Brian has Harvey ported manifolds (sorry I'm British not American) little to be gained from changing the up-pipe on substantially standard cars like yours.

Simon

 

Hi guys,

I bought Harveys ported headers and uppipe for my 2006 FSTi (had a Litchfield Performance Pack so turbo-back sports cat Milltek and Ecutek already in place).

I travelled over from Northern Ireland to Harveys at Christmas just past (in Darlington) to coincide with one of Bob Rawles visits so had the car remapped at the same time.

I only did a couple of miles up to about 30mph after the headers/uppipe were fitted and before the remap - but everything Harvey says is true. There is notably better torque from the instance you let the clutch out and it definately spools a good few hundred rpm earlier.

After the remap (I believe boost was capped at 1.3bar), the car was simply much stronger at every point in the rev range. When going for it, it is quite savage when it comes on boost but very progressive thereafter. Whilst previously there was a very significant drop off around 5,500rpm, the car still pulls well to almost 6,500rpm. Bob warned me that the engines detest the limiter being hit so probably a good thing the power doesn't keep going all the way to the redline.

[I also had my downpipe wrapped, a K&N panel filter in place, colder plugs and a set of larger injectors fitted (just in case). Harvey, Darren Moore (mechanic) and Bob were all fantastic value for money.

I have no before or after dyno prints, just seat of the pants observations, but if you've any questions, ask away.... though both Harvey and Bob couldn't have been more friendly and informative about what does and does not work on these engines...... and they are usually very prompt at responding to emails.

Steve

 

Hi Steve and thanks for the info.
I have exactly the same car so good to know.
Were the headers and uppipe you bought from and Impreza and if so which MY?
Did you also wrap the headers or did you use the OEM heatshield that they come with?
Did you part-ex your OE headers/uppipe?
I asked Harvey about the Forester Sti headers/uppipe but he was not sure whether Impreza ones will fit
Does the uppipe and headers have a slip joint , do you have any photos of them?
Does the undertray still fit in the car?
What plugs and injectors are you using?
Did you have to remove the downpipe to get it wrapped and was it an easy task?
I have heard it can be tricky due to the oil pipes of the turbo being near by.
Do you have any other mods (e.g. 3 port, boost controller etc.)?
I would be interested to see a dyno chart of your car.
Sorry for the so many questions and thanks for your help! :rock:

 

Fivos,

You forgot to mention suspension :biggrin::biggrin:

I swapped out my MY03FXT headers for a set of Impreza one's that I ported prior to fitting. I wrapped them but also fitted the OEM heat shields as well.

(Reason being MY03 headers are rather restricted (peashooter size)compared with all other model years)

The FSti up pipe, if it hasn't got the pre-cat, its probably the best option going.

If you want to wrap your down pipe the ONLY way to do it properly is by removing it first.

 

I had a set of ported headers on my TypeR about 8-9 years ago. I matched all the gaskets and made sure i did not open up any of the flow channels bigger that they needed to be, (This was the advice by Harvey, Andy Forest and the other guru's at the time).
I think it made about 5bhp on the next dyno, without a map tweek (Same dyno).

But I fitted a set of HKS tubulars and got an extra 15bhp on top of that later on. (same dyno again and after remap).

I could'nt do the same trick on my next scoob, as it was Twin Scroll, but it did produce a gain.

 

Fivos, mine has had nothing but the automotive equivalent of sherbet dip thrown at it and it still made 360. No need to fanny around with ported this and wrapped that to get more torque...just get it to the JGM and let him sort it.

 

Fivos

No worries re the questions. To be fair to Harvey, Darren Moore did the spannering but there was no suggestion of any difficulty in fitting re Impreza v Forester.

I asked Harvey for his headers and up pipe for a 2006 Forester STi and he gave me what he had on the shelf. He wrapped them both - doing a very smart job and when I went over the down pipe was removed and wrapped also. Darren is very efficient and easy to pay - I had all my fluids done at the same time - removing the down pipe was easy for him.

Everything looks the same except you can see the wrap! I can't comment re heat shield (not sure if the Milltek does away with it?) Surprised he wasn't absolute re Impreza v Forester - remind him I was there 5 weeks ago and it
might jog his memory.

Harvey kept my original headers and up pipe.

Under tray is still there - it was very important to me that everything looked
factory and it does. No slip joints on either headers or up pipe.

Plugs were 7's NGK as recommended by Bob. I got 555cc Nismo injectors from Lateral (Bob suggested this as a precaution - I don't know what they are
running at % wise so they may not be absolutely necessary depending on how
far things are pushed!). I also had a fuel pump fitted.

Bob said I didn't need a 3 port so I don't have one!

If you PM me an email address I'll forward you a few emails from Bob and
Harvey tomorrow.

I need my car to tow 1500kgs reliably so I asked Bob not to push things to
the absolute limit but he is obviously gifted and aware of the limits etc. My
biggest limiting factor was the fact that the only widely available super
unleaded in Northern Ireland is Bp Ultimate which both Harvey and Bob detest!

I have no photos or dyno graphs - to be honest photos won't show much and my butt dyno is pretty accurate re the improvements across the rev range. Economy hasn't changed.

On the outside of the car the only change is the noise the fuel pump makes.

Hope this helps.

Steve

 

There's a huge thread on NASIOC about ported stock headers vs tube headers. Upshot is that lots of tube headers are crap - the only one that got an unequivocal thumbs up was the GT Spec one - the later version has a mod which I forget but is better.

