yea, you will have to sign up at zchickz to read the whole thing...muwhahahaha
here is a breif excerpt for those not brave enough to venture into zchick territory...lol It started as a thread about the crawford plenum...
Courtesy of Tere at Zchickz:
"The photo below is of the modified plenum (an air distribution method). You can see how the front end of the plenum is raised by looking at the weld lines. With the original plenum (more tapered at the front), air flow to the the front two cylinders was reduced, so at the higher rpms, you're kinda running on 4 cylinders instead of 6 -- seems to explain some of the power drop off at around 6,200 rpm. Seems Nissan did this to be able to close the hood with the strut brace. Crawford's solution includes a new strut brace which mounts a little further forward (second picture). The black engine cover either has to be removed or modified with the Crawford plenum. Hope this helps! " and continues on farther into the thread
"What I found interesting is that a completely unrelated thread on My *censored*z reported carboning of the front two plugs. To me, that seems to support Crawford's findings. If the front two plugs carbon, then the cylinders are running rich. What then would cause a rich condition? Reduced air flow seems most likely to me, since the injectors are all dumping the same amount of gas. It meshes with Crawford's findings anyway. It sure seems to coincide with what I see in all the dynos -- power curve begins to flatten at around 5,500 and then drops dramatically at 6,200. So you've got an engine limping along at less than 6 full cylinders. "
"It's very possible than Nissan designed this as a safety factor -- rich cylinders won't be damaged, so you begin to shut down the power curve approaching redline. And then for the folks who insist on going farther, we have the infamous redline cutoff. Since Crawford is only modifying the stock plenum, it still probably has some inefficiencies at high rpms, but it does negate some of the front cylinder air flow issue. Have you seen the air intake on the crate VQ35? Whoa, not even close to our plenum, and I'll bet it doesn't have an air flow problem to any cylinder.
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