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Discussion Starter #1
This is a first time submission for me. I enjoy catching up on the techy input and mods...It is right down my alley. I have an idea that I would like to bounce off of you chaps...

My idea about having a 1-1/2" plenum spacer ring cut from a solid plate of aluminum by a computer driven plasma head which is available to me. In essence a doughnut the shape of the plenum gasket..about an inch wide and a 1-1/2" tall. The spacer would go between the intake and the stock plenum cover and would allow 1/2" more room over the front 2 cylinder intakes than the CrawfordZ Plenum V cover. It would obviously have machined through holes and the top and bottom edges would be machined flat. The crawfordZ plenum was designed for the 350Z which is limited by the 350Zhood height. Doug said in his video that he would like to provide more space but it is just not there. We don't have that problem with the FX. We have plenty of hood space. I think with a plenum spacer the black plastic cover will still be able to be used and the flow should be closer to 100% equal on all cylinders. This should provide a big savings (target cost around $100 and no core is required) and the mod will not be as apparent to dealerships that are warranty spys. The material would be 6000 series structural aluminum with a 900deg melting point. It gets soft at 350deg, but this should not be an issue..would it?. All the hps at a 4th the cost. What am I missing? Input would be greatly appreciated....Out..Monk

If this has allready been discussed or being made..Where can I get it?
 

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1st, welcome aboard :)

Interesting and promising idea if you had access to a flowbench and dyno to prove gains, etc. I think there was a spacer made for the 350Z from Esprit (?) that was basically the same as what you've described. Supposedly it didnt get any gains.... but then I wonder if that's the case, how can an aftermarket plenum gain HP, which is essentially the same thing? :?
 

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Yes, there was a spacer made by Esprit for the 350Z. Obviously not as thick as you are considering, but the flaw of the design (and your idea) is that the sloped stock plenum still sits atop it. This means that although you are increasing the total volume under the plenum, the sloped plenum itself still creates a differential in airflow between the front and rear cylinders.

It would, however be interesting to see if using a spacer under an already equalized Crawford plenum nets any gains...

All of this is my thinking only (and I recall some discussions on the topic re: the Esprit specer on My350Z), so don't take this as gospel, however, based on this thinking, I wouldn't blindly purchase one without accompanying flow bench and dyno results.

Actually, I'd suggest you call Doug at Crawford and ask him about the idea; he's a great guy and I'm sure he'd be happy to give his input. Wouldn't really be a conflict of interest for anyone, since he really only does Z parts and likely wouldn't be interested in trying this himself.
 

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I thought the aftermarket plenums simply increased the front and left it same as stock for the rear.

Maybe a spacer tha would equalize the plenum by increasing the height more up front? Like 1.5" in the front tapered down to 0.5" to the back.
 

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When I read the initial post my thoughts were exactly the same as ujmot's. Why not a spacer that pushes the front up only? Wouldn't this solve the problem which the Crawford plenum does?

I would be interested in this, but definitely would like more information, trial results, etc before buying...

Let us know if you are going to try this! :)
 

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Discussion Starter #7
I don't have access to a flow bench and I know it gets pretty serious when you start making changes in the airflow. Things that look like an obvious flow improvement are sometimes detrimental. The spacer height is limited to 1-1/2" due to in-stock material issues. Could probably increase it to 2" if patience is present. Although thickening the spacer will further highlight a shrinkage that occurs when the metal gets hot. It may be though keeping the bolts in the plenum..I'll call Doug. Thanks
 

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A tapered thickness one sounds like a good idea. I fyou could make it and the plenum had a good seal i'd try it out. Sounds like a promising alternative.
 

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As for Ujmot's and Ak1nza's thoughts, this was my first thought as well, but I didn't mention it b/c I thought things could get tricky if you tilt the plenum atop a sloped spacer. You'll also be tilting/changing the position of the throttle body (who knows what effect that might have?) and there could be potential alignment issues with the intake (though likely easily worked around).

I am deffinintely curious, though, if making the plenum taller for us could help. Let us know what Doug says.
 

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Discussion Starter #11
Too much thought and too many issues to address with a tapered spacer. I want this thing to be cheap and simple. After talking to Doug, and If there is even a possiblity of 15-20 extra hp from this mod, I'll make 2..ship one to the lucky chap with a G-Tech and the time to test it. By the way, does anyone have their plenum off now to do a quick "to-scale" tracing..it would save me some time...of which I have little to spare..Ya'lls (yep. I'm from the south) input has been helpful...Out..Monk
 

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I would definatley be interested in this, especially for the financially challenged like myself. :lol:

I will patiently wait for the results . .


