changing to a vf34
17 March 2006, 06:39 PM
#1
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changing to a vf34
hi i was just wondering what majority of you recamend with regards to headers. i've got a 2001 wrx with full decat exhaust an ecutek remap and an sti intercooler. but ive just bought a vf34 and was wondering whether i should change the headers to equal length ones and loose the burble, change them for slightly un equal ie. group s ones, get the standard ones ported or leave them as they are. im looking for around 330bhp. thanks in advance.
18 March 2006, 12:12 AM
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Originally Posted by TI7OJO
can any one else shed some light?
From the research I did it seemed that porting the oe headers was the way to go hence the reason I headed down that route...
Definitely worth getting in touch with Harvey as he's very helpful and one of these guys who doesn't pressure you into buying things that you don't need. (He posts on Scoobynet so he may see this thread and reply to you)
His website - http://www.geocities.com/harveysmith3000/
Good luck
Nick
18 March 2006, 11:13 AM
#6
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Depends what you want. Unequal length headers are an inefficient way of driving a turbocharger, hence why they are got rid of as soon as you are aiming for big power. But they are fine for the lower stages of tune and I'd be very surprised if aftermarket unequal length headers showed significant improvements over the factory ones, and sets of ported factory headers show great results. If only they were a little cheaper to get done.
Either leave them alone, get the factory headers ported or go to a proper equal length tubular headers if you're aiming for big power eventually. From a performance point of view, keeping the unequal length headers can't really be justified. But the sound is nice, so most people keep them. What IS pointless is replacing your factory headers with aftermarket unequal ones.
Either leave them alone, get the factory headers ported or go to a proper equal length tubular headers if you're aiming for big power eventually. From a performance point of view, keeping the unequal length headers can't really be justified. But the sound is nice, so most people keep them. What IS pointless is replacing your factory headers with aftermarket unequal ones.
18 March 2006, 12:59 PM
#7
Originally Posted by silent running
Depends what you want. Unequal length headers are an inefficient way of driving a turbocharger, hence why they are got rid of as soon as you are aiming for big power. But they are fine for the lower stages of tune and I'd be very surprised if aftermarket unequal length headers showed significant improvements over the factory ones, and sets of ported factory headers show great results. If only they were a little cheaper to get done.
Either leave them alone, get the factory headers ported or go to a proper equal length tubular headers if you're aiming for big power eventually. From a performance point of view, keeping the unequal length headers can't really be justified. But the sound is nice, so most people keep them. What IS pointless is replacing your factory headers with aftermarket unequal ones.
Either leave them alone, get the factory headers ported or go to a proper equal length tubular headers if you're aiming for big power eventually. From a performance point of view, keeping the unequal length headers can't really be justified. But the sound is nice, so most people keep them. What IS pointless is replacing your factory headers with aftermarket unequal ones.
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18 March 2006, 01:29 PM
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Silent running,
Nearly all of the aftermarket tubular manifolds are "unequal" length, whether they are the Gruppe-S/HKS, 3 bolt GT Spec' or the host of other styles.
All of these headers work very well, and are more efficient than the standard headers, even if they are ported, and wrapped.
Porting the standard headers certainly gives some improvements, but reducing the bore of the up pipe is the main reason for the improved spool up.
Mark.
Nearly all of the aftermarket tubular manifolds are "unequal" length, whether they are the Gruppe-S/HKS, 3 bolt GT Spec' or the host of other styles.
All of these headers work very well, and are more efficient than the standard headers, even if they are ported, and wrapped.
Porting the standard headers certainly gives some improvements, but reducing the bore of the up pipe is the main reason for the improved spool up.
Mark.
19 March 2006, 12:28 PM
#11
Thanks for your post Nick and I look forward to hearing how you get on when Bob has mapped the car.
Silent Running : I don't know where you get your information from but I can tell you from first hand experience in controlled experiments that with the right modifications Tubular Headers OF THE RIGHT DESIGN can give ultimately greater power, even when unequal length, particularly for very high power applications.
In addition to the actual design there are other considerations such as the cross sectional area of the primaries, the design of the collector and the uppipe. Generally when going for a set of tubular headers for high power there is a loss of spool and response because the turbo does not get the same high velocity air flow low down.
As many people can tell you, ported OE headers done properly will show a significant improvement over standard with no loss of spool and with a purpose designed uppipe there are further gains in spool and responsiveness that is quite marked as many people can confirm.
You may be interested in the results reported by Andy Forrest in issue 6 of Scooby Magazine page 58 which is in line with my findings at that time on ported only headers. With subsequent flow bench work there are further gains to be had.
