Intake & Exhaust Questions and info regarding various aftermatket exhaust systems for the G35 (Headers,Y-Pipes, and Cat-Back Systems)

Z Plenum on G35

Old Jul 2, 2003 | 06:20 AM
  #1  
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Z Plenum on G35

My350Z.com is talking about possibly putting the Z plenum on the G, and getting hp. Anybody know anything about this? Can someone explain the plenum, I know it connects to the intake pipe, thats about all. Thanks

G35C
 
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Old Jul 2, 2003 | 09:44 AM
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Re: Z Plenum on G35

i was reading about that too but i have no idea.

Jerome
2003.5 G35 Coupe aka Skyline 350GT [img]/w3timages/icons/tongue.gif[/img]
 
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Old Jul 2, 2003 | 10:00 AM
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Re: Z Plenum on G35

The Z Plenum they are talking about is a modified one with an enlarged section for the front cylinders. The stock plenum gets smaller in front and starves those for air, so they say. The plenums for the G and Z are the same, and the modified one fits both.

Lou

 
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Old Jul 2, 2003 | 01:43 PM
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Re: Z Plenum on G35

Doug called me this afternoon and told me he is shipping out my plenum today. I will give a full report on tuesday or wed. of next week after I have installed it. From what I have been told its BADA$$

 
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Old Jul 2, 2003 | 02:32 PM
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Re: Z Plenum on G35

Hey guys! mbarrad has posted pictures of his Z Plenum
on the thread "OMG!! Speechless about the HKS Exhaust".
Read it and enjoy.

God I love this car!
 
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Old Jul 2, 2003 | 06:34 PM
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Re: Z Plenum on G35

For a dumb fellow like me, What is a Z plenum! Explanation please! Thanks. Pics? What does it do? HELP! thanks

 
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Old Jul 2, 2003 | 09:02 PM
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Re: Z Plenum on G35

They are all talking about parts from the 350Z. Plenum in car parlance usually means 'intake manifold' or to be more specific the large aluminum 'thingy' bolted to the 'head'.
Here though it has been used in 2 different ways, 1) to describe the plastic piping that starts behind the MAF sensor and runs to the throttle body or 2) the intake manifold.

Hope this made sense.[img]/w3timages/icons/smile.gif[/img]

 
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Old Jul 2, 2003 | 10:33 PM
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Re: Z Plenum on G35

Shoot, I wish I had one! Whoever puts one on, I need pics and stories!!!! [img]/w3timages/icons/cool.gif[/img] Let us know what happened.

 
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Old Jul 2, 2003 | 10:49 PM
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Re: Z Plenum on G35

How much does the plenum cost?

 
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Old Jul 3, 2003 | 09:45 AM
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Re: Z Plenum on G35

Some answers, with the disclaimer that I may be oversimplifying:

1. It's not a Z plenum. It's a plenum taken from our VQ engines and modified. The G and Z have the exact same stock plenum.

2. The plenum is what you're connecting all those fancy aftermarket intakes with the shiny pipes to. It's the unattractive blob that you see when you remove your engine cover. It's job is to make the air available to all six cylinders.

3. The theory behind this modified plenum is that the stock plenum on the G and Z is not doing a good job distributing air evenly. A couple people who have changed their sparkplugs after a decent amount of miles have reported that the plugs for the front cylinders are much more soot-covered than the rear cylinders (the ones closer to the air intake in our bizarre design), indicating that there's a higher proportion of fuel-to-air in the front cylinders (i.e. they're not getting enough air).

4. My understanding is that the modified plenum is not so much larger than the stock plenum as that it makes it easier for air to get to the front cylinders by removing the unneeded(?) bolt pillars through the middle and replacing the slope towards the front with a flat plate. There may be less surface resistance too (it looks like there's less texture to it). The exterior dimensions do change enough though so that Z owners can't re-affix their engine covers and have to relocate their strut bar. I would guess that the G's cover would still fit because it's larger, but I don't really know. There's no strut bar, anyway.

5. I thought I saw that the price is around $500, but it's initially $750 until you return your stock plenum to him, then he refunds that money. The reason being that he's making the new plenum from existing plenums, and this way your car won't be inoperable while you wait for him to weld the plate in and ship it back.

6. The only dyno so far reported a 9hp peak gain, but gains up to 19hp along the power curve closer to the redline. Meaning that, while it doesn't do as much for the maximum power rating (although 9hp would still be worth it), it provides outstanding gains at rpms where the engine was not making as much power as it could from lack of air.

That's the THEORY anyway. I'm just repeating what I read, which was said by the guy selling the product and one person who knows him who had it installed. Could all be a giant crock, but it sounds credible, and it looks like it's only a little more complicated than installing an aftermarket intake.

-Jack
Obsidian/graphite '03 Coupe premium nav
 
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Old Jul 3, 2003 | 11:25 AM
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Re: Z Plenum on G35

Don't quote me on this, but I believe "intake manifold" usually has to do with distributing fuel, not air.

-Jack
Obsidian/graphite '03 Coupe premium nav
 
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Old Jul 3, 2003 | 03:40 PM
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Re: Z Plenum on G35

No it's Air

 
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Old Jul 4, 2003 | 08:56 PM
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Re: Z Plenum on G35

So then the Plenum and intake manifold are the same thing?

 
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Old Jul 5, 2003 | 11:42 PM
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Re: Z Plenum on G35

yes!

 
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