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Just another word on the OBX shorty:
Monkeypee made 210 rwhp with the SRT intake and L-tuned Exhaust on the SRT dyno on a 2004 5 speed.

I was there when it was done. I have this header now with a Joe Z and L-Sportline exhaust and the butt dyno is very pleased. I hope the throw in the BC stage 2 over the summer though!
 

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So anyone with Megan header dimensions?
I wrote them down before I installed my header, but since I have lost the data.

All I remember is that the shortest runner was appx 18 inches and the longest 24. Roughly
 

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Discussion Starter #46
I wrote them down before I installed my header, but since I have lost the data.

All I remember is that the shortest runner was appx 18 inches and the longest 24. Roughly
Owe you some rep.
I am curious though, what is the diameter of the primary and secondary runners? Can you get those for me? I know being installed you can only get the external/outside diameters but that is enough for what I am looking at
 

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Owe you some rep.
I am curious though, what is the diameter of the primary and secondary runners? Can you get those for me? I know being installed you can only get the external/outside diameters but that is enough for what I am looking at
Um....Ya I am sure I will be able to stick my measuring device somewhere in the engine to measure the primary/secondary OD runners. I will do that after work.
 

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So here is another twist on the issue. First a question, What is the Stock diameter and length of the runners? If they are the same as the aftermarket headers and designed to work with stock internals (which according to others in this forum the after market headers are designed to work with stock internals as well) Who better to the designe a header that has the right length and diameter for the proper scavanging effects than the Engineers that designed the stock header. So here is my suggestion, you are already going through the effort of cutting and welding why not take the stock headers and cut the CATs out and weld in Striaght pipes the same diameter of the of the CAT pipe? The CATs are the main restriction point on the Stock header right? Just curious as to how this may, or may not, help your research. Thanks for reading my rant.
Scott
 

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The stock header is a stamped POS that was designed to be easy to manufacture and package

 

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Discussion Starter #51
Except look at the merge. Even the stock header has a continuously merging collector between the primary and secondary runers. The dumped collector is my biggest problem with the OBX. Short runner headers make the most HP up top with the lowest low end power. However if you notice, the OBX does not make anymore power than say the Megan/Mazzuri or Xerd.
 

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Weren't there some tubular headers from Lexus installed on a GS300 sold in australia or somewhere. I think they were pretty basic but maybe you can get some insight from those as well.
 

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Discussion Starter #54
Ok got the info on the Megan/Toyomoto/HP styled headers and surprise surprise, they are bigger than the rest. Thanks to IS3_FTW!!!

So a recap (will also update the first post):

Xerd:
Primary=1.36"-int; 1.5"-ext
Secondary=2.1"-int; 2.25"-ext

Mazzuri:
Primary=1.34"-int; 1.5"-ext
Secondary=1.88"-int; 2.0"-ext

Megan styled:
Primary=1.5"-int; 1.6"-ext
Secondary=2.13"-int; 2.25"-ext

That can explain a bit why the Megan type seem to hold power up top over at least the Mazzuri. However the difference between the Megan and the Xerd (0.14" or 3.6mm) is small enough to where I am not so sure the diameter difference matters all that much.

At this point, I am not so sure we necessarily need another Mazzuri to make the power of the Mazzuri full exhaust. That exhaust made 24rwhp and about 30rwtq. But that was a full 3" exhaust plus the very long runner header with a very good component, merged collectors!
The Xerd header plus Ypipe, coupled to the HKS exhaust made 17rwhp and over 20rwtq (dyno tested and reported in the DIY section on this site by Tony the site admin)
I think we can simply swap collectors on either the Megan or the Xerd and make nearly the same power as the Mazzuri most likely more. It seems the primary runners on the Mazzuri are not nearly as equal as we initially thought with as much as 7" difference between them
 

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Ok got the info on the Megan/Toyomoto/HP styled headers and surprise surprise, they are bigger than the rest. Thanks to IS3_FTW!!!

So a recap (will also update the first post):

Xerd:
Primary=1.36"-int; 1.5"-ext
Secondary=2.1"-int; 2.25"-ext

Mazzuri:
Primary=1.34"-int; 1.5"-ext
Secondary=1.88"-int; 2.0"-ext

Megan styled:
Primary=1.5"-int; 1.6"-ext
Secondary=2.13"-int; 2.25"-ext

That can explain a bit why the Megan type seem to hold power up top over at least the Mazzuri. However the difference between the Megan and the Xerd (0.14" or 3.6mm) is small enough to where I am not so sure the diameter difference matters all that much.