Silent Running : I don't know where you get your information from but I can tell you from first hand experience in controlled experiments that with the right modifications Tubular Headers OF THE RIGHT DESIGN can give ultimately greater power, even when unequal length, particularly for very high power applications.
In addition to the actual design there are other considerations such as the cross sectional area of the primaries, the design of the collector and the uppipe. Generally when going for a set of tubular headers for high power there is a loss of spool and response because the turbo does not get the same high velocity air flow low down.
As many people can tell you, ported OE headers done properly will show a significant improvement over standard with no loss of spool and with a purpose designed uppipe there are further gains in spool and responsiveness that is quite marked as many people can confirm.
You may be interested in the results reported by Andy Forrest in issue 6 of Scooby Magazine page 58 which is in line with my findings at that time on ported only headers. With subsequent flow bench work there are further gains to be had.
19 March 2006, 03:11 PM
#12
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Originally Posted by harvey
Thanks for your post Nick and I look forward to hearing how you get on when Bob has mapped the car.
Silent Running : I don't know where you get your information from but I can tell you from first hand experience in controlled experiments that with the right modifications Tubular Headers OF THE RIGHT DESIGN can give ultimately greater power, even when unequal length, particularly for very high power applications.
In addition to the actual design there are other considerations such as the cross sectional area of the primaries, the design of the collector and the uppipe. Generally when going for a set of tubular headers for high power there is a loss of spool and response because the turbo does not get the same high velocity air flow low down.
As many people can tell you, ported OE headers done properly will show a significant improvement over standard with no loss of spool and with a purpose designed uppipe there are further gains in spool and responsiveness that is quite marked as many people can confirm.
You may be interested in the results reported by Andy Forrest in issue 6 of Scooby Magazine page 58 which is in line with my findings at that time on ported only headers. With subsequent flow bench work there are further gains to be had.
Silent Running : I don't know where you get your information from but I can tell you from first hand experience in controlled experiments that with the right modifications Tubular Headers OF THE RIGHT DESIGN can give ultimately greater power, even when unequal length, particularly for very high power applications.
In addition to the actual design there are other considerations such as the cross sectional area of the primaries, the design of the collector and the uppipe. Generally when going for a set of tubular headers for high power there is a loss of spool and response because the turbo does not get the same high velocity air flow low down.
As many people can tell you, ported OE headers done properly will show a significant improvement over standard with no loss of spool and with a purpose designed uppipe there are further gains in spool and responsiveness that is quite marked as many people can confirm.
You may be interested in the results reported by Andy Forrest in issue 6 of Scooby Magazine page 58 which is in line with my findings at that time on ported only headers. With subsequent flow bench work there are further gains to be had.
What I am trying to say is that IMHO you either do something properly, or you don't. If you're bent on replacing your headers, then do it for a reason. As you've said yourself, you have to have a good design of unequal length headers and then they give you good results. Ported OE headers give good results. Tubular aftermarket headers off ebay, from what I've heard from others on here, do not give good results. I'm not exactly sure what everyone's point is here in trying to attack me on this.
But one thing's for sure as far as I'm concerned, and this I will not back down on - you can't tell me that driving an exhaust turbine with unequally timed exhaust pulses is efficient. It simply is not. The unequal length OE headers are a packaging compromise because of the layout of the engine, but luckily they sound great and do the job in standard and mildly modified tune.
Yes there are different ways of getting an exhaust to work by tweaking diameters, lengths, collector designs etc, I'll quite happily agree to that. But let's imagine you have two 'identical' designs of header/uppipe combo...same pipe diameters, construction, porting etc, but the difference being that you average the lengths of the different header pipes and use that as the pipe length for your EQUAL length headers. Which are going to perform better, in every single test you could possibly do?
19 March 2006, 04:04 PM
#13
Silent Running : You may feel under attack because the information you have given is wrong or you have not expressed yourself clearly.
The design of the headers is probably far more important than whether they are equal or unequal.
I do not think for one minute that you have anything against my headers and that is not what I have said or even hinted at. In the main I was referring to tubular headers for big power.
I accept that in theory a set of equal length headers could be superior but in practice with space constrictions I am yet to come accross a set of equal length headers that are sufficiently well designed to out perform well designed after market tubular headers at high power output ie. approaching 600 bhp. If anyone knows of equal length tubular headers for use around 600 bhp that will out perform my existing unequal length I would be very happy to hear from them. Cash waiting.
