Want about 20% more induction noise, more throttle response, and a more willing engine to rev above 5500rpms? It's pretty simple, but you are going to end up cutting the Power Duct if you choose to do this. Basically you're cutting the lower lip off the Power Duct cover and regluing it and/or using a peice of material (foam, plastic, metal, whatever) effectively enlarging the opening. My buddy sold his G and gave me his old airbox so I had an extra Power Duct cover at my disposal. I believe the duct cover is about $22.

I didn't want to overdo it, so I only increased the opening from 1 5/8" stock to just under 2". That size seemed make the most sense to me. One thing that is important is you need to make sure to seal up the duct seal so that the only air being drawn is from the induction (ie no gaps to pull in air from near the radiator). Why is this important? Because the OEM intake tract becomes pressurized at speed and is responsible for strong throttle response and that power surge immediately after a gear change. Any leaks negate this design.

Does this mod add power? Highly unlikely. I've datalogged the MAF voltage and my results were inconclusive on before and after runs over the course of 300 miles. Granted the density altitude in Kansas City has been hovering in the 4000-4800' range for the past 10 days, but I don't think that's going to influence the data other than the car is just down on power by about 10%. I think the reason the mod adds noise is because more air is being drawn through the less restrictive duct rather than the over radiator snorkel, effectively making it perform more like the 350Z airbox.

Comparison of modded duct and OEM duct. I plan on using liquid rubber to make it look pretty.



Installed to show the size of the opeing. I can now take my hand and easily put it through the opening.

 

I might have to try this since I still have my 04 airbox. I'll just mod the powerduct from that.

What did you cut it with?

 

Thanks as always Dave. Couple of questions for you:

1. Why replace the original foam around the forward facing frame?
2. Where did you spot potential leaks? At the bottom of the opening where you
enlarged it?

Keep up the good work.

 

Dave,

Have you tried capping off the snorkel section so that the only air being drawn in is from the powerduct with this mod?

I don't think the 350z has the over the radiator snorkel like we do.

I'll probably try it at the track this thursday if it doesn't rain.

 

also the Z draws air from an entirely different location

I wouldn’t really call this similar to Z at all.

BTW Dave, I'm not saying this to start a debate... I read this thread earlier and had the same thought, but decided not to mention it... but I'm following up on Derek’s comment.

 

The Z draws from the same general area and the pressurization effect is occuring, but you're right, it's not the same exact thing. The Z setup is more ideal as it's lower and less restricted. The G design is more for noise reduction hence the point of the radiator snorkel. What I was trying to say was that doing this mod allows the motor to pull more air from this point (very close to the Z setup) rather than pulling from the radiator snorkel. Since air is going to take the path of least resistance, the motor will be pulling more air from this point hence the increased induction noise.

 

Yeah, I did cap off the snorkel when I was doing around with various setups. With the snorkel capped, the Power Duct just doesn't seem to be able to get enough air, even with the duct modified. The snorkel does appear to have some benefit.

You're right, the Z doesn't have the snorkel. Their airbox only has one induction point and it's about 30% larger than the Power Duct opening.

 

Thanks.

1) I modded this thing a while ago and ran it without the lower lip for a while. I removed it because I didn't like that throttle response in the lower rpms lagged a bit and my intake temps went up because of the opening near the radiator. I removed it and tossed the lower lip. A few months later, I came up with this idea.

2) Where you're going to get the leaks is between the airbox and bumper support unit. You basically need to make a ramp from bumper support down to the airbox. With the OEM setup, it's flat. With this setup, you'll have to ramp it down to compensate for lowered lip. Hope that makes sense.

There is lots "stuff" you can buy at Home Depot to this thing to work. You'll just have to be crafty. The best stuff I've found when doing mods like this is Marine-Grade "Goop" sealant/glue. It's great at bounding plastic, foam, and metal.

 

Not exactly… the Z draws air from the cutout in the radiator support… so its actually pulling air in font of the radiator from outside… on the G, the snorkel is designed to pull cold air from the outside as well, being drawn from the grille (not for noise reduction).

Cutting up the G airbox power duct is not going to accomplish the same thing as the Z, at all.

 

In a way it is. Since you're adding more induction area at the Powerduct, the intake is going to draw more air from than point rather pulling from the snorkel 8" to 15" downstream. Path of least resistance.

 

Personally I would not favor that over colder air… and in any event, you aren’t getting more air into the combustion chamber by opening an area before the filter – so that part is moot anyway… the same amount of air is exiting the filter whether you use the snorkel or not.

To each his own. Like I said, I’m not mentioning it to debate – it was simply an observation and statement… thankfully my car does very well at the track, so I’ll continue in the realm that works for me.

 

I'm not sure I understand why you'd cut the lower part of the duct. That part is basically blocked behind the metal crossmember (for lack of the official name), so how does it increase the amount of air that flows into the airbox? I just looked at my spare, and if anything, I would think cutting the top back to maybe just in front of the words "Power Duct" would be a better option. You'd have to extend the foam back an inch or so, and possibly build it up a little higher so it stays in contact with the hood, but that's relatively easy. You'd also be cutting through the rubber seal piece, but the new foam would cover that up.

 

Who wants to be brave enought to trim out their radiator support?

 

its been done... DaveO did it a long while ago... eventually I probably will - but I'm sure that stuff is a b!tch to cut.

 

Did he like it? I'm sure it's not diffiuclt to cut. It's a type of plastic. You happen to have pictures of this handy though?