So one more time, HEADERS! - Lexus IS Forum
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post #1 of 78 (permalink) Old 03-26-2009, 05:25 PM Thread Starter
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So one more time, HEADERS!

In the lifetime of the IS300 we have theorized, practiced, been excited and disappointed in the quest for bolt on and NA power. In the area of headers there has been many a design and ideas all of which has provided power but in different ways, some more than others etc.

So what makes them different?

Let start with the Megan/Toyomoto/Alphawerks:
Runner length is unequal and averages out to that of the Xerd with the shortest being much shorter than, and the longest being much longer than the Xerds
It gives the best higher end potential between it and the Mazzuri, and matches the Xerd from the one dyno I have seen. It does give increased power in every part of the rpm due to its long runner design, though not as much down low.

Now to the Xerd (or BFD):

These are what the Megan/Toyo/Alpha should have been. However the only question in my mind right now is if the Xerd's primaries are the same diameter as the Megan/etc etc or not. I suspect it has a smaller diameter, but I could be mistaken. The outside diameter of the Xerd's secondaries are 2.25" each. The inner diameter is about 2.1x"

Now the Mazzuri:

Hands down the most potential with these on a near stock car. After measuring mine (V1) and comparing them to the Xerd, I realized they are the same diameter for the primary runners. The secondaries are larger than the Mazzuri. The outside diameter of the Mazzuri's secondaries are 2" each. They also have the longest primary and secondary runner lengths of all the headers discussed so far limiting higher rpm potential

So what makes the Mazzuri have the most potential especially since it has the same primary diameter and smaller secondary diameter as say the Xerds? The use of the right header building components. One being merged connectors which have been known to give 20-30rwhp on mustangs/LS1/LS2 over comparable headers with the cheaper dump collectors. Also the much longer runner length means it works with the the stock powercurve as much as possible, getting you the most power even with the stock rev-limit (think TeamLexus).

So now that the Mazzuri is no more, how can we achieve what the Mazzuri did and possible more? I just acquired a set of the Xerds, I have the Mazzuri on my car currently. I intend to replace the dump collectors on the xerd with merged pieces and see how that compares.
I will update and we can keep up with this road to discovery and possibly a better replacement for the Mazzuri (fit and fitment has been terrible for most of us) and especially for those who will be running BC cams.

So what is the point of this thread?
Once I get all the info I am looking for, this summer I intend to be able to get the information for people looking for a Mazzuri header replacement on a near stock car, a replacement for those running camshafts and without the fitment issues that plagued the Mazzuris.
The low-end torque will never be matched to the Mazzuri due to runner length issues, but we will be close enough to where it will not matter much (especially when you see the up-top gains)

EDIT:
Thanks to Mikedtrd I have detailed measurements of the Mazzuri V2 header. I was hoping the primaries were closer in lengths, but I have seen from 31" (cyl #6) all the way to 37" (cly #2/3). So they are good, but not that great. The diameters are 1.5 outside but only ~1.34 internally where it counts. The secondary runners are 2" externally, but 1.88" internally (vs the Xerd that is 2.25 external and over 2" internal). The V1 and V2 are very very similar in dimensions so I will from now simply refer to them as Mazzuri.

Now for a recap:

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 19rwtq (dyno tested and reported in the DIY section on this site by Tony the site admin)Review: XERD Header and Mid Section Race Pipe
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

So my final thought for this till I do my dyno tests this summer:


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

Last edited by kponti; 04-22-2009 at 11:41 AM.
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post #2 of 78 (permalink) Old 03-27-2009, 07:09 AM
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What about the OBX Shortys?

Poster, I mean poster. What have I done?
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post #3 of 78 (permalink) Old 03-27-2009, 07:45 AM
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wow...good writeup...def a must read for everyone trying to get some additional power in their n/a's

2005 MSM Lexus IS300

Stock?
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post #4 of 78 (permalink) Old 03-27-2009, 08:10 AM
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Where'd you find the XERD headers? Are they still available somewhere of did you hunt them down used?

