richard1522

iTrader: (2)

Hi all,

I have a blobeye which i have spent alot of time and money on (as every scoob i'm finding) but after a blow in mt new up pipe and a chat with my mapper i have been thinking about upgrading my headers and the up pipe to again to maximise air flow.

I have heard of alot of different different headers but not entirely sure which is best suited or the difference between them.
Can you help?

I have had a email from harvey about his Ported headers mkIII and up pipe but whats the different from tubular headers,Ported headers, Unequal and equal???

I currently running about 320BHP using, VF43, pink injectors,3" straight exhaust,STI,TMIC,Walbro pump and a cosworth panel filter.

Any light would be great fully taken on board.

Thank you

Scooby see-Scooby do

iTrader: (3)

equal headers will remove the flat four burble so thats a + or a - depending on how you feel about the sound of your car (if you want it to sound like a corsa with a 'zorst' get the equal length). Thats as far as I can help

bunsofsteeeel

iTrader: (1)

if you speak to bob rawle he does'nt reccomend unequal headers.

daijones

Ported unequal length headers probably better up to 400bhp, tubular equal length headers after that. There's a comparison by Andy Forest here:
http://www.geocities.com/harveysmith...omparison.html

richard1522

iTrader: (2)

From what i hear harveys ported headers and up pipe are the ones to go for but still after reading that i'm a little confused to what the difference is between the two

daijones

As I understand it:
The length issue is to do with the path from the exhaust ports on the engine to the uppipe into the turbo. The turbo is located to one side of the engine, and because the engine is a flat four with the cylinders in two horizontally opposed pairs, one pair of cylinders has its exhaust ports further away from the turbo than the other pair. The headers are basically pipes that carry the exhaust gas from the engine ports and combine them into the uppipe. The standard headers have shorter pipes from one bank of cylinders to the uppipe than the other bank, hence the phrase unequal lengths. That gives the burble, but it means an irregular pulse of gas coming up the uppipe into the turbo. Equal length headers are designed to have equal pipe lengths from each bank of cylinders, making the flow of gas up the upipe more even but eliminating the burble through that evening.

Porting is a process that machines the headers to improve the flow of gases, making it more efficient. The standard headers aren't optimally machined, being mass produced to a budget. Basically you want the exhaust gases to get from the engine to the turbo as quickly as possible, and porting helps speed this up. Wrapping the headers helps to keep the heat in the exhaust gases, and hot gas flows more quickly, so wrapping is a good idea if you're changing the headers anyway.

As far as I know, tubular just refers to the way after market headers are constructed, and after market headers are generally equal length, so the two terms are sort of, though not necessarily, synonymous. After market headers are more carefully produced than the factory standard, so are less likely to need porting.

You can see porting as a cost effective way of improving the performance of the standard headers, and equal length headers as a more expensive improvement. However, equal length headers involve a compromise. Evening out the flow of gases to avoid the pulsing of the standard headers is good, because it makes the flow of gas into the turbo less turbulent giving more even spool. However, it means the pipes from one bank of cylinders is longer than necessary, since they're lengthened to match the length of those from the other bank. So, with equal length headers you can get more out of the turbo, but at the cost of longer spool up times. At lower power levels people will often prefer to maximise spool up, so go for improved, ported, standard headers. At higher power levels with big turbos spool is going to be slower anyway, but also less of a problem because of the sheer amount of power available, so people prefer equal length headers.

In either case, it's worth getting a new uppipe also, since the standard uppipe suffers the same problems of mass production etc. Harvey is the master of all this stuff, and has designed custom uppipes to match both his ported headers and selected after market equal length headers

Having said all that, I could be talking bollocks and stand to be corrected!

daijones

As I understand it:
The length issue is to do with the path from the exhaust ports on the engine to the uppipe into the turbo. The turbo is located to one side of the engine, and because the engine is a flat four with the cylinders in two horizontally opposed pairs, one pair of cylinders has its exhaust ports further away from the turbo than the other pair. The headers are basically pipes that carry the exhaust gas from the engine ports and combine them into the uppipe. The standard headers have shorter pipes from one bank of cylinders to the uppipe than the other bank, hence the phrase unequal lengths. That gives the burble, but it means an irregular pulse of gas coming up the uppipe into the turbo. Equal length headers are designed to have equal pipe lengths from each bank of cylinders, making the flow of gas up the upipe more even but eliminating the burble through that evening.

