The great HFC question for newbies

Dan37TZ

Has anybody done a dyno comparo between Berk HFC's vs. F.I. HFC's, like directly with an aftermarket exhaust? Some members have shown gains as much as 36whp using a Stillen exhaust + Berk HFC's.

I assume the F.I. HFC's didn't gain much because it uses a 300 cell metal substrate cat. Which isn't that much better than stock. Tony from F.I. claimed that HFC's don't make that much of a difference because once he put his high flow cats on after his exhaust, it only gained maybe 5whp. That's probably because his HFC's are a lot more restrictive than Stillen and Berk's. Member's here on the370z have been spreading this misinformation on since then.

The Stillen and Berk HFC's uses 200 cell metal substrate cats, which is MUCH higher flowing. When I switched out my 300 cell high flow cat on my STi to a Magnaflow 200 cell unit(which is a similar one that Berk uses), it gained 14whp after a little tuning to comphensate for the extra flow. That extra 100 cell difference actually restricts the exhaust more than you guys think.

The reason why I think F.I. chose a more restrictive 300 cell design is probably less chance of triggering the check engine light. Think about it guys, when I had a 300 cell high flow cat on my STi I didn't even need a 02 sensor fix.. Once I put on a 200 cell unit, I had to rig up a non-fouler 02 sensor fix.... Just shows how much more a 200 cell unit will flow.