In 5 years I will have the worlds fastest IS300... because everyone else will have parted out and bought an M3.
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post #5 of 78 (permalink) Old 03-27-2009, 09:43 AM Thread Starter
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Where'd you find the XERD headers? Are they still available somewhere of did you hunt them down used?
Got it used, don't even know why I bought it except to dissect it lol
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post #6 of 78 (permalink) Old 03-27-2009, 09:46 AM Thread Starter
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Originally Posted by -Tom- View Post
What about the OBX Shortys?
I have not found any info on that, I am thinking it will probably have the same primary diameter as the Megan/Toyos/etc. However with its extra short runner, I really think it will be the worst header for the IS. Also that HUGE dump collector (even the stock collector is superior in design) mean lots of restriction at all points. Not to mention it has now gone the way of the dodo.
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post #7 of 78 (permalink) Old 03-27-2009, 09:47 AM
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Hey kponti, I have a set of V2's sitting in a box at home so if you want some information or detailed pics let me know!

2012 IS F Series 2 (Starfire Pearl)
2004 IS300 Sportdesign II (Onyx Black) - Sold
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post #8 of 78 (permalink) Old 03-27-2009, 09:56 AM Thread Starter
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Hey kponti, I have a set of V2's sitting in a box at home so if you want some information or detailed pics let me know!
Oh hell yes!!! Please measure the diameter of both the primary and secondary runners, both internally and externally. Also please measure the length of the runners, just pick two (whichever is shortest and longest visually to you) and give me an average lengths.
Thanks a lot and +rep!!!

So now who has the Megan available to be measured?
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post #9 of 78 (permalink) Old 03-29-2009, 10:31 PM
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Nice thread.

Has it really gotten so ridiculous that your actually re-writing up, write ups to save time

I think I am going to start a new write up, How to use the forum search; tips and tricks. Maybe I will contact Video Professor to make us a DVD that can be played and followed on the computer.. group buy?

----467rwhp IS300 -sold----
---402rwhp CTS-V-sold---
--321rwhp M3 vert-sold--
-429rwhp e92 335i- 538rwhp CLS55 -
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post #10 of 78 (permalink) Old 03-29-2009, 10:39 PM Thread Starter
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Originally Posted by is300cb
Nice thread.

Has it really gotten so ridiculous that your actually re-writing up, write ups

I think I am going to start a new write up, How to use the forum search; tips and tricks. Maybe I will contact Video Professor to make us a DVD that can be played and followed on the computer.. group buy
The last time I wrote that thread about headers was at least 3 years ago and things have changed since then. More mods come into play IE camshafts, TB modified intake manifolds, etc. Old, great ideas can now become the source of restrictions (comparing the Mazzuri to the Megan for instance). I know of two cars with 264 type cams both making near 230rwhp with Megan headers (called other names by the owners but still the same crap). I am beginning to notice people here making 220 or less with these cams and they are running the Mazzuri, makes me wonder, when does the Mazzuri become a restriction? After all three cars with the Mazzuri, no camshafts (all auto/eshifts) have hit 219-222rwhp.

I picked up the Xerd header expecting to find larger primaries than the Mazzuri and was surprised to find the same size primaries etc etc..questions came to mind. It was said you can only get 10rwhp 3 years ago with headers. We now know you can get 20-30 or more rwhp with headers now. But different applications for different combinations, that is what I am trying to investigate

Last edited by kponti; 03-29-2009 at 10:46 PM.
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post #11 of 78 (permalink) Old 03-29-2009, 10:50 PM
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Naa the last time I wrote that thread about headers was at least 3 years ago and things have changed since then. More mods come into play IE camshafts, TB modified intake manifolds, etc. Old, great ideas can now become the source of restrictions (comparing the Mazzuri to the Megan for instance). I know of two cars with 264 type cams both making near 230rwhp with Megan headers (called other names by the owners but still the same crap). I am beginning to notice people here making 220 or less with these cams and they are running the Mazzuri, makes me wonder, when does the Mazzuri become a restriction? After all three cars with the Mazzuri, no camshafts (all auto/eshifts) have hit 219-222rwhp.
Hmm. Yeah that is interesting, maybe I should read your write up.

