Cooling ducts to cool underhood?

[Da Hawaiian Punch]

Hmmm, funny that I ran into this subject, I was today talking to a couple of my freinds one being "Hawaii 5-Lo" the other is works with carbon fiber and fiberglass.
I'm designing a removable hood scoop, so that I can not only show off the polished things that I have and will someday have, mainly, the polished plenum, but also designing a mold area on the hood to where the air will be funneled to the air cleaner which will be dirrectly bolted onto the throttlebody it's self.
I'll have the plans drawn up soon after a little more thought into the design of the scoop that I want.

 

[hawaii-5-lo]

aloha,.
QUOTE-from Whale Pirot:"i know the effectiveness of this from my last set,in both underhood BTUs and thermal efficiency".
how are you measuring BTUs of the ambient air temp under the hood.one of my steam generators at work puts out 10,000,000 BTUs per hour max(depends on load).
BTU-the quantity of heat required to raise the temperature of one pound of water,one degree.not trying to be a smart butt,just curious how you are measuring the BTUs?
later,Todd.

 

[Vettelt193]

I have always had an idea of a hood scoop in the back of my head.... a single scoop like the Viper, with a direct link to the intake. the way our engines are set up, with the curve of the hood, it is possible to set one up to have a direct flow into the engine if you could fabricate a good air cleaner to fit between the scoop and the intake.

Ken, the old hood scoop from '67 was not functional from the factory. there is a black plastic insert to stop the air from flowing in. However, '65 and '66, with the side air intakes, were functional.

 

[Ken]

Re: My thread?

I thought it was YER thread!!

Mike, I meant your "cooling duct..." thread, where you are looking to get fresh air in/hot air out for your Corvette.

Hawaiians, keep us up to date with your progress designing a hood. :cool

Thanks for the info on the early scoops Bob. I didn't know the side vents were functional on the '65-'66 Vettes; I thought they were dummys.

_ken

 

[Tom Bryant]

Bill is on the right track here. As long as you have a good low restriction air intake that gets cool air to the engine I can't see where a scoop will do that much more. The big thing is to get the hot air and underhood air pressure out. Just the addition of a couple grills on the hood top toward the rear to allow all of that heat and air that rushes in through the radiator to excape will do wonders for underhood temps. It will also reduce the air pressure under the front of the car that causes lift and the front of the car to wander around at high speed.

Tom

 

[WhalePirot]

how you are measuring the BTUs

I measured BTUs primarily in melted plastic parts! While not scientific; quite applicable in my real, Corvette world.

Thanks for the definition. My science and engineering books are musty from years of storage!

front of the car that causes lift

My car did not get light at 150. How fast U talking, Tom?


mike

 

[Rowdy1]

Makes A Difference

I can actually change the performance of the 62 with one simple move. When I open the cowl vent which is located directly in front of my windshield and in front of the intake for my hood scoop, it changes the entire air flow BIG TIME, to the point where it sounds completely different and runs completely different. Of course it's of no advantage to have the hot engine air blow in the car, but just as a curious thing, I opened the vent and I was amazed at how MUCH of a difference it makes.
With the cowl open, it doesn't allow the air to enter the scoop. Search on BroKen, search on.

 

[Ken]

We has been merged Mike. Ok with you?

Getting cool air into a C4 isn't an issue I don't think; the obvious places are the front license plate for the ram setup, or the inverted airbox with an opening cut in the radiator shroud.

Getting hot air out is another story. I sorta like the idea of extractors cut into the hood near the rear outer edges (on top), but it would require some time and effort (read: money) to do the job right.

Let's keep playing with these ideas.

Mike, if you want me to split 'em (the threads) again, I will. Just ask.

_ken

 

[Tom Bryant]

Mike,

Since the C5R Corvettes have an air outlet duct for the radiator as well as vents over the front wheel wells I would say they probably come into play closer to 200. However it depends a lot on aerodynamics. The C2s could make good use of such a system below 150. Look at the Grand Sport hoods. The 1960 Cummingham team Corvettes at LeMans used a short air foil stragicically placed on the hood with a vent grille behind it. Not only did the foil create a low pressure area just above the vent to help scavange out the hot underhood air but it kept the rain off of the windshield at speed. The 1959 Stingray racer used hood grilles to relieve pressure and heat also but unfortunately the production '63 Stingrays only got imitations.

Tom

 

[WhalePirot]

merged. Ok with you?

I may be cheap, but I'm easy. And here I thought I was tangled up in thread.

FYI, I tried driving with the hood 'popped' and while no scientific method was employed, my empirical result seemed that such deliverd no appreciable difference.

As to the aero model, anytime the airflow curves (Bernoulli) to allow expansion of a flow area, as over the front wells on many Vettes, there is a low pressure area, creating lift AND a potential area for exhaust ducting. Other areas, where flow area is compressed, like the base of the windscreen, will be higher pressure. That area is complex with the over/through body flow, plus the hood ending, wipers, etc. Flow will be turbulent and difficult to analyze until someone films it with small strips, at various speeds. The 'Ken" study is interesting, but very simple; a good starting point.

I think the front plate could be employed IF a smooth internal duct directed the air, with minimal loss, to the engine bay. I would expect a reduction in frontal positive pressure and a possible reduction is radiaor effectiveness as that air flows througfh and not around, the nose, partially grabbed by the spoiler.

