Ported factory headers and upgraded cross/uppipe

[Stoffa]

Since I've had so many people asking about it I thought I'd start a thread with the details

After reading about Grimmspeed and a few other companies are doing I thought I'd have ago myself as I hear so many problems with stainless headers cracking and also losing some low down torque.

So I started off by porting out my factory collectors and gasket matching them all, just did a quick/rough job, about 4 hours porting all up.

Heres a before and after

The factory cross pipe has a very smalll inside diameter and even drops to 36mm through the bollow/flexi, which cant be a good thing, so out it went, I got some flanges laser cut the same size as the gaskets for it (46mm inside diameter),

Then got a new flexi a little bigger than I needed so I could get a slipjoint made inside it, as the flexi's with the crisscross stainless wire inside them can melt being so close to the exhaust ports, then took it to a mate of a mate to get the new cross pipe made, it now has an ID of 46mm the entire way through and the 2 joins on the inside have a very small step where they meet the flared bits in the slip joint but step in the right direction of the flow to cause minimal turbulance.

pics with factory one next to my new custom one

I also bought a Trust uppipe which is mandrel bent with no flexi, I was told its a good idea to keep the turbulance to a minimum the closer you get to the turbo. (sorry no pics its already on the car) also the factory one has some messy squashed bends and another small flexi that steps out interupting flow.

My upipe's flange is the same size as a factory gasket but does have the pipe itself on the inside of the flange so a small step there unfortunatly.

So everything is port matched from the heads to the turbo, including the turbo exhaust housing (thanks to Steve Murch MSE)

I then heat wrapped with good DEI wrap not the crappy stuff that falls apart, also soaked the wrap in a bucket of water which makes it easier to work with and it shirks a bit tighter once its dry. Then I stainless wire tied in to keep the wrap lasting even longer, then (after it was dry) used the DEi high temp silicone spray paint which soaks into the wrap and bakes in when it gets up to temp stopping any water getting into the wrap.

finished product

[Stoffa]

Heres some threads that helped my research

heres a thread about the factory cross pipes

http://forums.nasioc.com/forums/showthread.php?t=1230511

heres some flow test done by grimmspeed, I believe my cross pipe is a few mm bigger than the grimm speed one

http://forums.nasioc.com/forums/showthread.php?t=1942411&highlight=grimmspeed+flow

uppipe thread with sizes

http://forums.nasioc.com/forums/showthread.php?t=1561572

grimmspeed review

http://forums.nasioc.com/forums/showthread.php?t=1205915

grimmspeed thread

http://forums.nasioc.com/forums/showthread.php?t=1237071

grimmspeed porting

http://forums.nasioc.com/forums/showthread.php?t=1221016

[WRXONP]

Great stuff what's the id of the turbo inlet and Id of the outlet on the manifold where up pipe bolts on ?

[Stoffa]

my uppipe is 46mm ID the whole way through, some aftermarket ones get smaller as they get to the turbo. but couldn't really find much info about the trust one, just took a punt and ordered it.

the turbo is gasket matched, I think its about 48-50mm from memory, my uppipe flange matches the gasket and turbo perfectly but the pipe itself is welded on the inside edge of the flange, but its probably stronger there

[WRXONP]

Ok - the only thing I don't get Is that why does the c

X over pipe need to be the same diameter as up pipe ? The up pipe carries all 4 cylinders exhaust gasses and the x over only 2 cylinders worth ? Wouldn't the x over pipe want to be smaller than the up pipe ?

May be wrong just trying to get my head around it

[Stoffa]

It doesn't need to be the same. just turned out that way.

the big thing is getting the restrictions out of both pipes.

have a read of some of those links

[sultan]

Im in belief that any improvements to flow only make the turbo spool later and gain a few kw more up top. Rob peter to pay Paul. But your work looks really good, i look forward to feed back of how it performs

[WRXONP]

I thought unceasing flow would increase spool and top end ?? And a larger x pipe and up pipe would have a better top end but take longer to fill creating slower response ???

Basically let them answer them self tho I think - will be awesome to see results

[sultan]

Velocity for spool, flow for peak

[Stoffa]

And ported heads to make it have more of both

But if my crosspipe is 10mm (20%) bigger than factory and uppipe only 4mm (10%) bigger, percentage wise I've increased the cross pipe size and flow more than the uppipe so hopefully i'll end up with more velocity in the uppipe which will help spool.

[maserati mick]

nice work

[WRXONP]

Flow as in smoother transition between flanges should theoretically increase both shouldn't it ?

 sultan said:

Velocity for spool, flow for peak

[Jord]

Nice one, I think it was Wildturkey that did a similar porting job on his RS headers. Some of the factory casted ports have massive lips where they join esp. on the crossover pipe.