Is it done yet? . . . .



How 'bout now? . . .

:p
 

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monkfx said:
After talking to Doug, and If there is even a possiblity of 15-20 extra hp from this mod, I'll make 2.. ship one to the lucky chap with a G-Tech and the time to test it.
Hmm, guess that would be me? :D I have the Crawford plenum, but with the support of the HFXA crew, we can easily test it with the stock plenum as well. 8)

Install would require an additional plenum gasket and new, longer bolts for both the outer perimeter of the plenum AND the center bolts. Tubular bolt spacers and rubber gaskets (to go between the bolt spacers and the existing molded spacers for the center bolts) would also be required to seal it all up and avoid vaccum leaks.
 

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Discussion Starter #14
Doug is a hec of nice fellow. Thanks for the que. He said that someone had tried this before and it had no effect, but the previous spacer was not near an inch and a half thick. He thought that it should work. I suggested sending him a sample to put on the bench. He said naw..make it and bolt it on the car..if it works you'll know it . He said the bench is not always right. He said that he has actually picked up + cfm on the bench and it has shown up as a loss in hp when used on a car..huh..its all magic..freakin magic. He was moderately interested in the idea and commented that if it worked it would be an FX only mod.. made some suggestion as to how to make up the inside edges and sailed on...

Anybody's plenum off their car so they can mail me a schetched pattern???

Out..Monk
 

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I too would be very interested in this concept. I always have been a bit skeptical of the complete worth of a 350Z plentium on a FX since it really is a compromise in height based on the 350Z's hood. Yes it makes proven power as is but I know there has to be a lot more available power with more height. We can clearly go much taller and the taller the better.

Good luck Monk!
 

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Golden Boy said:
We can clearly go much taller and the taller the better.

Good luck Monk!
Is this neccessarily true on an NA car? I'd think the larger the plenum volume, the lower the air pressure would be inside it, given the same amount of air going in, or at least a larger differential in pressure varuiations based on throttle input. Well, one way to find out... You build it, we can test it for you. Nobody I know around here has their plenum off; I'd ask Doug or hit up one of the guys over at My350Z that has a Kinetix plenum and their stock one collecting dust.
 

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MustGoFastR said:
Golden Boy said:
We can clearly go much taller and the taller the better.

Good luck Monk!
Is this neccessarily true on an NA car? I'd think the larger the plenum volume, the lower the air pressure would be inside it, given the same amount of air going in, or at least a larger differential in pressure varuiations based on throttle input. Well, one way to find out... You build it, we can test it for you. Nobody I know around here has their plenum off; I'd ask Doug or hit up one of the guys over at My350Z that has a Kinetix plenum and their stock one collecting dust.
I come from the SBC mentality and I have never seen a larger intake manifold loose power. The rule of thumb is always the biggest intake that you can get to clear the hood.

Of course this is a slightly different engine design and I can be all wet. I agree with you MGFR, if he builds it, we will test it! :D
 

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Well, if Doug thinks the idea has merrit, we should deffinitely try it out. I was just recalling some radically different plenum designs that popped up on My350Z a while back that had big volume, but not neccessarily the best flow characteristics. It was determined that these designs would be a detriment to NA performance, but would work well for FI.
 

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I've seen spacers for intakes done before. From what I heard, this mod is great on carburated muscle cars, but coming from my previous car ('87 Camaro EFI) and researching and choosing parts when the Camaro was my project, a spacer was a waste of money.

Now, the spacer for the Camaro was right after the throttle body and before the plenum. In the FX's case, the spacer is after the plenum and before the intake manifold (is this correct?) In either case, you are increasing the volume in the plenum and decreasing the air pressure into the cylinder heads. PV=nRT (Already said before)

Unfortunately, I'm comparing apples to oranges, V8 to V6, domestic to import, whathaveyou, but I think the engine theroy is still the same. Find the limiting factor in the engine as a whole (in this case the plenum) and fix it.

You guys are awesome for thinking outside of the box!! I commend you all for having the marbles (edited) to experiment with your FXs. I'll be definitely following up this thread.

NEED MORE POWER!! :D

Is there a group buy on a Stillen Superchager? hehe :lol:
 
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