At this point, I am not so sure we necessarily need another Mazzuri to make the power of the Mazzuri full exhaust. That exhaust made 24rwhp and about 30rwtq. But that was a full 3" exhaust plus the very long runner header with a very good component, merged collectors!
The Xerd header plus Ypipe, coupled to the HKS exhaust made 17rwhp and over 20rwtq (dyno tested and reported in the DIY section on this site by Tony the site admin)
I think we can simply swap collectors on either the Megan or the Xerd and make nearly the same power as the Mazzuri most likely more. It seems the primary runners on the Mazzuri are not nearly as equal as we initially thought with as much as 7" difference between them
That's exactly what I ran back ....back ....back in the day.

SRT intake, HKS cam gear, Xerd header, oem Y & B, HKS Hi-Power. I can remember exactly what I dyno'd, the above numbers sound about right. I might have a dyno on my old computer, I'll check it out. Lol, heres an old youTube vid
 

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I believe you can still get an XERD header, one of our vendors- MVP has this on their website; (it looks a little different, though?)

MVP Motorsports 2JZGE Header! said:
Part # MVP Header SC
How does 17rwhp for less than $500 sound? That's exactly what the MVP Motorsports Exhaust Manifold gives you. For years people have been using the XERD Exhaust Manifold and while it's always been a great product, the service from XERD has been poor and has resulted in this item being very hard to get.

Not anymore! MVP has contacted XERD's manufacturer direct and is bringing it to you at the same price as before while keeping it in stock at all times for quick delivery.

When it comes to increasing horsepower on the Lexus, nothing comes close to offering the gains for the money spent as the MVP Exhaust Manifold does!
It's listed at $449.00 on their site but pm [email protected] and see what he can do for you.

Or... you can buy used from our marketplace forum ;)
 

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Discussion Starter #57
So I think we may have found another way to get what the Mazzuri offered with better fitment and more top end power. IMO this is how it should go.

Stock camshaft/stock heads/bolt ons
= 1st Mazzuri will be the best overall; 2nd Megan/xerd with merged collectors; 3rd Megan/xerd out of the box

HKS/BC camshafts(264)/stock heads/bolt-ons = 1st Xerd with merged collectors: 2nd Megan with merged collectors will be a close second: 3rd out of the box Mazzuri/Xerd/Megan

Reworked heads/Camshafts (264 or 272)/TB with modified intake manifold/bolt-ons = 1st Megan with merged collectors; 2nd Xerd with merged collectors; 3rd Megan and Xerd with dump collectors; 4th Mazzuri will be last here (probably not really even worth it at this point)

This IMO will be the best order for picking headers. You have to match your setup with your exhaust, so if you are sure this is the route you are going (especially in the near future), this will be the way to go.

I have the Xerd header in my possesion and will be doing some dyno testing between the Xerd with merged collectors against the Mazzuri this summer. After which I will be installing camshafts and repeating the dyno tests
 

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So I think we may have found another way to get what the Mazzuri offered with better fitment and more top end power. IMO this is how it should go.

Stock camshaft/stock heads/bolt ons
= 1st Mazzuri will be the best overall; 2nd Megan/xerd with merged collectors; 3rd Megan/xerd out of the box


So, from what you are saying, mazzuri still offers more hp/trq for bolt-on setups like myself. I only have aftermarket intake/exhaust cam/2.5"exhaust on a auto 01. I installed the mazzuri V2 couple months ago, I do notice a lot of low end torque loss and relatively gain on the high end(cuz I don't drive on high way that much). I will try get it dyno this summer and see how much I got out of the whole set up.

BTW: Thank you for your hardwork and efforts at providing these valuable info to myis members!!
 

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Discussion Starter #59
That's exactly what I ran back ....back ....back in the day.

SRT intake, HKS cam gear, Xerd header, oem Y & B, HKS Hi-Power. I can remember exactly what I dyno'd, the above numbers sound about right. I might have a dyno on my old computer, I'll check it out. Lol, heres an old youTube vid
Sounds pretty good. I had the Dragger cos I felt the Hiper had too much drone, but not too bad
 
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