The shoulder areas Ken talks of would likely allow a higher pressure air to exhaust, but would do lots more, at speed, with a small spoiler to create a low pressure area.

I still think MY biggest issue is static state.

 

[Ken]

...static state.

:confused As in sitting in traffic?

 

[WhalePirot]

modded spoiler angle

I decided that since the spoiler was partly removed for the aborted ducting install, that I'd redo the middle part to direct more air into the engine while moving. Yes, Ken, traffic IS most of the issue; here, Atlanta, Seattle and to a much lesser degree, Anchorage.

My goals: 1) lightweight, 2) stock look/no new holes to extent possible, and 3) find stuff in the garage that satisfy 1 and 2.

I used sheet metal and angle brackets, with hardware from the 8-billion-piece Chinese screw assemblage, bought years ago. Where else could one find metric heads on standard screws? At least the lousy metal breaks under minimal torque!

I straightened the angle brackets to about 135 degrees and attached them to the body with existing mounting screws for the spoiler piece; to the spoiler with the infamous hardware. The brackets lend the pimary strength, while the sheet metal holds the spoiler at its new angle. If it bends at speed , I can double the sheet metal. I seem to get enough air at highway speeds, but I hope to get more at city speeds.

The only new holes are in the (eroded) spoiler. With new black paint, the hardware disappears. Headers come of next for Thermo-Tec wrapping and painting.

I found the burnt 'glass: where the Y-pipe is touching the tranny hump! I will wrap to the cat!
mike

 

[bill mcdonald]

Whalepirot. can you post pictures of what your doing?

My air damn was worn out and broken. I pulled it off, cut 2 holes for the air ducts, and drilled 100 holes into it.
I put fiber glass on the front and back, to built it up again, this time to ~4" tall. those holes allow the fiberglass to bond front to back.
I built my own brake ducts out of cardboard, and put glass over those as well.

I put the part back on the car and bolted the 3 pieces together. then I removed the and glassed it into one piece. so now I have a 1 piece fron air damn about 4" tall.

I thought for sure I would have broke it off the car by now. but it is pretty strong. I did not put any fiberglass on the mounting surface at the top of the air dam. I think this allows the finberglass part to flex when it hits thing, not snapping it.

It scraped on driveways and speedbumps. I am waiting for it to stop wearing down then I am going to pull it again, and build a splitter on it. I hope this way more air gets pushed up into the radiator plenum. I am doing this is because I am building a forced air box for the engine out of fiberglass as well.
I basically rebuilt the air box out of cardboard, and mounted the air filter on the bottom side like the other kits, but my air box area will be a lot taller. I am actually still trimming it to be as tall as possible and still clear the hood.

I have not hooked up my brake ducts yet, I think I am going to put some black screen mesh on them to hide those big holes a little better. It should blend into the rest of the front air damn this way.

I have never used fiberglass before either. I could of done better on the front of it. but my belt sanders, belt broke, so I did not get to finish smoothing it out. I will fix this later when I do the front splitter.

Anyway, just wonted to post what some of us other guys have been doing.

 

[WhalePirot]

cardboard and glass

Reminds me of my customized '71. My handmade tilt front end had a huge spoiler, courtesy of a refridg box. It flowed through wheel flares, into Hooker side-pipe covers, to rear flares.

I became concerned that the (about 4") spoiler was limiting my top speed.

Bill, I was working on posting the pics, as you posted.

 

[Ken]

Here's an idea guys...

The September issue of Chevy High Performance magazine has an article on the Hotchkis Media Day Challenge at Buttonwillow Raceway in Bakersfield, CA.

What caught my eye though, was a picture of the cool air intake set-up that editor Jeff Smith has on his '65 Chevelle. It utilizes the wiper motor hole, located in the high pressure are at the base of the windshield.

Now, if I can only figure out how to run the hose, because my DFUs are gonna be in the way for that set-up. The left side DFU is directly in front of my wiper motor hole, but I do have room between the two, where the distributor used to reside.

What do y'all think of the pictured set-up?

_ken

 

[94conv.]

Guys, I just got the new vette mag in the mail and it has a vette in there set up for road racing and it has a small lip, like a plastic strip bolted to the inside of the fender well on the front and sticks out about an inch and says it creates enough vacuum from air crossing over it to pull heat off the brakes, wonder if it would do the same for under the hood heat?

 

[bill mcdonald]

94 conv

The callaway LM has the same thing on the fender as well.

I removed my inner fender wells to allow air to escape. Maybe the lip would help out a little here. it would interesting driving around with it. lol

Ken, you have a mini ram on there right? that would free up a lot of room as well to run ducting.

A while back I was doing a search on aero pressure on the net and came across some write up about a pressure sensor being used with a volt meter to measure air pressure at certain points on the car. the sensor was like 20 bucks, but it was from some foreign place that I did not wish to deal with.

I am starting to think it might be worth getting to run some tests.
I would like to see what the 180 degree air filter does vs the license plate ram air.

this would also help with checking pressure at the windshelid base.

 

[oldace84]

Yes.....Yes...and Yes.....
tony

 

[Ken]

This is what we C4-er's need:

That'll vent some hot air don't ya think? :cool

_ken

 

[Mad-Mic]

now your talking! but turn the ones on the clam shell the other way and snug up a filter on the backside from some serious Ram Air