pic below? the way I see it, that black ring of carbon is where exhaust is hitting the edge of the exhaust manifold and therefore cant be the best flow, porting it out would create better flow and therefore better spool/throttle response?

the port on the left has been ported, the one on the right shows the black ring of carbon I'm talking about.

also, up pipe where it bolts to exhaust manifold...

before

after

any thoughts guys?

[Guest boostcut]

that black ring aint nessesarily where the ports dont match, its just where the gasket sits away from the edge, you could however prt both head and manifold to suit each other, this is called "match porting" really only cruicial on big hp turbo or na engines

[wildturkey]

Stoffa has done the same thing and made a real good job of it too........nice clean flow. I found the pics he sent to me I'm sure he won't mind me posting these.......

http://img10.imageshack.us/img10/9678/74325070.jpg

http://img10.imageshack.us/img10/2927/72659487.jpg

This is an interesting read as well.........

http://ken-gilbert.com/wrx/porting/pp_exhaust_manifold.htm

[DRFVDR]

will make a difference,whether a big one or a small one will depend on how much restriction there was before hand

[Stoffa]

the factory cross pipe drops down to 31mm through the flexi, so thats a huge restriction, I've had some new flanges cut and getting a steam pipe cross pipe made up thats 48mm I.D right through, every join is match ported to the gasket and I've got a trust up pipe on its way (41 automotive) which is 50.8mm I.D which is almost (1mm out) a perfect match to the factory gaskets which will line up with my ported turbo inlet.

I'm not chasing mega power so I figured its alot cheaper than good headers and it wont be cracking in a hurry.

If you have a read of that thread wild turkey posted up, you'll see just how much meat i've removed, I'm still not quite finished porting, but it HAS to make a difference.

The guy who laser cut my 2 flanges has the file still, he charges a bottle of jim beam if anyone want them, he can make them from stainless although mine are mild steel

[scottiescottiescottie]

Anyone else out there done this?

Sorry to resurrect a dead ol thread but... I am thinking about match porting the headers on my LGT. I recently single turbo'd my mates old twin turb legacy and the ports were badly miss matched which got me wondering if the newer turbo castings were any better or not...

Grim speed sell ported stock manifolds but don't say anything scientific or measured about any power increases.

I was also surprised at how many people were porting them out to the exact size of the gasket!? This won't help the life of the gasket surely!

Also has anyone ported the actual alloy head exhaust ports to match the size?

Thanks

PS I am really after some qualified info of an improvement in doing this mod. Has anyone measured an improvement?

[Stoffa]

I got my heads ported by jason liefting on my car. he said port matching the exhaust ports to the manifold had little gain. he spent a day porting my heads to get the dog leg exhaust port flowing almost evenly with the straight port. he said theres big gains to be had there.

not dyno tuned yet so no results yet sorry

[rex-leggy]

i have nothing to compare but i did alot of porting + matching ..... from what i hear it would benifet more greatly from bigger cams which is what im planning next

[Stoffa]

I got a new custom crosspipe made up with a bigger internal diameter as well, the factory one drops down to 31mm from memory inside the bellow/flexi, I also got a trust up pipe with no flexi and a few mm bigger ID than a factory one.

****IMPORTANT NOTE**** a mesh flexi WILL melt on a subie manifold, my exhaust guy made a slip joint inside the flexi which is bigger ID than the rest of the pipe. So melted bits dont end up stuffing the turbine in your turbo.

So I ended up with the same ID with no big steps on the inside, nice and smooth

looked like this all wrapped up

heres a few pics of my exhaust porting, he just tidied up the casting marks on the intake side

[rex-leggy]

heres my intake ports

intake flipped and matched

also comparison between stock ports and the work i had done

[scottiescottiescottie]

 Stoffa said:

****IMPORTANT NOTE**** a mesh flexi WILL melt on a subie manifold, my exhaust guy made a slip joint inside the flexi which is bigger ID than the rest of the pipe. So melted bits dont end up stuffing the turbine in your turbo.

So I ended up with the same ID with no big steps on the inside, nice and smooth

looked like this all wrapped up

heres a few pics of my exhaust porting, he just tidied up the casting marks on the intake side

Awesome. I think even if it's just for the fun of it I'm gonna get out the dremel!

Tell me did you leave a 1mm rebate of material for the gaskets or port right tithe edge of the gasket?

[Stoffa]

right to the edge of the carbon build up, I kept checking it with the used gasket to make sure I didn't take too much out.

I used brand new genuine multi layer steel gaskets, the crush part is a few mm thick so no drama with leaks.

heres more pics of my heads, they were done on a flow bench...

