Gernby

Well, I put the T1R header back on with the 70mm HFC and 70mm ASM to see what it would do. Surprisingly, it didn't make nearly as much power as the OEM header with the same combo. It was basically opposite from the results with the 60mm test pipe and exhaust. So it seems that the T1R header does better than stock when a 60 mm test pipe and exhaust is used, but the stock header does better than the T1R when a 70mm test pipe and exhaust is used.

I wonder if it's due to the size of the collectors. Could it be some issue with the size of the "steps" in diameter between them? As I mentioned earlier, my 60mm test pipe is a bit larger than the output of the stock header AND T1R header, but the output on the T1R header is a tad smaller than the stock header. We definitely saw that having a big difference in test pipe diameter and exhaust diameter sucked balls, so I wonder if the step size from the header causes a similar issue. Would it be beneficial to have a test pipe with a smooth / gradual transition (like a cone) that matches the header's diameter on the front, but matches the exhaust's diameter at the rear? Does anyone make a test pipe of HFC that has a 60mm front and 70mm rear?

H22toF20

I believe I posted this already but the collector seems to be the most important part in header design.

I'm from an H22/Prelude backround and 95% of the headers ether have the OEM sized 2" collector and the JDM ones have the 60mm. A common thing to do is to cut the collector off and weld a 2.5" collector on for noticeable gains. I believe they put these small collectors on to be mated to the OEM or aftermarket exhausts which are typically 60mm; it wouldn't make sense to have a collector of 2.5" if you're exhaust is only 60mm. This is my educated guess on this topic. Even more interesting is that all of the hand made headers, that make big gains on OEM longblocks, all use ether a 2.5" or 3" collector.

I'm noticing that all of the JDM headers for the s2k are 60mm and yours even seems to be smaller than OEM. Could the same thing be happening here?

Gernby

I don't see how you could really replace a collector on a header without ruining it, unless you're talking about just cutting it off right after the merge is completed...

dan_uk

I am so confused by this thread maybe when you are done you should start a new summary thread

chuhsi

also waiting for a summary thread

Gernby

I honestly think the closest thing to a "summary thread" is what I just created about the TPs and HFC's.

H22toF20

Correct. This would be an interesting test on the s2k.

Gernby

BTW, I just added an "UPDATE:" note to the first post saying that my initial conclusions about my early testing weren't correct. Someone pointed out in a PM that some people might just read the first part of the thread, and not see that gains actually were possible if the correct diameter test pipe or HFC was used.

Gernby

While removing the 70mm single and 70mm HFC last night, I took the opportunity to measure the diameters of everything again (except for the 70mm TP that I no longer have). I was wrong about the diameter of the T1R header being smaller than the OEM header. It is actually 2 mm larger.

All of these measurements are INNER diameter:
Output of stock header - 54 mm
Output of T1R header - 56 mm
Input of stock cat - 60 mm
Input of eBay TP - 56 mm
Input of 70 mm HFC - 61 mm
Output of stock cat - 56 mm
Output of eBay TP - 56 mm
Output of 70 mm HFC - 66 mm
Input of stock exhaust - 56 mm
Input of ASM single - 66 mm

So it seems that my current setup with the T1R header, eBay TP, and modified stock exhaust is all perfectly matched for diameter. I wonder if that's part of the reason why it has such an awesome torque curve. There's only a ~15 ft-lbs variance in torque between 3.2K and 8K RPMs, and really doesn't have any sort of "dual cam" feel or sound.

punchdrunk

Seems like you've been feasting on humble pie

70mm FTW