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Old 11-06-2008, 08:05 AM   #1
SW00P_G
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Default GT-Spec equal length vs. unequal length headers

I'm thinking of swapping out my Perrin equal length headers to either a set of GT-Spec equal or unequal.

Can anyone chime in with some pros or cons of each??

FWIW my car has a built motor/35r combo and makes over 440whp @ 20psi as it sets. I feel the small diameter of the perrin piping is causing me power loss.

I would really appriciate some comments good or bad.
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Old 11-06-2008, 08:25 AM   #2
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What is the diameter of the Perrin ELH btw?
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Old 11-06-2008, 08:48 AM   #3
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My measurements say the primaries are ~1.25-1.3 inches and the up-pipe it 2 inches.


I don't think I've ever seen official specs though. Would be nice to know.
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Old 11-06-2008, 03:31 PM   #4
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I guess I'm looking for the pros and cons of each design.
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Old 11-06-2008, 03:45 PM   #5
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EL headers are designed (in general) to improve low and midrange power whereas uel's are gonna give you a bump in the top end. Kinda depends on what you're lookin for. Either will give you gains over stock manifolds.
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Old 11-06-2008, 03:59 PM   #6
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Quote:
Originally Posted by SW00P_G View Post
I'm thinking of swapping out my Perrin equal length headers to either a set of GT-Spec equal or unequal.

Can anyone chime in with some pros or cons of each??

FWIW my car has a built motor/35r combo and makes over 440whp @ 20psi as it sets. I feel the small diameter of the perrin piping is causing me power loss.

I would really appriciate some comments good or bad.
As per Corkey Bell, you want to have a rather restrictive exhaust system before your turbo. It builds boost quicker by keeping velocity high and a greater pressure differential across the turbo. Just my .02. I think for the amount of power your producing the perrin unit should be fine.

Also from what I have seen equal length headers provide better gains in power just about everywhere over un-equals. Even if you did lose a bit of low end you would more than make that up by the better spool characteristics of the equal lengths. I think the only reason people even really consider un-equals is because of the signature sound.
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Old 11-06-2008, 04:04 PM   #7
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Some ELH may loose a little in the top end but the midrange gains are worth it.

My dyno sheet of the difference of stock manifolds vs EL Maddad Headers. I made a buttload more tq in the meat of the power band and my butt dyno can tell.

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Old 11-06-2008, 04:19 PM   #8
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Thanks for the comments!!! What's the diameter of the maddadsby the way?
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Old 11-06-2008, 05:39 PM   #9
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Quote:
Originally Posted by akeric View Post
As per Corkey Bell, you want to have a rather restrictive exhaust system before your turbo. It builds boost quicker by keeping velocity high and a greater pressure differential across the turbo.
Yes, it builds boost quicker, but it KILLS power. Read alittle closer and you'll also find out that it's much better (for the engine, the turbocharger AND the dyno chart) to make 20 psi in the intake with 30 psi in the exhaust manifolds than to make 20 psi in the intake with 50 psi in the exhaust manifolds.

Swoop, the perrin's may be costing you a bit of power, but i don't think it's so much that it warrants a header swap. Switching to something with a larger primary might help power, but it will most likely hurt spool. Junior is using (successfully) the perrin header on a car with a single scroll 40r, so, it can't be all bad for power production, plus i believe he gets it fully spooled around 4800 rpm.
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Old 11-06-2008, 05:44 PM   #10
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UNEL GTSpec has been used in many high HP cars...check out the Proven power Bragging thread and youll come across many cars that use this header.

this is just one of a few good headers out there.

i personally have one in my car and i love it.
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Old 11-06-2008, 06:19 PM   #11
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if you go with the gt-spec equal length (which copies tomei's design). You would need to custom fab a new up-pipe to work with your EWG and the header's 3-bolt flange
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Old 11-06-2008, 09:14 PM   #12
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I already know all about the fab work that would need to occur. I'm just trying to figure out if it's going to be worth my trouble to make a change. I do know that the top rpm (6700-7200) power really falls off hard at 25+psi with race gas on the dyno.

Not a huge deal right now, I'm not trying to break any records. But the winter season is sitting in and I'm looking for ways to improve my powerband for the next season.

I think that the GT-Spec UEL setup will make a little more power. I just need to figure out if it's going to be worth the time and money.

has anyone seen a dyno graph of Juniors car??
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Old 11-07-2008, 05:26 AM   #13
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FWIW, i think the gains from changing to a different EL header would be negligible, especially from a bang for buck aspect. Perrin is a good brand too, I don't think it would be worth it at all.
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Old 11-07-2008, 09:00 AM   #14
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I think there would be gains going to a header that has larger primaries and a larger collector + uppipe. I went with a gruppe-s UEL header and a custom 2.5" ID uppipe and the results are great and my EGTs are really low now.
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Old 11-07-2008, 10:21 AM   #15
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well a 2.5" up pipe is MUCH larger than the 2" that comes with the perrin kit.

maybe I could just get an up-pipe fabbed and hog out the collector to match it.

How much boost are you running to get 505whp?
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Old 11-07-2008, 11:25 AM   #16
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Not a lot of boost. AVC-R is set to 1.50 kg/cm2 (21.3psi). The OEM MAP sensor reads 21.x PSI and the TXS MAP sensor reads 22.x PSI.

My old perrin rotated mount uppipe (version 1) was garbage compared to the new uppipe. And the perrin downpipe had wires hanging inside the downpipe from crappy welding at the spot where the EWG recirculates. Only way to see that is to cut the DP in half though.
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Old 11-07-2008, 12:33 PM   #17
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So what you are saying, I just want to make sure I have this clear.

You had the perrin up-pipe and downpipe, then you switched for a custom 2.5" up-pipe and custom downpipe? Seriously, 505whp is crazy man!!!


The perrin up-pipe does look like a peice of grabage compared to the other guys around town with the gt-spec kits.
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Old 11-07-2008, 01:16 PM   #18
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Quote:
Originally Posted by SW00P_G View Post
So what you are saying, I just want to make sure I have this clear.

You had the perrin up-pipe and downpipe, then you switched for a custom 2.5" up-pipe and custom downpipe? Seriously, 505whp is crazy man!!!
Yes that's what I did, the last couple feet of the perrin dp is still there, but the first couple feet of the DP after the turbo is all custom. We also swapped from a SSAC FMIC to a monster custom FMIC, stock header to the gruppe-s UEL, and a different set of hands assembled the motor this time around.

I still have the chopped up old perrin DP at home with the wires hanging out of the welds.
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Old 11-07-2008, 03:40 PM   #19
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ELH = more power.

UELH = boxer sound.
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Old 11-07-2008, 05:06 PM   #20
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What diameter are the primaries on the Gruppe-s piece??
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Old 11-07-2008, 07:18 PM   #21
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Full Race. End of story.
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Old 11-07-2008, 10:13 PM   #22
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Too bad I talked to fullrace on the phone and they said I could not buy the headers. Only a full turbo kit could be sold. That's a bummer!
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Old 11-08-2008, 07:05 PM   #23
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Quote:
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Too bad I talked to fullrace on the phone and they said I could not buy the headers. Only a full turbo kit could be sold. That's a bummer!
That's gay as a wet hot bucket of aids.
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Old 11-08-2008, 07:32 PM   #24
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Old 11-09-2008, 01:57 PM   #25
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That's pretty!
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