Unequal Vs Equal headers
16 June 2016, 08:41 AM
#151
Scooby Regular
I know the KB are made from 321 Stainless which is best choice,
I have managed to find a place happy to make a set from either material.
I understand the KB utilise CAD design for that perfect flow.
But what do you think of copying either that setup or even an existing RCM or other manifold in 321 stainless ??
25 April 2017, 06:30 PM
#152
Scooby Regular
I know this post has been dormant for a while but it has some good info so wanted to add to it.
Whilst lots and lots of people love the Subie rumble, it's not efficient and you won't find it on any of the JDM cars as they are all EL. They exist on UK and USDM cars because they are cheap to produce in the cast iron manifold form and are used across the board in terms of Subaru model range.
Lots of people are quick to jump on the manifold upgrade bandwagon and more often that not one finds GT2 spec UEL manifolds. However the size of the primary tubing, material used and overly large uppipe that they ship with totally shifts your power band to the right by a good 400-500rpm. And you suffer in the mid-range too. Gains are to be had at the top end over the OEM manifold providing you are shooting for 400bhp+
Keep in mind that the US guys only have the 2.5L engine and shoot for big numbers....they aren't interested in drive ability or spool and just about what they make up top.
If you look at the cost of a manifold, plus ceramic coating or wrap and maybe a different uppipe it all adds up and the last thing you want is for it to be cracking over time.
If you're interested in spool, more torque under the curve especially in the mid range, lower EGTs, lower cylinder temps then go Equal Length if you are going above 400bhp , in which case the sound issue shouldn't bother you. I think people are way to quick to ditch the stock manifold and instead should look at porting the stock manifold, getting thermal protection on it (eg. Nimbus GII etc), and a good uppipe like a Harvey trick uppipe and they should be more than happy.
The Tomei EL gets good reviews for a run of the mill GT2 spec EL manifold/header. So if costs were paramount and someone wanted an EL tubular without spending a fortune based on research that would get my vote but still prone to possibility cracking etc especially if wrapped.
Otherwise it's the Killer B Motorport Holy Header which also comes in a 2 bolt flange to keep your exisitng aftermarket uppipe or you can order it complete with their Vband uppipe. Check with Chris@KillerB for fitment.
Whilst lots and lots of people love the Subie rumble, it's not efficient and you won't find it on any of the JDM cars as they are all EL. They exist on UK and USDM cars because they are cheap to produce in the cast iron manifold form and are used across the board in terms of Subaru model range.
Lots of people are quick to jump on the manifold upgrade bandwagon and more often that not one finds GT2 spec UEL manifolds. However the size of the primary tubing, material used and overly large uppipe that they ship with totally shifts your power band to the right by a good 400-500rpm. And you suffer in the mid-range too. Gains are to be had at the top end over the OEM manifold providing you are shooting for 400bhp+
Keep in mind that the US guys only have the 2.5L engine and shoot for big numbers....they aren't interested in drive ability or spool and just about what they make up top.
If you look at the cost of a manifold, plus ceramic coating or wrap and maybe a different uppipe it all adds up and the last thing you want is for it to be cracking over time.
If you're interested in spool, more torque under the curve especially in the mid range, lower EGTs, lower cylinder temps then go Equal Length if you are going above 400bhp , in which case the sound issue shouldn't bother you. I think people are way to quick to ditch the stock manifold and instead should look at porting the stock manifold, getting thermal protection on it (eg. Nimbus GII etc), and a good uppipe like a Harvey trick uppipe and they should be more than happy.
The Tomei EL gets good reviews for a run of the mill GT2 spec EL manifold/header. So if costs were paramount and someone wanted an EL tubular without spending a fortune based on research that would get my vote but still prone to possibility cracking etc especially if wrapped.
Otherwise it's the Killer B Motorport Holy Header which also comes in a 2 bolt flange to keep your exisitng aftermarket uppipe or you can order it complete with their Vband uppipe. Check with Chris@KillerB for fitment.
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