[Stoffa]

yeah he saw mine and i pointed him in that direction, he ditched the rs headers and used v5 ones, the rs headers twist the flow in funny directions, also heut he has just ported each end of the factory cross pipe.

aparently made it have a bit more bark on his car and that was with the factory cross pipe.

so hopefully it all works as I want it too

[slystiguy]

can't wait to see the results! fantastic work an research! and good on you for sharing the information!

[Stoffa]

forgot to post a DIY I found

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

[soopersubaru]

There is no doubt that nice clean flow does assist turbo run up to speed. However Heat is what runs a turbine...Therefore the insulating of the header set-up plays a far more important role in reducing lag time.

The standard headers deliberately "step" down in size to increase velocity and create a slight vacuum as the exhaust valve closes. Allowing for better overlap valve cooling at TDC on exhaust stroke.

Larger headers are generally required for powers exceeding standard.... velocity is maintained at higher powers!

Then a larger waste gate is also needed to allow excess gasses to be discharged pre turbo under WOT.

[rex-leggy]

 soopersubaru said:

Then a larger waste gate is also needed to allow excess gasses to be discharged pre turbo under WOT.

boost dependent?

[WRXONP]

 rex-leggy']

[quote name='soopersubaru said:

Then a larger waste gate is also needed to allow excess gasses to be discharged pre turbo under WOT.

/quote]

boost dependent?

a larger diameter wastegate is only ever needed when u have boost creep (wastegate cant let enough gasses out)

and normally you will only get creep when trying to hold low boost - u need to bypass less gasses to hold higher boost

a harder spring is whats normally needed to hold higher boost (caused by EGBP pushing wastegate fully open) causing boost tapering off

[rex-leggy]

 WRXONP']

[quote name='soopersubaru said:

Then a larger waste gate is also needed to allow excess gasses to be discharged pre turbo under WOT.

/quote]

boost dependent?

a larger diameter wastegate is only ever needed when u have boost creep (wastegate cant let enough gasses out)

and normally you will only get creep when trying to hold low boost - u need to bypass less gasses to hold higher boost

a harder spring is whats normally needed to hold higher boost (caused by EGBP pushing wastegate fully open) causing boost tapering off

thats what i was getting at who cares just crank the boost up bro

thats what im doing anyway , saves $$ with only needing a 38mm

[WRXONP]

if you run a 38mm with a ebc (which puts air above the diaphram) it over comes the whole egbp overcoming the spring pressure anyway cos the air above the diaphram aids the spring even if its only a 7psi spring

edit ** are you running a wastegate off the up pipe?

[rex-leggy]

tru im liking the job youve done stoffa .

i must get my headers off and port match much like what you have done

[soopersubaru]

with true potential from both the engine and the turbo and with a "perfect turbo" with engine matching to reach full achievable power......a waste gate is required..

Perfect header design is also important when matching up the design with facts and reality.higher powers above original design are bigger. and a must...to get rid of more waste gases.

increase the diameter and volume increases and velocity slows. turbo inlet velocity will remain constant.

Increased diameters in the lead up to the turbo means that the pulse wave from each cylinder is further away from the turbo.

The more modern design of the subaru standard setup has "more squiggly internal manifold" bits to maintain tune of the pulse wave. Plus or minus the allowance for accuracy

Lining up and "fairing" is of definate benefit as it is allowing cleaner flow.

True and correct control of size ( length and diameter balance).. versus pressure wave balance through the pipe work... is but one key to reliability and balance of maximum horses/Kw/Torque

Insulation is of importance too in maintaining pressure wave evacuation performance and also greatly increases turbo performance. Especially with Subarus extended across to one side and back up and over, neat and clever setup.

32 mm a wee bit too small for me.(got white hot and split)

42 mm Sweet..equal length... matched with down pipe/ exhaust along with custom insulation..works for me.

[Koom]

 soopersubaru said:

However Heat is what runs a turbine...

If that were true I'd just stick mine in an oven and make it pump out 40psi :

Pressure difference across the turbine is what drives them. Heat being just a part of the perfect gas equation of state;

Which will then lead on to the mass/volume flowrate equations etc etc.

So in summation; heat is important, but so is flow. If you have untidy sections of pipework then you're just loosing flow through bad turbulence.

[Stoffa]

no external wastegate for me, no need!! I'll be running my VF36P2018G ;D ;D that Steve Murch made for me, with factory internal gate and an uprated actuator (14psi spring) from a PE1820 (thanks swee)

If it does blow open I'll simply upgrade it with a forge one with a 21psi spring

here...