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Just my opinion but I think you should tilt your spoiler a bit flatter. I know it has nothing to do with the hood issue but It was the first thing I noticed. hahaha

 

 

 

As for the hoods, I think 74_5.0L_Z's idea is a great one. Especially if it could be a longer scoop. hell, Ferrari and the Ford GT use this kind of design, it must work to some extent, right?

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Just my opinion but I think you should tilt your spoiler a bit flatter. I know it has nothing to do with the hood issue but It was the first thing I noticed. hahaha

 

 

 

As for the hoods, I think 74_5.0L_Z's idea is a great one. Especially if it could be a longer scoop. hell, Ferrari and the Ford GT use this kind of design, it must work to some extent, right?

 

 

 

i would do a hood scoop like that if i was running a v8, no question about it. with the l6, there is no room for a feature like that. that is why we are looking at other vent areas. as far as the wing goes, the safest spot in my garage right now is on my car. it is just sitting there not bolted on so. i have not even bolted it to the fg hatch yet to even start to adjust the wing to close to level. it is on my long list of things to do.:mrgreen: there's a ton of things on that list.

 

jimbo

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I like what you have taped off so far, but I thing the inner vents on the hood could extend down a few lines farther, just to balance out the look of the other vents. Plus I think there's plenty of air to vent to need it when you're going 60mph+ on a track.

 

I really like 74 5.0l Z's hood vent, and is along the lines of what I'll be doing if/when I get a S30. Kinda in the vien of the GT40 hood vent, let the air come in, and the push it right back out upwards. Depending on motor choice I'd mount the radiator at an angle as well to help, if there's room for it.

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I like what you have taped off so far, but I thing the inner vents on the hood could extend down a few lines farther, just to balance out the look of the other vents. Plus I think there's plenty of air to vent to need it when you're going 60mph+ on a track.

 

I really like 74 5.0l Z's hood vent, and is along the lines of what I'll be doing if/when I get a S30. Kinda in the vien of the GT40 hood vent, let the air come in, and the push it right back out upwards. Depending on motor choice I'd mount the radiator at an angle as well to help, if there's room for it.

 

 

even if you could mount the radiator at an angle (plus there is a fmic to deal with) i do not think there is enough room to have a vent like 74 5.0l. if some has made that happen i would love to see it. i think the only pic i have seen with a slanted rad is redbirds and if i remember right, there wasn't enough room.

 

heres the post

 

http://forums.hybridz.org/showthread.php?t=114152&highlight=redbird

 

i can add more vent towards the front though. thats easy.

 

jimbo

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The redbird car still had an L28ET in it too. I think there's plenty of room for it in most engine bays.

 

Consider the SR20 engine bays (pic from vildini, hopefully alex doesn't mind)

 

http://www.vildinimotorsport.com/gallery/Matt%20B.%20-%20240z/11.JPG

 

In any case it'd be interesting to see how much room you've got with the engine in. Sorry, but I can't remember what engine swap you've got happening in your Z.

 

I don't think a vent like 74 50 Z's is really "needed" per say, but I think it's the right direction for getting drag free downforce/lift reduction.

 

I'm curious though, those inner hood vents, are you planning on just removing that material, or cutting the leading endge and angling it in towards the engine? Your fender vents are pretty obviously drawn, I don't find the other one's quite so clear.

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the enging is going to be the l6 with a bw s400 turbo. lots of plumbing in there. the vents in the hood i was just going to remove the material and cover the bottom with a screen mesh to keep the crap out. i had thought about angling them up as well. not sure which is better.

 

jimbo

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I am in the process of flush mounting the windshield and hatch glass, and building a box to isolate the "cowl induction" intake to the carb/air cleaner.

 

The flush mounted windshield will interest many of you. I`ll get some pics in my album soon so everyone can see how i did it. It`s way to complicated to go into now but it has been and will be very time consuming to finish. I will say it does look sweet.

