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)
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:
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
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
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
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