[scottspeed]

If you decide to port them, make sure you stop about 2mm away from the gasket edge. These gaskets cant actually survive the exhaust temperatures that are generated, so need some shielding from direct heat (much the same as a headgasket is always larger in diameter than the bores). If you port to exactly the same size as the gaskets you will find gasket life is severely reduced.

[scottiescottiescottie]

 scottspeed said:

If you decide to port them, make sure you stop about 2mm away from the gasket edge. These gaskets cant actually survive the exhaust temperatures that are generated, so need some shielding from direct heat (much the same as a headgasket is always larger in diameter than the bores). If you port to exactly the same size as the gaskets you will find gasket life is severely reduced.

This was my conventional understanding but I saw MANY guys porting them all the way to the gasket.

I wont be dont worry

[scottspeed]

If your looking for easy power, a one piece up pipe, 1.750" diameter will add 10kw over the stock item. Ever wondered why people say twisting the turbo made more power, most cases nothing to do with the twisting, its that the new up pipe fixes the factory restriction.

[scottiescottiescottie]

 scottspeed said:

If your looking for easy power, a one piece up pipe, 1.750" diameter will add 10kw over the stock item. Ever wondered why people say twisting the turbo made more power, most cases nothing to do with the twisting, its that the new up pipe fixes the factory restriction.

True true

[Deforester]

 scottspeed said:

If your looking for easy power, a one piece up pipe, 1.750" diameter will add 10kw over the stock item. Ever wondered why people say twisting the turbo made more power, most cases nothing to do with the twisting, its that the new up pipe fixes the factory restriction.

Thats a good point, I always thought that twisting the turbo was a strange way to gain power

[Guest]

 Deforester']

[quote name='scottspeed said:

If your looking for easy power, a one piece up pipe, 1.750" diameter will add 10kw over the stock item. Ever wondered why people say twisting the turbo made more power, most cases nothing to do with the twisting, its that the new up pipe fixes the factory restriction.

/quote]

Thats a good point, I always thought that twisting the turbo was a strange way to gain power

I might be pissing in the wind but does freeing up the intake tract support higher power too? Maybe not a power gaining mod though like the up pipe mod above.

[scottspeed]

intake mods do change the power band, and freeing up will normally increase power. Depends on what you class as freeing up the intake tract as.

Changes to the runner lengths (std is too long for higher rpm power) and increases to the plenium volume will normally carry power higher up in the rpm.

Better intake hose to turbo will also increase performance, and ever replacing the end tank on the top mount closest to the throttle body with a custom tapered item will increase power.

[Pappu1]

will that up-pipe mod help for say 220-230kw atw range or the stock is fine for that?

[scottspeed]

stock up pipe is the worst for flow. A one piece one, just about always ads 10kw, on the power range your after the stock turbo is maxed out, but this would help on spool up and add slightly to overall power.

[Pappu1]

 scottspeed said:

stock up pipe is the worst for flow. A one piece one, just about always ads 10kw, on the power range your after the stock turbo is maxed out, but this would help on spool up and add slightly to overall power.

there are a lot of threads which keep saying bigger than stock ads lag (talking sub 230kw here)

stock or slightly bigger turbo

how does that compare to the one u are suggesting

10kw is a good gain ..

im sure lots ppl will be interested in such gains

[Guest]

Think 1.75" is stock size but without the flexi restriction? I had an up pipe for sale but gone now that was that spec.

When i made my twisted up pipe I went 2" coz it matched the gasket (I now know that was a bad idea) and wasnt too worried about lag. I get 15 psi now on stock size pipe by 3500 as opposed to about 3800-4000rpm by memory.

Proof is in the pudding.

is this your website? it wont come up http://www.scottspeed.co.nz/

[scottspeed]

Your definitely thinking along the right lines, I see so many 2inch or big up pipes that make the cars a dog off boost to drive.

Using 1.750" matches the ID of the OEM exhaust manifold so the speed of the exhaust gases don’t slow down (going into a bigger tube) or speed up and get restricted (going into a smaller tube).

If you use the proper size tubing it also means we have proper sized ports. The OEM gasket is a very high quality gasket and its designed to sit back from the extreme temps of the exhaust. When you over-port your flanges the OEM gasket is now exposed to the extreme temps and will burn out very quick.

I thought most people knew this trick of the up-pipe and wondered why so many people thought it was the twisting of the turbo made the power. Hence i thought i might join your site and see if i could help some of you guys with some proper technical info.

[scottspeed]

The decent japanese branded large 2 inch up-pipes, actually have a choke (like a carburetor venturi) fitted inside out of view, to actually give the exhaust gas a speed up to lessen the lag associated with a plain 2 inch up-pipe