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hood vents: ideas...


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hah, I was wondering if I was the only person who was doing this :-). I picked up a set of spare inspection lids and spent some quality time with my angle grinder to get pretty much the exact same result.

 

 

So, my question is regarding hood venting as well. I don't have a cowl induction hood and want to retain a fairly stock appearance. My 240z is driven almost entirely at road course events with an occasional autoX , so limiting front end lift while retaining cooling are very important to me. I'm planning on mounting a pair of stock vents from a 280z on my hood, but there seems to be a movement here saying that moving them forward would be a good thing. I feel I've already helped out reducing the 'parachute' at the firewall, but I'm interested in any advice on how far forward I should push my hood vents. Anybody got any ideas here...??

If it matters, my front aero is being supported with headlight covers, an MSA type 3 bumper, proper ducting and blocking off any unnecessary gaps up front.

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  • 2 months later...

I needed clearance for my 4bbl carb and since with the L28 it sits off center there were really no cowls or scoops that provided the clearance I needed. My fix was to cut the stock hood across the back and down each side, then raise the center section 3". I welded 1/8 rod around both openings and installed expanded mesh. Air flow is good, the car runs under it's 180 degree thermostat, and shows no front end float at 100MPH+ speeds. Basic Datsun lines were also maintained.

 

The stock steel hood lasted 5 years but is now showing some bubbles, so a fiberglass version is in the works.

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  • 10 months later...

I'm bring this thread back a year later :iospalo:

 

After reading through everything, I'm going to do a yarn test with the hood popped to the safety latch to see where air is flowing in/out. There will be indicators every few inches all the way up the fender where it meets the hood, and half way along the front of the cowl. I'll take video (magnetic camera mount on the fender or roof) of this and get it posted sometime within a week or so.

 

This should show if inspection lid vents are effective, as well as show how far up/down the hood any other vents need to be.

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I'm bring this thread back a year later :iospalo:

 

After reading through everything, I'm going to do a yarn test with the hood popped to the safety latch to see where air is flowing in/out. There will be indicators every few inches all the way up the fender where it meets the hood, and half way along the front of the cowl. I'll take video (magnetic camera mount on the fender or roof) of this and get it posted sometime within a week or so.

 

This should show if inspection lid vents are effective, as well as show how far up/down the hood any other vents need to be.

 

I have a inspection lid vented similar to buZy. Engine was running hot over the weekend at the track. Popped the hood and the temps did not change. Sting indicated that air was going into the engine bad from the back of the hood. Near the vented inspection lid air appeared to be going out but otherwise it's a high pressure area pushing more air into the engine bay. Again I saw no change in temps with the hood closed or popped.

 

Edit: When I turn on the electric radiator fan significant air comes out the vented inspection lid - like as in the strings go vertical so they do help vent air. Strings also indicate that air is coming out the vented lid at speed.

 

Cameron

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  • 2 years later...

bringing this thread back to life again after reading for hours about how to keep the car cool. X64v did you ever get any results or has anyone figured out anything different? Im thinking about pulling off the inspection lids and seeing how much of a difference this makes.

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X64v is or was a University of Arizona student. Have not seen any of his posts here in quite some time. As far as cooling the L28 6 cylinder there appears to be insufficient cooling of the cylinder heads of these type cylinder heads. The only way out of this situation is to carefully cut open scrap cylinder heads to see if it was a design defect or workmanship problem at the point of manufacture. Then figure a way to modify the supposed good cylinder heads to increase coolant effectiveness and flow.

 

As far as general engine cooling, there is an air gap at the top of the radiator support and the bottom of the hood that needs to be closed up. Also other holes in the radiator support need to be closed up such that most all of the air flow goes through the radiator. Then try removing the inspection covers to see if these fixes provide adequate cooling.

 

Personally, I am going to do all of this plus fabricating a tunnel from smaller opening in the front grille inlet to a large outlet at the radiator. This get the air flow from a higher to a lower pressure area and confines the flow though the radiator. With good flow through the radiator and out through the top of the inspection panel openings should provide good cooling.

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I did a yarn test, and it pretty much lay flat over the screen at speed. When I added the spoilers in front of the screen, the yarn stood right up. The car definitely likes the vents. I don't know how effective they are but they certainly don't hurt.

 

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  • 3 months later...

The lids are not big enough to take useful louvers, just look at the front grille intake to visualise the amount of air coming into the engine bay to get that in perspective. To be useful vents have to be correctly located and big, big, not cute little.

Edited by 260DET
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Agreed, but they would be better then no louvres at all? Also the effect of the wind passing over the louvers will help force out hot air in the bay (providing the louvers openings are pointing to the windscreen), hence the aperture may be small but still effective. Just based on my own simple logic..... Not proven by me.

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  • 7 months later...

For what its worth (which could be nothing) i know for a fact that a Z with a hood that isnt properly fastened will have lift in the nose at 130mph.(everyone knows that) When the fastening fails at the back the hood will raise up to roof height and stay there. When the hood pops open the car sucks to the ground briefly until your heart beats through your chest and you gather information about what just happened. At 100mph as you slow the hood continues to come down as you slow the car back to reasonable speeds it wont close until 30mph or so.

 

Note: even if you are young AND stupid. Dont attempt to hold the hood down with Zipties because its "hinged at the front and doesnt matter"

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Sounds like you speak from experience..... :blink:

 

 

I haven't been to 130 to verify, but since I installed the airdam I have not felt the front end get light like it did that one time at 120.

Edited by SleeperZ
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