Porting is a process that machines the headers to improve the flow of gases, making it more efficient. The standard headers aren't optimally machined, being mass produced to a budget. Basically you want the exhaust gases to get from the engine to the turbo as quickly as possible, and porting helps speed this up. Wrapping the headers helps to keep the heat in the exhaust gases, and hot gas flows more quickly, so wrapping is a good idea if you're changing the headers anyway.

As far as I know, tubular just refers to the way after market headers are constructed, and after market headers are generally equal length, so the two terms are sort of, though not necessarily, synonymous. After market headers are more carefully produced than the factory standard, so are less likely to need porting.

You can see porting as a cost effective way of improving the performance of the standard headers, and equal length headers as a more expensive improvement. However, equal length headers involve a compromise. Evening out the flow of gases to avoid the pulsing of the standard headers is good, because it makes the flow of gas into the turbo less turbulent giving more even spool. However, it means the pipes from one bank of cylinders is longer than necessary, since they're lengthened to match the length of those from the other bank. So, with equal length headers you can get more out of the turbo, but at the cost of longer spool up times. At lower power levels people will often prefer to maximise spool up, so go for improved, ported, standard headers. At higher power levels with big turbos spool is going to be slower anyway, but also less of a problem because of the sheer amount of power available, so people prefer equal length headers.

In either case, it's worth getting a new uppipe also, since the standard uppipe suffers the same problems of mass production etc. Harvey is the master of all this stuff, and has designed custom uppipes to match both his ported headers and selected after market equal length headers

Having said all that, I could be talking bollocks and stand to be corrected!

vindaloo

IMO for a 2 litre engine that's probably right. In theory, at least, correctly sized equal length headers will outperform the Subaru ones. Most tubular headers I've read of are either American market or copies thereof, to suit the 2.5 litre engines.

J.

STI Glenn

Recommended by Bob rawle i fitted Lateral performance tubalar headers worked fantastic

MaDaSS

Harvey has done extensive testing on this subject. Ported OEM headers and one of Harveys up pipes is all you need for your requirements. Harvey will not even recommend header replacement until going for over 400 bhp. At 320 bhp OEM ported headers will aid and possibly lower the spool up point for the turbo. When you change to other headers (as i have for around 330 bhp) you will, most definitely WILL lose out around 300 to 500 revs whereby your turbo will be spooling up later than it is now. It is NOT worth the money, expense, etc of doing this for what amounts to bugger all gain on such small power. Trust me, get your OEM ones ported and wrapped, or exchange them with Harvey as he does this regularly and knows his stuff. I spent hundreds on GT Spec II headers from Tracktive, they are ceramic coated (more hundreds) and I wish i had just stuck with OEM tbh.\
Your choice, but i would not do it again for power less than 400 bhp.

richard1522

iTrader: (2)

Oh ok so perhaps it is not worth doing at all?while i'm still under 400bhp? I was speaking to Duncan who mapped my car and he was very sure it would really help?

no1nutter

iTrader: (1)

porting the headers will definately help, as for changing them, well 400+bhp it would be a must, but sub 400, porting will improve performance.

daijones

Hard to comment cos I got my Harvey ported headers and uppipe at the same time as changing the turbo on my hawkeye WRX. I went from the standard TD04 to a Harvey-ported VF35. Now the TD04 is, AFAIK, by reputation a quick spooling turbo; the VF35 still quite quick spooling, but noticeably less so. Following a remap, my VF35 spools up about 100rpm slower than the TD04, which I believe, and I may be wrong, is a few hundred revs less of a gap than you'd normally expect. So I conclude, again possibly wrongly, that the quicker spooling ported headers made up for a fair proportion of the inherently slower spool of the VF35.

But i may just be telling myself that to make myself feel better

BTW, TD04 - 290bhp; VF35 330 bhp; dyno readout:
http://www.facebook.com/photo.php?pi...6&id=512040079