Do you have pictures of this? I'm interested in seeing how you flush-mounted the windshield.

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i can add more vent towards the front though. thats easy.

 

jimbo

 

Suggestion: extend the "rectangle" zone you already have most of the way forwards until its almost even with the hind side of the fender "zone" and then begin a horizontal taper towards the center of the hood, leaving you with a "zone" shaped like half of home plate, and the diagonal cuts from the center of the car then outwards.

 

I also don't like the holes/mesh idea.. but I DO like the thinking that a different shape to the vents themselves there would complement the "gill" vents in the fender, so maybe it will work better than I think. Any chance of finding a way to make gills that are somehow rounder (as opposed to the squarish look of the fender gills) so that the ovalish visual effect is retained, but its not just a straight hole?

 

 

 

Here is a question that has been burning my mind.....

 

Why not vent the intake/exhaust/turbo side of the hood (on L28ET cars) and leave the spark plug/battery side solid? Why waste that airflow when we can push it ALL past out intake AND exhaust tracts? Even on crossflow engined I6 vehicles, I would imagine it better to bias the flow on the exhaust side.

 

Obviously there is a potential for off-center drag/thrust in this concept; would such an assymetrical ventilation setup be detrimental in any way?

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My opinion on your cowl hood dilema is the understanding of it. I view a cowl to give a greater amount of volume in the engine compartment lowering the pressure. This is similar to limiting the air flow in while creating more downforce. With the rear of the cowl opening moderately close to the windshield, you will allow the air to exhaust over the car creating downforce. It would be impossible for the cowl to allow any backflow into the engine compartment or under the car. It is the same theory that creates lift for a airplane wing. When air flows around a object that has a larger surface area on the top than the bottom, the air on top has to speed up to meet back up with the air going under it. The faster moving air creates a low pressure area creating lift. This faster moving air pulls out the air in the engine compartment. This can be easily demonstrated by blowing compressed air across a full water bottle at about a 45 degree angle. Anything in the bottle will be sucked out.

Hope this helps you.

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That's the Bernoulli principle you're talking about with the bottle example. The problem is that there is a stagnant high pressure area right at the cowl, hence the invention of the cowl induction hood. The cowl induction hood takes the pressure that normally exists at the base of the windshield and forces it into the engine compartment where there is usually a big 4 barrel waiting. It wouldn't make sense to suck air away from your carburetor.

 

There are some things about the Z that make cowl exduction more likely, for instance the cowl itself is relatively deep and the windshield is pretty curved. One guy on here tried the yarn test and found the yarn alternately going into and coming out of the hood. In my mind a vent at the back of the hood is far from the best way to get air out. Bernoulli's Principle would work much better in the middle of the hood, since the cleaner and higher velocity airflow you have the stronger the suction created, and the farther you are away from the windshield and the front of the car the more airflow there is going to be.

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Thank's for the response.

If you dont mind I would like youre opinion on my situation and thought.

 

I am installing a turbo fuelinjected inline 6 in my '73 240z. The cowl induction theory wont be a performance robing issue in my eyes.

Now I believe that the induction could only ocur at lower speeds but even then the known positive pressure (high pressure area) in the engine compartment wouldent allow this. Most cars with cowl induction hoods have a small or almost no grill, unlike the Z.

The reasoning I am left with is, if the cowl isn't so great (large) to cause to mutch turbulence at the windshild the added volume to the engine compartment (from the raised center portion of the hood ie. cowl). And with the aid of the Bernoulli principle and posiably some reduction in the front grill. Then it will creat lower pressure in the engine compartment and give down force as the air is pulled out and over the car. As well as limit air from traveling under the car. The air under the car has more pressure than the air going over the car, making the air take the path of least resistance up and out. After all it is known that if you leave the hood unlached on a Z the hood will rise. This can't happen if youre induction theory is correct. In the case of a 240 Z I think there is somthing else going on.

Looking forward to youre response, Thanks.

 

It is all for the greater good of the Z.