Maybe with the cams, the secondary runner volume, until being evacuated into collector, becomes more important as opposed to the length and runner design to maximize scavenging.

----467rwhp IS300 -sold----
---402rwhp CTS-V-sold---
--321rwhp M3 vert-sold--
-429rwhp e92 335i- 538rwhp CLS55 -
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post #12 of 78 (permalink) Old 03-29-2009, 11:00 PM Thread Starter
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Hmm. Yeah that is interesting, maybe I should read your write up.

Maybe with the cams, the secondary runner volume, until being evacuated into collector, becomes more important as opposed to the length and runner design to maximize scavenging.
I am thinking the biggest weakness of the Mazzuri is also its greatest strength....ie the primary runner length. The length was optimized for the stock rpm band with emphasis on more low-end torque and definitely yes I felt that. It definitely has a big kick in the rear when tuned down low and in the mid range. After 6000rpm however, I just didnt think it had all that much more juice than the Megan I had on there. But due to using superior parts (such as equal length and merged collectors), it held its own even outside its range of operation
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post #13 of 78 (permalink) Old 03-29-2009, 11:01 PM
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I was just thinking about this for a second and by no means am I as learned as you are about this issue, but possibly with the increased flow(& higher rpm operation) of air into the engine with the cams, you've reached that point where exhaust design takes back seat to rate of exhaust evacuation. I'm using exhaust design for F/I applications as a precedent for this, at a certain point it just doesn't really matter how the exhaust is design, just as long as it rapidly moves it away from the engine.

I thought about my V, and many of the reputable tuners recommend with multiple NA mods such as TB, intake manifold, intake, aggressive cam, P&P, to actually swap your headers for the larger diameter F/I headers. In a V this goes from 1 3/4 primaries to 1 7/8, not a huge jump I know, but you can see 10-15rwhp from this and way more on a boosted car.

I'll shoot you some rep when this f--king website allows me to give it to people when they deserve, regardless of how long its been.

Wonder how long this would have gone on unaddressed had you not made it an issue. Again, nice thread.

----467rwhp IS300 -sold----
---402rwhp CTS-V-sold---
--321rwhp M3 vert-sold--
-429rwhp e92 335i- 538rwhp CLS55 -
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post #14 of 78 (permalink) Old 03-29-2009, 11:12 PM Thread Starter
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Originally Posted by is300cb View Post
I was just thinking about this for a second and by no means am I as learned as you are about this issue, but possibly with the increased flow(& higher rpm operation) of air into the engine with the cams, you've reached that point where exhaust design takes back seat to rate of exhaust evacuation. I'm using exhaust design for F/I applications as a precedent for this, at a certain point it just doesn't really matter how the exhaust is design, just as long as it rapidly moves it away from the engine.

I thought about my V, and many of the reputable tuners recommend with multiple NA mods such as TB, intake manifold, intake, aggressive cam, P&P, to actually swap your headers for the larger diameter F/I headers. In a V this goes from 1 3/4 primaries to 1 7/8, not a huge jump I know, but you can see 10-15rwhp from this and way more on a boosted car.

I'll shoot you some rep when this f--king website allows me to give it to people when they deserve, regardless of how long its been.

Wonder how long this would have gone on unaddressed had you not made it an issue. Again, nice thread.
You just hit the nail on the head! Those were my thoughts exactly. However even that can be improved on, but you gotta allow the exhaust to flow, all your fancy add-ons will do nothing except restrict flow if actual flow has not been addressed

Thanks
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post #15 of 78 (permalink) Old 03-30-2009, 09:48 AM
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so in regards to the 2jz....is back pressure a bad thing when major N/A mods come into play. for example, intake, throttle body, cams, p&p, intake manifold ? i know on my previous car, back pressure was absolutely needed in order to make any kind of torque...
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