*****

 

The good news is at least your sti7 heads are not he small port variety.

You may with to open the injector port into the TGV housing, but to be honest, it might not be too bad. If your concerned, the best thing I can advise it to get the manifold, TGV and head assembly flow tested, or at least the manifold and tgv bit.

Paul

 

Paul, Tumbler assemblies are not in the new set-up Heads will be flow tested before & after.

 

I know you are getting the custom inlet manifold. Although I would ask yourself why prodrive use a my92-96 manifold reversed. Although probably due to rules, they can't currently fab a new one, because they did in 2000.

Head wise, the vavles are already quite large, although thre is room for larger ones, it's probably more trouble that it's worth. Although you can probably go 1-2mm larger with the same seats. Any larger means offset machining new guides and valve seats. A large port subaru head does flow very well as it is.

If you're interested in selling your inlet manifold, throttle body and TGV housings, drop me a mail, as I can think of a use for them.

Paul

 

Paul, what does the MY92-96 manifold look like, do you have a picture? By reversed I assume you mean throttle body at the front?

I will probably let the STi inlet manifold and tumbler housings go eventually but I'm hanginging on to them at the moment. They will be up for sale as soon as the STi V7 short motor is ready for sale.

Valve sizes are not decided yet, may change the valve seats becuase they are very poor ( on this engine anyway )

Conrad

[Edited by RSVR Racer - 11/23/2003 4:56:25 PM]

 

What do you mean by "very poor"?

If you mean poor condition, they can be re-cut, preferably with a multi angle cut, as part of the porting/flowing work. You will most likely want to get some work on the chambers too, which will usually mean a valve seat cut.

I wouldn't be very happy about putting in new valve seats, as the heads often crack from the plug hole and inlet valves, where the material is perilously thin.

Get your heads stripped, cleaned and crack tested before anything else, you may have a nasty surpise.

Paul

 

I mean very poor in the way they are fitted as standard, probably just the usual mass produced finish I'm looking at. I'm used to looking at seats in WSB Ducati engines . It will all be taken care of.

 

got any nice bits for a 996??

David

 

"way they are fitted"

Erm, they are fitted like every other vavle seat in an alloy head.

I take it you mean the finish around the seat, and the small step the often occurs when they finish machine the internal diameter.

As heads go the finish is good as standard. But if you get the heads ported, and it sounds like you are, the valve seats would be blended into the port.

Paul

 

I was referring to the quality of the finish. It'll be sorted in tdue course as you pointed out.

When's your engine going to run, interested to see how your cam profiles work.

Conrad

 

I have no date for engine fitting, need some stuff first.

But camwise Adam's engine which is very similar, has 268 duration cams, and still has more torque everwhere in the rev range than a UK turbo.

Paul

 

I am glad to see you have spoken to your engine builder about head port sizes. Prodrive have even sleeved down the ports on their engines for this very reason, although now I bet they are using the smaller port head to start with.

However, for your targets, which I can only assume from the way you've been posting must be pushing 600hp, you do need to seriously look at high flowing heads. But that doesn't mean huge ports, just correctly shaped ones.

Part of the problem with the subaru engine is the layout. The long branches of the inlet manifold will limit top end HP, I wonder if this is the reason some of the other aspects seem so wrong (like large ports), to balance it out. Doesn't seem like the right way to me, but it seems to work to a fashion.

If you are getting a custom inlet manifold, then you can look at getting a shorter run on the branches, and a larger plenum. If you get rid of all the fuel line and breather crap underneath, you would easily be about to run a pipe over the top to go from turbo to intercooler, something to think about. An easy way might be get an early manifold, weld on new flanges for heads and a new plate for throttle body to mount on (flip manifold round and redo existing throttle body mount).

Paul

 

paul that last paragraph sounds just like a conversation I had with someone in a pub about a week ago..

 

I have seen this hybrid manifold done before when a guy fitted a MY99 engine to his MY95 WRX. He cut the last 2" off the Ph2 manifold and welded it to the Ph1 manifold. There was a bit of a step though, I think the floor height of the inlet ports differs between Ph1&2 heads.

A tubular/sheet alloy manifold wouldn't be too hard to make up to your own spec though ? May as well build in individual TB's too and pair the cylinders 360 degrees apart , not like the JUN car where they paired them 180 deg apart....doh

Oops did I say too much

Andy

 

Conrad,

I am curious what the sticker on the cam belt cover tells with your engine. There are a lot of differences with my engine! Is it a eurospec version?

