I autocross my car so midrange tq gains are always our goal. With that said I'm debating on the toda torquie-kun header or hytech header. I also have a t1r 70mm single.

I'm trying to gain mid-range and alittle top end should I go with the berk 63.5mm HFC or the 70mm one that would match my exhaust?

the out dia. of the torquie-kun is 60mm and ofcourse my single is 70.

so

A) 60-63.5-70

or

B) 60-70-70

 

c) 60-3"-3"

 

any real reason behind this or are you just saying?

ps- 70mm is 2.7559"

 

Whoops misread didn't realize you had a 70mm single. Totally fubar'd this, might as well do 70-70

 

On the subject of HFC, can anyone explain the difference between a Renault cat and a metallic core?

 

Josh, I have that same dilemma.

I recently got a Berk header, am going to get a 70mm HFC from Berk or used. I have a K&N FIPK already and going to get a Flash Pro and have it dyno'd.

I'm stuck on wether to get a 70, 75 or 76mm exhaust. Like you said, I dont need top end HP I want Mid Range Tq. I'm stuck as well, but im leaning towards 70mm.

 

I recently asked GT Motoring about this. They stated that the Renault is the highest flowing cat that Hytech has ever tested. The Metallic Core is a spun body alternative that "should be" a 300 cell (could not verify at that time). No flow numbers were provided or available.

 

I deff wouldn't go bigger then a 70mm exhaust.


From what I've read in the past an 63.5mm HFC flows like a 60mm test pipe and a 70mm HFC flows like a 63.5mm test pipe. I don't know how true that is though. I just dont know if I should go from a 60mm header straight to a 70mm HFC and exhaust.

Also I'm after mid-rance more then top end so I'm curious if I would gain more mid-range with the 63.5mm HFC over a 70mm HFC.

any dyno sheets out their of just swapping HFC's and testing?

 

The F2Xc engines flow more than enough gasses to accomodate for a 3" setup even N/A. A lot of this 70mm talk is old information passed down; those cars weren't running 13:1+ AFR's N/A. I forget if it was Evasive or GT Motoring who did the dyno's showing a positive correlation for piping sizes up to 3" N/A, I know one of them did. Since you most likely won't take my word for it.

I'm at around 122 lbs/tq at 5000 rpms, with my vtec window set @ 5800. I'm now at 4.8k, but will be lowering it again to 4.5k (I'd go lower, but it is my DD and want some leway on highway cruising speeds) however I've yet to dyno my car to see how it's looking, but I will be after I put on my Comptech Header I just bought. Your best best would be to tune your car and hit vtec earlier somewhere between 4k-5k depending on your liking; and have the piping to accomodate that amount of air. Logic would then suggest, if there's a positive correlation up to 3", then 70mm would still be a bottleneck

 

Keep in mind, the 70mm is as much the mating flange diameter as anything. The HFC is a patch of 70mm tube, a much larger diameter tube with ceramic core in it, and then it drops back down with another patch of 70mm tube.

At the header side it probably wouldn't much matter, but behind the catalyst there's no reason to drop down to 63mm after the ceramic core, then back up to 70mm for the exhaust. So if you have a 70mm exhaust now, I'd get the 70mm HFC.
__

And all I've seen lately indicates that a 3" setup will make power over a 70mm setup, even NA. That said, my car is NA and is my DD, so I went with a 70mm Q300 with a 70mm HFC. I don't want the noise, and the $600 price was great. For turbo guys the noise is muffled, the power difference is magnified, and they've already put a lot more money into the cars.