Up to somewhere beyond 350 bhp, properly ported OE headers and purpose designed uppipe have to rate very highly for consideration as they produce power, do not suffer turbo lag and improve responsiveness very noticably. It is the driveability with increased power and no downsides that makes them score over the tubular aftermarket.
Depends what you want. Unequal length headers are an inefficient way of driving a turbocharger, hence why they are got rid of as soon as you are aiming for big power. But they are fine for the lower stages of tune and I'd be very surprised if aftermarket unequal length headers showed significant improvements over the factory ones, and sets of ported factory headers show great results. If only they were a little cheaper to get done.
I do not think for one minute that you have anything against my headers and that is not what I have said or even hinted at. In the main I was referring to tubular headers for big power.
I accept that in theory a set of equal length headers could be superior but in practice with space constrictions I am yet to come accross a set of equal length headers that are sufficiently well designed to out perform well designed after market tubular headers at high power output ie. approaching 600 bhp. If anyone knows of equal length tubular headers for use around 600 bhp that will out perform my existing unequal length I would be very happy to hear from them. Cash waiting.
Up to somewhere beyond 350 bhp, properly ported OE headers and purpose designed uppipe have to rate very highly for consideration as they produce power, do not suffer turbo lag and improve responsiveness very noticably. It is the driveability with increased power and no downsides that makes them score over the tubular aftermarket.
19 March 2006, 04:28 PM
#14
Scooby Regular
That's fair enough then Harvey, good reply. My contention was that all other things being equal (excuse the pun), equal length headers are a more efficient way of driving a turbine than unequal.
Now that we're talking about space restrictions then OK, that's a different story, and you clearly have actually tried stuff out and put the work in to find out. That approach is what I respect.
Just out of interest, have you found any weaknesses in the physical construction of the factory headers i.e. points where they tend to crack, mileage limits, rust spots etc etc?
Now that we're talking about space restrictions then OK, that's a different story, and you clearly have actually tried stuff out and put the work in to find out. That approach is what I respect.
Just out of interest, have you found any weaknesses in the physical construction of the factory headers i.e. points where they tend to crack, mileage limits, rust spots etc etc?
19 March 2006, 10:20 PM
#15
Glad that is cleared up.
I am yet to find an O/E set of headers that has cracked although I have come across a couple of failed up-pipes at the flexi joint. The cross pipe which runs across the front of the engine between the sump and the radiator is of the same construction but I am yet to find one of those that has failed.
The O/E cast headers can get very rusty, especially if the car is kept at a coastal location but as far as I have seen it is not detrimental to the actual cast headers which are very robust.
When I get headers for porting, I can tell which cars are from sea side locations. It is very noticable.
I have first hand experience of two sets of quality/expensive tubular headers, both fitted to my own cars, which have failled in service due to cracking or splitting. One set were ceramic coated and in ignorance, I then exhaust wrapped them. My assessment is that this trapped too much heat, beyond the design temperature of the stainless steel used for the headers and compounded by the high EGTs I was experimenting with.
When I removed the exhaust wrap, the ceramic coating fell off in flakes. I tried to reuse these headers after welding up the collector welds and did it a second time before concluding they were scrap. Much the same happened with another set of quality headers (different manufacturer) which were not ceramic coated but exhaust wrapped. With continual heat cycling they became brittle in time.
Depending on design, leaks on aftermarket tubular headers are frequent but I know of no issues with O/E headers other than those caused by careless or inexperienced fitting.
I am yet to find an O/E set of headers that has cracked although I have come across a couple of failed up-pipes at the flexi joint. The cross pipe which runs across the front of the engine between the sump and the radiator is of the same construction but I am yet to find one of those that has failed.
The O/E cast headers can get very rusty, especially if the car is kept at a coastal location but as far as I have seen it is not detrimental to the actual cast headers which are very robust.
When I get headers for porting, I can tell which cars are from sea side locations. It is very noticable.
I have first hand experience of two sets of quality/expensive tubular headers, both fitted to my own cars, which have failled in service due to cracking or splitting. One set were ceramic coated and in ignorance, I then exhaust wrapped them. My assessment is that this trapped too much heat, beyond the design temperature of the stainless steel used for the headers and compounded by the high EGTs I was experimenting with.
When I removed the exhaust wrap, the ceramic coating fell off in flakes. I tried to reuse these headers after welding up the collector welds and did it a second time before concluding they were scrap. Much the same happened with another set of quality headers (different manufacturer) which were not ceramic coated but exhaust wrapped. With continual heat cycling they became brittle in time.
Depending on design, leaks on aftermarket tubular headers are frequent but I know of no issues with O/E headers other than those caused by careless or inexperienced fitting.
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