Hey guys,..

I recently installed my Invidia gemini Dual exhaust cat-back system.. and love it. It's quite loud at low rpms -- From 1000-2900rpm -- Then it becomes about 3-4 times quieter (not sure why.. but that's the way it seems to run.)

I want to do one more mod before I bring my car in for a Tune.. and I've decided on putting Berk HFC's in there (and just leaving the factory headers based on what I've read.)

My question is (and I've searched and read for a while about this.. but wanted your recent opinions if you don't mind) --

How much louder will adding Berk HFC's to my 2008 350Z that already has the Invidia Gemini Dual Cat-Back Exhaust make my Exhaust?

I'm very happy with the noise level I have now.. and between the 1000-2900 rpm it's actually quite loud in the cabin and you have to speak up to talk to someone.. but it's a very deep smooth sound.

Now.. I can handle a TAD louder.. no big deal, probably will like it. I am just about to buy these Berk HFC's today and don't want them to like double the loudness of my exhaust.

While I know it's hard to put into words how loud something is, -- But about what can I generally expect from adding the Berk HFC's on my already modified exhaust setup?

Appreciate your opinions, advice.

 

Replacing your stock cats with HFCs will make your exhaust significantly louder. If you don't like loud exhaust setups you are probably better off keeping your stock cats on your car. As always, it would be better if you could hear the difference in person, but I'm sure there are YouTube videos that can give you an idea what to expect.

 

Thanks for your 2 cents.. I was just trying to gauge it.

So I talked to R&D at Berk USA.. and they explained it well to me -- Essentially in my setup the Berk HFC's will raise the dB's by 1-2dB .. On a scale of 1 -10

Stock = 0
Aftermarket Catback = 6
Adding Berk HFC's = 7

Obnoxious Exhaust = 9+.

I'll have the Berk HFC's on next week .. so I'll post the sound difference then. I have an inclination that since the Invidia Gemini true dual setup I have on now is really only "loud" between Idle and 2900rpm.. That the Berk's are going to significantly increase the 3k+ range.. which is what the Invidia Gemini needs.

We shall see.

Take care,

 

you should like it, i had the kinetix hfc with my gemini at first, it was a good sound. do any and all breathing mods before you tune, i essentially changed everything and had to get a retune, but in the end i gained 12 more horses changing things

 

I have the Gemini and actually think its rather tame compared to others. It gives the VQ a slightly more "exotic" sound in my opinion. I just went over 105k miles with stock cats and want to replace them with HFCs since I suspect some of my "boginess" may be due to clogged or dirty catalysts. Thinking about taking my intake back to stock (have JWT and Kinetix) just to eliminate unneeded heat soak. Great exhaust though!

 

Both your replies sort of go together.

I , with this HFC install, have done all the breathing mods I *think* will make any difference for my VQ35HR..

I run K&N drop in's with the stock airboxes (not so much due to money.. but because the $500+ intakes just don't perform better.. or there is too much debate about it .. ) -- If I did anything more on the Intake I'd possibly cut holes in the bumper and put in the Varis (sp?) snouts.. but they are SO small I don't see how it could really help.

Then I run the Invidia Gemini which changes the stock Y pipe to single to muffler to a larger piping , true dual exhaust,.. And now am putting in the Berk High flow cats (Which according to my calculations is BY FAR the biggest single gain in a breathing mod you can do to this particular 2008 350Z)..

Given the stock cats is surely the largest bottleneck in the entire well designed stock breathing setup front and back..

I think the HFC's are going to open things up and I fully expect 10hp from them.. and with a Tune I think I'll grab another 5-6+hp maximizing the Gemini and that will pull the arguable 1-2hp from the stock airboxes and K&N's.

I can see , post tune,.. having an extra 20-30hp from $950 exhaust, +500 HFC's, and $100 drop ins.. and $500 for Tune + Dyno.

When it all boils down.. with the 07 and 08 350Z's .. you just don't have much you can bolt on to add horsepower.. it's really quite amazing how little there is to do to the car before you start building the engine and/or going forced induction.

Removing the Spare tire will give you more HP than any other mod that I haven't done (am doing now).. if I'm missing something fill me in!

The older models at least had the plenum spacer.. that's gone .. It's good and bad.. I suppose the 07/08 models just got refined and essientially eliminated the spacer mod, and air intake being better.

Put it this way.. If I had a 2003-2005 I'd put in the airbox I have on this car instead of a Long tube CAI.

The pretty piping/engine dressing is appealing.. but power for power..

And.. yes I LOVE my Gemini -- In fact I'm so glad my Nismo S-Tune (used) deals fell through.. because while I'd like my S-tune.. the Gemini is more powerful and louder (and frankly, I now think has a better sound..) *I may be biased though*.

I'm looking so forward to the HFC's.. wish I could install them myself without "demon bolt" issues.. I've installed everything else, but I found a guy who does Nissan and builds Custom Exhausts for sports cars who has an unbelievable $60 an hour rate... who said he would do the HFC's. He said 1-2 hours .. So I'm probably looking at 60-90$ for the install, for what "could" happen with the demon bolt(s) -- That sounds like a fair number.