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i did it. took the dremel to the hood.

 

IMG_4394.jpg

 

IMG_4396.jpg

 

IMG_4397.jpg

 

i made the area of the vents a little larger than what i had taped out before. i have yet to hit the fenders with the vents. not sure weither to cut out a rectangle of the fenders, add the vents, then put them back in. or try patching a new piece of metal in with the vents. i am thinking to use the old metal because the fenders are contoured and im afraid it will not match back up if i do not.

 

jimbo

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im thinking that the air will blow through the scoop and help draw out more engine air. its my theory anyway. all of my ideas so far have been verfied by the wind tuneel tes, so im "hoping" im right on this as well. if not, it looks mean as hell i think.

 

jimbo

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I have a different impression of what the cowl induction openings will do. This depends on a lot of unknowns, but...

 

The air at the base of the windshield is pretty high pressure. The rear cowl-opening will almost certainly take in a lot of air.

 

The front opening is pretty small in area, but it is also in a place that will have a lot of air flow, NACA inlet, etc...

 

I am willing to bet that BOTH the front and rear openings will see a lot of airflow if the opening can dump it under the hood.

 

I'll bet that a true COWL-induction airbox will see fairly high pressure. With a limited amount of airflow consumed by the engine, I think that the front opening will be overcome by the air entering the rear opening. Flow into the front will stall and possibly even allow airflow BACKWARDS, out of the front opening.

 

 

Here is what I have come up with so far....

 

aircleanerheight.jpg

 

undersidebaffle.jpg

 

aircleanerfitment.jpg

 

passthru.jpg

 

rearinlet.jpg

 

 

 

...

 

If the front opening was larger, perhaps by dropping the NACA inlet floor and enlarging the entry opening, You would begine to see flow through the cowl box from front to rear.

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Basically making a sort of pressure box right?

 

There's a guy my dad knows with a notchback VW that runs I THINK in the 9's (it does at least 140 in the 1/4) anyways, he has both his carbs fully sealed in a pressure box, with naca ducts running to them. He said that it gets up to around 3lbs of pressure on his runs, so I suppose even that would help the car get a little more power. Especially on a really high compression N/A car.

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I think Owen did exactly this, but he did it with more of a JGTC flair and put several vents one in front of the other.

 

sjgtcday212.jpg

 

So is that Owen or some JGTC flair :D

 

In case you don't realise Jon, its a bit hard to concentrate on tech when the woman is standing there :twisted:

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I'm 98% certain that Owen fabbed those vents. He was quite good w/ fiberglass. Just for shits & giggles, I'll share some pics from the racetrack today that might inspire. I've already made my one-off hood that will be unveiled in due time using directional louvering & NACA duct. The guy that did the louvering was one of THE old school Rat Rodders that essentially invented the technique. He is about 80 yrs. old and still does kickass work! Pics from the track, an '09 Evo Pace Car hood:

 

09EvoHood2.jpg

 

09EvoHood1.jpg

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Been meaning to post these pictures in this thread for awhile now. I'm hoping that my louvered vents will help evacuate hot air thats directly above the intake manifold and turbo as well as giving the pressurized air thats under the hood a place to escape. I don't have and hard evidence or data beyond my own observations, but it seems that the underhood temperatures are not as severe as the used to be. Eventually this summer I plan on sticking a temperature probe under there and finding out, as well as a string test at mid-highspeeds.

 

IMG_6211.jpg

IMG_6210.jpg

IMG_6207.jpg

IMG_6208.jpg

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WTF??!! Has anyone else had their photobucket pics spontaneously disappear?! Let's try this again...

 

 

09EvoHood2.jpg

 

09EvoHood1.jpg

 

 

"Sparky", I'm almost disappointed to see the public posting of those inverted louvers. I thought that I was the only one...hadn't seen them on ANYONE else's. Got inspired by an old 60's Jag. Oh, well, brilliant minds think alike ;~)

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