I have the small port heads and big manifold.....

My sticker tells: EJ207NW5CR-156 this is a MY03 eurospec STi engine.

From what I can see in the pictures, your intake manifold looks quite restrictive!

Mark.

[Edited by EMS - 11/24/2003 8:47:55 AM]

 

Andy, if you find any suitable tb's let me know...

I was thinking similar.. I hadnt thought about the pairing though.. why would you do it that way??

I was thinking along the lines of flybywire throttle using stepper motors to control the throttle's would also help with antilag as I wouldnt have to use either a throttle kicker or a valve..

David

 

Andy, Paul, David, will you three stop thinking about this inlet manifold set up....lol Heres the idea....

The setup will consist of 4 (2 pairs)throttle bodies mounted directly to the heads. A short inlet tract towards each pair of throttle bodies will meet up with two plenums that sit over the top of each throttle body pair. Quite how i split the single intercooler feed evenly I'm not sure yet, i'm sure some sort of balence pipe will follow between each plenum. What you end up with is air compresed air sitting behind each throttle body butterfly and thus a very short inlet tract. When the GO pedal is pressed the air is there, it doesnt have to travel from the butterfly down the spiders legs manifold like the existing system

Paul, here what your saying re port size, its all in hand, the port size has to be a specific ratio in its volume to the size of the inlet valve, it can be bigger but it won't do jack sh*t
As you rightly said big ports are not always neccessary, it can be down to port velocity.

Conrad

 

Sounds like you must be working with Steve, in which case heads and cams shouldn't be an issue. If you are going to throttle bodies, then that's about the best solution.

Paul

 

Not working with Steve Steve Who? From SMG?

Conrad

 

Yes Steve from SMG. Mainly on the basis that I know he has a throttle body solution sorted, just as you describe, and he also knows what's what on the cylinder head front.

Paul

 

Oh well, I always find out that little bit too late, still theres more than one way to skin a cat as they say. Plenty of stuff to do before the manifold....

Conrad

 

Of course! That is why Subaru is using the bigger port heads on the most powerfull versions....

I will put them on a flow bench later to see the differences.

Mark.

 

Mark, bigger port heads is not neccessarily bigger power, as I quoted the port size is a direct ratio to the valve size, if the port is any bigger than that it has no further effect. This why Subaru have probably gone down in port size with the later cars.



Conrad

 

 

Paul, your point is.....

 

Last week you were a headless chicken with a power complex, now you are a head expert!

The subaru valves are on the large side, 36mm inlet valves? I think that an evo uses 34mm valves. The stock 'large' subaru ports are not that large in relation to valve sizes.

There is a lot more to the port/valve layout and proportions that one ratio, you would do well to find out, as I am sure you intend to. I'm not saying I know everything, and I certainly don't know enough to suggest that flow testing small port heads verses large port heads would be a pointless exercise.

Paul

 

The "big port" heads are fitted as standard on all of the latest JDM STi´s. The "small port" heads are only used on the "normal" WRX and on the Eurospec STi. Probably for gains in the lower rev range. I don´t think the "big ports" are too big, the shape of the ports looks very well indeed.

Mark.

 

Paul, at which point did I claim to be a I didn't thankyou. I was merely passing on what my engine tuner told me when we were discussing port volumes. I don't mind constructive criticism but posting with no text is of no use to anyone. Your reply was much better, keep it up

NB: headless chicken mode is still off at the moment, I've given up on that one.

Mark, I would'nt like to guess (as I don't know or havent been told ) why the JDM cars have larger volume ports. Do the JDM cars have the same inlet valves / camshaft? When chatting with my engine tuner I was discussing with him how the WRX seems easier to get over the 400 BHP mark than the STi. I believe the WRX has a more agressive intake cam (duration wise) and this could be the main difference?

Having chatted today, we are seriously considering ditching the VVT, it seems to serve more purpose for emission control rather than power gains. Oh well....

 

Are you sure about ditching the AVCS?

I will have to get the link to a NASIOC thread, it shows it's good for about a 500rpm improvement in spoolup on a given turbo

Paul

 

Paul, I'm not sure really, I bought that engine specifically for the VVT, Could have picked a non VVT one up a lot cheaper. Everything seems stacked against it, ECU's require extra programs, theres no drop in cams (I know you can organise regrinds for me), vernier pulleys don't exist etc. Its my engine tuner who's trying to sway me....

At the minute my minds on getting the car "as is" to run properly before I go further down the line with this one.

Conrad