Hey guys,

I'm trying to beef up my exhaust note and gain some power while keeping the stock tone. I was curious how beneficial it would be if I only installed aftermarket headers (with or w/o a aftermarket y-pipe). I also don't want to deal with HFCs or test pipes. How restrictive is our stock exhaust system anyway?

Headers in question: http://www.stillen.com/product/heade...s0dntjegst7341

Thanks for any input!

 

The stock cats are the primary restriction in the exhaust. Unless you go with a long tube header you're not going to get any noticeable gains (because you aren't touching the cats with shorty headers), and even a long tube header setup isn't going to do much in and of itself (really needs supporting mods further up the chain to shine). Sound-wise you may get a little more volume, but the stock exhaust manifolds aren't bad. They're typically the last thing addressed in the exhaust on most in depth builds. As far as the rest of the exhaust system, cats and manifolds aside, it's not bad. Unless you're cramming a lot more air into the engine you aren't leaving much on the table, any gains you might expect due to intake track related mods are going to be eaten away by the stock cats.

 

Headers on these cars are also a huge pain in the dick to install. Most guys say it's not worth the effort / cost of putting them in, and often enough they're correct. If you don't have a ton of work done to the engine already, it's not a good dollar per power place to start.

 

If you have a non rev up engine it is worth it in my opinion. Especially if you are able to get a shop to install them for a descent price. Took me about 1 full day of work to get mine in with a whole lot of $ spent on every swivel and ratcheting attachment in the hardware store.
You don't "deal" with HFC's. You install them and get a tune lol. No need for o2 bung spacers or anything. Still 100% legal in most states.
If you installed headers you would really need a new tune ASAP. It's your choice, headers will add a deep growl while HFCs will just make it louder and more open sounding.

 

The only thing "shorties" are going to do is make the exhaust louder.

 

I'd hold off on the headers in my opinion. As OBsessed mentioned earlier, the stock exhaust manifolds are decent and the install for aftermarket headers is a beast. From everything I've read, the stock cats are the most restrictive part of our exhausts. HFCs will make it louder but keep in mind a good that they most often result in a rasp around 3k rpms.

I recommend you wait to upgrade the headers until you've addressed other areas of the exhaust. Do you have or thought about a plenum spacer?

 

Only if you like to waste money for minimal gains... Or if you are going to go long tube headers and make your car too loud to drive...

 

I popped in HFC's it gave me the grunt I wanted.
I agree with everyone, start with these.

 

I do have an MD 5/16 that I will be installing within a month.

I should clarify that many of the HFCs Ive seen are not Cali legal except Magnaflow...
The new law of the land: http://www.magnaflow.com/02catalytic...california.asp

If anyone has any experience with MF cats I would love your input.
Thanks!

 

According to Z1's site, http://www.z1motorsports.com/350_g35...oducts_id=2299 are CARB compliant (which ... refresh my memory, that's what you need right? I haven't been to Cali in a while) so that's another option. Berk is the typical go to and obviously you've seen already that they won't work for you. Magnaflow is a company that's been around for a hell of a long time though, they make decent products. I don't have any first hand experience with their cats, but I'd be willing to give them a shot if I need to go that route.

@yossip: If you have a rev-up engine and a tune (with the right mods) you're actually going to get better results from a good set of headers than you will on a non-rev. This is due to the variable exhaust cam timing on a rev-up. That's not to say they aren't worth while on the right non-rev build, but they're definitely much more useful on a rev-up. They still won't do much for you with basic bolt-ons though. Once you start going above and beyond z-tube / mrev / spacer you'll be ready to open up the exhaust some, but if that's the extent of what you're doing to push air in, the stock exhaust manifolds will be fine.

Also keep your long term goals in mind. If you ever plan to go with a turbo / twin-turbo setup even way way down the road, skip the headers for now as you'll end up replacing them.

 

Infiniti changed the design of the headers from non rev up to rev up is what I'm saying. I saw a huge difference because my OEM headers were so restrictive in my 05'. exhaust from cylinders 5 and 6 had to travel forwards before looping around to enter the collectors. Ridiculous! I read through quick but don't know for sure if OP verified what year he drives. I don't buy the whole "headers aren't worth it" deal regardless of what year because if you drive an older model the manifolds are extremely restrictive. If you drive a newer rev up you'll have variable exhaust valve timing to squeeze some power out of a small physical difference from OEM to aftermarket manifolds.

If you decide to go for HFCs I recommend AAM brand but don't know if they are legal in your state like you need. Berks are thin metal and make a raspy tone which you really don't want in addition to them no longer being CARB legal. Call RDZ motorsports in CT to have some AAM's drop shipped.
Mine were about twice as much $ as my headers were to install but you're looking at the high end of the header market. The high end ones aren't worth it for the average joe $ wise. From everything I've done (not read) both the stock cats and headers are a joke. if you want to make power do them both... Topspeed headers alone gave me over 20 whp when teamed with HFC's (20 on top of 23 from HFC's). I would expect 10 from headers with OEM cats and you'd be completely legal.

 

To clarify, I'm the last one that's against headers. I'm all for them, and I'm usually put on blast for supporting them (there are still some out there who will say that absolutely no matter what there's no case for them period end of story, that isn't me). Your gains with headers aren't typical of what most people see, but I'm glad to see more positive results!

I still don't think it's a good first mod - there's more to be addressed before you'll usually get full gains off the headers, and a good tune is still pretty high on the list of bang for buck mods, but headers as part of a well thought out build are a must, imo. Just a matter of when you'll get the most out of them, and that's not typically on a bone stock engine.

 

You're saying you gained 43whp from just headers and HFC's alone??? I would like to see that dyno sheet.

 

Anyone know the diameter of the outlet on stock headers for the de?

 

2.1250"