Z Intake Plenum Constructoin

[240zdave]

And Dave Plott, your plastic thingy that goes in that hole in the radiator support that feeds cabin air thru the hood ledge (or, as the parts fiche calls it "food ledge") is missing.

Point taken. That's a photo of Old Yeller, the car that got wrecked beyond repair at the Saturday rain race last July at Barber. It did not have the plastic thingy on it when I bought the car back in 2001. I'm working on the replacement car now, and it will have the plastic thingy in place. It will cut down a little on the air coming through the radiator support, but as it turns out, the carbs are not sucking up all of the air they are getting now. I know this because the neoprene that seals the trailing edge of the heat shield to the fire wall gets blown over toward the header (back) side of the shield by the end of a race / track session. I intentionally cut the neoprene a smidge long, and before I go out on track, the edge is curled toward the master cylinder (driver's side) of the car where it touches the firewall. After coming off the track at the end of a session, the back edge has been blown over and is now pointing toward the battery side, indicating to me that surplus air has been escaping in that direction.

[ITZ34]

I used one of the TWM units with a cone filter . Dynoed it vs a foam style filter right on the carbs and picked up almost 4 hp with foam filter. I don't know how TWM unit would work with 260. It's available for sale.

[Ron Earp]

You mean you gained 4 rwhp with the foam type on the carbs versus a TWM style?

[kthomas]

Sounds like he gained 4hp with a cone filter intead of a foam filter. Wonder if that TWM unit had velocity stacks inside. Wait, is he talking about a ZX?

Need pics!!

[Ron Earp]

I ended up making something of a heat shield to catch air from the fron of the engine bay and used two individual round K&N filters. That plenium piece from TWM was far too large to fit in the available opening without just hacking it all to pieces. What I have not can use some improvement for sure, but I think it is a damn far sight better than the foam pieces I had that you couldn't even blow through with compressed air - no kidding!!!

[Parrish57]

[quote=Ron Earp;260608]I ended up making something of a heat shield to catch air from the fron of the engine bay and used two individual round K&N filters.quote]

It sounds like you are headed in the right direction but you might have to make some modifications. Not to the car, it's your terminology that needs tweaking. You see, a "heat shield" is not allowed but a "modified stock air cleaner assembly" is allowed by ITCS D.1.c. :

c. Air cleaner assemblies may be modified, removed or replaced. Velocity stacks, ram air or cowl induction are not permitted unless fitted as original equipment.

You also have to be careful that your "modified air cleaner assembly" doesn't "perform a prohibited function". Since our normally aspirated Zs came with velocity stacks that were an integral part of the air cleaner, they may modified, removed, or replaced. But what you can NOT do is create Ram Air Induction. As Katman pointed out, removing the "plastic thingy" is the first part of going down that path. If you then create an airtight box that utilizes the ram air from this new hole in the radiator support you might be crossing the line. That was my concern with the TWM peice.

So just to be on the safe side, make sure your modified air cleaner only attaches where the stock unit attached, leave the thingy in, and don't create a forward facing airtight ram air box.

Of course, this is just my interpretation of the rules. I've heard many other opinions over the years.

[Mike Mackaman]

Two thoughts on this:
1. Doesn't the fact that the 240 and 260 come factory with a velocity stack pretty much allow us to do whatever we want from the velocity stack standpoint as it is a replacement?
2. Playing around with a piece of string on the flow bench, what is more than 1-2 diameters in front of the openning doesn't even come into play. Several diameters to the side does however, even with a velocity stack. This may give you some direction to make sure you are ok.


Steve, I will call you , I have been out of town and then covered up at work and home. We'll work something out to get you the torque plate.

Mike

[Ron Earp]

[quote=Parrish57;260660]

So just to be on the safe side, make sure your modified air cleaner only attaches where the stock unit attached, leave the thingy in, and don't create a forward facing airtight ram air box.

Of course, this is just my interpretation of the rules. I've heard many other opinions over the years.

I think mine is okay, but what is the thingy?

Bear in mind I have never seen a stock 260Z setup. I have two K&N filters on the carbs bolted on using three bolt holes in the body of the carbs, a "not a heat shield but a piece of aluminum that sort of keep radiator air away from the carbs and is attached to the header". Mine is far from "air tight" though, it is mainly wide open. Definitely not a forward facing air tight ram air box. I get semi-fresh air from two factory holes that are right beside the radiator.

[ITZ34]

i gained the 4 hp with the foam type vs the twm with cone on the dyno. the cone was ducted to the openings in front by the radiator with a heat shield blocking heat from the radiator and directing air to the filter
not sure what the effects of air flow with the car moving are.Obviously the car was stationary on the dyno. I had the stacks on in both cases. The engine builder had said that the TWM unit created too much turbulence inside it.I had run it like that for anumber of years but decided to check it out while the car was on the dyno

[ITZ34]

here's picture of twm with cone filter