Questions about FI bolt-ons
 

(1) Does the Nismo have the same cats as the base 370Z (i.e. can I expect the same gains that FI quotes on their website for HFCs or test pipes)?

(2) FI offers 300 cell and 100 cell HFCs for the 370Z. Is there any disadvantage to using the 100 cell cats on a naturally aspirated Nismo? It specifies that they were designed for turbo/supercharged vehicles, but they are lighter and (presumably) less restrictive.

(3) The test pipes appear to be heavier than the HFCs. Is this right? The test pipes are the pipes minus the extra hardware as I understand it.

(4) Can anybody comment on the FI exhaust volume without resonators vs 12" vs 18" vs stock Nismo? Any of the above would be much appreciated.

Thanks in advance... decisions, decisions! :)

I know one thing, calling them could answer all this at one time. My buddy was going to order their product and they helped him by phone no problem. Answered all his similar questions...

(1) Yes. They all have the same cats.

(2) Not too sure on this one, but I remember Tony told me it's for tuning. More cells gives you extra band.

(3) Test pipes shouldn't be heavier than HFCs coz they are just straght pipes.

(4) If 10 being the loudest and 0 being no volume at all: FI CBE = 9, stock Nismo = 0. Naw... just kidding. Stock Nismo = 5. Resonateors and non-resonateors are no big deals IMO. It's just used to cancel out the in cabin drone.

Thanks for your well spoken response. I've got a call in to Tony, but I think they're in the midst of a move because they haven't answered my email and I got an auto-response saying something to that effect.

So, it sounds like with less cells on an NA engine, I'd be sacrificing some of the powerband for a minimal HP gain. Am I understanding that correctly?

I would rate stock a 1 nismo a 3.5 and F.I. a 6-7 personally.

?que?

More or less this is a correct approximation of the situation. Within reasonable design limits, if you remove some restriction from the exhaust the torque peak moves upwards in revs. Since HP = Torque*RPM, this increases "Peak HP", but that peak will come at a higher rev than before. That doesn't necessarily mean you improved the total area under the curve on the torque graph, depends on a lot of variables whether a given exhaust change does that for the rev range you care about.

Most people driving on the street will dislike a change that pushes the HP Peak up the graph, because they spend most of their time in the lower rev range and it'll feel like a loss. On the other hand at the track I spend most of my important engine time in the 4K -> 7.5K range, and below say about 3K RPM I just really don't care if my torque drops off sharply, as long as I get solid gains in the range that matters to me.

^^^

Correct me if I'm wrong here, but isn't this why you want to get the car uprev tuned if you significantly mess with the exhaust flow. HFCs will make your low-end seem sluggish and unresponsive. The tune balanaces the car out again, right?

My friend who is a Mechanic for Nissan said anything you change that has to do with the engine needs a new tune! He even said trying to let it reprogram itself isnt the best way, it wont always figure itself out correctly.

I got a Cold air intake and he retuned it. My MPG went up by 3. But then I decided to cut the resonators off. My MPG went down. No joke, I noticed it right away. Went and had him retune the car, and it went right back. I know people say cutting the resonators off should not do anything or need a tune, but I did.

I pulled a few spark plugs a couple days ago and it looks like I'm running lean. I only have G3 intakes and a CBE, so I need a tune asap. I'm waiting till I get my HFC's installed. I'm also waiting till it cools down here in Texas because I'm going to probably end up losing power getting it dynoed in 100f+ weather.

yea, Its over 100 here as well.. I try not to drive in that heat! Cant wait until I can roll my windows back down and cruise.

stock, as in a non-nismo exhaust, the regular 370Z exhaust.

A tune helps, although (IMHO) the car is mostly self-tuning for light mods, and a tune isn't really *necessary* until you've done a fair amount of changes. A tune, however, cannot completely erase low-rpm torque loss from a way-too-wide-open exhaust.

^^Now, that is a true statement! I always laugh at people saying added few bolt ons(CBE, HFC, CAI...), the car feels like day and night different in power and so on. That's just misleading people here! I had all of them on my car and the car feels sluggish and lack of throttle response big time in low rpm. It only feels some power when you rev up to 6-7k. When I swap everything back to stock, the car really comes to life. Everytime I hear people rock their biger exhaust on the street I'd take on them with my stock exhaust and I beat them everytime coz I know they'd be slow at low rpm.

There are other reasons to tune besides performance. Running lean on your car over time can cause all kinds of issues. Seriously, why would you spend $30k+ on a car, a couple of thousand on mods and skimp on $500 to get it tuned correctly? That's asinine.