hey I'm going to be ordering an exhaust next week and from what i understand the most restricitve part of the exhaust system are the cats. I know test pipes will give me better gains but I hear that even the resonated ones give that riced out sound which i deff don't want. So I'm thinking about HFC's. I was wondering if they affect the exhaust note at all. If so how? Also what kind of gains would I see with these compared to Test pipes?

By the way I spent this weekend reading all about exhausts in the intak exhaust forum and searching. I couldn't really find much with regard to how the HFC's affect sound and everything that I did find with the horsepower increases from test pipes and high flow cats was conflicting. One guy said test pipes only give you 2 hp another said hfc's give you ten and then another guy actually stated that test pipes gave him 40 hp.

 

oh. and my last question. I also read that HFC's have a limited life span and then must be replaced. Is this true? I also read conflicting reports on this.

Thanks

 

HFC's will most likely yield you about 7whp, test pipes will do a bit more but no way in hell are they anywhere near 40whp, it would be a freak to even get half that from HFC's. The 2whp comment seems way too low. IIRC crawford rated their HFC's at around 6-7whp

 

Are you willing to have your car smell really bad? If your not test pipes arent for you

 

hfc's do nothing for me but make the exhaust louder (stock exhaust) sounds the exact same only louder.

And considering I made 13hp by tuning after putting on hfc's and popcharger on stock exhaust I think that's pretty good.

 

so how much of that would you attribute to the hfc's wired?

 

did you put your popcharger on yet?

popcharger made the car I'd say 30% louder.

The cats made it about 10% louder, the difference is whether the sound is coming from the engine or the exhaust.

No rasp with the HFC for sure...


As for the power I made...

I got about 12hp from adding the mrev2 and 5/16" spacer. (compared to bone stock)

Then I added HFC and popcharger. Almost no hp increase. But then with tuning, got 13 more hp.

So I'd say the HFC are good for most of that increase, but you will never notice a real difference without tuning or a reflash.

 

HFC sound a little louder with a small amount of rasp.

Jermaine from TXS made 28rwhp w/ tuned test pipes. He hit 300+rwhp w/ bolt ons and a nice UTEC tune. I dont know what kind of dyno he used, but i was impressed by his tuning skills.

 

is jermaine on this site?

 

so would you do the hfc's again?

 

Bolt-ons? No way to make 300 legit whp without cams. No way.

 

what would be the disadvantages of going cams wired? you say it like there would be something wrong with it. I know its expensive to buy and install but other than that are they unreliable or do they sacrifice drivability or something?

 

I'm not sure because I've never driven a Z with cams.

But generally speaking, the cams put a little more stress on valve springs by going with higher lift, I'm not sure how badly this affects reliability. And from what I've read, it can make the idle very rough but I have the capability to raise my idle, which helps smooth it out.

I'm actually considering doing cams. Maybe after I get an exhaust... Looks like cams are going to run well over $2k though for parts+install

 

The truth is you really don't know how much hp the HFC's added by themselves. You gained an additional 13hp with hfcs, popcharger and tuning, but I thought most of that hp was the tuning part which adjusted your lean condition in the midrange primarily from the MREV2 +spacer.

I am considering going HFC's myself, I dont want buy them if they just make my car louder. I currently have popcharger and nismo exhaust, and will be installing MRev2 + 5/16" then purchasing a UTEC and tuning. Wondering if I should also go hfc's... I wonder how much hp you would have gotten without the hfcs, wonder how close to 13.....

 

You're right. The only way to find out would be to put on stock cats and put it back on the dyno. (that's just not going to happen)

But if you look at the stock cats inside, versus HFC inside, there is WAY WAY WAY WAY more restriction in the stock cats... reducing restriction is a good thing...

Also, the stock cats weigh a frigging ton. I am not really sure why. But they suck for sure, in every way (except in controlling emissions )

 

whats the weight difference?

 

Damn if test pipes made 40 HP this entire board would be Cat. free.

 

https://my350z.com/forum/intake-exhaust/200485-ultimate-racing-hfc-install-and-oem-comparison.html

This post gets into a direct comparison of OEM and Ultimate Racing HFC's with Pic's.

UR's weigh about half as much as OEM. Key reason is length of cat honeycomb section...see pic's.
Is a definite difference in sound which I measured with a sound meter. The vid's are no load so not really able to hear the difference that well.

Having about 2,300 miles now, I like the HFC's. They have nicer sound, are louder and seemed to help throttle response. HP gain? Not so sure as car was new and it's hard to measure gain from the seat without a side by side comparison. Possible hint of rasp with OEM system at around 3,000 RPM......all good though.