My other mechanic I like charges $95 an hour.. So this guy is quite a bit cheaper.

I'll post The car with Gemini only, and Gemini + Berk HFC's video(s) next week when the HFC's arrive.

 

not trying to burst your bubble but you will only get around 10-15 whp. my first tune with kinetix cats, and the gemini i got 8hp more from the baseline and it took me to 274, after i ditched the cats and went to ART pipe and TXD2 combo then a retune ... i got to 286 whp. the hr's dont respond as well to the tune as the de's do. just dont get your feelings hurt when you see the number

 

Dang, I know dynos are all different, but I dynoed at 276hp/248tq with JWT pop chargers(installed when I bought the car) and my GReddy with NO TUNE. I'm also debating Berks HFCs new or saving for ARTs used. I don't know when I would be able to tune since I live in Iowa so if nothing else I'm looking for a different sound until I can tune.

I'm very interested in hearing before and after.

 

if it was a dynojet, yeah it will read higher. mine was done on a mustang dyno which are kinda known for being little low, but i would rather have a more realistic number than an inflated one. it really depends on the day, temp, humidity, the calibration of the dyno, and the car itself

 

I can't remember what dyno it was.. I know out in Cali there is a place called Church's that dynoed a DE with bolt ons at 302 before the tune so I know there are inflated numbers for sure. I think that dyno is the one where the wheels are off of the car...... not 100% though.

It was about 75(as it always is in San Diego) and somewhat humid with only one fan at the front(uphill in the snow both ways-lulz back in my day)

 

if you have the wheels off you have less rotating mass, and you dont have to spin the drums of the dyno which are heavy. most of my buddies with tuned de's are around 240, and one with headers is like 260

and the uphill in snow part, you forgot that you are supposed to be barefoot

 

Yea, I'm aware of the less rotating mass. I don't claim my numbers to be golden, but there are a few guys running around saying "dang I got high numbers" and not knowing the difference.

There was a guy in a twin turbo G that said it was reading low that day... but that may be back to my barefoot 100mph wind uphill both ways business

 

If that's the result, that's the result. A tune is still worth it at this point having Air intake done, Berk HFC's, and going from Stock Single to Invidia Gemini Dual Exhaust.

Though a 10 hp gain from that + whatever a tune will do seems a touch low.

My feeling won't get hurt regardless of what it turns out to be.

As for HR's being less responsive than the DE's on a tune, is that just anecdotal from looking at other Dyno results? Or is there some mechanical reason you know of? I know my engine is 80% different than the DE, according to Nissan anyways.. Shrug.

This tuner does more Mustangs than anything else, so I'm willing to bet it's going to be the more "realistic" numbers, though he does Tune every car from a company in the region that does Z turbo setup's , and engine builds, so who knows.

If you are referring to my before and after tune,.. I'll definitely post it up.

Agree I'd rather have an accurate number, however how can we really know if the higher numbers are wrong vs. the lower numbers? It's all running through computer software in the end, maybe the higher numbers are closer to the VQ motors true HP? Who knows.

But, where I live the temp is super high and humidity insanely high from late March through October,.. so I doubt I'll get any help from the weather here in the Southeast.

Half the reason for the tune is to get my Base model's Cruise control active and to have the other "convenience" maps (IIRC this car stores 5 maps?).

I'm in the process of acquiring all the pieces to get this 08 Base all set with the Pedal Switches, Steering Wheel buttons, PAC/Axxess Module, Swapped Instrument Cluster (For the proper Lights), etc.. Once I finish piecing all that out I'll go in for the tune,.. the hardest thing so far to find is an 07-09 Cluster .. Most listed are not the 7500 Rpm Redline, even if advertised as such. (Yes I know I could use a mislabeled Cluster but I am trying to keep it exact.)

 

it is all on how the dyno is calibrated..... the HR engine was a HUGE improvement over the DE so it is hard to make it better. tuning it does make it snappier and you will like it

most guys with the HR's are usually within a couple HP of what i have.

 

My Berk HFC's finally Arrived!
http://www.flickr.com/photos/111739693@N04/12785769734/This is the Proper way to hold your baby,.. -- Still in the plastic, Hopefully the weather holds out and I can put these on tomorrow.
http://www.flickr.com/photos/111739693@N04/12785771304/

Going to try to get them installed Tomorrow if possible.. Curious to what kind of change they will do to my exhaust note from the Invidia Gemini Dual exhaust I have now...

I do have a Corded Impact wrench at 8amps that does 350 ft/lbs .. From my "testing" of this gun it hasn't met a lugnut it doesn't pull off with ease.. I have not tried to pull the insane torqued nuts of a Crankshaft pulley, etc.. But I have torqued up a nut with a torque wrench at 350ft/lbs to test it, and it pulls the rating in reverse.