All cars where the stock headers were ported and wrapped had better spool, better top end and more torque. Some people seemed to think that installing them accurately was a big help as the exhaust ports and the headers can be 'off'.

STI headers are better than WRX or Forester ones which I think are the same. Perhaps.

I've been meaning to do this for ages. I had a set of STI headers in my sights on fleabay before Xmas but gave up when I realised I was bidding against the seller.

I suppose the easiest way to do it is to buy a set, port and wrap them then swap for the ones on your car so you're not car less while you mess about with them. Then you can give me your old ones.....

 

I suppose the easiest way to do it is to buy a set, port and wrap them then swap for the ones on your car so you're not car less while you mess about with them. Then you can give me your old ones.....

Yes, that is just what I did and it took quite awhile ! I did my own porting rather than buy Harvey's. No problems.

Brian

 

The problem with headers generally is that they have a bigger internal volume than the stock pipe so they take longer to fill and pressurise therefore spool takes longer. Of all the tested ones GT Spec seems best and some say spool is better. If you think about it a larger turbo takes inherently longer to spool so adding headers will not make the whole thing better it will make it worse. Large turbos + headers = lag but big power. Can't argue with the laws of physics.

I saw the custom headers on the Zen race car and they were tiny - I mean the diameter was like a piece of copper radiator pipe. Well almost. Didn't stop it making 700hp though.

Problem is people want BIG headers cos they think they'll make more power. So manufacturers make big headers because the customer is always right....:crazy:

There are those who know what they're talking about who are quite sure that headers can make good power improvements and better torque as well as making the car quieter (surprisingly) and lowering engine temperatures.

I suspect that a decent set of cams and a good set of headers (arguably the two biggest 'roadblocks' in my engine) would give me 50ph or near without really affecting reliability. Fuel consumption might drop a little :shrug: And the gearbox would probably give the f&ck up :icon_sad:

 

I was interested to note from a recent conversation with Hayward & Scott that the latest batch of de-cat up pipes are of a slightly smaller diameter to improve gas speed and reduce lag.

 

Unless you are going for big numbers, smaller is nearly always better with turbo exhausts, the biggest source of back pressure is the turbine housing anyway, so if correclty matching an engin you can go down on exhaust size and up a fraction on turbine sizes to get better responce, lower back pressure and greter efficiency!

Simon

 

So what's the whole fuss about porting then?
As I understand porting will open the entry of the pipes to make them smoother.
I agree that bigger means slower gas speed which means it takes longer to spool the turbo.
Smaller diameter makes sense indeed.

 

Porting smooths any obstructions which will reduce turbulence and therefore improve laminar flow resulting in higher gas density and speed.

 

Hi,
fpan invited me over from another forum for a chat,
I'm running an md321t+ turbo, gt30 based standard position turbo rated for 475 bhp,
I am on my 3rd set off tubular headers, with the heat and abuse they warp out of shape and leak badly, a lot of the different brand tubular headers are made in the same factory, and company's just put their label and mark up on them,
If this most recent set break again, i'll be putting harvey ported headers on her,
It is mentioned above that bob rawle says you don't need a 3 port solinoid, I had a td05-20g fitted and the boost was all over the place, so if going bigger turbo, Defo get the 3 port, mine was mapped by bob,
Also when my car used to hit the rev limiter, the power would just go for a few seconds, which was very inconvenient if you happen to be half way around a bend sideways, so I had Andy forrest map her and he made it so when the rev near the limiter, the ecu reduces power so you don't just whack the limiter, and that works beautifully,
Also, you loose a bit of the rumble with tubular headers,
If I was to do of all again, the setup would be, a small gt30 based turbo, for maybe 390 bhp and 400+ lb/ft, with 740cc's, 3port, in the wing cold air feed, ported headers fuel pump. And remap, maybe an impreza sti intercooler, and mapped by either Andy forest or JGM, and she'll be reliable and very very quick, about 25mpg is realistic,
That would be the very best bang for your buck,
Also, 20mm bolt on spacers work really well with the fsti's standard alloys
Best of luck, whatever you do,

Dan

 

This is something that I once wanted to do, but have held off because almost every build with ported manifolds is accompanied by a remap. I have found this rather old post on another forum that really helped me to decide to skip it. I hope you all find it as helpful as I did.

Subaru Impreza WRX STI Forums: IWSTI.com - View Single Post - OEM exhaust manifold porting

 

Link to harveys earlier post on porting:

http://www.subaruforester.org/vbulletin/f75/porting-promised-38170/

 

When I did mine there was no attempt whatsoever to widen the tubing. It was cleaned out to remove the carbon build up and just smooth out very slightly the interior faces. The major effort was to make sure that the pipes , gaskets and manifolds all matched and there were no lips, intrusions or buffers to halt a smoother flow. There were some excellent write-ups on this forum that a diligent search turned up and good photos. It was quite surprising that the opening of the manifold sections did not match very well when putting one face to its matching piece.

Brian

 

Out of interest, what BHP/Torque figures are you after ?

 

Interesting info Dan.
At least you have tried and you know what works/not which is good as opposed to people suggesting this and that because everyone says it.



Mid 300 I think is more than enough.
Although the headers are not going to gain you more than 5bhp, the only reason I thought about them is if they move the torque curve to the left.

 

I gasket matched mine but never fitted them..

Surrey Scoobies

 

The beard is strong in this thread