I also have a Dewalt 20v XR Impact Gun/Driver -- but it's just 125ft/lbs..

350Ft/lbs isn't enough to do this myself is it?

I don't even have the extensions to get to the bolts -- Looked locally and each 10-12" extension is $10 .. So I think you need 3 feet of extension? Is that right? To get to the bolts from the engine bay.. So That's $30-$40 (tax) in tools.

I have a guy who installs at $60 an hour,.. which is the best rate I've found.

Just curious what would be the best course of action in your opinion with the Header bolts being a potential issue (I know I can get the Catback loose.)

Also, anything to mention to whoever installs (me or a mechanic) about the HFC install? IE: O2 Sensor issues? etc?

A Berk Tech mentioned to me this...
But I imagine most people use Impact to get the bolts off if they have them to use anyways..

 

you wont need an impact for them, if you put an impact on them i would worry that you are going to break the stud in the header. a little pb blaster on the bolts, let sit for about half an hour and they will come off. if you have a harbor freight tool around you do there and get a single 3ft ext and a breaker bar, that should be all that you need. the sound will get a little louder since the HFC is more free flowing

 

Awesome reply man.

No Harbor Freights here.. Just Home Depot and Lowes.. -- All I"ve noticed are the 12" or so Extensions for $10 a piece.. Maybe they have some longer ones if I look closer. Seems damn expensive for extensions.. but such are tools.

I'll also need to get a breaker Bar..

What about removing those O2 sensors -- I've seen O2 sensor wrenches,.. Advisable to buy one? Or not?

The DIY I saw, showed that the O2 Sensor threads will be jacked up when you remove it?

As for the PB Blaster.. Would going ahead and Jacking it up and spraying the bolts /nuts down now and not installing till Say Monday still work ? Or does Pb Blaster "wear off" after a day or so?

 

pb blaster will just get rid of the rust and kinda oily like wd40 i dont think it would hurt it..... if there is no harbor freight, what about a northern tool? or even a pawn shop... if it was me i would get the 1/2 inch drive vs the 3/8. i have never used an o2 sensor wrench.... take the factory cat off and then take it out with a regular wrench, hell pb blaster that too. we have the same year of car and mine were pretty easy.

there is a harbor freight there

BIRMINGHAM, AL #00095
136 GREEN SPRINGS HWY
BIRMINGHAM,AL 35209
205-290-0354

 

Chromatic-shut up and install these so I can hear the difference!!!!!! :P

 

Great help! lol.. yup there is one.. That's "down town" if you will.. I live about 20-30 mins from Downtown.. That store is about 45 mins away from me.. + traffic.. But if they have what I need I guess the gas is worth it lol.

So I guess the longest break bar I can get (that's reasonable) due to leverage.. I should go ahead and buy a solid 1/2" regular wratchet as I only have 1/4 and 3/8 ratchets.. and I'm always using adaptors for the Half inch stuff.. only my Impact stuff runs 1/2" .

If I need it anyways,.. hell why not right?

BTW: Man, you've been insanely helpful --
[quote]


haha.. I don't mess around typically.. but I'm not trying to get myself into a situation where I've broke a bolt, stripped a head completely.. other otherwise made it where some shop is going to charge me an extra hour working on a jacked up bolt/nut head situation..

The guy I talked to yesterday at $60 an hour.. Can do I Monday.. So I'm about to call him back to clarify that I found a ride and am going to drop the car off Monday morn.. and come back that afternoon to get it.. To leave him alone and give him whatever time he needs without feeling pressured.

He anticipates 1-2hours.. But as with ALL mechanics that you aren't on a "friend" basis with you.. there's no gaurantee of price.. It's just however long it takes.. Could be an hour if no bolts are troublesome.. could take 2.. Three hours if I have multiple Super DEMONIC bolts

But there's about a 50% (and growing) chance that I'll go get this stuff and try this on my own this weekend.. Send good vibes (or prayers (If that's your thing)) my way..

This mechanic says he remembers doing this on 3-4 350's several years ago.. but he said he did it all from the bottom of the car..

I was like.. Yeah, I'm sure it's possible to do it from the bottom with the right tools, etc.. But for us DIY mechanics without lifts,.. we have to use every advantage we can get.

He said.. "I do remember how they have that one bolt (or two) flipped up towards the top, .. I don't know what they were thinking. Whenever I replace the cats I always flip them around to the bottom so it's easier if you have to get back to them later."

I have one link to a DIY guide on the HFC/Test pipe install for the 350.. If you guys have any more links to some DIY's, pics, etc.. More info can't hurt. Cause I'm getting this strange feeling I'm going to do this Saturday myself (or try).. as I've yet to use a mechanic or anyone to install anything when I've said I was going to get a pro to install my audio system.. nope did it myself.. ok.. Exhaust , don't want to get stuck on bad bolts.. so Mechanic time.. Nope,.. did it myself.. and so on.

Why break the trend?